Home Forums Reloading Big Game Rifles Bullet Runout When Resizing?

I got some new Lapua 260 Remington brass and they measure .001-.002 runout out of the box, measuring on the neck. I resize using a brand new Redding Master Hunter full size reloading die in a RCBS single stage press. After resizing most of the cases have .003-.004 (a few even even .005) runout. I have been measuring each case before and after resizing. Does this make sense? Any idea what is causing this or what I am doing wrong? Thanks.

The Master Hunter set comes with a standard full length sizing die. It is not a match grade die, and has the sizing button in the standard location, at the end of the decaping pin. The further down the decaping pin the sizing button is located, the greater the opportunity for the introduction of additional runout.

So, is there anything I can do to lessen this problem, short of changing dies?

Try this: Size a piece of brass without the expander in place. Measure the neck outside diameter. If it's more than two or three thousandths smaller than a case neck that has been over the expander ball, then the die is sizing that particular brass more than necessary. This contributes to runout.

I'm also not a big fan of the standard straight sided Redding expander ball, if that's the one your die has.

It can.

I have never measured runout but if I am following this correctly, if I decap with a universal decapper, then move my expander up as high as I can, it should help make better brass? miles

It can help.

Just don't move it so high it binds the brass in the neck portion of the die. Go to Forster's website, it's a feature of theirs.

Look at the Notice box on page 2:

http://www.forsterproducts.com/clie.../Full_Length_Sizing_Die_Instructions.pdf

Just ran to reloading room. New brass (right from box) is fairly consistent at .291 measured on the outside of the neck, at the case opening. Removed the decapping pin and resized; outside diameter went to .284 and runout stayed at .001. Reinserted the decapping pin and didn't screw it in as deep (less pin showing) and runout went to .004 and exterior diameter went to .292.

I think it is "straight walled"- has shallow checkering for maybe 1/16th inch right above the pin; is not a "ball".

It's sizing that Lapua brass more than necessary. Conventional FL dies are usually made to work OK with the thinnest brass on the market, which means they're less than optimal on everything else.

There is no need for you to size the new brass.

If you want to continue using the FL die in the conventional manner, then consider springing for the carbide expander ball Redding offers.

If you want to go to sizing and expanding in separate steps, which often does help runout with standard dies, get a tapered expander ball from Redding.

I believe your die set came with Redding's good seater, so if I were in your shoes I'd look at a Lee collet die for neck sizing. I tell you from long experience that a Lee collet die and a Redding competition seater (or a similar Forster) is a very effective combination for producing low runout cartridges.

Mathman- Think I will try the tapered expander ball first and see if that help, and go to two steps. Will update results in a week or so when I get it. Thanks.

Consider getting a tool to measure case neck wall thickness. Bad case necks will cause trouble no matter the die set.

Your Lapua should be good, but since you're interested in precision you should know for sure.

Mathman- Forster can custom hone the inside neck diameter of their full length resizing die for Lapua brass which evidently has thicker neck walls than normal. Think that is part of my problem, so I just shot them an email to ask how to order. Thanks for all your help on this.

One of the easier solutions for good brass (like Lapua usually is) would be one of Redding's "S" sizing dies, with interchangeable bushings in the neck section of the die so the neck can be sized down exactly the right amount. Then, if you decide to use another brand of brass, another bushing can be easily interchanged for that brass's neck thickness.

In a similar direction I mentioned the Lee collet die earlier.

Bingo.

Die parts for both Reddings and Forsters are a godsend for these situations; rod assemblies, floating expanders and even different size or shape expanders can make standard dies even run oversize cast or overtly thick cases behave at match grade levels.

Looking at the Redding S dies, they make the 260 Remington bushing in .001 increments from .287 to .295. If my Lapua brass is consistently .291 outside diameter at the neck opening, does anyone have any idea what size(s) I should get?

The average outside diameter of empty brass doesn't provide the right information.

You need the average thickness of the neck itself. You can measure this with a caliper or specialized tool, but a simple (and good) method is to seat bullets in a few cases and THEN measure the neck diameter. (Or maybe you're doing that?)

What you need is a bushing that will size the neck .001-.002" under bullet diameter. For instance, if the neck thickness of your brass is .012", then you need to double that (there are two sides to the neck). That comes to .024". To end up with a .263" inside diameter on the sized neck, you'd need a .287" bushing (.287 minus .024 = .263).

The thing about bushings is, it's hard to get away with just one per chambering. Measuring OD or ID with calipers is just not that precise.

The way I do it is measure the OD of a loaded round (or preferably a few rounds) subtract .002" from that, buy that bushing and the one just above and below it so you have it bracketed.

Sometimes a simple solution fixes the problem. Try turning your expander ball stem 1/8 turn at a time and checking run out after each turn.

Before doing that remove the expander ball and stem. Leave the die a little loose in the press and run a piece of brass up into the die,then lock the die down.This will center your die as best as it can. Maybe not perfect

I do not have anything but standard RCBS dies and can turn out rounds with less than .003 runout consistently, maybe with 3-4 out of a hundred more than that and that is with Rem ,Win,Federal and a little bit of Norma brass

Mule Deer- if I understood you correctly: I seated four different bullets (Nosler and Hornady) and everyone was .294 on the outside of the neck.

So, .294 - .263 = .31.

So, if I want .263 I add the .31 and order the .294 bushing (and maybe one above and below)?