BR Discussions > Centerfire Discussions

Neck size diameter

<< < (4/4)

duceman:
next node sitting in line..............

Mr. Jeffery:
  this is 26.9 at 300 yards. mild wind -1-4 mph.  as you can see by the one flyer that meessed up the group. I got second place for this.. 1st place was 0.856 or some such nearby number

danyboy:
 I am new in benchrest. When you guys say '.001-.002' neck clearance, do you mean total (for both sides) or per side ?  Just built myself a 6BR with a Shilen Barrel that has a .272" chamber neck. Loaded case neck using brand new Lapua Brass is .270". Fired case neck is .271". I bought a Forster bump/neck sizing die and currently trying to purchase the wright size bushing. Virgin Lapua Brass neck OD is .267". 
 Would a .267" bushing be appropriate ?

hendershot:
Hey danyboy,

When the guys talk about clearance, they are referring to total clearance. .002" clearance would be .001" per side for example.

With regards your particular situation, the neck clearance of your Lapua brass looks like a good place to start - .002" No need to turn the neck diameter down unless you want to clean the necks up a bit and/or feel like adding more clearance for whatever reason. As for neck bushings, I would try a few different sizes and see what kind of neck tension your rifle/load likes. Perhaps .267" on the tight end to .269" on the loose end? I don't shoot a 6BR so can't really say what a 6BR likes for neck tension. Another thing to keep in mind is that your bullet could have a pressure ring at the base of around .0005" The bullet makers in the crowd can confirm or deny this dimension. What this means is that your actual loaded OD could be .2705" measured at the pressure ring with the bullet seated. If you're using longer bullets in your 6BR, the bullet's base could be down below the neck/shoulder junction. Just measure the bullet at it's base and compare that measurement with a measurement taken just a tad further up the jacket. Some will argue that tight neck tension is a good thing because if you're running a compressed powder charge, the tighter neck tension will keep your bullet in place where as minimal neck tension could push the bullet out some. Seating depth considerations are an important step in load development and consistent seating depth is one of the critical aspects to shooting small groups. Consistency is key, even if you're doing things all wrong, do so consistently.  :D

Navigation

[0] Message Index

[*] Previous page