mcb Posted October 20, 2006 Share Posted October 20, 2006 The short CAR gas system does not make much sense to me on a 16 inch barreled AR. I thought the short gas system was for the 10.5 inch barrels? A 16 inch barrel is more than long enough for a mid-length system, why are so many AR's coming with the short system. The short system will run higher pressure, give you less forearm to grab, a shorter sight radius and IMHO just plain ugly. So... is there a good reason to run a short gas system on a 16 inch barrel AR? Curious Ramblings mcb Link to comment Share on other sites More sharing options...
warpspeed Posted October 20, 2006 Share Posted October 20, 2006 JP Adjustable gas block under a full length or specter length FF handguard. All problems solved Link to comment Share on other sites More sharing options...
George Posted October 20, 2006 Share Posted October 20, 2006 So... is there a good reason to run a short gas system on a 16 inch barrel AR? For 3gunnin' Nope! Reducing the "amount" of gas flow doesn't solve the early gas pulse and the unlock timing issue that actually drags the cases out of the chamber before they fully contract! No way would I run a shorty gas system on any bbl long enough for anything else. Link to comment Share on other sites More sharing options...
wsimpso1 Posted October 20, 2006 Share Posted October 20, 2006 The reason that there are any shorty gas systems with 16" barrels is because when the US military wanted a shorty, Colt and the Army put the gas port the same distance from the muzzle as on the 20" barrel, and then set everything up from there. Us civilians have to use 16" barrels, so Colt just made 16" barrels on the CAR15 pattern. That is how we ended up with little dinky handgaurds and a too short gas tube and a too short sight radius... Now, shorties can be made to run. Some work fine from the builder, and others need to be fussed over, but after the chamber is polished, if it still wants to yank the rim from the case instead of extracting the case, you have to fuss with vents or adjustable gas ports or Pigtails or Fat Tubes... Now if you insist upon having a 16" barrel, you can build with a mid length fore-end, get a better handle, longer sight radius, reliability, and get a softer cycling rifle too. But I will tell you the really hot ticket. Just build a rifle length gun, and if you want it to be handier, just have it made 18" and an adjustable stock. Billski Link to comment Share on other sites More sharing options...
cking Posted October 20, 2006 Share Posted October 20, 2006 I will take issue with full length gas tube on less than 20 inch barrels. Armalite did a study on 16/20 inch barrels to find the sweet spot for the port. What they found was an interaction between distance from bore and the muzzle in how the gas pulse looks. If gas port is too close to muzzle then a problem develops of pulse isn't long enough to supply sufficient gas for cycling in all conditions. Dirty guns high altitude. What I've found from my guns, 16inch regular port, 16inch mid port, 18inch mid port, 20 inch regular port. Is that 16inch regular port is really yanking on brass. It has always worked but brass is showing stress from extractor. Even a little deflection of the rim. Thus I don't reload brass from 16incher. Rest of guns don't beat the brass so bad. All my AR have oring in extractor. Link to comment Share on other sites More sharing options...
mcb Posted October 20, 2006 Author Share Posted October 20, 2006 (edited) That's basically what I thought it was easy and/or cheaper to just make 16 inch barrels with the short handguard rather than put the mid length system on the 16 inch barrel like it probably should have had. I can certainly see the usefulness of a short 10.5 inch barrel CAR if your a soldier fighting alot of urban fighting. It just seems and looks goofy to me put those short forearms and then have the extra 5.5 inches of barrel sticking out there beyond the front sight and forearm. I couldn't think of a good reason to do it so I figured I would ask. Personally I went with a 20 inch barrel and full length forearm. I plan on mounting my front sight just behind the muzzle break. Now if my order would just come in. This waiting is killing me. thanks mcb Edited October 20, 2006 by mcb Link to comment Share on other sites More sharing options...
