Runout...

[hlee]

For those of you that read my earlier thread on the troubles that I experienced with throwing charges of IMR4064, you may remember that I was attempting to recreate the FGGM 168 SMK load. Like (what I like to think is) many people, I occasionally get a "flier" in a group that is otherwise very good. Not a called "whoops, I really shouldn't have let that one go" but more of a "why the hell is that THERE?" kind of flier. Anyway, looking for ways to improve my loads and my shooting, I started researching runout. I had heard of runout before but, I had relegated the measurement and elimination of runout to "benchrest stuff." You know, Nth degree stuff like sorting brass by the volume of 100% ethanol that each case holds, sorting bullets to the 0.1 grain, sorting bullets by base to ogive distance, and trimming meplats. Surely, one or 2 THOUSANDTHS of an inch in concentricity can't have an effect on the meager and amateurish shooting that I do... Anyway, I had 70 of my FGMM "clones" sitting in the closet with nothing to do- and I found a few dollars in another closet- so, I went to the local gun shop and purchased an RCBS Master Case Gauge and started measuring case neck and bullet runout. Now, all of these cases were once fired through my lr308 and had been sized on my RCBS press with the standard "green box" RCBS dies. Measuring case neck runout, I had a "normal" distribution with a peak at 0.002 and a tail that extended to 0.005.

Runout....Number
0.001.....13
0.002.....27
0.003.....21
0.004......9
0.005......7

The bullet runout for the 0.001 group ranged as high as 0.002 and for the 0.005 group ranged from 0.005 to 0.007.

In addition to those loaded rounds, I have 5 100 boxes of lapua brass in 4 different lots, 0ne box of which has been shot through my Lr 308. Of these, 30% measured 0.001 (or less), 50% were binned at 0.002 (more than ~0.0015 but less than 0.0025), and 94 (20%) were binned as 0.003 or greater. These measurements were all taken after the cases were run through my dies, as some of the case mouths needed rounding.

Given the above observations, here is the first experiment.

I took 5 "random" cartridges from the 0.001 case neck runout group and shot them against 5 cartridges from the 0.005 case neck runout group. Surely, this small difference will not affect my precision- especially from a budget gas gun...


Measurements are outside edge to outside edge. The FGMM was used for functional adjustment of my gas block, so do not pay attention to that "group."

That was the hope anyway. Looks like I need to start paying attention to runout. But, I may have found a cause for at least some of those unexplained fliers...

Do you measure runout?
If so, where do you draw the line on what is acceptable to shoot "for score" (whatever score you may be keeping)?
Do you have empirical evidence for picking ths cutoff?
Is there a way of correcting case neck and/or bullet runout?
I have seen the Hornady runout tool. If you have used it, how well does it work?

Now to the second set of observations. Remember that I said that 100 of those lapua brass had been through my gun? Ok, follow me on this. Out of 500 brass, 94 had a measured runout of 0.003 or greater. Of those, 10 had a runout of 0.004 or greater. Of those 94, only 10 had been previously shot, and none of those 10 measured greater than 0.003. So, 84 out of 400 unfired brass were 0.003 or greater (21%) and 10 out of 100 previously fired brass were 0.003 (10%).

Hypothesis- Shooting a cartridge causes the brass to expand to the dimensions of the chamber of the gun in which it was fired. Ok, we know this. But, this expansion allows the resizing die to better do its job (because there is some brass to move) and align the case neck with the case body- in addition to getting everything back down to unfired size specifications.

Any thoughts? Unfortunately, I cannot rule out lot to lot variability of the unfired brass, as i did not take any runout measurements of the "shot" group when it was still unfired. Aswell, I do not have any more from that lot. And, I haven't shot any from the other lots to test the hypothesis that blowing out the case allows the sizing die to improve concentricity.

Note- I was able to shrink the runout for the 0.004 group by running them through the dies again, but it was not a huge gain. They were able to be binned with the 0.003 group.

 

[ZiaHunter]

Runout of .002 or less at the ogive is generally considered acceptable for precision ammo. The two major contributing factors to runout are inconsistent neck wall thickness and the expander plug/ball being drawn through the neck during sizing. I only use FL bushing dies for my precision loads without the expander and this has significantly reduced runout. Lapua brass is generally uniform with minimum neck wall thickness variation. The same cannot be said for other brands which generally require turning the necks. If the variance in new brass is greater than .001 the probability of achieving low runout is low regardless if you neck turn.

 

[No1]

From a gasser loading to mag length runout is important so that bullet can make the jump as straight as possible. I sort ammo <.002" is for serious shooting and >.003" is for under 400 yds just messing around.
Did you measure the runnout on your Fed GMM?

 

[BuzzBoss915]

I don't shoot loads with that kind of runout. There are solutions. BB

 

[bigedp51]

You can't make a silk purse from a sows ear and you can't make accurate ammunition from brass that is not uniform in thickness.

You need a neck thickness gauge to sort your brass and weed out the cases with excess variations in case neck thickness

You will also need to mod your RCBS case mastering gauge OR "take it back and get your money back". The RCBS gauge is the worst gauge for measuring runout due to the V-block movement up and down. You will need to clamp down the rear of the V-blocks to prevent movement. And in a short time the paint will rub off the V-blocks and your cases will drag on the bare aluminium. I'm saving for the Sinclair concentricity gauge. (subliminal suggestion, hint, hint)

Having said that the RCBS gauge is the best thing going for checking for stretching and thinning in the base web area of the case instead of using a bent paper clip.

Full length resized cases are supported by the bolt face and the bullet in the throat of the chamber and the neck and body of the cartridge case do not touch the chamber. As long as you have .003 or less runout the case should have minimal influence on bullet alignment with a normal factory chamber.

Good quality uniform brass thickness is key to better accuracy, and uniform neck thickness and neck tension will improve your groups. The Redding neck thickness gauge pictured above is just as important as measuring runout when sorting cases for accuracy.

