Gas Port Sizing VS Gas Block

[Falshooter]

I recently picked up a Geissele Super Gas Block off the EE here, and unknowingly it's an "FBI HRT Restricted Flow," and it looks to be marked with a gas port opening of 0.680". I'm not too worried about it being undersized for function. What I'm wondering about is if I'll see any issues with a smaller port opening on the block than on the barrel. I assume it'll function the same as an adjustable gas block with the gas turned down, but I wanted to double check.

[alx01]

Can you post pictures? First time I hear about Geissele doing this.

[Clint]

If you're looking to duplicate an 11.5" FBI HRT setup, it should work great.

[markm]

I would have to imagine that the block's inlet is larger than .068, and that it chokes down to that diameter. Otherwise, alignment would have to be very precise.

I too have never heard of this.

[prepare]

I'm running a .067 BRT Custom Tune GP on a 11.5 that has been flawless. The recoil is almost the same as a stock 6920. DD Barrel .075 GP, A5 Buffer System, Surefire 3 prong flash hider/suppressor mount.

[Rogue556]

OP,

Is the block tapped with a port insert installed or is this block some kind of specialty Geissele block that has a reduced size straight from Geissele? If it's the later then I didn't even know these existed.

Any way you could post some pictures?

Sent from my SM-N910P using Tapatalk

[GH41]

I would have to imagine that the block's inlet is larger than .068, and that it chokes down to that diameter. Otherwise, alignment would have to be very precise.

I too have never heard of this.

More than likely it was done like Clint does with his custom tune setup. Might even be his.

[Falshooter]

wrong post.

[MQ105]

I'm assuming you meant the above ^^^ post to be in another thread...?

Anyway, what barrel are you planning to run it on?

[markm]

I'm assuming you meant the above ^^^ post to be in another thread...?


Yeah! :sarcastic: I was wondering how we went from gas block to 6.5 grab ass in mid stream.

[Clint]

The block is not our MicroTUNE, but uses a similar concept.

It is a special variant Geissele did for the FBI and is not commercially available.

It is said to mitigate the effects of gas port wear in the barrel.

[markm]

It is said to mitigate the effects of gas port wear in the barrel.

I really don't believe this to be a legit concern. I know that tear drop erosion in the bore area can cause a small expansion chamber. But I'm very unconvinced that this translates into functional issues.

I'm willing to be wrong, however.

[Inkslinger]

The block is not our MicroTUNE, but uses a similar concept.

It is a special variant Geissele did for the FBI and is not commercially available.

It is said to mitigate the effects of gas port wear in the barrel.

I though gas port erosion occurred in the bore? How would a restricted gas block affect wear?

[markm]

I though gas port erosion occurred in the bore? How would a restricted gas block affect wear?

I THINK the concept is that somehow the whole port could open up due to erosion. And the block would continue to choke the gas down to .069 or whatever.

I could be completely wrong, as I've never seent the thing, but no block is going to impact port erosion.

[Inkslinger]

I THINK the concept is that somehow the whole port could open up due to erosion. And the block would continue to choke the gas down to .069 or whatever.

I could be completely wrong, as I've never seent the thing, but no block is going to impact port erosion.

That makes sense. For whatever reason I was interpreting Clint’s comment as the block would reduce the erosion of the barrel instead of compensating for the effect of it.

[Clint]

How it will work depends on many factors.

What are you building?


I recently picked up a Geissele Super Gas Block off the EE here, and unknowingly it's an "FBI HRT Restricted Flow," and it looks to be marked with a gas port opening of 0.680". I'm not too worried about it being undersized for function. What I'm wondering about is if I'll see any issues with a smaller port opening on the block than on the barrel. I assume it'll function the same as an adjustable gas block with the gas turned down, but I wanted to double check.

[jerrysimons]

Are you interested in selling this gas block?