Standard Deviation and Extreme Spread

[Floridaboy]

I set out to solve my excessive Standard Deviation (SD) and Extreme Spread (ES) values by being extra careful in all steps of my reloading process. I weighed bullets. I weighed brass. I double weighed my powder measures. I was very careful of seating depth for both the bullet as well as the primer. I was confident that I would meet my SD goal of 6 or less and my ES goal of 12 or less. Turns out, I missed both numbers by as substantial amount. SD was 25.8 and ES was 82 for a string of 25 rounds. At 100 yards the groups were acceptable averaging 0.524 MOA.

I am shooting Sierra Match King 52gr bullets (.224 #1410) using Lapua Match brass, Federal small match primers and 26 gr of Varget. Velocity averaged around 3100 fps from a Remington XR100.

What steps should I take to reduce the SD and ES values?

Target is attached.

 

[BuildingConceptsllc]

I'm not the guy to provide this info to you but you will need to tell what kind of die your using, and how you're annealing , ect to get some answers. Do you use a bushing die or mandrel , or a regular elliptical?

 

[Skeptic1]

Get some federal brass and full length resize. I'll probably take a beating here for saying this but...... it is my favorite brass to load.

Lots of folks overthink reloading IMO.......

 

[memilanuk]

A few things come to mind...

First... assuming you're talking .223 Rem... it's one of the harder cartridges in my experience to get good ES/SD numbers from.

Second... with light weight varmint bullets, presumably for use at say, 300yds and in... ES/SD really aren't a huge concern. Not saying that better isn't better, but maybe not worth worrying too much over.

Third... very little in the reloading process you mentioned would have a significant effect on your ES, other than weighing powder.

Finally... I'd consider trying a different primer, or possibly powder. Some combinations don't work well together in all guns. I realize that in the current climate, changing primers may not be a viable option, but it'd be my first step if'n it were me.

Also... it's entirely possible for the problem to be the firearm, not the load. The ignition system (firing pin, spring, etc.) can be a significant source of variability in ES/SD.

 

[rustyinbend]

You've gotten some great advice here ... especially from @milanuk ... I'd humbly add that I'd try laddering down in velocity using 3-cartridge groups and see if you stabilize SD and ES to lower values with less velocity. If you get some 3-shot tests that look good, then use that mix to build 10-shot tests and see if you get some better results. I tried this, albeit with 6.5-CM and the same problem, and backing down the charge helped a lot.

 

[RegionRat]

Varget is a great powder that tends to really do well in 223/5.56 starting at around 69 grains and up.
It will work in the example of your 52 grain, but it may be difficult to get really small velocity stats unless you try other powders or find the primer it likes.

I will suggest you try for optimal groups with a 52 grain rather than agonize over the speed stats.

The distances where velocity stats make a bigger difference are best left to the 77 grain and up bullets in 223. When the game is 600 to 1000 yards, you will certainly need decent velocity stats, but you won't be using those 52 grain bullets.

In F-T/R, Service Rifle, Mid Range and Long Range, we struggle to match this cartridge to the 308 in terms of getting good speed stats, but they do get there with Varget and the heavier for caliber bullets.

 

[Yondering]

Did you take steps to make sure your neck tension is consistent for each round? And then did you do good load development to find low ES, or just try a random load? You can't just measure carefully and expect to have a consistent load, but even if you accidentally landed on a very low ES/SD load that doesn't mean it'll shoot well, and vise versa.

Not saying this is you, OP, but some guys get super meticulous about minutia that doesn't matter, while missing and not understanding the things that do. One of those things that does matter, aside from how to lower ES, is knowing what ES matters for your application. As already pointed out above, with a 52gr varmint bullet you're likely not using it (effectively) at ranges where a really small ES/SD matters. Knowing how much does matter at your ranges will save you from chasing your tail.

Aside from that though, why are the positions of your groups on that target so different? T2 in particular is way different than the rest. Were you adjusting the scope, or is that different loads, or ??

 

[Doom]

Just my 2 cents worth. The 223 is not a cartridge that it’s realistic to expect single digit SDs from. Some may achieve it but I don’t think it will hold up.

I shoot 52-53 Berger and SMK and can hold about 0.4 MOA 5 shot groups at 300yds (Rem 700 Varmint). I think you might consider a powder change. I have used 8208 XBR for years and recently began using N135 with comparable accuracy. I would also suggest you try the flatbased bullets as opposed to the BT’s.

My 8208 loads are around 3105 fps and the N135 is around 3330 fps.

Looking at you target you have some significant vertical spread. T2 looks like you might have some setup/trigger control issues. I would suggest you either looking a a seating depth test OR work with the load.