 

[morganlamprecht]

You can't make a silk purse from a sows ear and you can't make accurate ammunition from brass that is not uniform in thickness.

You need a neck thickness gauge to sort your brass and weed out the cases with excess variations in case neck thickness

You will also need to mod your RCBS case mastering gauge OR "take it back and get your money back". The RCBS gauge is the worst gauge for measuring runout due to the V-block movement up and down. You will need to clamp down the rear of the V-blocks to prevent movement. And in a short time the paint will rub off the V-blocks and your cases will drag on the bare aluminium. I'm saving for the Sinclair concentricity gauge. (subliminal suggestion, hint, hint)

Having said that the RCBS gauge is the best thing going for checking for stretching and thinning in the base web area of the case instead of using a bent paper clip.

Full length resized cases are supported by the bolt face and the bullet in the throat of the chamber and the neck and body of the cartridge case do not touch the chamber. As long as you have .003 or less runout the case should have minimal influence on bullet alignment with a normal factory chamber.

Good quality uniform brass thickness is key to better accuracy, and uniform neck thickness and neck tension will improve your groups. The Redding neck thickness gauge pictured above is just as important as measuring runout when sorting cases for accuracy.

lol at needing all that for accurate ammo...rem brass, win brass, lapua brass, hornady brass...it dont matter, ill shoot em all and they work...never checked runout once. heck send me your bad brass, ill use it!

 

[hlee]

Bigedp51, thanks for the detailed reply. Yes, the sinclair gauge does look very good, but the RCBS was available locally, for a not terrible price. I have already found that the v blocks are not ideal and will be looking into the sinclair as soon as I come up with a few more dollars. The movement of the v-blocks does add a bit of art to the measurement, but I have found that a smooth motion rotating the cases gives a reproducible result. A neck thickness gauge, or at least a micrometer to measure neck thickness will need to be another purchase. And, then I'll need a neck trimmer. Then, I'll have to step up to bushing dies. My god, it's like fishing. There's always something to buy. Thankfully I am "saving money" by reloading...

No1, I did measure the runout on the FGMM that I shot, but I do not remember exactly what they were running. I believe the case neck runout was averaging 0.002. I took out a new box and measured the neck runout and the bullet runout for 20 FGMM cartridges. This may not be as representative as 100 or 500, but it is a "random" box that I have on hand.

Neck runout...

Bins are: 0-0.001, 0.001-0.002, 0.002-0.003, 0.003-0.004

Bullet runout...

Bins are: 0-0.001, 0.001-0.002, 0.002-0.003, 0.003-0.004, 0.004-0.005

 

[mdmp5]

I don't know how much runout contributes to precision. I have measured mine before, and it is very good, but what could I really do about it if it wasn't? If you use quality equipment, your runout should be negligible.

 

[No1]

That would explain that group you shot above. I bet if you shoot groups sorted by bullet runout you will see results similar to your handloads that you sorted.
Try a box of Hornady Superformance Match 168g Amax. I've checked 3 or 4 boxes couple years ago, average RO is right at .001" with no single bullet being over .002". This ammo consistently shoots .3 from my AR10.

 

[Victor N TN]

Make sure the inside your case necks are clean. I use a bronze bore brush to get the burned carbon off the inside necks. Keeping them cleaned will greatly improve your runout numbers and your groups.

 

[bigedp51]

lol at needing all that for accurate ammo...rem brass, win brass, lapua brass, hornady brass...it dont matter, ill shoot em all and they work...never checked runout once. heck send me your bad brass, ill use it!

I have two AR15 rifles and a Savage .223 bolt action with a 26 inch heavy barrel and the brass is sorted into two piles and the good brass is shot in the bolt action.

The crooked warped banana shaped excess runout cases are fired in my AR15 carbine, and used for covering suppressive fire in Zombie attacks.

The good cases are used for long range head shots.

I'm glad you have such low standards, its guys like you who make the more talented reloaders look good.

 

[morganlamprecht]

I have two AR15 rifles and a Savage .223 bolt action with a 26 inch heavy barrel and the brass is sorted into two piles and the good brass is shot in the bolt action.

The crooked warped banana shaped excess runout cases are fired in my AR15 carbine, and used for covering suppressive fire in Zombie attacks.

The good cases are used for long range head shots.

I'm glad you have such low standards, its guys like you who make the more talented reloaders look good.

dont use 'talented' like anyone else cant waste time doing it, some of us just choose not to...too each, their own...but dont say you have to jump thru all those hoops to load accurate ammo

both done today at 100 yds, bipod, rear bag...testing a .308 barrel that was just cut down yesterday...no load workup, just Fed Gold medal match duplicates using 175 SMK seconds, 2 sighters to verify POI after rifle disassembly then dialed to zero

175 SMK factory seconds, no sorting of any kind
Fed Brass, same as above
IMR 4064
Win WLR primers

cheap ass lee collet neck sizing dies

loaded and shot...without all the wasted sorting/prep time you are suggesting is a must for OP...i guess some like looking for excuses but some of us just like shooting...im fine with my low standards

 

[Sniper Uncle]

An acquaintance of mine from Scotland, told me of his experience in this area. He bought the Hornady Concentricity Guage, and used the built in adjustment feature to "true" the cartridges with excess run-out. He said his "fliers" all but dis-appeared. I do think there is something to the concentricity theory. I have the RCBS CaseMaster Gauging Tool, and have not checked very many, but what I did check for my 338LM in Lapua Brass was very consistent and concentric---between .001+.0015 max

I did just get the Hornady tool, and can't wait to get home and try it.

 

[M40_A1]

both done today at 100 yds, bipod, rear bag...testing a .308 barrel that was just cut down yesterday...no load workup, just......loaded and shot...without all the wasted sorting/prep time you are suggesting is a must for OP...i guess some like looking for excuses but some of us just like shooting...im fine with my low standards

Are you really saying that with a straight face? You do realize that those of us that go to such lengths don't do it to shoot well at that short range, right? Now, take your loads and try them at 600 or 800 yards and see what happens then.

