Neck length

[krallstar]

I am making 7.62x40 brass from LC 223 for ar15. The specs call for a neck length no longer than 1.570. i measured the throat using a sized case. Cut most of the neck off. Then cut another small piece of neck off another case. Seated the bullet to mag length. Slid the small piece of neck over the bullet and then chambered the round. oal stayed the same. I got a neck length of 1.590. My question is do i want the neck as long as will fit in chamber. Is there any benefit to a long length neck.

[BK7saum]

A neck length that is close to max of the chamber would be beneficial if you plan to shoot cast boolits. For jacketed bullets, it won't matter. Cast can bump up in the gap between the neck and throat and cut a ring from the boolit as it is forced into the barrel.

[Larry Gibson]

"My question is do i want the neck as long as will fit in chamber. Is there any benefit to a long length neck."

Yes.

Better consistent alignment, especially with cast bullets. Less room for unwanted obturation of bullet prior to entering the throat. Covers more of the lubed part of a cast bullet and better potential of keeping all or part of GC in the neck.

[krallstar]

Great, Thought i read something about the cut ring.

[Bashby]

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