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..