 

[bigedp51]

An acquaintance of mine from Scotland, told me of his experience in this area. He bought the Hornady Concentricity Guage, and used the built in adjustment feature to "true" the cartridges with excess run-out. He said his "fliers" all but dis-appeared. I do think there is something to the concentricity theory. I have the RCBS CaseMaster Gauging Tool, and have not checked very many, but what I did check for my 338LM in Lapua Brass was very consistent and concentric---between .001+.0015 max

I did just get the Hornady tool, and can't wait to get home and try it.

The Hornady concentricity tool is in the upper left of the photo below, it works in making more concentric ammunition, and also makes more accurate ammunition. What must be remembered is perfect brass with uniform case wall and neck thicknesses is few and far between and most of us use "average" grade brass. And with the Hornady concentricity tool you can make above average ammunition.

 

[morganlamprecht]

Are you really saying that with a straight face? You do realize that those of us that go to such lengths don't do it to shoot well at that short range, right? Now, take your loads and try them at 600 or 800 yards and see what happens then.

I shoot my .260 out well past 600 (along side others who check these same things, and others that dont) and gun shoots right with em...not talkin bench rest in some Big rest ...I am always the weakest link...I'm not saying factory 2nd bullets will shoot with worked up loads at range, but correct me if I'm wrong, arent OPs groupings 100 yard examples, as are mine. I was tryin to compare similar results. If so and that spread is caused by 'runout' I wouldn't even keep that gun...if OPs groups are at 3, 4, or 500 or whatever and I
Missed it, then I apologize

 

[delixe]

I have spent all sorts of time and money trying to eliminate runout.
Coax press
Redding Type S dies
Redding competition seating dies
Lapua brass, neck turned.
Fire forming then neck sizing only

I still haven't eliminated runout.

Recently I bought 4 boxes of FGMM 168 and measured the runout.
There's an average of .005" TIR runout and some of the rounds are much worse.
Nonetheless, it shoots like FGMM, sub MOA out of a good rifle.

 

[hlee]

I shoot my .260 out well past 600 (along side others who check these same things, and others that dont) and gun shoots right with em...not talkin bench rest in some Big rest ...I am always the weakest link...I'm not saying factory 2nd bullets will shoot with worked up loads at range, but correct me if I'm wrong, arent OPs groupings 100 yard examples, as are mine. I was tryin to compare similar results. If so and that spread is caused by 'runout' I wouldn't even keep that gun...if OPs groups are at 3, 4, or 500 or whatever and I
Missed it, then I apologize

The groups are at 100 yards. The gun is a lr308 semi auto. I have no doubt that that a bolt gun with a match chamber in 260 rem will shoot very tight groups. I'll take 0.6 from a semi auto every day of the week.

 

[hlee]

The Hornady concentricity tool is in the upper left of the photo below, it works in making more concentric ammunition, and also makes more accurate ammunition. What must be remembered is perfect brass with uniform case wall and neck thicknesses is few and far between and most of us use "average" grade brass. And with the Hornady concentricity tool you can make above average ammunition.

As the hornady tool indexes on the base of the case, and the rcbs tool indexes on the body of the case, do you find a large discrepancy between the two tools in measured runout? Does a concentric round on the hornady tool measure as more "out of round" on the rcbs tool? Thanks.

 

[morganlamprecht]

The groups are at 100 yards. The gun is a lr308 semi auto. I have no doubt that that a bolt gun with a match chamber in 260 rem will shoot very tight groups. I'll take 0.6 from a semi auto every day of the week.

U are missing the point...my Budget stock AR will shoot inside that group on the right with multiple hand loads with no special prep/sorting...have fun chasing your tail, hope you catch it and get it worked out

 

[hlee]

U are missing the point...my Budget stock AR will shoot inside that group on the right with multiple hand loads with no special prep/sorting...have fun chasing your tail, hope you catch it and get it worked out

This gun and my budget ar (both dpms, the horor!!!) will both shoot inside the group on the right with factory ammunition. The point is "at what point does accuracy fall off?" And, it should be noted that the group on the right was shot with all rounds at 0.005 runout or greater. In the 600 or so cases that I have measured, I had 7 that were that out of round. Your "cheap lee collet die" is regarded as being able to produce cases with the least runout of any dies on the market. So, in your willful ignorance of the subject you may well have stumbled onto a solution to a problem that you didn't know you didn't have. Unfortunately, the lee collet die is not well suited to reloading for a semi auto- especially without a crimp- due to the relatively low neck tension it produces. As I have not stepped up to neck turning yet, I am constrained to using an expander ball in my sizing dies which is known to increase the probability of increasing the runout in brass.

As I said in my opening post, I have shot many good groups (with both factory and hand loads) but occasionally run into that "where the f did THAT shot come from" flier that doesn't have a good explanation- a good explanation being generally some variation of "my god, my swing feels like an unfolding lawn chair" pulled or pushed shot (Thank you Tin Cup!). These fliers lead me to explore runout more closely as a possible cause for some of the error. The experiment above shows pretty clearly that a low dosing of high runout cartridges CAN produce the occasional flier I have observed. It also shows that the effect of even large runout may not be entirely apparent, as 3 of the shots from the right hand group would superimpose over the left hand group and still be moa or a bit better. So, ~600 cases measured, 7 observed to be greater than 0.005" in runout. But even still, only 2 of the 5 fired would have opened a 10 shot group (5 with high runout and 5 with low runout) to 2moa, from a semi auto 308- 8 out of those 10 shots would be moa accurate. All in all, runout does play a role in accuracy, BUT; the worst offenders are very rare (1% from my cheap ass rcbs green box dies with expander ball) and, the effects of even these worst offenders may not be completely apparent in the absence of careful sorting.

