BRT OPTIMUM Barrels

[everready73]

Clint total side bar, but thoughts on port size for 11.5” cut down SOCOM barrel? 50/50 suppressed use.

Will .0625 run?


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@jpmuscle

I bet it would run based off of the below vid of a guy testing the Sionics ERGP 11.5 barrel. I could be wrong but believe .0625 is the port size on that barrel.

The guy tests both suppressed and unsuppressed with several ammo types and buffer set up

I am sure Clint has info as well, just a good short video showing actual testing

https://www.youtube.com/watch?v=USKt2byOuFc

[jpmuscle]

Yea I’m tracking. My reading says it should shoot well.

So, .0625 it is.


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[1168]

14” cycles blanks with yellow BFA, H1, and Sprinco Hot White, in case anyone’s wondering.

[Clint]

Good info.

Thanks!

14” cycles blanks with yellow BFA, H1, and Sprinco Hot White, in case anyone’s wondering.

[jerrysimons]

Was NP3 considered for barrel extensions? If so why did you choose NIB. Thanks

[jerrysimons]

These are some excellent points, so let's parse through them.


Its true; a light rifle will tend to move around more than a mid-weight rifle.


A brake tends to add a little gas drive, while a light weight reciprocating assembly requires less gas drive.

The combination of the two points to a smaller port size.

There are many factors to consider and we don't want to sacrifice reliability just to get ultra light recoil.

Again, the standard gassing is setup for full weight reciprocating parts with an A5 buffer.

Overly strong springs are generally not helpful with our barrels.

Yes, a strong spring can absorb more recoil energy, but then it returns more energy during counter-recoil, producing higher bolt closing speeds, more muzzle dip and bolt bounce.

OPTIMUM gas drive does not provide for gobs of extra energy to work extra power springs with weak ammo.

The ejection pattern is interesting but also one of the intentional results of our configuration.

OPTIMUM is relatively insensitive to ammo selection.

The ejection angle and cyclic speed with different ammo changes relatively little compared to other configurations like 16" MID or CAR.

This is a good thing, as we'd like any ammo to run nicely and don't always get to choose the loadings ( issued, availablity, stockpile, etc)

Due to proper timing, OPTIMUM is relatively sensitive to changes in reciprocating mass or buffer weight.

This is also a good thing, as we can generally control the buffers and carriers used.

Shorter gas systems show a variable amount of unlocking friction.

With them, lighter buffer unlocks sooner under more friction, so it gets lets impulse to cycle, but needs less due to the lighter weight.

Similarly, a heavier buffer unlocks later under less friction, so it gets more impulse to cycle, but needs more due the higher weight.

This effect is somewhat self defeating when heavier buffers don't slow down the action as much as expected.

With OPTIMUM, the unlocking friction is low and relatively constant, so a lighter buffer cycles faster and a heaver buffer cycles slower, as expected without the variable unlocking friction forces.


The lightweight reciprocating assembly and aggressive brake need a bit smaller port to run best.

Just reread this whole thread. This post here is Gold. I can’t tell you how much I like what you are doing. All the stuff I have messed with over the years tunning ARs are just band aids. This right here is how to do it right.

The principle of lengthening the gas port relative to the barrel length to not only to replicate the power/dwell time of the 20” rifle length gas but to also scale it to the point where the gas port accesses the pressure curve at the right spot is the missing link in my puzzle. Sure you can restrict the gas port on a 16” mid length but the BCG is still being pressurized at higher pressures inside the barrel which nets earlier BCG charging and movement/unlock. This helps to understand why it is possible to restrict the gas port on 16” mids and still run LMT e carriers with heavy A5 buffers and SpringCo green. It gets to the point of absurdity compensating for the less than ideal gas port sizing AND port location of most barrels, which also comes at the expense of high cost, increased barrel dip when return battery and overall weight.

[scooter22]

A couple questions, Clint:

1) Would the following set-up be feasible? 11.5 EXC tapered shoulder + 5/8-24 Cherry Bomb/Plan B + YHM Turbo K

2) Can we expect to see a 12.5" BRT?

3) What are your general thoughts on 10.3/10.5" CAR systems? Any particular reason you haven't offered one?

Thanks

[AndyLate]

Clint, does your Covert Comp appreciably increase gas drive? I am currently running one on an 11.3" carbine gas 5.56, and am a fan.

Thanks
Andy

[Clint]

No they don't seem to add much Gas Drive.

Clint, does your Covert Comp appreciably increase gas drive? I am currently running one on an 11.3" carbine gas 5.56, and am a fan.

Thanks
Andy

[Clint]

Yes, the SBT/CB/PlanB/TurboK is going to be an awesome combination.

We may do a 12.5/13" EXC if there is interest.

Many other companies produce a variety of configurations, seemingly without rhyme or reason.

We only offer OPTIMUM configurations.

The 10.x" CAR configuration is a little short for general purpose unsuppressed use.
The 11.5 CAR is better for that.

We do offer the 9" PDW for something more compact than 11.5".

A couple questions, Clint:

1) Would the following set-up be feasible? 11.5 EXC tapered shoulder + 5/8-24 Cherry Bomb/Plan B + YHM Turbo K

2) Can we expect to see a 12.5" BRT?

3) What are your general thoughts on 10.3/10.5" CAR systems? Any particular reason you haven't offered one?

Thanks