Home Forums Hunting & Shooting Ask The Gunwriters concentricity problems caused by seating

I am increasing neck run-out mostly from bullet seating. Run-out is consistently around .002" from sizing and then jumps up another .003-4" from seating Barnes tsx using RCBS dies. In your experience, what is the most likely cause? I have always had more run-out created in the sizing process but not in this case. Thank you.

Do you seat 1/2 ways and then turn 180 degrees to complete seating?

Could be uneven neck thickness, uneven chamfering, or a poor match between the shape of the bullet and seater stem. But standard seating dies, unlike more sophisticated dies, don't have a relatively bullet-diameter cylinder to hold bullets reasonably straight while they're being pushed into the case neck.

mr. saddlesore: No on your 1/2 seat and then rotate. Apparently you've found that to help. I'll give it a try.

And no Mr. B, haven't neck turned with these cases but will also give it a try with a couple to see.

thank you much for your input.

You don’t necessarily have to neck-turn them. Instead you can just select for reasonably even neck thickness, not more than around .001” in variation.

ruffedgrouse, I do similar process as saddlesore,only I fully seat, then rotate 180 degrees. It seems to work pretty well. memtb

Try for very even inside neck chamfering with a gentle angle.

The reloaders Foster inside/outside tool I have's inside angle must be 30 degrees.

The tool I use from my late dad's tool box is marked 15 degrees. That does an excellent job.

I fixed my concetricity problems by buying Forster seating dies .

Neil

There are a number of other good seating dies as well. One of the best bargains in the business is the standard Hornady.

Another + for Forster bench rest seating dies. Hornady could be great too but I have never used them.

With a standard RCBS seating die there's an extra step I do that may help you.

Set the die in the press so the crimp shoulder does not contact the case mouths and lock the die down. Back the seating depth adjustment screw out all the way. Now turn it back in a tiny bit so it's not in a bind.

Now try to seat a bullet. Depending on the bullet it may not even start in the case, or it may start in a little bit. Either way, adjust the seating stem so it starts the bullet into the case a small amount like .04" or .05".

Seat all of the bullets this way.

Once they're all long seated go back and adjust the seating stem to seat the bullets to the desired final overall length.

If your brass isn't plagued with bad necks and you're careful with your technique you may find the runout is cut down a decent amount.

RCBS tool

thanks all for your help. I do have a Forster seater for my .270s but not for this round. Will start implementing suggestions and let you know the progress.

dan

So FIRST, how does it shoot loaded as is?

I do the 180 thing out of habit, even with good dies... fwiw.

but I'd worry on the paper first and then if thats not satisfactory, go to solve the now exising problem.

I first experienced this 40 years ago.
The first thing you need to take a serious look at, is the press itself.

Change dies and cartridges and see if you are getting the same thing across all of your cartridges as some cartridges are less effected by this misalignment and others are not scrutinized as much if not perceived "Highly accurate" cartridges.

Also, take into consideration the age of the press you are using.........An older press is more likely to have misalignment between the die holder tapping and the shell holder, which can also mean the primer shaft alignment.

Naturally, it is/was more prevalent with turret style presses because of the multi drilling necessary to accommodate all of the dies. Having the turret head as an additional press component to align didn't help either.
John

That depends on the turret press. I load 6mm PPC’s on my Redding T7 using Redding Competition dies, and without any tricks like turning the case 180 degrees during seating, the rounds come out averaging around .0005” runout with 65-grain Bergers.
I also must comment that I’ve tested turning the case after seating the bullet halfway many times, using conventional seating dies in many cartridges, and have yet to find it makes any significant difference in consistently seating bullets straighter. Evidently it makes a difference with some dies, in some instances, but I have never seen it.

A technique that has worked for me sometimes is to seat the bullet a couple of millimeters, then spin it on the runout gauge. You can then straighten, spin it, straighten again if necessary. Then seat the bullet to desired depth.

It doesn't always work, (i.e. with neck thickness problems) but it's worth a try.

And people say my extra step is tedious.

I found that one brand of seating die may work better than others. I found a RCBS seating die gave me straighter ammo than a Lee seating die.

Your mileage may vary......

All of my RCBS seating dies turn out .003" TIR or less. It's all about how you adjust them... Hint..

