Full length sizing.

[dtknowles]

I just neck size for my bolt guns. Each gun is marked with a small painted square on the receiver, and the ammo for each gun has the same color painted on the case, and the boolit powder coated to match. It makes life easier when the boys and I shoot multiple guns of the same caliber.
Anyway, why full length size for a semi auto if the brass is going to be shot in the same gun? The chamber doesn't change.

Do you truly neck size, use neck sizing dies?
Why do you neck size? Brass life, don't like lube, or other reasons?

Neck sized brass grows with multiple firings until it becomes quite tight in the chamber, partial full length resized grows even faster.
Tim

[jss227]

I use neck sizing dies. To extend brass life. Don't mind lube.

[dtknowles]

I never heard that neck sizing extends brass life. High power rifle brass usually fails with neck splits or loose primer pockets. Keep the pressure low and the primer pockets will not get loose and anneal necks so they don't split. I neck size for my 6mm PPC bench rest rifle using bushing dies because it was the thing at the time but now many bench rest shooters full length size with no harm to accuracy or so they claim.

How do you think neck sizing extends brass life?

Tim

[blackthorn]

Quote: "How do you think neck sizing extends brass life?"

If you have a tight (or match) chamber it will not. If your chamber is cut on the large size it will because the brass will not be subjected to over-working. I think neck sizing will likely also aid in producing concentric ammunition as it will not interfere with the perfect brass-to-chamber fit.

[dtknowles]

Theory and practice. What seems logical is not always better in the real world. The part of the case that gets work hardened by full length sizing does not get over worked to the point where it fails so full length sizing does not reduce case life. I have never seen a case that fails in the body from work hardened cycling. Cases fail due to neck splits, primer pocket expansion or case head separation. None of those failure modes are exacerbated by full length sizing if the sizing die is set properly. Pushing the shoulder back too far can lead to case head separation due to improper head spacing. Best practice for setting up full length sizing dies is discussed elsewhere on the forum but might benefit from reiteration. Improved accuracy from neck sizing is a sometimes, maybe even most times thing. Like I said, I use bushing neck sizing dies on my 6mm PPC because it was the thing that was best practice at the time.
If a chamber is not concentric to the bore a fired case will be cockeyed and when neck sized will remain cockeyed. When the round is chambering the clocking orientation of the cockeyed case will be random so the case will bear unevenly on its neck (pushed to one side) not always the same side but randomly. The better the bore to chamber alignment the less this is an issue, and you would think that with precision rifles this would be less of an issue, but bench rest shooter are more going back to full length sizing albeit with precision dies that are made to match the chambers more precisely than stock dies.

The only way to know if neck sizing improves accuracy is to try full and neck sizing and see which is better with a given gun, case, die, bullet combination.

Tim

[trails4u]

bench rest shooter are more going back to full length sizing albeit with precision dies that are made to match the chambers more precisely than stock dies.

Bingo! THIS is why all the best BR shooters are now claiming FL sizing is their go to. If I had a FL sizing die cut from the same reamer as my rifle chamber....I'd probably feel the same way!!

[Rapier]

I neck size my fire formed bolt gun or single shot gun brass. Any gun that I can manually seat loaded brass into is neck sized. The brass scatterers get full length sized. All brass gets a full preparation top to bottom, fire formed then segregation by H2o capacity, marked on the base with a dental burr. Alloy is made in 100# lots, Bullets are segregated by weight to 1/10th grain, then lubed. All loaded ammo gets the "plunk" test in the barrel they will be fired in, before we go out to the match. In silhouette competition there is no mulligan, you have a gun or ammo failure, you loose a target and you loose the mach in the higher classifications. Very simple rules. The practices of the 6Ps cross over to all reloading I do.

[MostlyLeverGuns]

My experience with partial resizing is that the more taper a case has and the longer the neck, the more likely partial resizing will work, does not work for me in .243 Win or .308, does in the thin-brass of the 30-30. Semi-autos sometimes unlock faster than the brass can 'contract' after firing, stretching brass. Mild loads do much to extend brass life, as do carefully adjusted sizing dies. I use Redding Competition shellholders so that my full-length sizing works the brass just enough to allow rechambering without 'squeezing/pushing/forcing' bolt closing. Many light loads can actually shorten brass due to the primer force on the case pushing the case forward in the chamber. I carefully full-length resize when reliability is really critical(hunting) and the 223'ss that are used in a Mini-14 and a couple AR's. My range rifles, it depends on whether the fired brass chambers easily before processing, YMMV.