BRT 16" OPTIMUM Barrel w/ Extended Length Gas System

[elephantrider]

Yeah
..I didnt word that correctly as accuracy and barrel life are user dependant. I knew better, so apologizes there.
The gas length is interesting. What was the impetus behind this length?

No worries. Re: Gas system length; here is my mildly informed readers digest version. I believe KAC started their version of the intermediate in the SR-15, and Noveske did theirs on 18" barrels. Reason? As you lengthen the gas system the pressure at the gas port is significantly reduced, which also can shorten the recoil impulse, and reduce the stress on the bolt. Google AR-15 gas port pressure, and you should see some graphics illustrating this. So in theory you get a barrel that is a little softer shooting, and puts less stress on the bolt, and possibly slightly less gas port erosion.

[BufordTJustice]

No worries. Re: Gas system length; here is my mildly informed readers digest version. I believe KAC started their version of the intermediate in the SR-15, and Noveske did theirs on 18" barrels. Reason? As you lengthen the gas system the pressure at the gas port is significantly reduced, which also can shorten the recoil impulse, and reduce the stress on the bolt. Google AR-15 gas port pressure, and you should see some graphics illustrating this. So in theory you get a barrel that is a little softer shooting, and puts less stress on the bolt, and possibly slightly less gas port erosion.

Correct. Moving the gas port further from the chamber also has the side effect of permitting slower unlocking of the bolt during the firing cycle if gas drive (gas pressure and duration determine overall gas volume) is optimized.

And, Clint has most assuredly optimized this system because he wasn't chained to anybody's existing print regarding port location or port diameter.

[Glockman1968]

Ah..now we're getting somewhere.

What would the difference be with a "properly" gassed 16 middie with a Vltor A5H4?

[C1-2DG]

Clint,

I really like where you've gone with this barrel. Would it be possible to order the 16" Optimum, pre-drilled for the Micro Pin/Tune gas block (but the gas block not installed), and the Micro Pin/Tune block with a pre-installed 0.073" port, a spare 0.076" port, and a spare spring pin?

Basically out of the box I want to slide an ALG barrel nut on, pin the gas block without a need to drill, test it at 0.073", and switch it out using the 0.076" port if needed (using that fresh pin for the second install).

Thanks for bringing this product to market!

S/F

[Clint]

Lengthening the gas port location does a few things.

It starts the gas pulse later and at lower pressure due to the port being farther down the barrel.

It also increases the gas delay due to the gas tube being longer.

Moving the port also doubly reduces the total gas impulse (which is Pressure x Time) available at the gas port and reduces the Power Time (sometimes called dwell time).


It takes time for the bullet to exit the barrel and the pressure to blow down.

Starting the cycle later also allows the pressure to blow down more before the action unlocks, which reduces the effort required to unlock and extract.

This all add up to cycling that starts later at lower pressure, lowering stresses while unlocking and extracting.


As with everything, there is a balance here. Go too far and the total gas impulse is too low and too short to reliably cycle the action, regardless of how big the gas port is.

[Glockman1968]

No wonder BufordTJustice snatched one PDQ..well I'm damn interested to see what the block will do thats
coming. So if I'm getting it, it will be softer than that?

I ordered a .076 block from Clint for my gassy 16in middie w/ Vltor -4.

Mighty intriging indeed.

[elephantrider]

Ah..now we're getting somewhere.

What would the difference be with a "properly" gassed 16 middie with a Vltor A5H4?

A properly gassed mid-length should not need a buffer that heavy. If it runs reliably, which many will with that buffer combo, it just absorbs more of the recoil impulse, but may also give a little more muzzle dip as the BCG goes back into battery. If it is gassed correctly, I can't see anything heavier than a A5H2 adding anything to the overall reliability, or performance of a carbine. Pretty sure the A5H3/4 buffers were intended for piston/suppressed guns.

[Clint]

A properly gassed mid-length should not need a buffer that heavy. If it runs reliably, which many will with that buffer combo, it just absorbs more of the recoil impulse, but may also give a little more muzzle dip as the BCG goes back into battery. If it is gassed correctly, I can't see anything heavier than a A5H2 adding anything to the overall reliability, or performance of a carbine. Pretty sure the A5H3/4 buffers were intended for piston/suppressed guns.

Exactly.

His existing MID barrel has a large gas port (~13% more gas drive) that isn't tamed with the H4 and green spring.

That's where our MicroTune Gas Block comes in, making the barrel properly gassed.

[Glockman1968]

Exactly.

His existing MID barrel has a large gas port (~13% more gas drive) that isn't tamed with the H4 and green spring.

That's where our MicroTune Gas Block comes in, making the barrel properly gassed.

Oh how I enjoy learning.

Now to your barrel Clint. So in theory (my words), your barrel would be "softer" than a "properly gassed" 16in middie with a A5H2?

Buford, where are you? I very much would like to hear more of your take on this innovation as well. Lol ...I'm going to wind up getting one. The suspense will kill me if I dont...damn AR's..

[BufordTJustice]

Oh how I enjoy learning.

Now to your barrel Clint. So in theory (my words), your barrel would be "softer" than a "properly gassed" 16in middie with a A5H2?

Buford, where are you? I very much would like to hear more of your take on this innovation as well. Lol ...I'm going to wind up getting one. The suspense will kill me if I dont...damn AR's..

Your assumption is correct if overall weapon weight is the same. Weight reduces recoil on a 1:1 basis. Double the weight, you get half the free recoil. Hence the qualifier.

I'm 100% in agreement with Clint and elephant rider. I've got one on pre order.

Clint and i have been saying for a while now that this intermediate gas system with an optimized port size is simply a better mousetrap than any 16" middy. ESPECIALLY considering the proliferation of suppressed setups being employed by users.

Clint has developed the best combination of gas port diameter and gas system length, that functions in the widest variety of setups (suppressed and unsuppressed, light bullets and heavy bullets, SAAMI ammo and NATO pressure ammo, clean and fouled, etc) that you can shoe-horn onto a 16" barrel.

Now, it is certainly possibly to make a 16" rifle length gas system barrel work. Several companies already have. But it won't have nearly the margin for function when dirty or the breadth of operation with varying conditions (bullet weight, ambient temperature, amounts of fouling, etc) as Clint's barrel. And, that's not opinion, that's just math.