With Lee products the theory of operation is often quite good, but the execution of manufacture can be spotty.

As MD mentioned, the Hornady seating dies are good, but the Forster seaters are better, or so says my run out gauge.

I always suggest that the way to remove any inaccuracies in a standard 7/8" seater is to go to an arbor press, and Wilson dies.



It removes the influence of any potential inaccuracies of the axis of the press's threads, slop in the cencentricity of the die and its threads, tolerances between the threads of the die and the press, flex of a non O-frame press, etc. It has a tight-tolerance chamber which is indexed of the seater-stem's pilot hole--a seater you can swap for either a standard, or VLD style bullet. As a bonus-if your pursuit of accuracy finds you tiring of factory chambers and having custom barrels installed by a decent gunsmith, you can have the dies dimensions cut the same as your chamber, further refining the fit.

I think it provides a more positive and consistent seating depth, as it has a definite, hard-stop, and is not influenced by any potential lash of the ram and lever, or flex in a press.

Lastly, the portability of the whole system allows you to easily develop loads at the range bringing little more than what's shown in the photo.

I concur in that, however with different tools.
Arbor press, Lee dies and Lyman 55.

I'm also astonished at the concentricity of rounds from my Forster mic-seating die set. It averages about 1.5 thousandths runout.

Buy this first.

RCBS tool

Do you have any compelling evidence at all that such a meticulous non-issue makes any difference at all in translating into accuracy "?

I use my run out gauges and re-adjust the bullets all to center zero deviation. I haven't seen any discernible difference at all in group sizes.

If we are talking about hunting loads it's totally immaterial. If it's championship, competition bench rest shooting - show me any importance at all.!

I've blind tested the effect of runout by having a friend who is a good trigger man shoot the ammunition in a rifle known to be reliably precise. He was not informed what he was testing.

In short, runout made a difference.

Put me down as another handloader that seats the bullet half way, spins the case, and finishes seating the bullet. It certainly gives me hunting accuracy with some rifles and loads consistently under 1 MOA. That's all I need for my purposes.

mathman, was it a "significant" difference or did it actually matter in real life?

perhaps a little more info would be helpful here to my original question. This is a hunting rifle that has been tuned: proper bedding, trigger stoned over a bit, good quality scope of known performance and a new douglas barrel that has only around 50 rounds or so thru it. However, it has been a challenging rifle to get shooting well. My original question wasn't intended to get into overall ways to improve accuracy of the rifle, but only to address the concentricity issue. I've read some conflicting info on how much out of round will actually cause measurable changes in hunting rifle accuracy, but getting the bullet started down the barrel straight seems to make sense. On the other hand, another rifle I've played with this year seems to shoot surprising well with like .010-.012 run-out which really surprised me. Because of the difficulty of getting this rifle to shoot as good as I'd like, I'm looking for all the simple inexpensive ways that just MIGHT affect accuracy. If I could see another 1/4" or so of improvement, I'd be worth it to me. Right now 3 shot groups, and this is with a bullet weight that would not be my first choice, runs around 1 1/4" at 100 yds. The bullet weight I'd prefer doesn't do that well.

So perhaps another question might be how much bullet run-out have you seen actually affect HUNTING rifle accuracy and to what degree?

Thanks again all for sharing your expertise.

Dan

ruffedgrouse: I learned this stuff from Mule Deer's writings, who said that runnout of .005 and under would show good results in hunting rifles,and experimenting with some troubled rifles showed this to be the case.

So, the stuff that measures .005 and under gets shot for groups and the stuff over that is used for off hand. It works pretty well with factory ammo, too.One 30/06 simply bug holed 150 gr Fusion factory ammo, after I culled anything over .005.

Anyway this is what I have seen myself.

Interesting thread. I found this link informative.

http://www.gunnersden.com/index.htm.rifle-reloading-bullet-run-out.html

That I am nowhere near there in my reloading, goes w/o saying.

The need to chamfer and deburr with "machine like accuracy" is overstated. I achieve low runout after using hand tools to perform those operations. Also I use a Wilson trimmer which produces more consistent/square trimmed cases that the RCBS the author touts, and which I also have.

The RCBS competition seater, while a step up from the usual seating dies, is not quite in the same league as the Forster and Redding competition dies according to the runout checking fixtures I've used.

