Home Forums Hunting & Shooting Ask The Gunwriters bullet run-out from seating

I'm getting an additional .005-6" bullet run-out from seating. Using Sinclair concentricity gauge for checking: Neck run-out prior to seating is .001-2" and .007-8" after seating. New brass and using Forster Bonanza bench rest seater. Neck mouths have been chamfered. Sierra .270 130s. Suggestions? thank you.

Check neck thickness. See if it is even all the way around.

What bullet? Your seating plug should fit the nose of the bullet. If using a VLD type of bullet the plug should be a VLD style. I have made "custom" seating plugs for specific bullets by using the same plug or an oversized plug and filling with JB Weld to match the countour. I wrote it up here if you do a search or I can find it for you. It made a huge difference in my .358 Win and 225gr Woodleigh and in my 6.5x54 M-S and 160gr Horn RN

Redding supplied me with free plugs and even made suggestions on what size to get after I told them what I wanted to do.

What Sakoluvr posted--especially about checking for even neck-thickness.

Above plus rotate the case 90 to 120 deg while partially seating the projectile each time.

Sheriff Joe,

I have heard that suggestion dozens, if not hundreds of times, so finally decided to check it out, thoroughly testing it when loading several cartridges. It never worked consistently--while checking for even neck-thickness has, along with checking neck-straightness on sized cases.

Sorry to hear that, Mule Deer...I get great results with everything else above considered, am getting .001-.003 (usually) and try to reduce concentricity runout to .0015 or less for 6.5CM, 7mm, .270 and .308/7.62.

Never had ANY of my Forster BR seaters (.260 Rem, 270 Win, .308 Win, 300 WSM) add 5-6 thou runout. +2 thou is about max for me with 0-1 thou more typical.

Something else going on here. Like previously said, see how the bullet engages/contacts the seater plug. Could be the seating stem hole is not concentric with the die body.

What's bullet runout at the ogive? That's what matters.

I still neck or FL size new brass, before chamfering, and even with a VLD chamfer tool, I still like to wrap 0000 steel wool around an undersized brush to polish the sharp edge that still occurs in the neck.

New brass is sticky.....try some motor mica, or moly powder on the bullet.

thanks for your input. To address some questions: run-out is .007" at the ogive. The bullet (130 gr. Sierra SP) seems to fit just fine in the seating stem. Contact of the bullet in the stem is just forward of the ogive. I have seated one bullet with the lock ring of the die not tightened. This reduced the run-out on this one bullet to .004". I've checked neck thickness at 4 points inside the neck and with a caliper it varies about .001- .0015".

How does the the Sierra seem to fit just fine in the seating stem? If you remove the stem and hand-insert a bullet into it, can you feel any wobble? A Redding VLD stem won't let a typical high-BC bullet wobble at all with that same test.

A caliper really doesn't do the neck-thickness job accurately, mostly because the angle of the caliper "jaws." The most accurate measurement is a tool uses a dial gauge to measure the thickness as the neck's spun around a mandrel. Though with typical hunting rifles, trimming the brass and then lightly chamfering, then looking DOWN at the shiny case-mouth with a magnifying glass will reveal obvious neck-thickness differences.

Well said, Mule Deer!!

It is surprising how accurate the human eye can be at capturing even slight unevennesses in neck thickness by just looking down at the shiny, newly trimmed case mouth!

Alvaro

Your seater die is not set up properly.

The USAMU has some great write ups on setting up dies. They have been published on several sites. A quick Google search should locate them and others.

1. Are you measuring the runout in the same place before and after seating?

2. Full length size your new cases to see if you can improve run out.

I suspect you are measuring the bullet after seating instead of the neck. In angular misalignment, the total misalignment appears to get worse in direct proportion to how far you are away from the original reference point. In reality it does not get worse but appears so.

Sounds like inconsistent neck wall thickness. Turn and ream.

The fact that you can reduce run out by seating tells me there is nothing wrong with your die. In fact, there is very few dies that can do what you accomplished.
If you start with runout on the case, you will get runout on the loaded round.

Any case wall thickness variation at the neck is also in the shoulder and upper body of case too. Scrap the cases that have wall thickness variation that you feel is unacceptable.

Short read here

well, it appears that the issue is the brass. Here is what has occurred. I decided to re-size a group of my old used Winchester brass. The procedure was to full length size with the expander button left out. Then decapped with a Lee universal decapper. Finally used a Sinclair expander die for the neck. Prior to seating, I chamfered the inside necks to a greater degree than I have before. Neck run-out before seating was a consistent .001- .0015". Then seated the same Sierras I'd tried before. Bullet run-out is now running from .001 to a max. of .004". The new brass I was using originally, Starline, was very consistantly running .007" after seating. I had not annealed the new brass prior to prepping it. My target shooting cousin, a VERY experienced shooter and reloader, says he always anneals new brass. I can feel a difference from bullet to bullet as it slides into the neck: the smooth, less resistant feel always ends up with less run-out. Not sure of what is causing the inconsistency. So the issue is definitely not the seater die. thanks for all the input.

Good info.

This is how I set up my seater die..
This was written by AMU
http://bulletin.accurateshooter.com/2019/06/tech-tip-how-to-reduce-run-out-with-seating-dies/