RIFLE LENGTH GAS SYSTEM ON 16IN.BARREL

[newguy]

Considering a new build.

What are your thoughts on a rifle length gas sys on a 16 in. barrel for semi auto only.

What would be the neg's and positives of this system.


I know how highly thought of the middy's are as far as parts wear.

I like the rifle length site system on a 16 in.

Would this be a good set up since I want a fixed FSB and rifle length rail

[kmrtnsn]

The only company that I know that makes a 16" barrel with a rifle radius FSB is Bushmaster and it still retains a carbine length gas system and is 1/9. Why not just go 18"?

[xrayoneone]

Colt tried this with the model 605. It had the full length gas system and the 16" barrel. It was unreliable and only saw limited service.

I have one of the Bushmaster Dissipator barrels and like kmrtnsn says it has the carbine length gas system. The gas system is located in a cut down FSB behind the full FSB. With A2 style hand guards there is no modification needed. Mine is an accurate barrel and I used it to build a retro style carbine with A1 style hand guards on a Colt A1 upper. With those handguards I had to trim a little of the aluminum heat shield to get them to fit. I like it.

Some rail handguards may not fit on this barrel due to the cut down FSB but others seem like they would do fine.

[newguy]

I saw this setup on CMMG web site it got me currious if COLT had bad luck with it maybe its not a good idea

[The_Biased_Observer]

I have an old SP1 upper cut to 16 inches. Took some breaking in to get to where I could fire a mag without a malfunction, since then though it fires m193 reliably.

I don't remember though if the smith enlarged the gas port or anything and I'm currently running a rifle buffer in it.

[spamsammich]

I would think a rifle length 16" barrel wouldn't have enough dwell time and you would have to muck around with port sizes to try and get enough gas in the system to cycle reliably.

[orionz06]

If you want the longer sight radius go with a longer rail. A 13.2" rail will cover the block on a rifle length gas system.

Check this link for images: http://www.laruetactical.com/pics/Charts/StealthProfileSheet_Rev-3-16-09.jpg

I know LaRue and Troy make rails longer than 13", so you should be set there.

[SPDGG]

If you want the longer sight radius go with a longer rail. A 13.2" rail will cover the block on a rifle length gas system.

Check this link for images: http://www.laruetactical.com/pics/Charts/StealthProfileSheet_Rev-3-16-09.jpg

I know LaRue and Troy make rails longer than 13", so you should be set there. +1 Agree. IMHO: Anything 16" the max gas port length would be Mid-Length 9". Which you can find barrels & gas tubes much easier, Has become Std. Items from most vendors. Also, the not so common Intermediate, believe thats 10"??? Would think getting gas tubes for the Int. 10" system would be a lot harder.

[lindertw]

.....

[LOKNLOD]

I used to have a 16" barrel that had been cut down (by a reputable guy who supposedly knew how to get these to run) from a 20" Gov't profile barrel.

I loved the balance, handling, and appearance, but it did not function reliably. It would run for a while if it started out clean and heavily lubed with hot ammo, but would begin short stroking quickly as it got a little fouled. And you could forget about using any .223 or lower pressure ammo. I wanted to keep it to tinker with and make into a KISS plinker, but unfortunately I ended up without the original FSB so I didn't bother.

As others have said, there is a dwell time gremlin at work on these, much like the shorty-short barrels, but I think it's exasperated even further with the longer system. The rifle system has the lower port pressure, and a larger volume gas tube, so it needs even more dwell time to get the gas back to work the action. That's going to require a pretty large gas port to compensate for the lack of barrel forward of the port.

[Tangotag]

I have a chopped 20" to 16" rifle length gas gun, the recoil impulse is noticeably soft. Compared to all other gas setups.
It may be more trouble than its worth some are not reliable, mine is fine though.
I would have gone with a Middy barrel but they were not an option back when I chopped my 20".


Another barrel option:
ADCO Cruiser Barrel (http://www.adcofirearms.com/acc/ProductLine_.cfm?product_category=Barrels&subcategory=5.56 Barrels) 1:8 SS Wylde chamber and middy gas.

[orionz06]

I have a chopped 20" to 16" rifle length gas gun, the recoil impulse is noticeably soft. Compared to all other gas setups.
It may be more trouble than its worth some are not reliable, mine is fine though.
I would have gone with a Middy barrel but they were not an option back when I chopped my 20".

Any tweaks needed to get it to run reliably? And the bigger concern of the OP seems to be the sight radius, not so much recoil, but I could be wrong. The best solution of reliability and sight radius is a middy gas system on a long rail.

[Tangotag]

Any tweaks needed to get it to run reliably? And the bigger concern of the OP seems to be the sight radius, not so much recoil, but I could be wrong. The best solution of reliability and sight radius is a middy gas system on a long rail.

Not sure it helps the OP but here is the evolution of this rifle and my experience with it.
It was a 20" decent shooter for a couple years first.
Other than cutting the barrel and re-threading it I did nothing to the gas system.
The rifle for many years was a .22LR M261 adaptered plinker and had no need for the gas system being blowback.
Years later and after a good weeks worth of cleaning to remove lots of soft lead residue, I finally shot 5.56 ammo down the barrel with no problems.
I initally shot the 5.56 because I was thinking it might jar loose any lead built up in the gas hole easing the cleaning.

But after that I packed up the M261 adapter and just shot 5.56 since.
I had a A2 buttstock on the gun for many years with just a A2 flash hider, never took any pictures of it with that though.

With getting back into ARs from time spent in other directions. The last year I started to upgrade some of my stuff.
Last fall switched it over to mil-spec extension with a H buffer and new carbine spring. But I added the KX3 to boost back pressure.
This spring I plan to use a standard carbine buffer and A2 flash hider on this one. I don't suspect there will be any problems since it functioned fine with a rifle buffer, spring, and tube.
http://i228.photobucket.com/albums/ee73/tangotag_bucket/IMG_4106.jpg

[M0rtarMan]

Hi all,
I tried this same build last year. It was a 16" CMMG Barrel 16" w/ Rifle Length Gas Port, only I added an Adams Arms Piston Conversion. It went badly.
Initially it would not cycle, lack of "dwell time" from gas port to crown of muzzle.
The only way I could get it to cycle was adding a PWS Diablo Brake/Booster.
This fixed the "dwell time" issues. However I scrapped the idea. and re-barreled it with a 16" Carbine Barrel.
I dropped this same barrel setup onto a DI rifle this year and it worked great (55gr, 62gr, 75gr). In this case DI seemed to trump Piston. However I only run piston guns so I took the barrel setup off that rifle. The PWS Diablo booster is nearly identical to the KX-3 in function, it looks a little different, and has an integrated flash hider, and actually traps more gas due to it's design. I ran a KX-3 on it too, which seemed to work just fine. I am partial to the PWS as I am a fan boy of their systems: Here is a picture of a Diablo upper with a Diablo Booster installed

http://i119.photobucket.com/albums/o135/jnortham/DSC_1335.jpg

Needless to say I have a nearly new CMMG 16" With Rifle Gas Port and a PWS Diablo Brake/Booster. If you are interested in this setup, make me an offer. Anything reasonable will be considered.

[SoDak]

Here's a thread we had on this issue.
https://www.m4carbine.net/showthread.php?p=547340