I do not use a chronograph when developing loads for 223 and light bullets. The targets tell me everything I need to know.

 

[Dstoenner]

A few things come to mind...

First... assuming you're talking .223 Rem... it's one of the harder cartridges in my experience to get good ES/SD numbers from.

Second... with light weight varmint bullets, presumably for use at say, 300yds and in... ES/SD really aren't a huge concern. Not saying that better isn't better, but maybe not worth worrying too much over.

Third... very little in the reloading process you mentioned would have a significant effect on your ES, other than weighing powder.

Finally... I'd consider trying a different primer, or possibly powder. Some combinations don't work well together in all guns. I realize that in the current climate, changing primers may not be a viable option, but it'd be my first step if'n it were me.

Also... it's entirely possible for the problem to be the firearm, not the load. The ignition system (firing pin, spring, etc.) can be a significant source of variability in ES/SD.

Everything he said. I found that 8208 does better on light bullets than Varget

David

 

[wadebrown]

What type of chrony did you use? I ask because many of the optical chronys that do not have a light source will give different results as clouds move in, ...

Just a thought.

 

[alamo5000]

Second... with light weight varmint bullets, presumably for use at say, 300yds and in... ES/SD really aren't a huge concern. Not saying that better isn't better, but maybe not worth worrying too much over.

This.

Maybe I missed it but I did not see what distances the OP wants to shoot.

With that bullet and an extreme spread of 100fps at 500 yards it has the potential to create roughly 6 inches of vertical.
At 300 yards with a 100fps ES the potential vertical could be around 1 inch. Those estimates are using a 100 fps ES.

Again it depends on the goal here to determine if the itch is worth the scratch.

 

[SporterII]

H 4895 is what I like in this combo. 205m, Lapua, 52 SMK.
I get a lot more velocity though.
26 Varget is filling that case , probably compressed. Variation in how compressed each round create some speed variation?

 

[smoothy8500]

with light weight varmint bullets, 300yds and in... ES/SD really aren't a huge concern.

Exactly.

A lot of people get wrapped up over SD's without really focusing on whether it's of any practical importance. The attention to detail will be more important in tightening the group.

 

[SporterII]

It’s a fair question to ask. Answers here are solid and help the OP.
I learned , from scratch, on this forum. The original.

 

[b6graham]

what scale are you using?

ES of 12 from a 223 is gonna be tough from even the best procedures.

If I can be below ES=30 i'm happy (FX120 Autotrickler V3, and i don't add/remove single kernels if im 24.78-24.82 thats good enough for 24.8 charge weight. i stopped adding/removing single kernels for everything competition related)

 

[Doom]

What type of chrony did you use? I ask because many of the optical chronys that do not have a light source will give different results as clouds move in, ...

Just a thought.

I will add that my chronograph (RCBS) seems to give much greater spreads than the targets display.

If that 26 gr load is compressed then the COAL may be changing after loading. I found this to be the case with 26gr of N135.

When looking at the ballistics I get about 5” of drop which is +/-0.5 MOA for a 100fps spread. 500 yds is about the limit for the 223 with a 1 in 12 twist. The M16 considered 460m as the maximum effective range.

 

[memilanuk]

I found that 8208 does better on light bullets than Varget

H 4895 is what I like in this combo. 205m, Lapua, 52 SMK.

Something else that comes to mind... with the cartridge and bullet weight in question (.223 Rem and 50-55gn) out of that gun - I'm assuming that 'XR-100' is a Remington bolt-action pistol, the repeater version of the old XP-100, with about a 14" barrel... I'd definitely be looking at a powder faster than Varget. 8208, 4895, H335, W748, TAC, N133, N135, etc. etc. etc.

 

[Floridaboy]

Wow ! Great responses and I thank you all for being so quick to respond with some very good suggestions.

I have a few answers to some of the questions that were asked of me.

The Remington XR100 (Rangemaster) is a single shot rifle designed for short range (100 - 200 yd) benchrest shooting. I bought the rifle new back in 1999 and have been shooting with it in local competitions here in Florida since then.

T1 is 5 fowlers.

The groups float around the target because I adjusted my point of aim from T1 to T2 then a final point of aim adjustment for T3.

T3, T4, and T5 are all shot using the same point of aim.

On this load I used a .223 RCBS die to full size the case. I also use a Redding bump die to make sure the shoulder was bumped .002. I used a mandrel (.222) to make certain the neck tension was set to .002.