Your shots are all touching in the post above. You might be shooting ragged holes with more time spent with case prep. Then again, it is a cost/benefit problem and in "tactical shooting" any hit is a good hit. If you are happy with your results then by all means do not let me stand in your way.

If I had been happy with good enough I would still be shooting remington green box core-lokts out of a marlin 30-30 and letting McBrides Guns in Austin sight it in for me every deer season. And, I would spend the time and brain resources that I do now learning about marksmanship and loading for precision rifle on something more applicable to my profession or personal life.

As it is, I prefer it here as journals put me to sleep and I never wanted to learn French anyway...

 

[bigedp51]

As the hornady tool indexes on the base of the case, and the rcbs tool indexes on the body of the case, do you find a large discrepancy between the two tools in measured runout? Does a concentric round on the hornady tool measure as more "out of round" on the rcbs tool? Thanks.

1. A cartridge case with unequal case wall thicknesses will show excessive runout on either gauge.
2. The Hornady gauge shows less runout BUT you are measuring runout/concentricity two different ways.
3. Again full length resizing reduces the cases influence on bullet alignment with the bore.
4. The Hornady gauge measures concentricity from the center line of the case and bullet.
5. A standard runout gauge measures runout based on the external case dimensions at the base of the case and shoulder area.

A case with unequal case wall thickness will expand more on the thin side of the case and this causes the case to warp. In reality you end up measuring a egg shaped case. When the warped egg shaped case is full length resized the body of the case and neck are not touching the chamber walls and have minimal effect on bullet alignment. The Hornady gauge directions state that anything under .003 concentricity will have very little effect on accuracy.

If you start with good quality brass that has very little variation in neck thickness you should have very little runout. When I use my Sinclair neck thickness gauge and it shows very little variation in neck thickness. And then the case is full length resized without the expander button the case should have very little runout at the neck. When the case is sized with the expander button in place and you have runout it is induced by the expander button. The same applies after seating a bullet and runout increases, meaning something is out of alignment.

The majority of us do not have custom made rifles and custom dies so you just take steps to "reduce" the cartridge cases influence on misaligning the bullet with the bore. And in a stock factory rifle you have plenty of wiggle room in the chamber to reduce case misalignment with the bore.

Again a full length resized case is supported by the bolt in the rear and the bullet in the throat and the body and neck of the case is not touching the chamber. Meaning with good quality brass the case has minimal effect on bullet alignment with the bore.

 

[Sniper Uncle]

Yeah, what he said.

I agree with BigEdP. I would also add that you may not need to buy fancy dies. I just took the expander ball off my RCBS green box die, and put a decapping pin holder on instead----an expander ball that is way undersized, essentially. Then, I use a Sinclair Expander die with the correct size mandrel. I get extremely low run-out with this set up, and didn't spend a fortune to get there.
The Hornady Concentricity Guage indexes off the case head and the bullet tip. It has a thumbscrew which can be used to apply pressure to the case neck and re-align the bullet/case so they are on the same axis, thus reducing run-out. That, according to my friend Andy, has made a difference in the occasional flier, like the OP is talking about.
OP, you have a very interesting and logical bit of info from your experimenting. It does make perfect sense that possibly only some of the bad run-out cases actually result in a flier. I looked again at your pics, and you are absolutely correct that the two groups could be superimposed on one another, and the resulting group would have 8 sub moa shots in a nice cluster. I am assuming the POA was the diamond in each group??? I am sure it is, and the bulk of the flier group is almost perfectly centered on the center of your non flier group if you place the one group directly on top of the other.

 

[M40_A1]

Recently I was noticing that shoulder bump was not as consistent as I would like to see, as they varied by as much as .002". I learned that turning the case 90-degrees before running it a second time into the die gave me much, much better consistency, giving me .000" on the RCBS gauge which matches my chamber. What does this have to do with runout? Well, doing this noticeably tightened up runout also. I would expect that between more consistent shoulder length and less runout I should see tighter groupings.

 

[Unknown]

I sort my precision ammo by run out. .0015 and less is super good. .0025 to .0015 is excellent. .0035 to .0025 is good, .0045 to .0035 is practice ammo, and anything over .005 goes into close range practice, or drills on cadence and other drills where really great precision is required.

The things that cause run out for me:

1. the expander ball jerking the neck as the case exits the die (loosen the expander ball, so it can move a bit, and lube inside case necks to make it less likely). A really good cure that I haven't bought is a floating carbide expander ball.
2. inconsistent case wall thickness (cure it turning cases)
3. dirt inside the seating stem that pushes the bullet off the center axis
4. dirt inside the rim of the shell holder that causes the entire case to be held off axis during sizing
5. a bent bullet seating stem, or bent expander ball rod

Once I fixed these items, I find out I get about 85% of my ammo coming out with .0035 and less runout. Of that, only maybe 5-10% are between .0025 and .0035 inch runout. I consider this acceptable.

I have one of the runout correction sets from Europe (Bersin) and it really works, but it takes lots of work if you shoot lots of ammo. It is VERY accurate. However, as it works by pushing the bullet back into alignment, a gas gun's feeding system would ruin any improvement the Bersin tool puts into the round. For a bolt gun it works great though.

 

[Killswitch Engage]

I sort my precision ammo by run out. .0015 and less is super good. .0025 to .0015 is excellent. .0035 to .0025 is good, .0045 to .0035 is practice ammo, and anything over .005 goes into close range practice, or drills on cadence and other drills where really great precision is required.

