wildcat cases and neck tension

[gene so]

Hello,
I have a 29.5 inch Krieger 6.5 barrel chambered for a shortened .308 based cartridge called a 6.5 IHMSA. This cartridge has the same liquid capacity as the 6.5 x 47 Lapua.

Its been some time since having this made. Lapua Necks are turned .010 to fit the chamber. I noted when after making the cases that when fired a few times, the case necks did not expand enough to need to be sized. This left me puzzled as the loads were warm for this sized case.
I also noted the fact that a well known name in 1,000 yard competition when using the 6.5 size rifles turns his necks so he has .004 neck clearance in his chambers and that this extra clearance results in excellent accuracy.

Since I am making up some new cases from .308 Lapua, I am wondering if the lack of expansion on firing, and the factor of extra neck clearance for better accuracy cannot somehow be related? This barrel gave me 1/2" groups at 200 years ago and has not been fired since.

Thanks in advance for any experienced answer in dealing with this situation.

 

[Immike]

If you cannot put a bullet in a fired case or it doesn't need resizing then you want to do some measuring. The release is important for pressure consistent shooting and just a better setup. I have ran them too tight and pulled some hair out doing it.

 

[FergusBailey]

Based on what you are describing, you do not have enough neck clearance. If you cannot easily push a bullet into a fired case, you are compromising accuracy and may be operating at dangerous pressures. You need to turn the case neck after forming your cases.

 

[CatShooter]

When I first started shooting my 6mmBR, I cut the necks close (1 thou total clearance).

It shot well, but was a real princess. and needed the case necks and chamber necks cleaned all the time.

The necks were like yours - I could reseat a bullet without sizing.

But the whole thing drove me crazy, so I re-turned the necks for a 3 thou total clearance, and it became an instant joy to live with.

 

[gene so]

Hello,

This weekend has involved doing a lot of measuring on all possible reloading components and also some loaded ammo. Things learned: one sizing die I have is out of whack, the second ( custom made one) is correct and keeps the necks concentric after sizing. Now the loaded ammo when measuring the neck is only .001 less then the chamber neck, despite the fact I turned these necks exactly to .010 and should have had .002 ( I used my pumpkin turner) clearance. This really startled me, but made sense as to why the cases never expanded ( seemingly) when fired. I shall now be turning the necks to .009 and foresee, as you have stated regarding the 6BR, that these problems might all disappear.

I really appreciate the experienced insights to this problem. Thank You