My chronograph is a MagnetoSpeed

My take away from these responses is:
1.) Don't expect great ES/SD numbers from a Remington .223 round.
2.) At the distance I shoot this rifle, (100 - 200 yards) bullet seating depth is much more important for accuracy than getting low ES & SD numbers.

Thanks again to everyone for your information.

 

[Mike Casselton]

Something else that comes to mind... with the cartridge and bullet weight in question (.223 Rem and 50-55gn) out of that gun - I'm assuming that 'XR-100' is a Remington bolt-action pistol, the repeater version of the old XP-100, with about a 14" barrel... I'd definitely be looking at a powder faster than Varget. 8208, 4895, H335, W748, TAC, N133, N135, etc. etc. etc.

XP = pistol

XR = rifle. It looks like a solid bottom model 7

XP-100R = repeater pistol. Same bolt handle as model 7.

 

[memilanuk]

XP = pistol

XR = rifle. It looks like a solid bottom model 7

XP-100R = repeater pistol. Same bolt handle as model 7.

Ah. Been a long time since I kept up with the Remington ecosystem. Wish they still made the old center grip XP-100 - wanted one so bad back in high school; by the time I was out of the military and could reasonably own personal firearms again they'd quit making them

I'd still say that the faster powders are a better choice with that bullet weight than what he's using (Varget).

 

[DocRDS]

Captain Obvious would like to ask if your flyer was included in the chrony and if so, what was the reading for that one.

(aka is your data a "true" bell curve, or are their outliers in your chrony data.)

 

[SporterII]

3100 fps.

 

[Mike Casselton]

Ah. Been a long time since I kept up with the Remington ecosystem. Wish they still made the old center grip XP-100 - wanted one so bad back in high school; by the time I was out of the military and could reasonably own personal firearms again they'd quit making them

I'd still say that the faster powders are a better choice with that bullet weight than what he's using (Varget).

XPs are just crazy priced now.
I had a 15" center grip 223. Total tack driver.
My holy grail would have been a center grip, Herrett's stock and chambered in 250 Savage or 6-BR.
I let go of the 223 back in 09 to pay divorce lawyer bills. Stupid move.

 

[BuildingConceptsllc]

Wow ! Great responses and I thank you all for being so quick to respond with some very good suggestions.

I have a few answers to some of the questions that were asked of me.

The Remington XR100 (Rangemaster) is a single shot rifle designed for short range (100 - 200 yd) benchrest shooting. I bought the rifle new back in 1999 and have been shooting with it in local competitions here in Florida since then.

T1 is 5 fowlers.

The groups float around the target because I adjusted my point of aim from T1 to T2 then a final point of aim adjustment for T3.

T3, T4, and T5 are all shot using the same point of aim.

On this load I used a .223 RCBS die to full size the case. I also use a Redding bump die to make sure the shoulder was bumped .002. I used a mandrel (.222) to make certain the neck tension was set to .002.

My chronograph is a MagnetoSpeed

My take away from these responses is:
1.) Don't expect great ES/SD numbers from a Remington .223 round.
2.) At the distance I shoot this rifle, (100 - 200 yards) bullet seating depth is much more important for accuracy than getting low ES & SD numbers.

Thanks again to everyone for your information.

I wouldn't even use a chrono is you are shooting 100-200 . I would focus only on my group, and you will get better groups with something like TAC (it's also more available than others) or one of the other similar powders suggested ITT. I assume you've already done a seating depth test, and it sounds like you have a solid loading regiment. I'd just switch powders and see how tight you can get your groups and roll with it. You should be able to get in the .2" 's or .18" or so at 100yds, center to center. I've not been able to get better than that but that's pretty dang good and should get you to the point where you know a miss is your miss.

 

[Floridaboy]

I

I wouldn't even use a chrono is you are shooting 100-200 . I would focus only on my group, and you will get better groups with something like TAC (it's also more available than others) or one of the other similar powders suggested ITT. I assume you've already done a seating depth test, and it sounds like you have a solid loading regiment. I'd just switch powders and see how tight you can get your groups and roll with it. You should be able to get in the .2" 's or .18" or so at 100yds, center to center. I've not been able to get better than that but that's pretty dang good and should get you to the point where you know a miss is your miss.

I think I'll take your advice and load up some using TAC. I just got 2 pounds of it. What measure do you recommend?

 

[BuildingConceptsllc]

I

I think I'll take your advice and load up some using TAC. I just got 2 pounds of it. What measure do you recommend?

