Converting a mid length 16" to rifle length 18"

[snowplow]

Hey guys, I'm converting my mid-length gas system 16-in AR to run an 18-in barrel with a rifle length gas system. I'm no expert at this so I want to run this by you guys to make sure I'm on the right track.

I was doing a little reading last night and it sounds like I may be able to get away with my original buffer and spring and just tune it with a adjustable gas block? I was going to run the riflespeed adjustable gas block. Then if there's any trouble I could always mess with the buffer weights. Does it sound right?

 

[Bacarrat]

Why would you need a adjustable gas block on a rifle length gas system? IMO you are way over thinking this.

 

[USK308]

Hey guys, I'm converting my mid-length gas system 16-in AR to run an 18-in barrel with a rifle length gas system. I'm no expert at this so I want to run this by you guys to make sure I'm on the right track.

I was doing a little reading last night and it sounds like I may be able to get away with my original buffer and spring and just tune it with a adjustable gas block? I was going to run the riflespeed adjustable gas block. Then if there's any trouble I could always mess with the buffer weights. Does it sound right?

For a simple barrel conversion to 18", you really just need to put a rifle-length gas tube into your gas block. No need to get an Adjustable Gas Block for the barrel swap.

 

[VargmatII]

Just swap the barrel and the gas tube and you are good to go.

You will appriciate the lower felt recoil and if you run a suppressor, it should also feel a bit less gassy.

I swapped for a rifle lenght gas system last fall and it worked great.

 

[snowplow]

Sorry, I forgot to mention I will be running a suppressor at least plenty of the time. I was under the impression that at that point I pretty much needed an adjustable gas block to have it run well both with and without the suppressor.

 

[VargmatII]

Sorry, I forgot to mention I will be running a suppressor at least plenty of the time. I was under the impression that at that point I pretty much needed an adjustable gas block to have it run well both with and without the suppressor.

It should runt just fine with a regular gas block.

 

[tekmann2377]

You don't necessarily need an adjustable gas block with a suppressor. A pleasant side effect of your switch to an 18" rifle gas is they tend to run smoother and be much less prone to overgassing than shorter barrels/gas systems.

I shot out an 18" rifle gas barrel (over 9.5k rounds) with almost 100% being suppressed. Didn't use ang type of low back pressure can either. It ran with extreme reliability and I can't recall ever having a single malfunction over the course of its life. I didn't do anything to the standard H buffer and carbine spring either.

 

[Bacarrat]

MK12s run perfectly fine without a adjustable gas block.

 

[snowplow]

Awesome guys! Thanks so much!

 

[snowplow]

Okay guys, one more question. I was going to start another thread but it seemed like a waste because the title would be the same.

Now what time if it was the same scenario on an AR-10?

16" mid length gas sys to 20" rifle length gas sys. RRA LAR-8 .308.

Do I need an adjustable gas block?

 

[tekmann2377]

Maybe, maybe not. Shoot it and see. Too many variables to assess.

I have one large frame AR that ran like crap without being tamed with an AGB. Another one was a Criterion 16" rifle gas. That ran like a sewing machine right out of the box with no issues. Didn't even use a fancy heavy buffer.

 

[Bluedog82]

Okay guys, one more question. I was going to start another thread but it seemed like a waste because the title would be the same.

Now what time if it was the same scenario on an AR-10?

16" mid length gas sys to 20" rifle length gas sys. RRA LAR-8 .308.

Do I need an adjustable gas block?

AR-10s are much more likely to be overgassed, especially with a can. Adjustable gas block is a great idea.

 

[Jmccracken1214]

I feel like AGB is always good to have when running a can.

Ive been slowly switching over to superlative arms piston kits so I dont have gas in my face on my semi's

 

[O.G.]

I built a rifle length gas AR with an 18" barrel and eventually had to open up the hole because it wouldn't cycle.

 

[tekmann2377]

I built a rifle length gas AR with an 18" barrel and eventually had to open up the hole because it wouldn't cycle.

That is a problem with the barrel, not necessarily an intrinsic problem with the 18" rifle gas setup

 

[O.G.]

That is a problem with the barrel, not necessarily an intrinsic problem with the 18" rifle gas setup

Indeed. But I thought it worth mentioning. I also have a midlength 14.5 from a different man'f that I had to do the same to. Point is, it seems that many are simply shortening the barrel, from 20 to 18 or 16 to 14.5, etc, without any adjustment to the gas port so don't be surprised if there are cycling issues. Depending, of course, upon the source.