View Full Version : GAS PRESSURE

16 January 2011, 10:12
Long time reader, new member and first time poster. I need to know about gas pressures when operating with a suppressor. I have found a short comment on them increasing the pressure and gas on a system but at what point does it "over gas" and start to do damage to the suppressor and/or gun in relation to shortness of barrel. The build is a 11.5 inch barrel and standard low profile gas block. I am a casual shooter so no constant use and firing thousands of rounds a month here. Is tweaking the gas block or gas tube required? Obviously ammo type and pressure will play into this.

16 January 2011, 10:16
It will raise he pressure but nothing to be worried about unless your AR is overgassed. Running something like a switch block will help or even an adjustable gas block

17 January 2011, 08:35
It's not the pressure, it's the time under pressure that increases with a silencer. This will increase you cyclic rate and wear on the bolt. I wouldn't be concerned about casual use at all.

Here is a good explanation of what is going on and our solution to it. The main benefit is reduced recoil and gas blowback but it's not something you need to have to shoot with a silencer.

17 January 2011, 11:26
An overgassed rifle won't damage the suppressor, and mostly just increases wear on the host weapon due to an increased gas volume coming back and the biggest AR specific change is that the bolt carrier velocity increases (assuming same ammunition used). The gas port on your 11.5" should be adequate for unsupressed use, and will run with a suppressor - just a bit more wear, and there should be a bit more noticed recoil, as well as more burnt powder to clean out when you're done. Increasing the reciprocating mass can minimize this somewhat (Auto BCG, heavier buffers, stiffer action springs), but going past H2 buffers can start to exhibit short stroking when running it unsupressed.
A smaller gas port, or restricting the amount of gas between the port and tube (switchblock) can reduce the gas pulse so that only enough gas to cycle the action is sent back when running suppressed, which helps a lot if you'll be shooting a lot with it suppressed, but if you're using the suppressor a small part of the time, then I wouldn't even worry about it.

18 January 2011, 07:44
Thanks guys. See that's why I like this forum, ask question, get good answers! I just wanted to make sure. How do you find yourself with an over gassed system in the first place? Barrel length and gas port size taken together shouldn't allow more gas than necessary, I would expect.

18 January 2011, 11:01
A lot of rifles that tend to have undersized chambers and oversized gas ports will see this: in order to make a rifle more reliable without revising chamber specs or demanding that users stop using crap ammunition, they'll just open up the gas port a lot to make sure that even if the user is being an idiot: running it dry, dirty, and feeding it low powered junky ammunition; that the rifle will still cycle. Run these with 5.56 spec ammunition, properly lubed, and with a suppressor and you've set it up for some massively accelerated wear and more felt recoil, whereas some manufacturers have made rifles and openly stated 'will not run with junk ammo', and wound up later revising that specification (the SR15E3 has gone this route).

While a 16" carbine gas system with an H2 buffer has a pretty huge range of operational parameters where it will run, the longer gas systems (the SR25 system on the SR15E3; Noveske's Intermediate system) that run so well with high powered stuff and really shine suppressed will short stroke repeatedly on dirty, low powered stuff.

20 January 2011, 08:51
It sounds like good ammo and a clean gun should have no worries. Maybe an adjustable gas block to equal things out. Ammo choice will work itself out in time. One thing I have never seen is a progressive wound buffer spring. They exist in other places.