I will come back and edit this after I check my book so I can give you legit numbers but I think I'm at (Edited - 25.2gr TAC- 75eldm, BR4 , lapua, 1.855" BTO- MV = 2986fps )

I'd just start at 24gr and work up by .25gr per, and find pressure, then back off a half gr or so. Then do your seating depth test and start at .005 off the lands and go deeper by .003" per doing 3 or 4, rounds per ( I like having 4 so if I pull one I can call it and not blow my test). Do that with 10 sets at .003 each and I'd bet you will find one of them that shoots like a laser and a few behind or before that group that are almost as good. That's when you will know. Then I usually go .002 towards the two groups that were almost as good as the best and then I'm there. That gives you a little wiggle room on either side of your chosen seating depth.

 

[RegionRat]

I

I think I'll take your advice and load up some using TAC. I just got 2 pounds of it. What measure do you recommend?

Maybe it got lost in all the posts... what twist is this barrel?

Before folks suggest bullets much heavier than your original post where you are running 52 grain, we need to make sure the barrel twist works with the suggestion to try 75 ELDM.

 

[BuildingConceptsllc]

Maybe it got lost in all the posts... what twist is this barrel?

Before folks suggest bullets much heavier than your original post where you are running 52 grain, we need to make sure the barrel twist works with the suggestion to try 75 ELDM.

Actually, i thought OP is who suggested he was going to run that bullet......

 

[RegionRat]

Actually, i thought OP is who suggested he was going to run that bullet......

If he did I can't find it with a quick scan back. I took a quick glance for the twist and can't see that either.
Folks are just trying to help, so no worries.

The twist/stability question is still pretty important.
If the twist isn't right for 75 ELDM, then we go round in circles.

 

[BuildingConceptsllc]

If he did I can't find it with a quick scan back. I took a quick glance for the twist and can't see that either.
Folks are just trying to help, so no worries.

The twist/stability question is still pretty important.
If the twist isn't right for 75 ELDM, then we go round in circles.

Yeah you're right, he does need to have a barrel twist that will stabilize it, which would be a 1-8twist or a little faster. (Though I know guys who shoot them with a 9 and 10twist and they do fine).

I thought I read where he said "maybe I will just go ahead and shoot a 69 or 75 " or something like that but I can't find it now.

 

[Doom]

It a 1 in 12 twist assuming original barrel.

 

[Partsunavailable]

I didn't read everything, but I'd try a different powder. Mine really likes h322 for the 50 grainers. H335 has significantly higher es and SD for me.

 

[ballisticdaddy]

The only thing I tried that really helped to lower the ES in 5.56 is using the CCI 450 magnum primer. If the load is already shooting .5 MOA in a factory rifle what are you looking for?

 

[Floridaboy]

Maybe it got lost in all the posts... what twist is this barrel?

Before folks suggest bullets much heavier than your original post where you are running 52 grain, we need to make sure the barrel twist works with the suggestion to try 75 ELDM.

I can't go any heavier than a 55 grain bullet. Flat base or boat tail doesn't seem to make a difference at the distance I am shooting (100 - 200 yards). Flat base is probably better. It's a 1 in 12 twist on the barrel.

 

[Floridaboy]

I will come back and edit this after I check my book so I can give you legit numbers but I think I'm at (Edited - 25.2gr TAC- 75eldm, BR4 , lapua, 1.855" BTO- MV = 2986fps )

I'd just start at 24gr and work up by .25gr per, and find pressure, then back off a half gr or so. Then do your seating depth test and start at .005 off the lands and go deeper by .003" per doing 3 or 4, rounds per ( I like having 4 so if I pull one I can call it and not blow my test). Do that with 10 sets at .003 each and I'd bet you will find one of them that shoots like a laser and a few behind or before that group that are almost as good. That's when you will know. Then I usually go .002 towards the two groups that were almost as good as the best and then I'm there. That gives you a little wiggle room on either side of your chosen seating depth.

Thank you very much! I will follow your direction and see how it turns out. I'll post results and targets. Thanks again !

 

[BuildingConceptsllc]

Thank you very much! I will follow your direction and see how it turns out. I'll post results and targets. Thanks again !

Sure. You can do the same thing of course with a lighter bullet. I don't know where I got the 75gr from , maybe I got it confused with another thread or something.... probably a 62gr is going to be the biggest with a 1:12 barrel but a lot of guys have very good results with the eldm bullet for 223. That's the only caliber I shoot a Hornady bullet but those eldm 's work really well for many in 223. Smk is also popular for 223.

 

[RegionRat]

I can't go any heavier than a 55 grain bullet. Flat base or boat tail doesn't seem to make a difference at the distance I am shooting (100 - 200 yards). Flat base is probably better. It's a 1 in 12 twist on the barrel.