The things that cause run out for me:

1. the expander ball jerking the neck as the case exits the die (loosen the expander ball, so it can move a bit, and lube inside case necks to make it less likely). A really good cure that I haven't bought is a floating carbide expander ball.
2. inconsistent case wall thickness (cure it turning cases)
3. dirt inside the seating stem that pushes the bullet off the center axis
4. dirt inside the rim of the shell holder that causes the entire case to be held off axis during sizing
5. a bent bullet seating stem, or bent expander ball rod

Once I fixed these items, I find out I get about 85% of my ammo coming out with .0035 and less runout. Of that, only maybe 5-10% are between .0025 and .0035 inch runout. I consider this acceptable.

I have one of the runout correction sets from Europe (Bersin) and it really works, but it takes lots of work if you shoot lots of ammo. It is VERY accurate. However, as it works by pushing the bullet back into alignment, a gas gun's feeding system would ruin any improvement the Bersin tool puts into the round. For a bolt gun it works great though.

i use the hornady concentricity tool and straightnen anything thats above .003 tir. it all shoots the same at that anyhow. i have chambered in many different weapons, concentric ammunition and found no induced runout when i extracted it and put it back on the gauge. there is a degree where doing this shit provides minimal return. one would be better served spending more time shooting then at the reloading bench in my opinion.

 

[bigedp51]

M40_A1

I think in this forum someone posted a link to a YouTube video where the reloader was pausing for three seconds at the top of the ram stroke, then lowered the ram and rotated the case 180 degrees and sized again holding for three seconds.

By doing this he had much more uniform shoulder bump and less runout, his die had the expander button removed. By pausing at the top of the ram stroke he was letting the brass know who was the boss and to stay put after sizing. Meaning far less brass springback and straighter necks.

But again having good quality brass to start with eliminates many headaches.

I have three five gallon buckets of once fired .223/5.56 cases fired by our local police department. This cheaper practice ammo was made up of Remington, Federal and Lake City cases and without a doubt the majority of the cartridges cases were seconds or rejects unfit for higher cost ammunition. The Remington .223 cases were the worst and had the most case wall variations and runout of any of the other cases.

Out of curiosity when in a local gun shop I picked up a box of Nosler custom brass for comparison and was amazed at the quality and uniformity of these new cases. Bottom line, the Nosler brass was worth the extra money because I didn't have to do anything to this brass. And I was spending hours and hours sorting through my "free" brass looking for good cases.

 

[Unknown]

Killswitch,
I agree with you about spending more time shooting than reloading. I see much of reloading like I do bench rest shooting. Although it is interesting to find out what is possible to do, I have to sort out what is realistically useful for me to actually do. Once I identify the things that induce runout, I fix them. When I load up 850 rounds of ammo, I might cull through it for what I actually need for a match, but most of it just goes into the "shoot it up" ammo can.

I think that lots of guys want to experiment with what is possible, and what actually helps. That is part of the fun in experimenting with things. However, once dialed in, I think much more benefit will come from actually practicing from true field type positions rather than shooting off a bench.

Ned Roberts' uncle had an accuracy test for a rifleman. He would shoot offhand at a 2" circle at 50 yards until he could put 4 out of 5 rounds into it. Then he would double the distance, and target size until he could again do it...then increase distance and sizde to 150 yards. In the end, he was shooting at a 8" circle at 150 yards with a black powder rifle, offhand, with open sights. 4 out of 5 hits on that target, and Roberts' Uncle would declare him a good shot. Yeah, I guess so! I may have some of the minor details of the test incorrect, but if I were able to do anything close to that sort of shooting I would be damned pleased!

 

[M40_A1]

M40_A1

I think in this forum someone posted a link to a YouTube video where the reloader was pausing for three seconds at the top of the ram stroke, then lowered the ram and rotated the case 180 degrees and sized again holding for three seconds.

By doing this he had much more uniform shoulder bump and less runout, his die had the expander button removed. By pausing at the top of the ram stroke he was letting the brass know who was the boss and to stay put after sizing. Meaning far less brass springback and straighter necks.

Yeah, I heard that. I'd like to get a metallurgists take on it though, as brass is a solid, not liquid, and if any flow were measureable, I would think it would be in microseconds where any "pause" wouldn't make any difference as long as the stroke was all the way to the top. I've tried not pausing and pausing and all that, and did not notice any difference in measurements. To make any difference seems to require a second stroke. Rotating the case between strokes just seems to help even out some inconsistencies due to shell holder and/or die misalignment.

A similar discussion came up about scuba cylinders. If a cylinder is over-filled to the point that elastic expansion had been exceeded, would immediately bleeding off the extra pressure allow the steel to spring back more than if the pressure was just left in the cylinder. An metallurgical engineer explained that time is not an element that affects spring-back, aka "elastic expansion". Brass cases are similar in that in firing and resizing they are experiencing both elastic and permanent expansion/compression.

 

[M40_A1]

one would be better served spending more time shooting then at the reloading bench in my opinion.

That's the cliche around here. The fact for me is that I cannot always be at the range (who can?). So, rather than rotating on my thumb at home, I'm better served making the best ammunition I can in my spare time. The extra time I spend on quality reloading doesn't cut into my range time in the least, but it does make my range time more meaningful.

 

[mdmp5]

Yeah, I heard that. I'd like to get a metallurgists take on it though, as brass is a solid, not liquid, and if any flow were measureable, I would think it would be in microseconds where any "pause" wouldn't make any difference as long as the stroke was all the way to the top. I've tried not pausing and pausing and all that, and did not notice any difference in measurements. To make any difference seems to require a second stroke. Rotating the case between strokes just seems to help even out some inconsistencies due to shell holder and/or die misalignment.

A similar discussion came up about scuba cylinders. If a cylinder is over-filled to the point that elastic expansion had been exceeded, would immediately bleeding off the extra pressure allow the steel to spring back more than if the pressure was just left in the cylinder. An metallurgical engineer explained that time is not an element that affects spring-back, aka "elastic expansion". Brass cases are similar in that in firing and resizing they are experiencing both elastic and permanent expansion/compression.