Paule Posted October 20, 2006 Share Posted October 20, 2006 16" carbines are the product of the NFA. The M4 (14.5") was designed to work with the standard M16 bayonet lug on the front sight tower. As stated, had to be same distance to the flash hider to work, so the carbine (short) gas system was used. Along came civvie wants for an M4gery, and the 16" M4 came about. Same carbine gas system, bayonet wouldn't mount (too far too FH), but it was tacticool. Hard cycling and tough on case rims, etc. But a lot were sold, and a new aftermarket to fix the porblems was born. 16" barrels with a mid-length gas system are much easier to set up. No early unlock timing issues, pleasant recoil pulse, etc. Gas post is 2" farther forward, tube is 2" longer. 18" (5.56) barrels work fine with either mid or long gas systems. AMU, Crane and Aberdeen all did extensive testing on the 18" rifle length SPR barrels designed at AMU. When they do cold testing, it is really cold, sometimes 40 below or colder. The 18" SPR did fine, and a lot are deployed today. (It gets pretty cold in Afghanistan in the winter and some of those mountains are pretty high). The gas port is larger than on a 20", but not so large as to cause any narrow-range cycling issues. 18" 6.8 SPC barrels work best with either mid or short length gas systems. The 5th Group/AMU design is a mid-length. A long gas system does not work well, primarily because the port pressure of the 6.8 is around 3000psi less than a corresponding 5.56/.223. I have even seen 20" 6.8's with short gas systems that run okay. All barrels are not equal when it comes to how they are set up for cycling. There are published lists of gas port sizes for different gas system lengths, but a lot don't account for barrel lengths, only assuming 11.5, 14.5 or 20", and full power ammo such as M855 or M193. Since quality milspec ammo is virtually impossible to get, at least for now, most of the available choices will require at least some tuning to get optimum results. Link to comment Share on other sites More sharing options...
Malak Posted October 20, 2006 Share Posted October 20, 2006 I think alot of people buy then cause they look 'cool' I sell a about 12 rock river AR's a month, and the more 'Tacti-cool' they are, the fast they move. The really well built stuff, that runs, normally does not sell as well. I always try and offer the midlenth gas system for the 16inch guns first, but I normally get the 'No thanks, I want a carbine length M16' type of answer. I then just grit my teeth, and sell them what they want. Got keep quite to keep sometimes, to pay the bills Link to comment Share on other sites More sharing options...
Jeff Matzka Posted October 23, 2006 Share Posted October 23, 2006 I should know the answer to this...but I don't. Is Bushmaster's "Dissipator" model a mid-length gas system, or is that full-length. Please pardon my ignorance. Thanks. Link to comment Share on other sites More sharing options...
uscbigdawg Posted October 23, 2006 Share Posted October 23, 2006 I just finished having Benny build me a 16" rifle on a carbine gas system. Mostly, 'cause it was available, cheap and I've wanted one for a while. Too, there are a couple of 3-Gun matches coming up, where the longest shots are under 250 and there are big swings in the CQ stages. My theory is to have a short, fast, fun rifle and go with that. Honestly, after shooting this rifle, there's no reason why a 16" couldn't work in 3-Gun, but I will say that the rifle length gas systems are definitely less harsh. For iron sights, 18-20" barrels are a must. Rich Link to comment Share on other sites More sharing options...
StealthyBlagga Posted October 24, 2006 Share Posted October 24, 2006 I should know the answer to this...but I don't. Is Bushmaster's "Dissipator" model a mid-length gas system, or is that full-length. Please pardon my ignorance. The Bushmaster Dissipator is a 16" barrel with a short (carbine length) gas system hidden under a full-length handguard. The front sight base is a sight only. I think they offer it with a heavy or light barrel profile, but both would suffer from harsh cycling and port erosion common with the carbine gas system. I would suggest you have a custom midlength dissipator upper made if you really have to have a dissy. Link to comment Share on other sites More sharing options...
SinistralRifleman Posted October 24, 2006 Share Posted October 24, 2006 for 16" barrels I prefer mid-length gas systems...all around they are a lot nicer to shoot, and seem to be more reliable long term than carbine length gas systems. My latest favorite set up is milling off the front sight, and using a rifle length rail system over the gas block with flip up iron sights. Link to comment Share on other sites More sharing options...
Jeff Matzka Posted October 24, 2006 Share Posted October 24, 2006 Where can you get a 16" barrel with other than the Carbine-length gas system? Such as - longer? The Carbine-length system is the only one I ever see. Link to comment Share on other sites More sharing options...
uscbigdawg Posted October 24, 2006 Share Posted October 24, 2006 SG, There are few, but they're out there. White Oak Armament, is the first that comes to mind. DPMS is working on them and then basically, wherever Cavalry Arms gets theres. There are more still, but can't think of them off the top of my head. It's definitely a harder to find item, but far from impossible. Rich Link to comment Share on other sites More sharing options...
Scott G Posted October 24, 2006 Share Posted October 24, 2006 (edited) Compass Lake will make one to whatever profile you want, and Rock River Arms has stainless and chrome lined one's made by Wilson. Edited October 24, 2006 by Scott G Link to comment Share on other sites More sharing options...
