Concentricity & Runout Correction

[22~308TargetShootr]

Ok, Long time Competitive Smallbore shooter, but I'm fairly new to Mid Range, Long Range, and Palma Competition as far as the reloading aspect of the game goes and only been reloading now for about a year for my .308 and those tournaments. I'm trying to pull out all the stops on precision and turning out consistant rounds. I do everything by hand , no case prep centers with power tools or anything. I know it takes longer but I enjoy the process. This season I've taken my process now into considering concentricity. I'm using the Sinclair Conc. Gauge, and I realized that some of the others had an advertised correction feature, but still went with the Sinclair. What I'm wondering is if anyone out there not using one with the feature to tip the bullet slightly, how do you attempt the slight correction, or do you attempt it at all, and if it's too far out of your acceptable range does that round just become a fouler or sighter ? I've been able to with a little slight pressure between my thumb and forefinger make a slight adjustment to the bullet if needed, and I can on average get my runout down to .001 or there abouts. My other concern is how much does anyone feel this alters neck tension adversely ?

C.D.

 

[ChrisGarrett]

Re: Concentricity & Runout Correction

I've got the Bersin gage/fixer to do 30'06/7 RemMag size carts and while it nudges the bullet to eliminate runout, I don't think it moves the bullet so far as to alter neck tension.

You can nudge it back and forth multiple times and in large increments and that will loosen the necks, but in reality, I usually make slight corrections.

Neco makes one that is static and it has a bunch of different holes on a vertical 'board' where one inserts the bullet's tip and then bends the case down, making corrections, but I like the Bersin tool better.

Problem is is that they're not cheap, but the dial can be moved across the various 'cartridge' bodies, so you save a little bit.

If you're consistently at .001" of T.I.R., I wouldn't worry too much about it.

Chris

 

[Tripwire]

Re: Concentricity & Runout Correction

I made mine...a gauge/straightener combination.

Infinately adjustable for where it reads, where you push on the cartidge, and for cartridge lenghts from .223 to 300WM, the cartridge rolls on four roller bearings.

I've since upgraded it with an adjustable-for-height "keeper" that hovers over the extractor groove to keep the case head from tipping up when pressure is applied to the bullet.

Works on the same principle as an arrow straightener....find the high spot and tweak it.

I check every round built for my bolt rifles.

My load practice generates between .001" and .003" concentricity, average.

Once in a while something weird will happen and I'll get .004" or .005".

I can correct everything to .000" if I want to.

I've seen a very small diiference in "accuracy" between .000"/.001" and .005". I've seen no difference in "accuracy" between rounds with .000"/.001" and rounds with .002"/.003"/.004"/.005" corrected to .000".

I wouldn't bother trying to straighten anything worse than .005" but rather would seek hard to find the cause of it, and correct THAT first.

Since I anneal after every firing, and correct such a small amount, I don't feel neck tension is affected.

YMMV..........

 

[427Cobra]

Re: Concentricity & Runout Correction

I use a Sinclair concentricity gauge, and have the NECO C.A.T.(cartridge alignment too), what I have found is these tools together work as advertised, springieness of brass that is work harden though makes rounds that are straight spring back somewhat to there previous run out if not shot within a coue of days, the solution is to anneal so the brass is soft again. Another thing I have discovered is my neck turned brass/rounds consistently have none to .001 TIR, I hardly check run out now, most will say that turning necks is a waste of time, while it is time consuming I don't consider it a waste.

 

[Killswitch Engage]

Re: Concentricity & Runout Correction

I have the hornady gauge and straightener and I love it. I've had an rcbs case master but no good way to correct excessive runout on some rounds. The hornady really works great and I am easily able to bring ammo to within .001 or less. I have found no change in neck tension whatsoever. If your brass isnt work hardened I think it has no change on tension.

 

[SPAK]

Re: Concentricity & Runout Correction

I used to use the CAT by neco, but found that on some rounds after "fixing" the runout the bullet would move and my OAL would increase .001-.002" or so. Probably not that big of a deal. Funny thing is when I went to reseat the bullet that small amount back into the case, the runout would return.

Those rounds that continue to exhibit runout above .003" TIR I just set aside and note it on the case.

Most of my rounds range from none to .002" at the worst. I don't bother using the CAT tool on those rounds any more.

 

[MALLARD]

Re: Concentricity & Runout Correction

all good advice

i would also try to determine the causes of runout rather then trying to reduce it with a tool.

but if your getting .001 runout , that is pretty good.

 

[Tripwire]

Re: Concentricity & Runout Correction

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Frogman77</div><div class="ubbcode-body"> Funny thing is when I went to reseat the bullet that small amount back into the case, the runout would return. </div></div>

Not surprised at all....your seater die and/or your shell holder and/or your ram is inducing run out. Try seating in four gentle pushes seating an equal increment each time, turning the shell 1/4 turn each increment until your full seat is reached. That may help reduce the runout.

