Today I was talking to a friend about hand loading rifle ammunition and the topic of accuracy came up. Accurate ammunition is usually very straight or concentric ammunition meaning; the case neck and the bullet, when it is loaded into the case, are parallel with the centerline of the case. Start a bullet down a barrel straight and it will generally come out and fly straight. Course, trigger pulling matters too but we can all shoot great from a bench – or we at least like to think we are Walt Berger!
Checking the concentricity of your brass before you load a bullet into it is the smart thing to do. (Ever seen an archer look down their arrow? Guess what they are doing!) You can do this with the RCBS Case Master. Just position the case so the ball tip rests on the case neck near the case mouth. First check the concentricity of fired brass. This will tell you if the chamber in your rifle is cut straight. If you are seeing a neck run-out of more than .003 in fired brass, you have a rifle problem.
If fired brass shows little or no run-out, size five cases and check the run-out of each case. If it’s over or varies more than .003, you have a problem with your sizing die and it’s likely the expander ball that’s causing it. Remove the expander rod and ball from the die and run those same five cases back through the sizing die. Odds are that case neck run-out will drop below .003 for every case.
I rarely use the expander ball when sizing cases. Most often I replace the expander ball that comes with the die with one from the next smallest caliber so I can continue to de-prime while sizing. This leaves the case mouth about .003 to .005 smaller than what it would be if the expander ball was used. I have yet to see this cause a problem when seating bullets – even flat base bullets – especially if the inside of the case mouth has been chamfered.
To illustrate the difference an expander ball can make I took 10, once fired, .243 Winchester cases and found the neck run-out of each case was less than .001. I then sized five cases with the expander ball still in the die. Neck run-out after sizing was between .003 and .006. I then sized five cases with the expander ball removed from the die. Four showed .001 run-out and one showed .002. I then re-sized the first five cases and all had run-out of less than .002.
To see how well lubrication inside the neck might help keep necks straight when using an expander ball, I sized five more .243 Winchester cases with lube applied to the inside of the neck. The results were better than when lube was not used but not as good as when the cases were sized without an expander ball. If you try this method just remember you will need to tumble your cases afterwards to remove the gooey lubricant inside the case neck or your powder will stick to the case neck when you try to put it in the case.
If you are not concerned with sub MOA accuracy, then I’d suggest you not waste your time with any of this. There are a lot more fun things to do with your spare time. For instance, you could go shoot or maybe watch a reality cooking show on TV.
Richard, I enjoy your writing but this is a topic that has practical application, thank you. As part of your test process I would also like to have seen the groupings for expander vs non-expander reloads. I know that two groups would be statistically insignificant but it would still be interesting.
Again, thank you and keep writing
John,
I’ve conducted tests like that with handloads and factory ammo. I’ve found that with bullet runout (after loading) of more than .005 it can be very difficult to shoot sub MOA groups. Its so apparent that you can sort factory ammo by runout and make rifles shoot better. (That’s an old gunwriter trick – No, I don’t use it when I’m testing guns.)
Richard,
I follow John Barsness’ practiced of removing the expander stem to resize the case. First run case into sizer die, then re-install expander and push it into the case on a second trip into the sizer die. This seems to do less damage to the case than pulling it over the expander.
jim
Jim,
John taught me that but I found out there is not reason to use the expander ball at all.
Richard
I’ve been doing the same thing, resizing without the expander ball for years. No loss in accuracy that I can detect. Stretches the brass slightly less also.
Awesome advice regarding run-out. Something i never thought about until reading your article.
Thank you.