Solution for possibly under-gassed 18" Rifle length gas.

[DenverGP]

I've got a PSA 18" stainless steel upper with rifle length gas system.

It's running a standard FA bolt carrier, standard 3oz buffer, and standard carbine buffer spring. And it's lubed up pretty well (more so than most of my other ARs).

When running with "milspec" ammo, it runs perfectly. But with some lighter loaded 223 ammo (PMC and federal "AE 223"), it occasionally fails to strip a new round from the mag and/or fails to lock on an empty mag.

So i'm guessing it's under-gassed. I've seen some suggestions of increasing the gas port, but it's not a big enough issue that I want to deal with drilling the barrel. So far the rifle has been very accurate with any decent ammo.

Should I:

Change to a lighter BCG
Change to a lighter buffer
Change to a lighter buffer spring
Leave it alone and stop using cheap ammo


I've got a spare standard buffer that I removed one weight from. Might try that with the cheap ammo just as a test.

[ray1970]

It?s my understanding that the 18? with the rifle length gas can be finicky.

I say it you find an ammunition that it likes just stick with it.

[whitewalrus]

I would swap to a lighter buffer and see if that helps it out with the cheaper ammo. The upside is you have less mass moving when the gun is fired. And this is likely your cheapest option.

I have an 18? barrel with rifle length gas on it and I run the A5 H0 buffer with an adjustable gas block mostly wide open. Seems to run most everything with and without a suppressor.

[ChickNorris]

Bowers

[esaabye]

Yep, they will sort you out quickly, just present the facts as you know them and let them look at the system. I was having some issues with my 18 and Rob figures it out very quickly.

As for the gas system on an 18 rifle length, never had a problem with any of mine and we run several in competition for a number of years. I run mine with adjustable gas blocks and play with different BCG weights.

[C Ward]

How bout checking the easy stuff first , built many 18" rifle gas guns and never any issues .

Check for gas leaks , misaligned gas block , loose carrier key , gas rings , misaligned gas tube binding in the carrier key .

[DenverGP]

Did some closer checks... carrier key is good, gas rings are good, gas tube is not binding at all. Pulled the free-float handguard off, gas block is on solid, gas tube is firmly attached. I do have a little carbon on the gas tube where it comes out of the block, but looks similar to all my other ARs.

[Madusa]

It’s the ammo,

[Not_A_Llama]

It will cost you nothing to gut your buffer and verify your theory.

You may even find that, despite the stories, there are no downsides, and only upsides, to keeping your buffer that way.

Past that, drill the barrel and pop in an adjustable block.

Or get a suppressor.

[Buff]

It will cost you nothing to gut your buffer and verify your theory.

You may even find that, despite the stories, there are no downsides, and only upsides, to keeping your buffer that way.

Past that, drill the barrel and pop in an adjustable block.

Or get a suppressor.

I pulled carbide slugs out of a buffer and replaced with aluminum and steel slugs to deal with a under gas problem on a Rifle length 18" 6.5 Grendel build after I open the gas port to .078". Also put an adjustable / tunable Odin gas block on it to dial it in.

[C Ward]

The gas block can be on and tight and still be misaligned , most gas blocks are designed so the spacing allows the original 2 piece hand guards to be installed . If the gas block is seated against the barrel shoulder it can block the port partially, only way to know for sure is too tear it apart and measure.

The buffer and BCG are typically weight matched to prevent / mitigate bolt bounce and the BCG driving the buffer in to the back of the buffer tube and coil binding the recoil spring . They usually need to be reduced in mass together.

[SA Friday]

It should cycle without having to open the port up. Bring it in and we can measure the gas port and go through the system. It sounds like you are either losing gas somewhere or losing energy from some sort of binding.