Sionics 11.5 barrel w/ reduced gas port function report.

[BufordTJustice]

I was fortunate enough to snag one of these very limited run barrels that were developed for a law enforcement agency's SWAT team rifles. They are used suppressed, with H2 buffers to great effect by the agency and I got in contact with SteveO at Sionics for a leftover from the run of barrels. I'm very glad I did.

I've assembled the barrel, a roughly medium contour barrel with true 5.56 NATO chamber and 1:7 twist (chrome lined), into a Rainier Arms forged upper with no FA, BCM KMR-A 10" w/ V7 Weapons Ti KMR barrel nut. I threw on an SLR Rifleworks Ti Sentry 7 set screw AGB and am waiting on a SiCo trifecta MAAD brake for my Saker 7.62 that's in NFA jail till February.

I used it on a buddy's SBR lower that uses the Vltor A5 system. I swapped in my A5H4 buffer and Tubbs 17-7 flat wire AR10 spring. Yes, you read that right. AR10 spring. It's stronger at the beginning of its stroke (in battery) than the SprinCo GREEN spring, but weaker at the end of its stroke (fully out of battery). It feels strange and has virtually no perceptible stacking effect. More pressure in battery and less pressure at the rear of stroke, allowing easier lock back. And the recoil stroke is really smooth on my 18" Handy Rifle.

I also used an LMT 4th gen e-carrier along with a Lantac NiB bolt and their domed cam pin. I also installed a SprinCo 5-coil CS extractor spring with insert (no donut), and McFarland single piece gas ring. Lubed PROPERLY with FireClean.

I was running no muzzle device on the Sionics barrel, so this was a worst case scenario for the given ammo (absolutely zero additional gas pressure provided by the muzzle device). I ran federal Brown box xm193 55gr NATO ammo in a magpul gen 3 PMAG and a Brownells aluminum 30rd mag with magpul follower. I started with the SLR gas block on full open (position 15 out of 15). Nice and smooth with lockback. I'll skip the boring part.

Onto position 5 from full closed and full lockback with no shoulder purchase and a lazy/floppy pistol grip. Reduced it to position 4 from full closed and same thing. And STUPID smooth. Position 3 from full closed and we had function with no lockback. A little too far.

Now, I know that Will and Steve HATE over sized gas ports, and that this was for carbines that were to be suppressed most of the time, so I'm going to measure it with some pin gauges tomorrow. But I bet it's horseshoes-and-handgrenades with the Crane spec, which is right around .070".

This isn't a testament to how over gassed the barrel is. Far from it. But it's an experiment (and a successful one, at that) into the use of the LMT e-carrier and Vltor A5 system and how they can be synergistically employed to significantly delay unlocking. This, necessarily, will have a significant effect on the amount of gas experienced by the users of suppressed rifles. Pix of the upper to come tomorrow.

My other buddy, who is a member of a local SWAT team had a select fire colt 6940 10.5" (or whatever model number their monolithic 10.5" is). It has a heavy profile barrel, grip pod, eotech optic, metal rear buis, foldable FSB, and streamlight TLR-1s. My upper had no sights, no buis, nothing. Despite being significantly heavier than my test setup, and using an H2 buffer, it was agreed by all shooters present that the Sionics setup was notably smoother, despite the enormous weight difference. And, frankly, the colt was VERY enjoyable to shoot.

EDIT: I used a buddy's pin gauge set to measure the gas port. It's .070-.071". Right on the Crane spec.

[SeriousStudent]

Very interesting. I'm ordering one of these barrels for a suppressed SBR build. I'll be quite interested in a thread update when you get your Saker.I have not picked out thee can I'm going to use at this time.

[BufordTJustice]

Very interesting. I'm ordering one of these barrels for a suppressed SBR build. I'll be quite interested in a thread update when you get your Saker.I have not picked out thee can I'm going to use at this time.

There MAY be more of these reduced gas port 11.5" barrels in the next few months. I'd imagine the std 11.5" barrel would be between the Crane spec and .078.

The Saker was an easy choice because I got SiCo LEO pricing. But the dead air sand man S and Rugged Razor 7.62 would be difficult to ignore if I weren't an LEO.

[Steve-0-]

I was fortunate enough to snag one of these very limited run barrels that were developed for a law enforcement agency's SWAT team rifles. They are used suppressed, with H2 buffers to great effect by the agency and I got in contact with SteveO at Sionics for a leftover from the run of barrels. I'm very glad I did.

I've assembled the barrel, a roughly medium contour barrel with true 5.56 NATO chamber and 1:7 twist (chrome lined), into a Rainier Arms forged upper with no FA, BCM KMR-A 10" w/ V7 Weapons Ti KMR barrel nut. I threw on an SLR Rifleworks Ti Sentry 7 set screw AGB and am waiting on a SiCo trifecta MAAD brake for my Saker 7.62 that's in NFA jail till February.

I used it on a buddy's SBR lower that uses the Vltor A5 system. I swapped in my A5H4 buffer and Tubbs 17-7 flat wire AR10 spring. Yes, you read that right. AR10 spring. It's stronger at the beginning of its stroke (in battery) than the SprinCo GREEN spring, but weaker at the end of its stroke (fully out of battery). It feels strange and has virtually no perceptible stacking effect. More pressure in battery and less pressure at the rear of stroke, allowing easier lock back. And the recoil stroke is really smooth on my 18" Handy Rifle.