SinistralRifleman Posted October 24, 2006 Share Posted October 24, 2006 (edited) here's the rifle length rail system with mid-length gas system I posted about earlier http://www.cavalryarms.com/guns/samson.jpg Where can you get a 16" barrel with other than the Carbine-length gas system? Such as - longer? The Carbine-length system is the only one I ever see. From Cavalry Arms...visit our dealer forum on the site, or give me a call 480-833-9685 Edited October 24, 2006 by SinistralRifleman Link to comment Share on other sites More sharing options...
uscbigdawg Posted October 25, 2006 Share Posted October 25, 2006 I'll be getting mine from Cavalry Arms! Rich Link to comment Share on other sites More sharing options...
gotm4 Posted October 25, 2006 Share Posted October 25, 2006 (edited) The carbine length gas system is most common on 16" barrels because probably because 99% of the companies making 16" barrels offer it. (it's the most common) The carbine length gas system has been around since the XM177 carbine as used in Vietnam by SF units. It survived all this time and was and is used on the XM4 and modern M4 carbine used today. I find the carbine length less desirable. I use a reprofiled (.625" under the tube) Rock River Arms 16" midlength on my 3gun rifle. I use a Yankee low profile gas block under an older JP free float tube. I use the midlength because cycles a little slower and doesn't suffer the hard extraction as some M4 rifles have. I use a standard H buffer as well. This makes for a pretty soft recoil even without a muzzle brake. My gun is a total Frankengun. Bushy lower receiver, Bushy lower parts kit, JARD adjustable trigger, Magpul MIAD grip and 93A2 stock, JP service/duty weight bolt carrier, Leitner-Wise 'Advanced Combat Bolt', PRI GasBuster charging handle, CMT upper reciever, JP tube, RRA bbl, JP Bennie Cooley muzzle brake, Larue scope mount, Leupold scope, JP irons on JP mount with YHM 1/2" risers. Edited October 25, 2006 by gotm4 Link to comment Share on other sites More sharing options...
mcb Posted October 25, 2006 Author Share Posted October 25, 2006 Nice gun gotm4, I really like the forearm setup, and the two-tone color scheme is pretty cool. SinistralRifleman where did you get that funky lower receiver? Never seen a one piece lower-stock-grip like that before. None-the-less it seem that a 16 inch barrel with a short gas system and forearm is just mostly tacti-cool as I suspected. mcb Link to comment Share on other sites More sharing options...
BigDave Posted October 25, 2006 Share Posted October 25, 2006 SinistralRifleman where did you get that funky lower receiver? Never seen a one piece lower-stock-grip like that before.mcb Uhhh...I think they manufacture them. Link to comment Share on other sites More sharing options...
mcb Posted October 25, 2006 Author Share Posted October 25, 2006 SinistralRifleman where did you get that funky lower receiver? Never seen a one piece lower-stock-grip like that before. mcb Uhhh...I think they manufacture them. Thanks BigDave I was being a little slow on the uptake. Nice looking rifles they have. mcb Link to comment Share on other sites More sharing options...
SinistralRifleman Posted October 25, 2006 Share Posted October 25, 2006 SinistralRifleman where did you get that funky lower receiver? Never seen a one piece lower-stock-grip like that before. Info on the receivers here: http://www.cavalryarms.com/MKII.html Link to comment Share on other sites More sharing options...
jkushner1 Posted November 22, 2006 Share Posted November 22, 2006 Stop your worries and get a DSA Gas Trap Carbine (the gas stops at the front sight block, then an FAL type piston is pushed mechanically back to assist the carrier assembly. Did you ever shoot 150 rounds thru a Rem 1100 or Win SX2, then shoot 150 rounds thru a Benelli, the bolt face is still as shiny as when the fest began on the Benelli, while the gas autos are like looking into an old auto muffler - carbon/powder residue galore. The ZM LR 300 (Al Zitta) I have is also a gas trap AR, with adjustable bleed, Shoot 500 rounds thru her and barely any residue - plus the recoil action of the top spring actually acts to bring the muzzle back down on target. JK Link to comment Share on other sites More sharing options...
David Thomas Posted November 22, 2006 Share Posted November 22, 2006 Where can you get a 16" barrel with other than the Carbine-length gas system? Such as - longer? The Carbine-length system is the only one I ever see. Look at the CMMG uppers and rifles. They have several 16" setups with the midlength gas system and at least one with a rifle length system. Their website is www.CMMGinc.com Also PK Firearms sells 16" Sabre Defense barreled uppers that uses the midlength gas system. Also the LMT MRP uses the midlength system on the 16" barrels. Most of the big boys have been late to the table. Armalite and Rock River are the only two "Big" name companies offering a traditional Ar15 with the midlength gas system. Link to comment Share on other sites More sharing options...
Polytech Posted December 19, 2006 Share Posted December 19, 2006 (edited) CMMG guns are top notch, and their customer service is excellent. They will also do diff. profiles on some of their barrels if you don't see one that you like. Edited December 19, 2006 by Polytech Link to comment Share on other sites More sharing options...
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