What is the shortest barrel for a Rifle Length Gas system

[sierra77mk]

I have come to favor the recoil impulse I get with rifle gas but am looking for a shorter-handier-lighter barrel for the short range cof's.

I have 20" and 18" uppers with rifle gas on them, and 16" with mid-length gas.

Can I run a rifle gas on a 17" barrel"

Does anyone make a 17" or is that a custom proposition?

[steel1212]

I think somebody on the Noveske team runs a 17" barreled gun with rifle gas. I've heard of 16s but you don't see many of them and I don't know who makes them. I know my JP 18" ultra light is lighter than most 16s.

[sleepercaprice1]

There are 16" guns with rifle length gas systems. Bushmaster has sold the dissipator for years.

[Bryan 45]

Bushmaster dissapator is a carbine length gas systems with a lo-pro block under the handguards. The DPMS version is a rifle length system though.

[Wakal]

I just put together a 17.3" barrel (so it hits 20" with the F2 installed)...started with a 20" barrel and hacked it short, recrowned, and threaded... Easy stuff. Feels smoother than the same configuration gun (full free float, ACE stock, flat top, dot, comp) in a 16" barrel.

Next time I have a free 20" laying around, I'll try at 16.3 and see what happens

Alex

[Mickster]

I have the DPMS 16" full length adjustable gas with adjustable gas block and all the JP low mass stuff in it.

Looks good, works good, feels good.

Also took a 20", cut it to 17", put in the JP low mass stuff and it also runs with no problems.

[grywlfbg]

Most commonly, 18" is the shortest you'll see w/ rifle-length gas systems. However, MSTN uses rifle-length gas systems on their 17's.

[Northern Xtreme]

I had an upper with a rifle length gas system and a barrel that was cut down to 16", stock rifle length buffer and spring..

It would not cycle Wolf ammo, the bolt would not go back past the magazine to pick up the next round, it would cycle fine with XM193's.

[esskay]

I think somebody on the Noveske team runs a 17" barreled gun with rifle gas. I've heard of 16s but you don't see many of them and I don't know who makes them. I know my JP 18" ultra light is lighter than most 16s.

What sort of profile do you have on your JP 18" ultra light barrel? Was it a custom order? The JP site only shows a medium profile available in 18":

.650 under handguard/.875 in front of gas block

Thanks!

[Sako92S]

I just put together a 17.3" barrel (so it hits 20" with the F2 installed)...started with a 20" barrel and hacked it short, recrowned, and threaded... Easy stuff. Feels smoother than the same configuration gun (full free float, ACE stock, flat top, dot, comp) in a 16" barrel.

Alex

Same here but 17" Colt Gov't barrel which was originally 20".

My wife instead has 14.5" mid length gas system stainless barrel and it's very smooth with F2 compensator.

Both uppers has VTAC rifle length free float tubes and adjustable gas system.

[StealthyBlagga]

Dwell time becomes a big issue under 18". The gun may run just fine under normal conditions with your chosen ammo, but will start to puke if the ammo changes, the gun gets fouled or if the environmental conditions change (e.g. you travel to another range for a match). If you MUST have a rifle-length gas system, consider getting the shorter length by using a more compact muzzle brake, or consider getting a lighter weight by having the barrel reprofiled. Personally, I would go with a midlength gas system with any barrel shorter than 18".

[GentlemanJim]

As said above..dwell time can become an issue under about 17"

To some degree you an substitute amplitude of the gas pulse to compensate for duration...(port size)..its NOT the best solution however

Lots of folks have done this with some success..In my testing it gave a little harsher feel to the gun..but it does work.

At 17" you can use a standard port with good results...but some barrels, guns, may require a little tuning.

We profile our 20" and 18" barrels for customer requirments ...It reduces weight by a full nine ounces.