Maybe that new Douglas barrel has the chamber itself out of concentricity. It wouldn't be the first time such a thing has happened.

I've seen a marked improvement going from .006"-.009" to less than .005" with a good shooter and an accurate sporter. This was with Lake City match ammo fired from accurate 308 rifles.

I agree, I've never seen it make a difference either.

One thing I have noticed is unsquare case mouths are disaster. Often putting fireformed cases, and cases that are full length resized between each firing back in the case trimmer and squaring them up it is plain to see some case necks will stretch on one side more than the other, usually ones that have large neck thickness variations, this is evident in that it takes a turn or three until a few or often several thou has to been removed until finally cutting around the whole circumference of the mouth making it square. When seating a bullet on an unsquare case mouth the base of the bullet hits the tallest point of the mouth pushing it off center and tips it crooked, doesn't stop tipping it hits the low side of the mouth. This starts the bullet down the neck off center and tipped and stays crooked until it's seated all the way causing runout. Turning it in the shellholder as you seat it doesn't fix this. Add to that uneven neck thickness and it's pretty hard to seat a bullet straight in that scenario.

Personally when I want to make straight ammo I don't fiddle with turning cases in shell holders, and trying to straighten them after seating, I think that just screws up neck tension. To make straight ammo I turn necks and make sure the case necks are 100% square. When this is done no matter what seating die I use I get pretty concentric ammo, it would be hard not to.

I've been switching form RCBS to Hornady and am pleased. Good products.

You need to use a little item made by Forester....(I think) that has three brushes and the container holds powdered graphite; brushes fit various calibers! If the button on your depriming pin is a little rough, the case mouth...when run down on one of the brushes picks up graphite and applies it to the interior of the neck. This application lets the case, when being pulled downward slide much easier over the sizer button. What can take place in some instances is the shoulder of the case can be pulled out of alignment because of being hard to slip over the sizer button. Also...putting an 'O' ring under the locknut on the resize die and not 'hogging down' the die (letting the die float) against the press helps!

Wilson inline seating tool is a valuable asset!!

I've recently seen interesting improved run-out numbers after switching to a Lee collet neck sizer, from both Hornady and RCBS dies in 7-08.

Bushrat,

Thanks for your observations—and your experiences with unsquared case mouths match mine.

The one tool I’ve found that helps straighten bullets without screwing up neck tension is the Tru-Angle, because it bends the neck slightly, instead of just pushing the bullet around inside the neck. But even then the run-out can’t be too bad before straightening. I’ll use it to correct a couple thousandths of run-out, but not much more.

What is your personal run-out correction limit? And why do you stop there? What have you found by correcting run-out "too much"?

The limit depends on the rifle. When I got my first of several concentricity gauges around many years ago, an RCBS Casemaster, the instructions said big game rifles rarely benefitted from bullet alignment less than .005”, and varmint rifles less than .003”. Over the next few years I found that to be basically correct, though it depends on the chamber. A custom big game rifle with a minimum SAAMI chamber can often benefit from .003” runout, or even less, but a factory big game rifle probably won’t. In my benchrest rifle I try for as close to zero runout, because it definitely benefits from as little as possible.

Aa a result of all that, for most big game rifles I don’t try to correct with the Tru-Angle that’s more than .007”. Above that and the corrected rounds still won’t shoot as well as uncorrected or minimally corrected rounds, probably because neck tension is compromised. With most varmint rifles I don’t try to correct runout more than .005”, for the same reason.

Dunno if that answered all your questions!

Thanks for taking to the time to respond. Your answer was exactly what I was looking for.

I finally had a chance to experiment a bit with the problem and the RCBS seating die I referred to in the original post. I neck-turned a few cases using my old Marquart neck turning tool which pretty much eliminates run-out on the neck O.D. and creates consistent neck thickness. I seated a few bullets with lock ring locked in place and got the same .003-004" run-out. Then I seated a few bullets but with the lock ring completely loose which resulted in just about zero additional run-out. As the bullet enters the case mouth the die flexes a bit but at least with those bullets, a Sierra boat-tail match, it made a huge difference. Perhaps it will be different by using conventional hunting bullets, but will report later. Thanks all who have shared.