Agree, that was the point in highlighting the concept of going heavier. With a 12 twist, you won't do well with heavy (long) bullets.

If you have the energy, look up the nearest Bench Rest club shoot in your area. You will get a look at the state of the art, and what to expect (and what not to) with a visit to a club match.

 

[Scottfree92]

I didn’t see any mention of your neck tension. If this is not consistent from round to round, it can all go to hell fast. This is a factor that I spend a huge amount of time on. I have been using Berger 52 gr target bullets with Lapua brass and have gotten excellent results from them.
What I do, first, I always anneal after every shooting to ensure proper consistent malleability from case to case. Then I always full length size. I use Whidden bushing dies, with Short Action Custom bushings, they produce the least run out, from what I have found anyway. I then use an expansion mandrel to get the cases right where I want them. I do check the necks with pin gages, to be sure of their diameter. My neck tension is just about always at 1.5 thou. I then charge with 26.0 grains of Benchmark powder. In many tests I did, I found that 26.0 was a great node for this powder. I then seat them. I use a 21st Century hydro arbor press that has a pressure dial on it. I have found that using the above steps to ensure proper neck tension, my seating pressure rarely varies by more than a few psi. I also shoot a 12 twist rifle

 

[Roperboy87]

I would try the bullet as long as you can .020 off the lands and start shoving it in till you get a good 3 shot group if you got the supply’s. Your powder and primer may not be the issue then again it could be. I would start with finding the right seating depth then worry about the powder and primer if that’s still the problem

 

[jrsnell]

Lots of good info, but no real facts.
Thats why I wrote Snell’s Notebook. No opinions, just facts.
ES and SD depend on uniformity of deflagration (the way the powder burn progresses as pressure increases).
Aberdeen Proving Ground found that loads with enough powder to act like a solid push the bullet out of the case before the pressure has rise rate stabilized. Loads with enough air space, and neck tension keep the cartridge together longer. In both cases if the bullet moves forward enough to change the available space at the right time, it can cause the rate of pressure change to drop significantly. In summary, Aberdeen reported that 5.56 NATO loads could (and often do) push bullets to up to three stopping points (where bullet velocity returns to zero), the last being when the bullet enters the rifling.

One key to accuracy is consistent ignition.

Cartridge fill to just before compression, or light compression often knocks the bullet into the rifling consistently with enough force to seal the barrel (works best when the bullet bearing surface is still in the neck at the moment forward movement encounters the forcing cone).

Uniformity of case neck thickness helps seal the cartridge and release the neck tension uniformly.

If you plan to ask questions, please read https://SnellsNotebook.us for the appropriate references first.
Click the Notebook link on my home page.
Find ‘Initial Physics’ In the index and click on it.
Read down to the header that starts with ‘The Primer Detonates’ - There are four links nearby. All apply, but the third link ‘Primer Output …’ is easiest to read, and is most related to this discussion.

I did not perform the research, and Aberdeen no longer publishes public information, but I captured what I could when I was researching. There is far more information than can be related in this post.

Snell's Notebook

 

[Yondering]

Lots of good info, but no real facts.
Thats why I wrote Snell’s Notebook. No opinions, just facts.

Well that's about as arrogant as a guy can get, right there. Respond to a thread that contains a LOT of facts, many of them more specific and appropriate than the general guidelines you listed, and then act like you're the only one with useful information? Pull your head out and look around a little.

You have some good info, but don't need to act like an arrogant jackass.

 

[Cfshooter]

Wow ! Great responses and I thank you all for being so quick to respond with some very good suggestions.

I have a few answers to some of the questions that were asked of me.

The Remington XR100 (Rangemaster) is a single shot rifle designed for short range (100 - 200 yd) benchrest shooting. I bought the rifle new back in 1999 and have been shooting with it in local competitions here in Florida since then.

T1 is 5 fowlers.

The groups float around the target because I adjusted my point of aim from T1 to T2 then a final point of aim adjustment for T3.

T3, T4, and T5 are all shot using the same point of aim.

On this load I used a .223 RCBS die to full size the case. I also use a Redding bump die to make sure the shoulder was bumped .002. I used a mandrel (.222) to make certain the neck tension was set to .002.

My chronograph is a MagnetoSpeed

My take away from these responses is:
1.) Don't expect great ES/SD numbers from a Remington .223 round.
2.) At the distance I shoot this rifle, (100 - 200 yards) bullet seating depth is much more important for accuracy than getting low ES & SD numbers.

Thanks again to everyone for your information.

What part of FL?

You can get better numbers then you have now for sure, but you are correct, at 100 yards, the target results are more important, actually at any yardage.