A side note on profiling...It is best to turn the barrel between centers on a CNC

If you just chuck one up...you inherit the runout on both the barrel thread and the extension..plus error stackup from original machining

Jim

[kellyn]

Dwell time becomes a big issue under 18". The gun may run just fine under normal conditions with your chosen ammo, but will start to puke if the ammo changes, the gun gets fouled or if the environmental conditions change (e.g. you travel to another range for a match). If you MUST have a rifle-length gas system, consider getting the shorter length by using a more compact muzzle brake, or consider getting a lighter weight by having the barrel reprofiled. Personally, I would go with a midlength gas system with any barrel shorter than 18".

I MUST have a rifle length gas system!

[olp73]

Dwell time becomes a big issue under 18". The gun may run just fine under normal conditions with your chosen ammo, but will start to puke if the ammo changes, the gun gets fouled or if the environmental conditions change (e.g. you travel to another range for a match). If you MUST have a rifle-length gas system, consider getting the shorter length by using a more compact muzzle brake, or consider getting a lighter weight by having the barrel reprofiled. Personally, I would go with a midlength gas system with any barrel shorter than 18".

I MUST have a rifle length gas system!

Mine is 17" (I got inspired by this article that I found on the net)

http://demigodllc.com/articles/evolution-of-the-3-gun-practical-rifle/

My MSTN Comp-Tac

For the last three years, I've been shooting an upper that Paul and I specced out to be extremely accurate and reasonably light weight and to give sustained accuracy with no zero shift even on long, high round-count assault courses. At the time, I had just witnessed several rifles fail catastrophically due to heat-related reliability problems and large zero shifts due to barrel heat, making the sights almost useless; I wanted an upper that wouldn't have these problems.

To retain the use of the rifle-length gas system for a more mild recoil impulse but to keep the handiness of the overall package, we went with a 17-inch barrel cut from a Krieger blank using a profile a little heavier than his normal lightweight competition uppers to better tolerate heat. The 1-in-7.7 twist rifling enables the use of heavy 75 and 77 grain ammunition which helps to beat the wind on long-range targets. The forend is a PRI float tube with heat shields, which accepts modular rails for front back-up iron sights (BUIS), vertical fore-grips (VFG), sling mounts, or bi-pods. A hard-chromed lightweight bolt carrier from Young Manufacturing completed the basic upper.

Since I shoot in "Tactical" division, I topped the upper with a 3.5x Trijicon TA11 ACOG, which provides more eye relief and a larger exit pupil than the TA01 and TA31 models. This optic requires some training to maintain high speed on close-range engagements, but enables very fast hits on long-range practical targets out to 400 or 500 yards. The rifle is completed with a lower housing a JP Enterprises four-pound single-stage trigger, and parts to suit my preferences: a Magpul MIAD grip, trigger guard, and UBR stock.

I've used my MSTN rifle at both local and major 3-Gun and practical rifle matches to rack up some wins and good finishes. When new, the barrel would deliver one-third moa groups shooting Black Hills 75-gr remanufactured ammunition. Thirty-six months and seven thousand rounds later, it still shoots moa and has proven very reliable.

[cold]

I think somebody on the Noveske team runs a 17" barreled gun with rifle gas. I've heard of 16s but you don't see many of them and I don't know who makes them. I know my JP 18" ultra light is lighter than most 16s.

Two guys on The NST run 17" barrels with rifle length gas, another guy runs a 16" middy.

[StealthyBlagga]

I MUST have a rifle length gas system!

Don't be so inflexible

I agree that a rifle length gas system is softer shooting. I favor a 20" rifle-gas barrel myself. However, at some point (IMHO below 18") the trade off of reliability versus softness starts to become unappealing. I have a 16" lightweight midlength, and it is also surprisingly soft shooting. For a match gun, I would not want to go to a gas system shorter than midlength though.

As I mentioned above, if you want a short gun you can get there with a shorter muzzle brake while still retainign a longer barrel... it makes no sense to me to chop the barrel to 16-17", only to add another 3" of muzzle brake.

Edited April 6, 2010 by StealthyBlagga