11.5" Barrel Optimum Gas Port Size

[tom12.7]

Just to add emphasis to what Clint is saying. One rotation is just shy of .036", 1/8 of a turn is just shy of .0045". Getting to your desired tension span with required alignment maybe in very small increments of shim thickness. You would never want to use an individual shim that adds 2/3 or less of rotation to a base shim. You want to use a individual shim ideally, or a combination of shims that are thicker than 2/3 of a rotation. When the shims get too thin, they can fall into places that can cause all kinds of trouble.
As for the prior post on the KAC MOD2 11.5" gas port size. I hope that is a measured deviant rather than a newer spec. Deviations happen during manufacturing, KAC does like to drill holes. Not my ideal way, but I understand why they chose their process and I'm fine with it. It's also possible that they changed some other things that would require that port change, it's not a huge difference no matter what. I can't drop a .070" gauge in any of mine, with one exception for their legacies, Christmas Cheers, MOD1, or MOD2 barrels. One MOD1 could drop that gauge, but that particular one shot accurate enough that I would rather mask it with a step up in buffer mass than send it back. That example was only one of very many without that issue.

[Biggy]

Clint, I am planning on getting one of your BRT-11-5-OPTIMUM-CQB-Barrels (http://www.blackrivertactical.com/co...tegory=1852006) that has the barrels gas port sized for **both suppressed and unsuppressed use.** I will also be using the new Surefire optimized long stroke bolt carrier group in this build when they become available along with the new BCM enhanced upper when they are released. For now the suppressor I will be using will be the Silencerco Omega 300, with the Plan B adaptor and Cherry Bomb muzzle brake by Q. My question to you is, when using a bolt carrier group that has a non standard cam pin slot/track like the Surefire or LMT enhanced carrier that increases the dwell time of the bolt unlocking, do these type carriers have any bearing on the barrel's ideal gas port size for my application and (buffer weight and spring assembly), which would be both suppressed 90% and unsupprerssed 10% of the time. Also, could I preorder this barrel now ? Are we looking at September or October availability on these barrels ? Thanks

[tom12.7]

I'm not Clint, but I can help you with some of your questions.
Delaying the cam timing does reduce the gas port size required to cycle the action to a satisfactory full stroke with a margin the same being for either being equal for the action mass and spring selected.
The production Surefire offering for the standard bolt isn't really in the wild yet, but I do not expect major changes. The Surefire offering for this has a cam timing delay in between the standard and the LMT enhanced. The LMT enhanced BCG stroke length is the same as a normal BCG. With the LMT enhanced offering, the extended cam path increase the AOL of the extended BCG. Having a longer AOL with the standard stroke distance reduces the distance in the bolt face over stroking the magazine. Reducing that distance can decrease the amount of time for the magazine to function, that can hurt reliability when we aren't careful about using an action system that aids in the time delay of that event. The Surefire standard bolt offering has the extended delay that is between the standard and LMT offering, the Surefire uses a longer BCG stroke length that gives more distance in travel in magazine over travel over the standard BCG, that helps with magazine reliability issues as it it gives the magazine more time to properly present the round for chambering. The Surefire system requires a shorter lower mass buffer, the buffer mass is complimented by an internal buffer in the carrier to bring the total reciprocating mass up. The longer stroke for relatively equal masses can increase the gas required for a full stroke slightly.
For the application above, dedicating buffer mass to either suppressed or not individually would be best. That can be highly variable due to the selected ammunition and condition requirements.
There are many pros and cons going with any of the options available. We want to keep the bolt locked for as much time as we can, we want more time in bolt over travel to the magazine, ideally no less than a 20" RLG rifle action. With all of our available options, you would want to address major concerns over more minor ones for the combination chosen.

[feraldog]

Sooo...when will we get the 10.3?

.....ported for dedicated suppressor use.

yes please, but in 1/2x28 for use with a brevis direct thread

.

[Clint]

That sounds like a real nice combo, especially with the Cherry Bombed Omega.

Special carriers have somewhat limited utility in Optimum configuration barrels.

We're shooting for October availability on all 5 of these new OPTIMUM series barrels.

We've got a couple things to line up and then we'll open up pre-order for them.

Clint, I am planning on getting one of your BRT-11-5-OPTIMUM-CQB-Barrels (http://www.blackrivertactical.com/co...tegory=1852006) that has the barrels gas port sized for **both suppressed and unsuppressed use.** I will also be using the new Surefire optimized long stroke bolt carrier group in this build when they become available along with the new BCM enhanced upper when they are released. For now the suppressor I will be using will be the Silencerco Omega 300, with the Plan B adaptor and Cherry Bomb muzzle brake by Q.

My question to you is, when using a bolt carrier group that has a non standard cam pin slot/track like the Surefire or LMT enhanced carrier that increases the dwell time of the bolt unlocking, do these type carriers have any bearing on the barrel's ideal gas port size for my application and (buffer weight and spring assembly), which would be both suppressed 90% and unsupprerssed 10% of the time.

Also, could I preorder this barrel now ? Are we looking at September or October availability on these barrels ? Thanks