THM7 Posted April 14, 2008 Share Posted April 14, 2008 Saber Defence offers their fluted SS barrel assembly's with a mid-length gas systems. Would there be any advantage/ disadvantage with the mid-length on a 20" barrel? Link to comment Share on other sites More sharing options...
Derek45 Posted April 14, 2008 Share Posted April 14, 2008 (edited) In my opinion, the longer the gas tube, the softer the gun feels. I like a 16" middy, and a rifle length 18-20" Shooting a 16" M4 side by side with a 16" middy made a believer out of me. Edited April 14, 2008 by Derek45 Link to comment Share on other sites More sharing options...
TRUBL Posted April 14, 2008 Share Posted April 14, 2008 +1 on rifle gas system being softer Just because a 20" barrel can have a mid-length gas system.....doesn't make it a good thing. I'm trying to envision any redeeming qualities in that concept.....anything to do with suppressed rifles (not my area)?? Link to comment Share on other sites More sharing options...
Chuck Anderson Posted April 14, 2008 Share Posted April 14, 2008 20" with a mid length, I doubt. 16-18" with a mid length, could be. There is a good article in Small Arms Review talking to Jim Sullivan, a guy who has designed a gun or two. His big issue with some of the modifications to the M16 system is that end of the bbl needs to be further from the end of the gas system. The pressure in the bbl drops immediately after the projectile departs. by having 7 ish inches of bbl after the gas port you greatly increase the reliability and durability of the system. Link to comment Share on other sites More sharing options...
Run n Gun Posted April 14, 2008 Share Posted April 14, 2008 20" with a mid length, I doubt. Hi Chuck, I talked to the Sabre guys at R&R Racing's 3-gun last year and they told me that they don't make a 20" with a rifle length gas system, they're all mid-length. I started to argue the relative merits of each system and then shut up. I didn't want to aggravate a major match sponsor... Ed Link to comment Share on other sites More sharing options...
bigsaxdog Posted April 14, 2008 Share Posted April 14, 2008 i just put a 20" HBAR regular length gas system sabre barrel on my gun, so i dunno about the mid-length thing.....i really don't think the mid-length thing would be the ticket, though.... Link to comment Share on other sites More sharing options...
Chuck Anderson Posted April 14, 2008 Share Posted April 14, 2008 20" with a mid length, I doubt. Hi Chuck, I talked to the Sabre guys at R&R Racing's 3-gun last year and they told me that they don't make a 20" with a rifle length gas system, they're all mid-length. I started to argue the relative merits of each system and then shut up. I didn't want to aggravate a major match sponsor... Ed They must have taken your conversation to heart because they are selling them now. Looks like the competition specific guns are mid-length with longer tubes though. Link to comment Share on other sites More sharing options...
fastshooter03 Posted April 14, 2008 Share Posted April 14, 2008 I've noticed the same thing with Sabre defense having a mid-length gas system. This is not a good thing for 20" unless they use a smaller gas hole diameter in the barrel. Only Sabre can tell unless someone has one of their barrels and would like to take off the gas block and measure the gas hole diameter. Nick Link to comment Share on other sites More sharing options...
HSMITH Posted April 14, 2008 Share Posted April 14, 2008 I have reluctantly been looking at the AR platform from a performance and reliability point of view, and this much I have figured out about the gas system: Gas pulse force is controlled by the volume of gas tapped, pulse duration is controlled by gas port location in relation to the end of the barrel, timing of gas delivery to the bolt carrier is controlled by the length of the gas tube. I am still sorting out the math on how pulse duration is going to affect the unlocking, at this point though all I know is that it is a valid concern. A mid length gas system is on the list of things to test. As with all things it needs to be proportional and balanced, but I have a ways to go before I have my version of what that proportion and balance needs to be. Link to comment Share on other sites More sharing options...
steel1212 Posted April 14, 2008 Share Posted April 14, 2008 Umm I gots ones of them thar barrels....but I ain't takin off the gas block to mesur its Seriously though, I have a PRI adjustable gas block on it and with that I don't see how a rifle gas system would be diffrent than a Middy WITH the adjustable gas. Honestly I've never shot a rifle length gas system with a 20" barrel so I couldn't tell you how they feel either. I did find it kind of odd that they went with the middy gas on their 18s and 20s. Link to comment Share on other sites More sharing options...
