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Posted: 7/28/2026 5:35:39 PM EDT
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I just assembled a rifle with a BCM 16" 300BLK barrel and Superlative Arms gas block. Gas block screw is 4.5 turns out, in the wide open position. If I open it up any more, the bolt won't lock back consistently. Ejection pattern is 3 o'clock unsuppressed and suppressed. I can't feel any gas when suppressed. Does this mean I can switch to a solid gas block and be done with it, or is the SA gas block likely bleeding a little gas out when suppressed? I'm using H2 buffer, extra power spring, the can is a Griffin GP7, ammo is 125gr supers on the mid-upper side of powder charge. |
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1, all adjustable gas blocks will leak a touch. 2, need to play the lets back it way up machine, since if rig is running 300blk sub sonic ammo fine with supressor, then can go non adjustable gas block. Hence adjustable gas blocks only allow the reduction of pressure (minus what is leaking out in the first place) and can not add pressure instead. 3. for more subsonic rigs in 300blk, and since they are using very fast powder which pushed the peak burn dwell way towards the chamber, you want the gas port to be as close to the chamber as possible. The barrel can be as long as you want it, but again, want the gas port/end of gas tube to be as close to the barrel instead. So think this with where the gas port would be on a pistol barrel and where the fast burn power used for 300blk will have it max peak point.  Now for subsonic ammo in the same barrel, here is where the adjustable gas block comes in play, to lessen the gas pressure to the B/C, since the powder for that round in super sonic, is going to have a peak burn rate much farther down the barrel. So again, if rig is running/cycling sub sonic ammo fine, leave the gas block in play, since going to need to use it to turn down the gas pressure with super sonic ammo that will use slower burning powder, to keep the rig from short stroking due to over function with bolt unlocking too soon. And to add, suppressor only deals with the Boom of the round report as it leaving the barrel, but does not resolve the sonic crack noise of the bullet going faster than speed of sound as it leaves the can instead. So unless your pushing the round long range with it super sonic (which your never going to do with a 300BLK), where removing the boom noise ends up with someone thinking that the shooter is much more forward of the actual position, not really making the rifle that much quieter with the suppressor, and lets face it, most suppressor will increase group sizes as well. Yes, will agree that close up and personal with 300BLK/300 Whisper sub sonic suppressed does have its place, but most never use it as such for its intended main purpose, and instead trying to push the round just way too far with super sonic loads instead. |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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I should mention I'm not interested in how the gun functions with subsonic ammo, it will only be used with supers. What I'm focused on here is, since the gun seems to function fine with the gas block wide open suppressed and unsuppressed, is this a case in which an adjustable gas block is not needed? If so,I would rather install a solid gas block and save my Superlative Arms gas block for a gun that benefits from it. I'm interested to hear from shooters with experience using the Superlative Arms gas block. Has anyone been in this situation and found going to a solid gas block caused over gassing? Did you find that your gun functions the same? FWIW, BCM says to run a H3 buffer with this barrel, and I'm only running a H2. So, if the gun gets a little more gassy with a solid gas block suppressed, I can go to a H3 if needed, right? Is this a logical way of looking at it? |
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Let me put it this way, if rig is running fine, then leave it alone. Hence replacement fixed gas block could just open a can of worms, with its port not aligned to the barrel gas port, it coming loose over time, or it leaking between it gas passage the barrel port. Also, to replace the gas port, this means at least the the suppressor adapter has to come off the barrel, it's either loctite/rocksett on, and to get it off, may end up distorting the last of barrel after the barrel shoulder with the barrel not longer printing tightly in the end. |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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Originally Posted By Dano523: Let me put it this way, if rig is running fine, then leave it alone. Hence replacement fixed gas block could just open a can of worms, with its port not aligned to the barrel gas port, it coming loose over time, or it leaking between it gas passage the barrel port. Also, to replace the gas port, this means at least the the suppressor adapter has to come off the barrel, it's either loctite/rocksett on, and to get it off, may end up distorting the last of barrel after the barrel shoulder with the barrel not longer printing tightly in the end. I see where you're coming from. I appreciate your input. |
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I decided to jack with my gun and switch to a solid gas block. Yes, I had a couple issues arise which are now overcome. Function is A-1 suppressed and unsuppressed. I'm glad I had the opportunity to deal with this while the weather was nice and before I attach a suppressor mount. Let's go back for a moment to my original quandary over the SA gas block and whether it was actually bleeding gas in the wide open position when adding backpressure. After studying the part and giving it a little thought, I don't believe it's possible. I'm thinking there is a slot milled in the adjustment pin that allows gas to bleed as you loosen it. So, if the slot in the adjustment pin is not creating a pathway from the barrel's gas port to the gas block's bleed hole, there's no bleeding taking place. I had attempted to ask the folks at Superlative Arms, but they responded with a simple, if your gun is not overgassed, you don't need it. Thanks for the help, everyone! |
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