I also used an LMT 4th gen e-carrier along with a Lantac NiB bolt and their domed cam pin.

I was running no muzzle device on the Sionics barrel, so this was a worst case scenario for the given ammo (absolutely zero additional gas pressure provided by the muzzle device). I ran federal Brown box xm193 55gr NATO ammo in a magpul gen 3 PMAG and a Brownells aluminum 30rd mag with magpul follower. I started with the SLR gas block on full open (position 15 out of 15). Nice and smooth with lockback. I'll skip the boring part.

Onto position 5 from full closed and full lockback with no shoulder purchase and a lazy/floppy pistol grip. Reduced it to position 4 from full closed and same thing. And STUPID smooth. Position 3 from full closed and we had function with no lockback. A little too far.

Now, I know that Will and Steve HATE over sized gas ports, and that this was for carbines that were to be suppressed most of the time, so I'm going to measure it with some pin gauges tomorrow. But I bet it's horseshoes-and-handgrenades with the Crane spec, which is right around .070".

This isn't a testament to how over gassed the barrel is. Far from it. But it's an experiment (and a successful one, at that) into the use of the LMT e-carrier and Vltor A5 system and how they can be synergistically employed to significantly delay unlocking. This, necessarily, will have a significant effect on the amount of gas experienced by the users of suppressed rifles. Pix of the upper to come tomorrow.

My other buddy, who is a member of a local SWAT team had a select fire colt 6940 10.5" (or whatever model number their monolithic 10.5" is). It has a heavy profile barrel, grip pod, eotech optic, metal rear buis, foldable FSB, and streamlight TLR-1s. My upper had no sights, no buis, nothing. Despite being significantly heavier than my test setup, and using an H2 buffer, it was agreed by all shooters present that the Sionics setup was notably smoother, despite the enormous weight difference. And, frankly, the colt was VERY enjoyable to shoot.

Thanks for the review. More are being chromed right now and should be available by the end of the month.

PS. Yeah, Will and I friggin hate oversized gas ports. Measured a 16" carbine today at .074... friggin disgusting.

[BufordTJustice]

Thanks for the review. More are being chromed right now and should be available by the end of the month.

PS. Yeah, Will and I friggin hate oversized gas ports. Measured a 16" carbine today at .074... friggin disgusting.

Steve, you guys hit it out of the park with this one. F*cking STUPID smooth. Brass looked great with no pressure signs; primers looked great too.

I have benefited from your hatred of whored-out gas ports.

EDIT: I bet that 16" shot like a 6.8spc, lol.

[BufordTJustice]

Pix added. They're shitty and blurry. I'm no Stickman. I doubt anybody is surprised by this news flash.

[SeriousStudent]

Thanks for adding the pics. I do like that barrel profile.

[tom12.7]

BufordT, a few questions about your porting strategy?
I agree about the LMT enhanced/A5 combo, I question the chosen mass?
With the adjustable gas block, why not gas it to an A5H2 for 5.56 without a can? Without changing the gas setting, you can step up or down in mass for different variables. Less mass for things like lower port pressure ammo, more mass for things like a silencer. Porting for the A5H2 for 5.56 without a can takes less gas than porting needed for the A5H4, less gas has many advantages. I Know when I'm adding a can, and adding in a buffer swap is pretty easy.
I do know and understand that a gas setting for the A5H4 can have a wide range of function, but that function may not be as preferable in use as more conservative gassing and simple buffer swaps.
I know little about the Tubbs spring mentioned. I stopped using them some time back due to issues, but those were CS. Do you know the L1 and L2 values?

[BufordTJustice]

BufordT, a few questions about your porting strategy?
I agree about the LMT enhanced/A5 combo, I question the chosen mass?
With the adjustable gas block, why not gas it to an A5H2 for 5.56 without a can? Without changing the gas setting, you can step up or down in mass for different variables. Less mass for things like lower port pressure ammo, more mass for things like a silencer. Porting for the A5H2 for 5.56 without a can takes less gas than porting needed for the A5H4, less gas has many advantages. I Know when I'm adding a can, and adding in a buffer swap is pretty easy.
I do know and understand that a gas setting for the A5H4 can have a wide range of function, but that function may not be as preferable in use as more conservative gassing and simple buffer swaps.
I know little about the Tubbs spring mentioned. I stopped using them some time back due to issues, but those were CS. Do you know the L1 and L2 values?

I forget the L1/L2 values. They were surprisingly close.

As for the buffer weight, I have found that while using the e-carrier, going to a lighter buffer such as the A5H3 or A5H2 did not allow me to reduce the gas setting on the gas block.

They also provided harsher recoil pulses than the A5H4. As I stated, there is a synergy with the current setup. The heavier buffer also registers a notably smaller difference in sight tracking between SAAMI pressure ammo and full house 5.56 duty ammo.

[mtdawg169]

As for the buffer weight, I have found that while using the e-carrier, going to a lighter buffer such as the A5H3 or A5H2 did not allow me to reduce the gas setting on the gas block.

Do you mean that they functioned the same regarding lock back as the A5H4 or that the gas block had to be set to fully open to run the A5H2 & A5H3?