Riddle me this - runout difference between presses

[selmerfan]

So, after several years of focusing on parenting five kids, the youngest two being now four and a half year old twins who were born at 24 weeks gestation and we adopted. I'm finally getting some time to tinker in the shop again. Last winter I picked up a Remington XP-100 in .350 Remington Magnum with a 16" full bull Douglass XX barrel on it with the intent to hunt Iowa's late muzzleloader season with it this year because my daughter claimed my TC Encore 18" MGM barreled .357 Max for deer hunting the late muzzleloader season.

I enjoy tinkering with new chamberings and I have a long love affair with the XP-100 platform, but haven't owned one for twenty years now (our oldest kid is 19, you do the math). I've got plenty of good bullet molds for it, including the Ranch Dog 190 LFNGC and NOE 215 gr, as well as a bunch of 180 gr. Speer jacketed. A month ago I quickly put together some loads just to make sure I have a load that will kill a whitetail in late December/January and put the first rounds down the tube with the Speers and RL-15 with acceptable, though not spectacular, results (1.25" groups at 100 yards - I've have XPs group much, much better). Good enough for hunting. But I want more, including cast options for more economical shooting.
I put together a bunch of cast loads for it this morning and foolishly decided to check runout on both the bullet and the neck of the loaded rounds. Not good. .005" - .010" runout on the bullets, .004" - .008" on the necks of the loaded rounds.

I'm using Redding FL dies that are setup to just touch the shoulder and for the cast loads, expanding with a Lyman M die. Using an RCBS A2 press because that's what I had clamped to the bench because I was experimenting with the Redding form/trim die to make brass for this gun out of .300 Winchester brass.
So I decided to start chasing runout. I took my resized cases and checked necks. .003" - .006". Not real great. Checked necks after expanding. .005" - .008". Also not great. First step was taking the decapping rod with sizing ball out of the sizing die. Brought runout down to .003" on a sized case, very consistently. Not what I've come to expect from Redding dies. Ran them through the M die, .004" - .007". Not great.

So I decided to clamp the Forster Co-Ax press on the bench next to the A2 and see what happened. Ran a previously sized and expanded case through the sizing die with no decapping rod or expander button. Boom .0005" runout. Maximum. Ran it over the M die in the Co-Ax. Back to .002"- .004" runout on the neck. It is possible that the M die mandrel setup is that far off? Or am I missing something? I'd like to get runout before seating bullets to .001" or less on the necks, hoping to ultimately reduce runout on the bullet. Ideas for how to improve it? My only guess here is that I'm dealing with an inconsistency in neck wall thickness that doesn't affect the case after going through the sizing die, but is obviously pushed to the outside when run onto the M die expander mandrel. Also, I'm surprised that the RCBS A2 produced .003" runout when the Co-Ax produced virtually zero. I mean, I shouldn't be surprised, as I have the Co-Ax from when I was chasing groups with a 6PPC and wanted absolute consistency without going to an arbor press and dies and I got it.

And yes, ultimately as long as the bullet goes where I tell it, it doesn't matter. This is a hunting rig, not a BR or silhouette gun. But it's fun for me to tinker in the minutiae after I haven't gotten too for several years. It's nice to be back at the bench messing with stuff for fun instead of just loading for the purpose of shooting and hunting.
Thanks for any advice you might have!
Selmerfan

[jetinteriorguy]

I’ve found the best way to practically eliminate runout is to first size with a Redding body sizing die, followed by a Lee collet neck die. But this is only using good quality jacketed bullets, for cast bullets I’d have no clue, but I’d guess it would be a pretty tough thing to accomplish and probably just not an issue.

[ascast]

^^? selmerfan, I think you got it in your 4th paragraph. I think one of two things. 1) M die is off 2) case thickness inconsistent. ! might be true, 2 certainly is. Can you gauge the M button itself? Anyway to mount that in a lathe or drill press and gauge it? And wound you actually be gauging a repeatable detail. For two, I think you have bumpy brass. When sized around the out side and measured on the outside, it does not show as the bumps are on the inside. But size the inside and measure the outside and you will see them. Are you set up to neck turn? Maybe someone can turn you a couple dozen to try.

[selmerfan]

All I need to neck turn is to get the .35 neck turning mandrel for my Forster trimmer. I’ve turned necks before. It’s one of my least favorite case prep tasks. I don’t have a good way to measure the M expander.


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[stubshaft]

All I need to neck turn is to get the .35 neck turning mandrel for my Forster trimmer. I’ve turned necks before. It’s one of my least favorite case prep tasks. I don’t have a good way to measure the M expander.


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For best accuracy, I prefer to neck turn my brass. I use a Lee case holder (from their trim set), chuck it in a portable drill and sit in front of the TV and go for it.

[porthos]

i've lost interest in shooting; but still have interest in reading about reloading and such. i'm on this site every day. so, here's how i set up my press when i did reload (i hope the interest comes back). i tighten the sizing die up, then crack it loose so that it has a little wobble. then tape a piece of duct tape over the lock ring taped to the press. it still wobbles, but, won't back off. i always thought that this will let the die float similar to a forester press. always wanted to run a test for runout with the die tight and cracked loose with a little little wobble so that it centers itself. something for you guys to try.