AR barrel throat depth

[beastep]

I plan on having the same way of measuring length but I just cant do it right now. I am also a firm believer in having as little unused volume in a round as possible.

[zcostilla]

BCA's chamber is a SAAMI chamber. They say type II to reference the 0.136 bolt face depth. I was confused about it at first, and wrote an email to them for clarification. As cheap as BCA is producing Grendel barrels, you might want to contact them, after all, they won't be out a ton of cash and labor, like Lilja would be.

[bj139]

BCA's chamber is a SALAMI chamber. They say type II to reference the 0.136 bolt face depth. I was confused about it at first, and wrote an email to them for clarification. As cheap as BCA is producing Grendel barrels, you might want to contact them, after all, they won't be out a ton of cash and labor, like Lilja would be.

Mmm. SALAMI.

[Crusty]

... and floor pie! Mmmmm
n6cNxBGnaufy-LHQyD15Nh1bsijGraU93J9yeX1Id68.jpg

[Redomen]

I was doing some load development for my 20” Radical firearms upper today.They use the type 2 clambering. I found my overall length to be 2.223 to clear the lands. My 16” Faxon barrel clears at 2.243. I was quite surprised.

[NugginFutz]

I was doing some load development for my 20” Radical firearms upper today.They use the type 2 clambering. I found my overall length to be 2.223 to clear the lands. My 16” Faxon barrel clears at 2.243. I was quite surprised.

Kind of makes you wonder what all the buzz about the Grumble II chamber solving all the short throat issues was supposed to be about.

As as far as I’m concerned, the GII was a solution in search of a problem, and only muddied what used to be clear water until all the type2 and GII nonsense started.

[Drillboss]

The group buy Faxon barrels did vary toward the maximum allowed by SAAMI. They still have the compound throat, but max COAL is a bit more generous.

[zcostilla]

Mmm. SALAMI.

My auto correct hates me

[grayfox]

Auto correct is more like Auto confuse.

[just_john]

beastep, have you measured to be sure that the correct depth bolt is, in fact, what you have? A .125 bolt will put the bullet into the lands.

[NugginFutz]

beastep, have you measured to be sure that the correct depth bolt is, in fact, what you have? A .125 bolt will put the bullet into the lands.

Likely, it would not. With a chamber headspaced for a .136" bolt face, the case shoulder would be set against the chamber, just as it would with a properly surfaced bolt. The bullet would not present any further into the throat. If anything, the bolt would be prevented from going fully into battery.

[beastep]

Good to know. This short throat thing on all these barrels really surprises me.

[beastep]

beastep, have you measured to be sure that the correct depth bolt is, in fact, what you have? A .125 bolt will put the bullet into the lands.

I have not but they were both ordered from BCA and the bolt is marked Grendel II. I dont think that would make any difference on presenting the bullet too close or into the lands anyway. But correct me if Im wrong.

[beastep]

BCA's chamber is a SAAMI chamber. They say type II to reference the 0.136 bolt face depth. I was confused about it at first, and wrote an email to them for clarification. As cheap as BCA is producing Grendel barrels, you might want to contact them, after all, they won't be out a ton of cash and labor, like Lilja would be.

I will contact them for clarification.

[LR1955]

Guys:

Lets say you have a piece of empty Grendel brass. Sized and ready to load.

If you tried to chamber it in a Grendel chamber using a 7/62 X 39 bolt, it would NOT chamber. The empty brass itself would not chamber, let alone a loaded round.

If you used a Grendel bolt (.136 face depth) with a chamber cut for the 7.62 X 39 bolt, it most certainly would chamber and would shoot. You would note the shoulder got blown out enough for you to see it with your own eyes. Kind of like shooting a .308 out of a 30-06 chamber but not as blown out. You will not blow up your rifle, either. I blew out a few pieces of Grendel brass this way deliberately many years ago in an experiment I was running. The experiment was a failure but I was never worried about damaging the rifle. No, I would not shoot a diet of ammo through this combination of bolt and chamber.

Short throating and head space are two different things. You can have a perfectly headspaced chamber with a short throat that won't let you chamber a live round without having to seat the bullet way deeper than any loading manual would advise.

Short throating is generally cured using a finishing reamer.

LR55