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So I'm looking at getting a new 10.4" barrel to build a SBR. I would like to shoot this suppressed 99% of the time. It looks as if the non-vented gas block is the most common to obtain for a short barrel.

I don't think the port sizes have been finalized but I'm curious on recommendations on which gb to use.

Are there any gas ports sizes that would work surpressed with a 10.4 un-vented gb. Or should I stick with a 14.5/16 vented gb and regular size port hole?

Other suggestions? I've been researching for a while and frankly the forums search function is awful and most the threads that talk details reference work done by IGF which is clearly not an option at this time.
 

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Since I just SBR'ed my MR556 and spent a long time researching and agonizing over it I'm happy to tell you what I did...

I had the MR556 "Competition" model which had a vented gas block. After I had ADCO chop the barrel to 10.5" the gun wouldn't cycle properly. It would send the bolt back enough to eject the casing but not far enough back to pick up the next round. This was unsuppressed. But even when I ran it suppressed it wasn't enough back pressure. But I'm sure that had to do with the fact that I run an OSS suppressor which has no (or very, very minimal) back pressure.

So, I had a gunsmith buddy weld the vent closed. Worst case scenario he could drill a smaller hole if it was over-gassed.

But nope! It runs great now! I've shot 6 different kinds of ammo through it (from cheap, steel case Wolf up to very hot 5.56) and it runs flawlessly both suppressed (with the OSS) and unsuppressed. I'm not sure how it would do with a baffle can but for what I'm doing it's running amazing.

I suggest getting the solid gas block and if you find it's over-gassed then have someone skilled drill a small vent hole in the front of the block.

Before:

RenderedImage.JPG

After:

57678515639__783045C0-1852-4B9B-AAFE-F356698A3C2B.JPG

Finished:

IMG_4495.jpg
 

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Since I just SBR'ed my MR556 and spent a long time researching and agonizing over it I'm happy to tell you what I did...

I had the MR556 "Competition" model which had a vented gas block. After I had ADCO chop the barrel to 10.5" the gun wouldn't cycle properly. It would send the bolt back enough to eject the casing but not far enough back to pick up the next round. This was unsuppressed. But even when I ran it suppressed it wasn't enough back pressure. But I'm sure that had to do with the fact that I run an OSS suppressor which has no (or very, very minimal) back pressure.

So, I had a gunsmith buddy weld the vent closed. Worst case scenario he could drill a smaller hole if it was over-gassed.

But nope! It runs great now! I've shot 6 different kinds of ammo through it (from cheap, steel case Wolf up to very hot 5.56) and it runs flawlessly both suppressed (with the OSS) and unsuppressed. I'm not sure how it would do with a baffle can but for what I'm doing it's running amazing.

I suggest getting the solid gas block and if you find it's over-gassed then have someone skilled drill a small vent hole in the front of the block.

Before:

View attachment 230966

After:

View attachment 230968

Finished:

View attachment 230970
The OSS is designed for the HK MRs. If you use a baffle suppressor you need a vented block and the barrel gas port bored out. Or you can try a non vented gas block with a different buffer/spring combo to reduce recoil and have BCG carrier cycle properly.

You can also use a 14.5”/16” vented gas block but once again the barrel gas port needs to be bored-out/tuned to the gas block. Inshallah did mine and they spin like tops. I used 10.4” vented gas blocks on my SBRs.
 
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