Grendel II chamber

[babaganoush]

Given my choice, I would always pick the SAAMI chamber in a gas gun. 2nd choice would be the LBC chamber, which has proven to be accurate with more than one bullet, though it was designed around the 123 Sierra and 123 Amax. The tighter neck (.295) most likely allows for better centering of the bullet in the bore. I actually just finished running a test on a 16" barrel in that chamber and it shot the 123 AMAX well. The last I would choose would be the GII, because it gives away the tighter neck AND the centering effect of the compound throat. Comparing the 3, the I can't find a single advantage in comparison to the other 2.

I agree, for the most part, Bill. Where the Grendel opted for a compound throat to keep (all) bullets better aligned to the bore, the LBC went to a slightly tighter throat to aid in bullet alignment. This reminded me of something I read in the not too distant past.

The throat of a rifle barrel is often an overlooked part of the chamber. The throat, however, is very important, especially as related to accuracy. The bullet engages the rifling in the throat. It's critical that the bullet make the transition from case neck to rifling without losing its axial alignment. It's possible for a bullet that is concentric with the bore while in the case neck to enter the barrel misaligned because of a sloppy throat. An oversized throat can allow the bullet to become distorted or canted as it enters the rifling. As a result the bullet will not be spinning around its center of form and has yaw while still in the barrel. When the bullet leaves the muzzle it will yaw even more, causing greater dispersion on the target than would otherwise be seen.

This information, not surprisingly, is found on one of the country's most respected barrel maker's site, Lilja Precision.

http://www.riflebarrels.com/articles/50c...50_bmg.htm

While written in the context of the 50, the fundamentals are the same.

Where I disagree with you is on the cause/effect relationship between the chamber and case neck. While I acknowledge your use of the words "most likely", I believe that without the Grendel's compound throat, it is more likely the case shoulders which provide bore alignment. The tighter throat will allow less deformation or off-axis movement on the part of the bullet.

The other benefit to the LBC's tighter neck is that the brass is worked less during resizing, though not a concern to those who shoot factory ammo, exclusively.

So, either way you look at it, the LBC has the potential to be more accurate than a similar chamber with a sloppier neck, the Grendel and its compound throat not withstanding.