I wasn't convinced that the extra time in the die really made the difference either in that video. I have found that if I size a piece of brass and it does not set the shoulder back enough, a 2nd pass usually does the trick. Some brass is more stubborn with springback, and may require that 2nd pass. What I also noted is that if the case came out of the die with some effort due to friction, the measurement was usually longer. A 2nd pass took care of that too. My theory was that if a case was sticking in the die, the friction was pulling the shoulder forward upon extraction. On the 2nd pass, the body is already mostly sized, and the friction is reduced dramatically, so there is no more pulling on the shoulder upon extraction. I studied this phenomenon over and over again, for hundreds of cases, and it is the best explanation I could come up with for the observation. Cases that come out with little to no resistance on the 1st pass measured correctly, and didn't need a 2nd pass.

 

[dmike]

hlee, great data. Each person has their own threshold for how far they're willing to go for consistency, but it was cool you methodically explored a question then shared your findings in a legit way.

 

[scottyr44]

Yeah, I heard that. I'd like to get a metallurgists take on it though, as brass is a solid

The only way holding the brass in the die or any metal in a die would have an effect, would be heat forming. Where you would wait until the metal cooled to a certain temperature before releasing it from the die.

Just my experience those cheap dial indicators are not repeatable to .0005, just because you can see half a thou doesn't mean the mechanism inside is capable reproduction on every measurement.

Some other factors to take into account just like you all do while shooting is temperature, some metals moves up to .0005 per degree.

I feel like some of the sorting and precautions people take for reloading is splitting hairs.

Have fun shooting.

Sent from my SCH-I605 using Tapatalk

 

[KYpatriot]

Nosler brass is the best I have seen by any measure so far. They are proud of it but it is great.

 

[KYpatriot]

there is a degree where doing this shit provides minimal return. one would be better served spending more time shooting then at the reloading bench in my opinion.

Assuming you have decent ammo to begin with this is undoubtably true for the individual, but this community is benefiting from the efforts of the many men who leave no stone unturned in the search for what does and does not make the shooter/rifle/ammo system more effective. I am glad of this, and support anyone who spends time advancing our knowledge this way. Also some people just enjoy the satisfaction of learning how to make the best ammo there is as it's own reward, in the same way a gunsmith gets satisfaction from building a rifle that is awesome though someone else will shoot it.

 

[Killswitch Engage]

Suppose any of us that have been reloading for 20yrs have tried and figured most
of this stuff out for you guys that are lookin for unicorns? I realize many of you are from Missouri and want showed but it's been done. No reinventing the wheel needed. How concentric is your chamber?

 

[Clark]

http://www.snipershide.com/shooting/snipers-hide-reloading/39404-concentricity.html
from "The American Rifleman" sometime between 1950 and 1968 when they put it in the compilation book that I scanned.

"Gauging Bullet Tilt"

THE MOST PRECISE AMMUNITION
FROM A LOT CAN BE SELECTED
WITH A BULLET ALIGNMENT GAUGE.

By A. A. ABBATIELLO

Other factors being normal, bullet
tilt with respect to the case center-
line affects group size. If the barrel
length and twist are known, it has been
found possible to predict the direction
from the group center in which the tilted
bullet will strike. If the amount of tilt
is known, the distance from the group
center can be predicted.
Significant score improvement has
been noted by those who have tried
such gauged ammunition.
In cal. .30 long-range shooting, the
best match-grade ammunition will group
in one to 2 minutes of angle under test
conditions. Part of this spread is due
to the bullet tilt with respect to the
case centerline, imposed by the bullet-
seating tool. This tilt displaces the bul-
let’s center of gravity slightly to one
side; in bullets such as the cal. .30 Ml,
the amount is about 1/8 the displace-
ment of the bullet point. It enlarges
groups by amounts up to one minute.
These deviations become proportion-
ately less as the tilt is reduced. Tilts
over .O04" do not seem to increase the
dispersion of the group beyond the ex-
pected one minute. Perhaps this is
because a well-fitting chamber has a
tendency to straighten any rounds
which are excessively tilted. Other ex-
planations are possible.
The gauge consists of a V-block
which permits rotating the round about
the bullet point and 2 tangent spots
near the case head. A dial indicator
which reads in tenths of thousandths of
an inch (.0OO1") bears on the bullet
near the case neck. Half the total indica-
tor reading is used as the displacement
for determining the classes into which
the rounds are separated. The high point
is also marked at this time for orienta-
tion of the round in the rifle chamber.
Rounds with .0O2" tilt or less can
be considered good enough for long-
range use, while those with .O03" and
.OO4" tilt are best used only at short
ranges. In general, it was concluded
from target results that each .0Ol" of
tilt will increase the group spread about
1/4 minute of angle, up to a maximum
of .OO4" as mentioned above.
Under test conditions, it was found
that when the rounds were chambered
with the high point always in the same
orientation, the groups were smaller
than when it was randomly oriented.
Gauging and orienting the rounds can
produce the smallest groups of which
that ammunition is capable.
These ammunition refinements are
becoming important, particularly in
long-range matches.
The essentials of the tilted bullet were
discussed in detail no less than 50 years
ago by Dr. F. W. Mann in his book
"The Bullets In Flight". He pointed out that
the balance of the bullet and the spiral
path of the center of gravity are of
high importance in accuracy.

Following a discussion between
George L. Jacobsen of Frankford Arse-
al and the writer at the 1959 National
matches, a trial of the effect of neck
concentricity was carried out by Jacob-
sen. He described his results in ".30-’O6
Cartridge Cases And Accuracy", which
appeared in THE AMERICAN RIFLEMAN,
January 1960, page 20.