Derek45 Posted April 15, 2008 Share Posted April 15, 2008 (edited) I have a 16" SABRE middy. It's not set up for 3-GUN, but it's a really nice barrel. Edited April 15, 2008 by Derek45 Link to comment Share on other sites More sharing options...
scirocco38s Posted April 15, 2008 Share Posted April 15, 2008 I have 3 midlength 16" guns and they shoot much better than a carbine gas system. My 18 and 20 inch guns run rifle lenght systems and though softer they seem to be a little sluggish compared to the mids. If you look at the pressure curves generated at the gas port rifle lenght is around 18,000 psi, carbines are 40,000psi and midlenght runs in between. I find midlenght much more forgiving than the carbines, the recoil impulse is smoother and still fast. Overall the best of all worlds. That aside the rifle lenght systems will shoot just as fast as you can. For any of these guns to run reliably you must have at least 4 inches of barrel in front of the gas port. If you get into the shorter systems then they start playing with the gas port size and gas tube size and recoil buffer systems to make them reliable. I have a factory 20 inch colt barrel from an old sporter and the gas port is around.080, the carbine ports run in the .064 range, but the 18inch barrels with the rifle length systems run a.100-.110 gas port. I havent measured a midlength gas port but would geuss it will be in the.080 range. Bear 1 other thing when choosing barrel versus gas system. The more barrel you have in front of the gas port increases pressure in other areas. I had a Krieger 24 inch barrel that would start showing pressure signs in the brass that was no issue for the 20inch gun. Also the gas port in the 24 inch was the same size as the carbine barrel. I ended cutting the barrel down to 19inches and increasing the size of the gas port as it would no longer function with the smaller port in the shorter barrel. I guess what I am saying is that the gas system and gas port size are interrealted to the amount of barrel in front of the gas port. Adjustable gas blocks can also help with the recoil impulse and make the gun shoot much differently than stock. If you shoot a friends gun and like the way it shoots and it is accurate then build or buy oyur gun that way and learn how it shoots. Link to comment Share on other sites More sharing options...
Chills1994 Posted April 15, 2008 Share Posted April 15, 2008 (edited) I went with a 20" barrel with a rifle length gas system because I wanted the gas block (with a little bit of rail) to be out in front of the handguard / free float tube. I was thinking ahead to the time when I might have a JP rifles adjustable gas block and it would make getting to the adjusting set screw so much easier, especially since I didn't have a JP FFT or some other ventilated FFT at the time. Actually, I still don't have some ventilated FFT. Hmmn.. I was also thinking ahead to the time when I might want to hang something off the gas block. That was before I knew if I was going to shoot Tac Optics (one scope only) or just Limited (iron sights only). Actually, I still don't know what I am going to shoot... Hmmmn.... I hear up close nothing is faster than irons, though I was looking for an 18" barrel with a rifle length gas system for the longest time but they seemed rarer than hen's teeth about this time last year. I don't know if that has changed or not. There were some barrels that were close to what I wanted including the Sabre Defence barrel the OP is asking about now. I tripped over a new semi complete RRA 20" upper for less than what the barrel makers were asking just for their barrels alone, so I snatched it up. (Hmm... what to do? what to do with that AR upper I still have? ) Previously, I had posted a few questions here about it and everybody's advice was to get the 20 incher. I could always get it fluted, cut down to 18" , bead blasted and re-threaded at a later time . Edited April 15, 2008 by Chills1994 Link to comment Share on other sites More sharing options...
THM7 Posted April 15, 2008 Author Share Posted April 15, 2008 Well I put a order in for the Saber 20" fluted barrel without too much thought. Then I read the article in Small Arms Review (Lawman..referenced) and a little research on this fourm and that got me wondering about this particular setup. In reality I am sure it will work fine and I can only assume production costs play a role. It seems the consensus is 20" barrel should use a rifle length gas system and anything else might be less than optimum. Worse case is I cut it back or use it as a spare for my M16. THX Link to comment Share on other sites More sharing options...
kurtm Posted April 15, 2008 Share Posted April 15, 2008 Fluting blows! turn that thang down to .80 or .75 under the handguards, stick a sight right out to the end of the barrel behind the comp and see what we are talking about...NBN, nothing beats iron up close!!!!! You know you want to, so just do it. As an aside I custom made a 24" barrel with an extended gas system, 3" past rifle length, and that thing would run out on the recoil spring with a standard spring making for the softest recoiling rifle I have ever shot, the down side was it would only run with GI 30 round mags and only clean and oiled! I will probably only use it over seas, but I think I am on the rihgt track. Benny makes a very nice 24" iron sight rifle and it is the heat!!! sight radius is 1" longer than an M1A and with the adjusible gas block and rifle length gas system it is as soft as any out there. I was playing with mine the other day out to 600 yds on flash targets and it was cool to see the sight on those tiny things. ( note at 600 yards, you had to just aim a bit below the flash cards as the 10" disc was invisible!) KURTM Link to comment Share on other sites More sharing options...
