Barrel and gas system lengths

[blksno]

So I've got a pair of AR10s and I use that term on purpose.
One is an Armalite AR10 that was originally a 300 SAUM. I rebarreled it to a 6.5 PRC with a 24" barrel and a +2 gas system. I've just about got it dialed in to cycle perfect...but the Armalite mags are dog-spit and I think I'm gonna end up having to 3d print a self leveling follower for their Gen2 pattern mags.
The 2nd is a Matrix upper lower set that is still the Armalite pattern, but takes SR25 mags...that one is 22" with a +2 gas system. Pmags don't work 100% but so far ACS mags have been doing great. Seems to be tuned and feeding/cycling but with both systems...I'm thinking I should have just made them 16 or 18? from the jump.

Has anyone ever taken a barrel with a +1 or +2 gas system and shortened the barrel down to 16 or 18"??
I assume this is going to drastically reduce the gas and potentially start short stroking, but with the buffer, springs and gas block I have...I assume getting it tuned to run suppressed again would be fairly easy.

Really thinking I should have gown shorter.

 

[rpol98]

probably gonna be like a True Dissipator. very finicky, which is why we have the fake Dissipator, and probably the fake news.

you might get it tuned just right for a particular load, declare triumph, take a victory lap. any variation from that one load, and it's back to the drawing-board if the dwell-time (gas-port to muzzle) is too short to give you a variance window.

if you can live with that handicap, then by all means, go for it! AR's are easy enough to tune, I'd use an adjustable gas block, and have the gas port drilled-out so it's overgassed, and then throttle it with the adj GB, play with buffer weights, springs. Take good notes. You can do a lot of science experimenting, worthy of its' own science fair booth (if only they allowed such things).

just my 2 cents.

 

[liber]

Has anyone ever taken a barrel with a +1 or +2 gas system and shortened the barrel down to 16 or 18"??
I assume this is going to drastically reduce the gas and potentially start short stroking, but with the buffer, springs and gas block I have...I assume getting it tuned to run suppressed again would be fairly easy.

I'm unclear on what you're calling +1, and +2 gas systems. I've always heard them referred to as pistol, carbine, mid length, rifle, etc...to be honest the 6.5 PRC that is almost dialed in sounds good, aside from the mags. LOL Have you tried different mags, such as the (tracking info removed) Lancer L7 AWM.

In response to your question, either of those rifles pictured could be shortened, it's pretty common for most AR gunsmiths. Most would cut it off and thread it so use a brake or suppressor, if you live in a free state. Without knowing you, since you're asking, I'm guessing it's not something you can do yourself, and it would require a lathe.

 

[bamban]

I'm unclear on what you're calling +1, and +2 gas systems. I've always heard them referred to as pistol, carbine, mid length, rifle, etc...

Not the op, but to clarify, +1, +2 refer to rifle length, plus.....

 

[blksno]

I'm unclear on what you're calling +1, and +2 gas systems. I've always heard them referred to as pistol, carbine, mid length, rifle, etc...

Rifle Length is generally 12"
+1 would be 13 and +2 is obviously 14"

 

[blksno]

I'm unclear on what you're calling +1, and +2 gas systems. I've always heard them referred to as pistol, carbine, mid length, rifle, etc...to be honest the 6.5 PRC that is almost dialed in sounds good, aside from the mags. LOL Have you tried different mags, such as the (tracking info removed) Lancer L7 AWM.

In response to your question, either of those rifles pictured could be shortened, it's pretty common for most AR gunsmiths. Most would cut it off and thread it so use a brake or suppressor, if you live in a free state. Without knowing you, since you're asking, I'm guessing it's not something you can do yourself, and it would require a lathe.

I run everything suppressed and a 9" Thunderbeast on the end of a 24" rifle is just silly. I should have known better.
I have plenty of people that can cut and re-thread for me, but the question refers specifically to cutting a barrel down to a point that you only get 3-4" of "meat past the gas port"

What happens is your system typically gets finicky because you have a short dwell time where gas is being fed to your carrier before the bullet exits the muzzle.
This is typically why you see a rifle length gas system on 18" or longer barrels but a 16" is typically midlength.
There are 16" 308 barrels that have rifle length gas systems and they can be picky with ammo.