SEATING TOOL A FACTOR

The effects which Jacobsen found,
though small, are essentially in agree-
ment with the work reported here.
However, he did not separate the effects
of neck eccentricity and the bullet cen-
ter-of-gravity location with respect to
the bore. The angular direction of the
bullet seating tool is a controlling factor
in the initial position given to the bullet,
rather than merely case neck eccen-
tricity. Case necks can be centered or
eccentric, and the bullet can be inclined
in completely random directions. The
tilted bullet is believed to be the main
cause for center—of-gravity side shift.
The cal. .30 boattail bullet of 173 grs.
weight was selected for these tests be-
cause it is in common use and is of
sufficiently high quality for use in the
National Matches.
Using the gauge shown, 42 ammuni-
tion lots were sampled and the high
point was marked on each round gauged.
These rounds were grouped in steps of
.OO1" bullet tilt, and the data tabu-
lated. The results gave a bell—shaped
curve for 829 rounds of match ammu-
nition, peaking at about .0O2" (see
illustration). Measurements on Service
ball ammunition produced a curve of
similar shape, but peaking at about
.0025" tilt.
This graphically illustrates that even
match-grade ammunition has appreci-
able variations. There is a large spread
among particular lots and boxes. In
general, 10% to 20% of each lot, de-
pending on ammunition quality, falls
into .0O3", .0O4" or even up to .O10"
tilt. Run-of-the-mill ammunition can
thereby enlarge groups to about twice
the size which the same ammunition
can show when it is gauged before firing.
Since the tilt angle of the bullet is
so small (about 1/4 °) it is difficult to
perceive visually. The gauge, however,
makes the sorting a fast, routine step.
A mathematical solution of this prob-
lem was also tried (see box) and is in
good agreement with the results ob-
tained. It is gratifying to find the math-
ematical solution and the experimental
results in agreement.



MATHEMATICAL SOLUTION

A laterally displaced center of
gravity moves through the rifle bore
in a helical (screw) path. The pitch
of this helix is the pitch of rifling,
and its radius is the lateral displace-
ment of the center of gravity. On
leaving the muzzle, the center of
gravity continues in the direction it
had at that point. For example, if it
leaves at top of the bore and rifling
is to the right, the departure will be
to the right. The bullet travels ap-
proximately 2l.5" in a 24" barrel,
making 2.15 turns in the 10" twist
of rifling. The number of turns
shows the orientation on emergence
compared with that in the chamber
before firing. The angle of emer-
gence is that angle whose tangent is
2 pi times the lateral displacement
divided by the rifling pitch. For
.004" point displacement and I0"
rifling pitch, the tangent is 1/8(2·pi)
(.004)/l0 and the corresponding
angle is 1.1 minutes.
The displacement on target from
this cause is proportional to the
range and can be obtained without
noting the angle. For example, ,004"
point displacement gives in l0"
rifling pitch, so far as this mecha-
nism goes, a target displacement at
100 yds. (3600") indicated by the
proportion .00l· pi /10=X/3600, from
which x =1.1".


The chamber throat will bend the neck straight by pushing on the bullet.

That happened to be 2.2 moa increase in group size calculated, and then verified in a SAMMI chambers 30-06 in the above work by the army, NRA and AA.

If you have some 6mmPPC chamber that is so tight that a spec of dust prevents easy chambering, then a crooked neck will have much less effect on accuracy. That non factory tight chamber will bend the cartridge almost perfectly straight.

In math terms, we have a linear relationship between accuracy and runout, until the runout is so large that it will not fit in the chamber that bent.

As the run out increases beyond what the chamber will straighten out, there is no change in accuracy, as at the time of firing all ammo has the same run out.... the most runout that fits the chamber.

The part of the chamber that affects this is the throat.

In a 30-06 the throat specification and ammo specification per the SAAMI drawings are so lose that the fit is unknown.

This is part of the reason that many rifles shoot better with the bullet jammed into the lands... at least one end of the bullet will be concentric.

 

[dmike]

Assuming you have decent ammo to begin with this is undoubtably true for the individual, but this community is benefiting from the efforts of the many men who leave no stone unturned in the search for what does and does not make the shooter/rifle/ammo system more effective. I am glad of this, and support anyone who spends time advancing our knowledge this way. Also some people just enjoy the satisfaction of learning how to make the best ammo there is as it's own reward, in the same way a gunsmith gets satisfaction from building a rifle that is awesome though someone else will shoot it.

My friend once told me "Pistol shooting is skill, shotgun art, and rifle science." Obviously that's a simplification and not trying to start any fights but I like how KYpatriot put this. Killswitch, you're right that the tried and true methods are all most of us need to reach excellence, the old "it's the indian not the arrow" idea. But it's also true that there are some crazy physics at play here and threads like this help push frontiers, someday people might be making two mile shots!

 

[Huskerhunter]

Suppose any of us that have been reloading for 20yrs have tried and figured most
of this stuff out for you guys that are lookin for unicorns? I realize many of you are from Missouri and want showed but it's been done. No reinventing the wheel needed. How concentric is your chamber?

You DO realize that most Unicorn horns have at least 5 thou runout?

 

[Unknown]

I have been reloading since about 1977, and have tried almost everything except loading rounds at the bench like bench rest shooters do. Although I find the possible precision to be an interesting experiment, because I shoot primarily from field positions under tight time constraints. Therefore I find it unlikely that I would benefit from ammo that shoots one eighth of an inch tighter groups at 100 yards than I would benefit from learning how to be more consistent with my marksmanship.

Looking for precision ammo to cure a problem with my marksmanship is akin to buying a more expensive optic in the hopes that it will improve my marksmanship. Proper practice would be a better solution than my looking toward premium ammo to fix a problem with marksmanship.

 

[BuzzBoss915]

I have been reloading since about 1977, and have tried almost everything except loading rounds at the bench like bench rest shooters do. Although I find the possible precision to be an interesting experiment, because I shoot primarily from field positions under tight time constraints. Therefore I find it unlikely that I would benefit from ammo that shoots one eighth of an inch tighter groups at 100 yards than I would benefit from learning how to be more consistent with my marksmanship.