 

[Tripwire]

Re: Concentricity & Runout Correction

Per turned necks....it's beyond me how anyone can expect a low runout with un turned necks. It's a physical impossibility if the brass has thick/thin necks...something I've found pressent even on the best of brass.

 

[SPAK]

Re: Concentricity & Runout Correction

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tripwire</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Frogman77</div><div class="ubbcode-body"> Funny thing is when I went to reseat the bullet that small amount back into the case, the runout would return. </div></div>

Not surprised at all....your seater die and/or your shell holder and/or your ram is inducing run out. Try seating in four gentle pushes seating an equal increment each time, turning the shell 1/4 turn each increment until your full seat is reached. That may help reduce the runout. </div></div>

Trip

I'm using a wilson inline die and arbor press... The run out only happens with a few cases out of a batch... I turn all my necks, and anneal every third firing.. But for whatever reason I get a case here and there that after seating will exhibit more run out than the others.


Out of 20 cases most will run almost no runout to a max of .002" tir with maybe two or three cases will measure .003-.005" tir on a loaded round... All my cases after resizing have virtually no detectable runout....

I think it's just some flaws in a few cases that will continue to exhibit run out no matter what I do.... So I just set them aside and use them for short range targets.

Fwiw I use lapua brass, sort by neck wall thickness, and neck turn in my brass prep...

I'm only cleaning up the necks, I don't do a full turn of the necks... For example my lot of lapua neck thickness ranges from .0140"-.0150" on average... A few will measure .0005" more or less. Those I'll set aside... The others I'll turn to .0145".

Trip and 427cobra, do you guys make a clean cut all around or just taking the high spots down?? If you had my particular lot of brass would you turn down to .0140"?? Would the .0005" make any more difference??

 

[Rookie]

Re: Concentricity & Runout Correction

I once saw a youtube vid where a guy would measure runut, and then stick the cartridge in a hole in his bench and bend it back into alignment, as proven by the concentricity gage.

I tried that for a while and my group sizes increased dramatically so I stopped. I dont know if it messed up neck tension or what, but it just didnt work.

Now I just resize and seat with smooth strokes and use comp dies with the built in sleeves. Runout generally stays under .003 and groups are good.

 

[boltgunluvr]

Re: Concentricity & Runout Correction

I use my inexpensive Lee press & dies, use smooth & consistent strokes, utilize the so-called cheap Hornady concentricity gauge, and all my factory rifles shoot within .5-.75 moa @100 yds. How can I gripe about that. A lot of fun on minimal $.

 

[427Cobra]

Re: Concentricity & Runout Correction

I turn my Win 7-08 brass that is resized to 260 Rem to .0135, some get turned all the way around, most don't, I use a 21st century shooting turner, I'm not a very good Indian so my bow n arrow needs to be the best it can be, I'm also cheap because I have a blue collar job fixing 737s, Lapua brass is nice, but the money I have saved using Win brass has more than paid for some of exspensive tools I own.

 

[CSAR]

Re: Concentricity & Runout Correction

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tripwire</div><div class="ubbcode-body">
I wouldn't bother trying to straighten anything worse than .005" but rather would seek hard to find the cause of it, and correct THAT first.
</div></div>

^^^^^ This! ^^^^^

And I feel if you try to straighten a round with this much or more out of roundness, you're going to have issues with neck tension. Fix your process and not the finished rounds.

 

[Fuzzball]

Re: Concentricity & Runout Correction

I've tried and rejected the "seat part way and turn" method; didn't do a thing for me. Did a series of concentricity tests after each step, found that a bullet which started crooked stayed crooked. All seating stems I've ever seen fit much too loosely to change anything by turning the cartridges.

Keep thinking I'm going to sleeve a seating cup and lap it to a snug fit in the die to see if that might make a difference. Haven't done it because of time and thinking I'd also need to hold the case body straight and that would force me to make a Forster/Redding full length body/bullet alignment sleeve for a conventional seater - which I AIN'T gonna do!

 

[Tripwire]

Re: Concentricity & Runout Correction

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fuzzball</div><div class="ubbcode-body">
Keep thinking I'm going to sleeve a seating cup and lap it to a snug fit in the die to see if that might make a difference. Haven't done it because of time and thinking I'd also need to hold the case body straight and that would force me to make a Forster/Redding full length body/bullet alignment sleeve for a conventional seater - which I AIN'T gonna do! </div></div>

It's pretty easy to buy them already made....from Forster and Redding.

Redding for me please..........

 

[Clark]

Re: Concentricity & Runout Correction

Ken Marsh, the guy who had the Cheap Scope Page 12 years ago, tells me that he has an old Lee sizer die that is crooked. He has the bend indexed.

He takes a round that is eccentric and put the bend in the round 180 degrees out of phase with the bend in the die. He sized. With spring back, the ammo is then straitened.

I have built elaborate fixtures to bend ammo necks straight.
In the end, I concluded that nothing fixes brass like being fired in a chamber cut with a reamer.

The trick is to never use expander balls or "S" dies.