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Posted: 11/4/2018 12:26:24 PM EDT
Upper: 6.5 Grendel, 18" Faxon fluted match barrel with rifle length gas system. Using a Sentry 7 clamp on adjustable gas block.
Lower: Aero receiver with JP SCS and H2 weights, carbine extension tube. Unsuppressed the rifle runs great with the gas block about 4-5 notches out from shut off. I put on a Sandman-S and the now I can't seem to close off the gas block enough. Even bottoming out the adjustment screw there is somehow enough gas getting by to fully operate the recoil system. It wouldn't bother me so much that my brass it kicking out at 2 o'clock but for whatever reason it's wanting to blow my magazine out after the last round is fired, and hence wont lock the bolt back. What has me scratching my head is how is the gas getting through a "closed" gas block. I have removed the adjustment screw and nothing appears broken or cracked. It turns freely and indexes nicely every 120 degrees. 
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Posted: 11/4/2018 12:52:34 PM EDT
[#1]
I've used eight Sentry 7 gas blocks so far (set screw version and then pinned). Each would not allow the rifle to function when closed off all the way. Sounds like a problem with your gas block to me. I'd call SLR and visit with them. They usually help restrict gas flow immensely, but I've had some SBR's that were still over gassed when used with the Sentry 7. They benefitted from heavier buffers.
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Posted: 11/4/2018 1:35:40 PM EDT
[#2]
have you tried taking the upper apart, blocking the chamber, and blowing through the muzzle with the gas block in the fully closed position to ensure no gas is going through the gas tube ? can't imagine gas forcing itself through a closed gas port under any pressure.
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Posted: 11/4/2018 1:50:14 PM EDT
[#3]
I’d hate to resort to that but I may need to. The flash hider is rockset in place so it may be easier to try and fit a silicone tube around the gas tube end from inside the receiver to test how well it restricts flow.
I’m going out this afternoon to see if it restricts enough without the suppressor to keep the action from cycling. Can anyone tell me with the adjustment screw snugged closed how much gap there is between the head of the screw and the face of the gas block? I’m measuring about .04-.05 inch. |
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Posted: 11/4/2018 2:38:39 PM EDT
[#4]
Pull the side screw detent plate bolt, remove the side plate and detent and spring, then remove the adjuster bolt from the assembly.
Now with it in hand, take a look at the end of it, and even down the channel for a bur that is not allowing the end of the adjuster bolt to seal off tight to the front of the adjuster threaded channel. Hence if the adjust is over tightened, it can break the front of the bolt off, and will never seal off the gas section correctly. With luck, it just milling swaft down the inside of the channel that you can pick out, and will allow the gas block to seal off correctly with the adjust bolt lightly tightened all the way in. With that cleaned up, use some 242 on the bolt detent plate once you have the parts assembled back together. And yes, install the adjuster bolt first, then the side detent, spring, side plate and bolt with 242 last. If you find that the end of adjuster bolt is broken off, or the end of channel is not milled correctly/a mess that the end of bolt has no chance of sealing off to, then entire block needs to be sent back for replacement. |
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Posted: 11/4/2018 6:59:12 PM EDT
[#5]
Quote HistoryQuoted:
Pull the side screw detent plate bolt, remove the side plate and detent and spring, then remove the adjuster bolt from the assembly. Now with it in hand, take a look at the end of it, and even down the channel for a bur that is not allowing the end of the adjuster bolt to seal off tight to the front of the adjuster threaded channel. Hence if the adjust is over tightened, it can break the front of the bolt off, and will never seal off the gas section correctly. With luck, it just milling swaft down the inside of the channel that you can pick out, and will allow the gas block to seal off correctly with the adjust bolt lightly tightened all the way in. With that cleaned up, use some 242 on the bolt detent plate once you have the parts assembled back together. And yes, install the adjuster bolt first, then the side detent, spring, side plate and bolt with 242 last. If you find that the end of adjuster bolt is broken off, or the end of channel is not milled correctly/a mess that the end of bolt has no chance of sealing off to, then entire block needs to be sent back for replacement. I did get out to the range this afternoon and tested the rifle with the gas block closed both with and without the suppressor. Unsuppressed and gas block closed the gun fails to cycle. Suppressed and gas block closed the action can cycle but it's not 100%. The magazine blowing out seems to be magazine related. It's only doing it with 1 of my 2 Elander magazines. |
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Posted: 11/4/2018 9:10:02 PM EDT
[#6]
If you need to further restrict the gas flow beyond the adjustment offered in your adjustable gas block, you could just intentionally move the gas block to slightly mis-align it with the hole to further restrict flow...however, perhaps a better solution would be to increase the tension of your buffer spring
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Posted: 11/5/2018 12:59:44 PM EDT
[#7]
Both of my SLRs turn my rifles into single shots when closed.
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