Looking for precision ammo to cure a problem with my marksmanship is akin to buying a more expensive optic in the hopes that it will improve my marksmanship. Proper practice would be a better solution than my looking toward premium ammo to fix a problem with marksmanship.

You obviously don't believe in MOJO. We anal types don't consider premium effort at the (loading) bench to be wasted. BB

 

[KYpatriot]

This site is geared towards tactical shooting and some of these methods are from the 1000 bench rest world. The precision world can inform the tactical/practical, and vice versa. Clearly, some of these "precision" methods generate accuracy improvements that are lost in the noise in hasty field positions.

I usually miss because of wind. The development of accurate laser rangefinders were a huge benefit to long range field shooting. An accurate way to measure average wind to the target would be the next holy grail of long range shooting technology. Perhaps we will see it one day.

 

[M40_A1]

Tighter groups at 100 yards is nice, but it isn't the name of the game to those of us loading precision ammunition.

A shot pattern is a cumulative result of many factors. The ability of the shooter, the cumulative quality of the construction of the parts of the rifle, the cumulative quality of the construction of the parts of the ammunition, environmental factors (e.g. wind, mirage, temperature change), plus others, I'm sure. That miss might not have been just wind, it could have been wind plus bullet runout. or, wind plus non-optimum torque on an action screw. It's all cumulative.

 

[Clark]

It's all cumulative.

If you work on a system where the most 50 important errors can be calculated, and then test the system, it is shocking how much errors cancel errors on average.

Monte Carlo method - Wikipedia, the free encyclopedia

 

[Sniper Uncle]

Tighter groups at 100 yards is nice, but it isn't the name of the game to those of us loading precision ammunition.

A shot pattern is a cumulative result of many factors. The ability of the shooter, the cumulative quality of the construction of the parts of the rifle, the cumulative quality of the construction of the parts of the ammunition, environmental factors (e.g. wind, mirage, temperature change), plus others, I'm sure. That miss might not have been just wind, it could have been wind plus bullet runout. or, wind plus non-optimum torque on an action screw. It's all cumulative.

And, I might add, most times in life, cumulative effects are greater than the sum of the parts. For some reason, most of the issues that add up to the situation tend to feed off the other issues, compounding the problem more than just the simple addition of the individual issues.

 

[Unknown]

You obviously don't believe in MOJO. We anal types don't consider premium effort at the (loading) bench to be wasted. BB

Quite the contrary, I think that effort at the loading bench, or shooting from field positions to improve marksmanship is NOT wasted time. Anything that improves the end result is worthwhile. I think all shooters need to evaluate where their effort will bring the most benefit for the type of shooting they do.

For example, a benchrest shooter will not get as much benefit from practicing field position shooting as he will from developing bench technique. The reverse applies to field shooters in that they won't gain as much benefit from bench shooting as from practicing field shooting. In both cases, shooting crap ammo will hurt performance.

However, for field type shooting, more benefit will be gained by improved marksmanship that allows the shooter to actually get their rifle/ammo combination (that may only be capable of shooting a 1 inch at 100 yards) to actually shoot inch groups from field positions, than they would gain by getting their rifle/ammo combination to shoot half inch groups from the bench, when their marksmanship skills are only capable of shooting 3 inch groups from field type positions. That was my point.

 

[Clark]

And, I might add, most times in life, cumulative effects are greater than the sum of the parts. For some reason, most of the issues that add up to the situation tend to feed off the other issues, compounding the problem more than just the simple addition of the individual issues.

Just the opposite is true. Cumulative effects are almost always less than the sum of their parts. I have found the cumulative effect to be a narrow Gaussian distribution in the center of the wide expanse of what is possible.

Getting worst worst worst worst case happens as often as you win the lotto.

 

[ArmyJerry]

Okay I have the Forster micrometer seating dies now, got the headspace gauges, measured all the chambers with the brownells chamber insert, use Ogive as OAL measurement for each rifle, the only step left is concentricity and neck uniforming. I shoot half inch groups with all my calibers right now, is it worth the last two steps?

 

[M40_A1]

If you work on a system where the most 50 important errors can be calculated, and then test the system, it is shocking how much errors cancel errors on average.

Monte Carlo method - Wikipedia, the free encyclopedia

Errors almost never cancel eachother. An error may reduce another error, and may even push past the first error in the opposite direction, if the second error is larger than the first, but to precisely cancel is very unlikely.

While it is true that errors can work in each other's favor, it is also true that they can compound each other. What we are striving for is precision and consistency. A smaller maximum spread is more precise that a larger maximum spread. The more closely the shots group together, the more consistent thay are. Any errors that can add upon another often will. When errors add upon eachother, the maximum spread opens up. Reducing errors increases precision AND consistency, and that is what we as marksmen want.

This is also why three-shot groups are usually meaningless, unless the system is truly capable of repeatedly and consistently placing each shot through the same hole. Three-shot groups are almost always less representative than five, or ten-shot groups.

In some three-shot groups, errors may reduce each other, giving a very nice group that represents better than the average the system would normally do. While in other three-shot groups, the group is larger because the errors are adding upon each other. The larger group would be more representative of the usual maximum spread that can be expected, but how often does one truly choose the larger three-shot group to show?

 

[bigjohn451]

Your ammunition should be loaded with the care and precision of the target your reaching for.

I shoot 1000yd Benchrest, when I load the ammo for that gun I take every minor step that can give me and advantage when shooting for our 3" X ring. I weigh every bullet and measure its bearing surface, my brass is sorted into 10 piece groups that are all within .1 gr of each other I want them to be as close to perfect as they can possibly be as I'm trying to put 5 rounds in the exact same spot my final sort once the rounds are loaded is runout. Anything over .002 goes for sighters.

Now then when I load for my 308 tactical gun I don't do as much fine prep as I only expect it to hit steel or maintain 2 MOA at 1000yds.