That said.
The 6.5 Creed and 6.5 PRC are both a pinch on the higher port pressure due simply to barrel ID. As it is now, both my adjustable gas blocks are quite closed, I have extra heavy A5 buffer weights (I'd have to weigh to knownfor sure) and ExtraPower SprinCo buffer aprings...so I have a feeling whatever issues MIGHT OCCUR, I have a feeling I can re-tune and get back in business.

Hopefully.

 

[Bert01]

I run everything suppressed and a 9" Thunderbeast on the end of a 24" rifle is just silly. I should have known better.
I have plenty of people that can cut and re-thread for me, but the question refers specifically to cutting a barrel down to a point that you only get 3-4" of "meat past the gas port"

What happens is your system typically gets finicky because you have a short dwell time where gas is being fed to your carrier before the bullet exits the muzzle.
This is typically why you see a rifle length gas system on 18" or longer barrels but a 16" is typically midlength.
There are 16" 308 barrels that have rifle length gas systems and they can be picky with ammo.

That said.
The 6.5 Creed and 6.5 PRC are both a pinch on the higher port pressure due simply to barrel ID. As it is now, both my adjustable gas blocks are quite closed, I have extra heavy A5 buffer weights (I'd have to weigh to knownfor sure) and ExtraPower SprinCo buffer aprings...so I have a feeling whatever issues MIGHT OCCUR, I have a feeling I can re-tune and get back in business.

Hopefully.

I would say with all that yes, I would do it without hesitation. Especially since you are running suppressed all the time.

 

[ARlife4me]

I'd have a gas system @ 5/8-3/4 the barrel oal to keep as much pressure down as possible. If you gat an oversized port you still might be in trouble running suppressors with the extra back pressure created from it ( maybe not a flo-thru). It easier to go smaller and increase size thru experience (especially if you can ream it yourself). Being @ +1i don't have a port size recommendation yet. Having a 22" 6.5prc w/+2 & 28" 7saum w/+2 (wish it were +3) that both are [email protected]" gas port as i don't have suppressors. My goal is to have a little recoil mass as possible. I'm way behind on testing to give a good answer on port size and distance for short mag cartridges.

Not really what you want to hear!

 

[cajun]

I think you have that backwards. I think the shorter barrel is more gas. Gas pressure drops the further down the barrel it travels. The thing with the longer barrels and shorter gas systems you get more dwell time. The time the bullet is past the port but still in the barrel. That is why you see the rifle + lengths. To shorten dwell time.

 

[ARlife4me]

I think you have that backwards. I think the shorter barrel is more gas. Gas pressure drops the further down the barrel it travels. The thing with the longer barrels and shorter gas systems you get more dwell time. The time the bullet is past the port but still in the barrel. That is why you see the rifle + lengths. To shorten dwell time.

if you're replying about my comment, then that's not what i'm talking about.

 

[cajun]

if you're replying about my comment, then that's not what i'm talking about.

No. I was replying to the OP's initial post.

 

[C-130 Dude]

probably gonna be like a True Dissipator. very finicky, which is why we have the fake Dissipator, and probably the fake news.

you might get it tuned just right for a particular load, declare triumph, take a victory lap. any variation from that one load, and it's back to the drawing-board if the dwell-time (gas-port to muzzle) is too short to give you a variance window.

if you can live with that handicap, then by all means, go for it! AR's are easy enough to tune, I'd use an adjustable gas block, and have the gas port drilled-out so it's overgassed, and then throttle it with the adj GB, play with buffer weights, springs. Take good notes. You can do a lot of science experimenting, worthy of its' own science fair booth (if only they allowed such things).

just my 2 cents.

I've been down this road more that I wanted too. The best thing you mentioned is to take good notes. When tuning, change ONE thing at a time. Then test what you did. Write down what you did. Then move on from there. The op may be in for a lengthy process. Tuning up AR guns can be real fun....