Overgassed or Undergassed? Or just right?

[DefenderAO]

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I took the SBR to the range today to check how its gassed. Ejection patterns were consistently at the 1/1:30. Bolt locks back on empty mag 100% of the time. From this, I thought "overgassed." However, randomly watching a video today I saw brass hitting the deflector which had a very similar sent-casing angle as I saw at the range today. Two other issues: 1. I do not have a spent casing picture to determine indentations or markings. 2. I never did check to see if the spent casing was hitting the deflector or going to 1/130 on its own (obvious).

Overgassed or undergassed? Or simply gtg?

Details:

- 11.5" barrel
- carbine gas system
- suppressed, Griffin Armament can
- gas port .48...made for suppressed only shooting. Yes, it's small.
- FA carrier; LMT bolt, no special extractor
- JP Rifles H2 buffer/sprong combo
- ammo - M193 Federal 55 gr

The only tell I have is this picture of the deflector. Apparently it is a common marking, but is this indicative of over or undergassing? I was going to upgrade to an H3 JPR system, but if the brass is hitting the deflector, I may need to go H system or lighter.

[Artos]

Ya know, I'm the last guy that should pipe up on the technical stuff with all the other sperts here knowing much more than me...if I'm running like a sewing machine & dumping brass at 1-2 ejection, I'm happy.


Welcome to the Forum!!

[Clint]

The brass always his the deflector.

It's just a matter of where and at what angle.

Hitting that inside edge and ejecting to 1:00 would seem to indicate over gassing.

How big is that gas port again?

[DefenderAO]

The brass always his the deflector.

It's just a matter of where and at what angle.

Hitting that inside edge and ejecting to 1:00 would seem to indicate over gassing.

How big is that gas port again?

.48. Will not cycle without a can. I'm pretty shocked with a JP Enterprise H2 spring/buffer, a .48 gas port, and a FA vs SA carrier I found a way to be overgassed. And I was not aware the casings always hit the deflector? So on an ideally gassed AR the hit the deflector and bounce to 4 o'clock?

[scooter22]

.48. Will not cycle without a can. I'm pretty shocked with a JP Enterprise H2 spring/buffer, a .48 gas port, and a FA vs SA carrier I found a way to be overgassed. And I was not aware the casings always hit the deflector? So on an ideally gassed AR the hit the deflector and bounce to 4 o'clock?

It’s not 0.48”. More like 0.048”.

Triarc’s 11.5” suppressed only barrel is 0.045” last I checked.

Locking back on an empty mag with suppressor attached shooting XM193 is appropriate.

Don’t overthink it.

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[DefenderAO]

It’s not 0.48”. More like 0.048”.

Triarc’s 11.5” suppressed only barrel is 0.045” last I checked.

Locking back on an empty mag with suppressor attached shooting XM193 is appropriate.

Don’t overthink it.

Sent from my iPhone using Tapatalk

.048 yes. I have read Triarc is .046 to .048. Either way I have not read of a smaller port size. BCM is something like .076, DD .069. I’m concerned parts may wear faster than needed and, when they do, best case is bad ejection become more pronounced and worst case, failures.

[scooter22]

.048 yes. I have read Triarc is .046 to .048. Either way I have not read of a smaller port size. BCM is something like .076, DD .069. I’m concerned parts may wear faster than needed and, when they do, best case is bad ejection become more pronounced and worst case, failures.

Triarc told me themselves that it is 0.045. Perhaps that has changed. Parts would wear leas quickly with a properly or conservatively ported barrel such as yours. Your rifle seems to be functioning fine.https://uploads.tapatalk-cdn.com/20200917/6b01cd7097628a9f40ba0806a1b97845.jpg


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[1168]

Which Griffin can?

[MikhailBarracuda91]

My LMT (non enhanced) BCG does the exact same thing. It ejects spent cases to 1:30, when I switch it out to a BCM BCG it throws the cases to 4:30.

Chris Bartocci form Small Arms Solutions says LMT designs their weapons like that. In my experience it's the BCG's

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[georgeib]

I've read here that a forward ejection pattern can sometimes be caused by the extractor spring. Do you have another spring, or bolt to try?

[MikhailBarracuda91]

I've read here that a forward ejection pattern can sometimes be caused by the extractor spring. Do you have another spring, or bolt to try?I read that as well, so I changed the extractor spring and ejector spring to a springco set in that LMT BCG and it was the identical results.

However, my brother has a LMT enhanced BCG in his M4 and that thing throws cases at darn near 5:00 into the neatest pile I swear lol

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[DefenderAO]

Which Griffin can?

Their M4SD-K can. As others are pointing out it may very well be a bolt extractor. Round count is around 250 at this point so a bolt swap is still in play without any headspace risks

[DefenderAO]

Triarc told me themselves that it is 0.045. Perhaps that has changed. Parts would wear leas quickly with a properly or conservatively ported barrel such as yours. Your rifle seems to be functioning fine.https://uploads.tapatalk-cdn.com/20200917/6b01cd7097628a9f40ba0806a1b97845.jpg


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I’ve gotten two different answers calling them. One was .048 and the other .046. The former was from a guy apparently who makes the barrels. Probably safe to say .045 - .048. I haven’t put it to rest by measuring

[1168]

Their M4SD-K can. As others are pointing out it may very well be a bolt extractor. Round count is around 250 at this point so a bolt swap is still in play without any headspace risks

Its a gassy can. I have one. It seems above average on gassiness, which is probably why it sounds as good as many full size cans. To be fair to it, most of my rifle can experience is with military cans and 7.62 cans. It and my Turbo K are my only 5.56 K cans, and they both work shockingly well.

The headspace is probably fine.

Many companies, including high end ones, use lame extractor springs sometimes they go unnoticed, sometimes they don’t. I only use Colt and the Sprincos that Iraqgunz (of Sionics) recommended. Mistwolf has some good rants about extractor springs and ejection, if you want to go through his post history.

[Clint]

Have you actually pin gauged your barrel?

It may be possible it has the normal port instead of the suppressed port.

.048 yes. I have read Triarc is .046 to .048. Either way I have not read of a smaller port size. BCM is something like .076, DD .069. I’m concerned parts may wear faster than needed and, when they do, best case is bad ejection become more pronounced and worst case, failures.


Here is another good clue.

Try swapping the BCG to see if anything changes.

My LMT (non enhanced) BCG does the exact same thing. It ejects spent cases to 1:30, when I switch it out to a BCM BCG it throws the cases to 4:30.

Chris Bartocci form Small Arms Solutions says LMT designs their weapons like that. In my experience it's the BCG's

[DefenderAO]

Have you actually pin gauged your barrel?

It may be possible it has the normal port instead of the suppressed port.

Here is another good clue.

Try swapping the BCG to see if anything changes.

I may swap the bolt vs the entire carrier. I bought some extra LMT and other mil parts post Sandy Hook and, frankly, I can’t tell them apart now. I will say the extractor retention pin is fairly easy to put in after cleaning. To me that would mean the tension is low and not a Herculean extractor trying to shoot brass through dry wall.

I’d be pretty shocked if Triarc gave me a wrong order. I may try and shoot it without the can. The Griffin van is a gassy one so it may just be the back pressure is that high.