BPiatt Posted April 15, 2008 Share Posted April 15, 2008 One of the AR's I use for my police work is the DPMS Tactical 16. It's a 16" barrel with a rifle length gas system. Kind of contrary to what has been posted here but here's the thought behind this gun. You have the handy 16" overall length, you have a full handguard to hold onto, and what I consider most important thing to me is a long sight radius. Another gun company offers the same configuration however their gas system is actually a carbine length under the handguard and they put a second front sight assembly up front just for sighting purposes. I have found ONE factory load that the gun would not cycle. It was old Israeli Samson 55 fmj, that someone donated to the department. Other than that, the gun eats anything I put in it. From 50 gr HP. American Eagle to 77 gr. military and everything in between. The gun feels as soft as the 20" gun I shoot in Tac. Iron. FYI, Tony Holmes just got the DPMS Tactical 16 barrel with a carbon fiber handguard and is using it for his current competition gun in Tac. Optics. He's already shot a 1 1/2" group at 300 yds with it. He has a titatium BCG in it and he says it's the best gun he's ever had. Now I'm just waiting for my new upper to arrive.... and guess what it looks like ;-) One more comment on the other posts. I've gathered from the posts that people are putting adjustable gas blocks on a gun and expecting to get more gas to the system. Remember that the port size in the barrel only allow so much gas out. What gas block you put on won't increase it at all, it can only restrict the amount of gas. Link to comment Share on other sites More sharing options...
kurtm Posted April 15, 2008 Share Posted April 15, 2008 Okay Bruce, I guess it looks like a 24" Benny Hill Iron Sight Special with a .045 front sight and full length gas system....did I miss the guesss?? KurtM Link to comment Share on other sites More sharing options...
Chills1994 Posted April 15, 2008 Share Posted April 15, 2008 (edited) Bruce Piatt wrote: I've gathered from the posts that people are putting adjustable gas blocks on a gun and expecting to get more gas to the system. Remember that the port size in the barrel only allow so much gas out. What gas block you put on won't increase it at all, it can only restrict the amount of gas. Thanks for chiming in Bruce. You too Kurt! Nahhh... I had thought about cobbling together my Franken-gun with an 18" barrel with a rifle length gas system and then outfitting it with a JP Rifles adjustable gas block. My goal was to assemble this gun from "scratch" and to learn something about building AR's along the way. I was intending to use the gas block as just a way to tune the gas down to the bolt/BCG, and hopefully, reduce felt recoil to the shoulder, giving it just enough gas to cycle the system. And maybe allowing quicker follow up shots. BUT.... BUTT!!! I called around and called around and it looked like getting an 18" stainless barrel with the rifle length system, that was also fluted, threaded and bead blasted was going to be a one off custom job and was going to cost over $500 just for the barrel. So I came back in here on this sub-forum and the consensus was to buy a 20" to start, and if I want to chop it down to 18 " and re-thread, flute it, and bead blast it, I could do that at a later time. So when I saw a semi-complete (sans BCG) RRA 20" stainless upper with a threaded on A2 flash hider for $450 (retail!), I snatched it up. Well, at least I got 2 out of my 4 requirements filled (stainless heavier barrel that had been bead blasted and threaded). So there went my perceived need for a JP Rifles adjustable gas block. <sigh> Maybe on the next build, whenever or whatever that will be.... <sigh> Edited April 15, 2008 by Chills1994 Link to comment Share on other sites More sharing options...
bigsaxdog Posted April 15, 2008 Share Posted April 15, 2008 great thread!! i said i just got a new 20" sabre HBAR, and one of the things that mike curlett(sp?) at sabre told me is that they don't gas them real hard, so no need for that variable gas block gizmo. i had some 40gr, fast powder loads that were cool in my old 20" dpms barrel, real soft, fast recoil impulse, blip, blip! wouldn't run at all in the sabre. 55's w/3031 turned the thing into a jam-a-matic. ran 69's and 77's w/varget great, so the lesson is....there's alot of voodoo in powder speed/gas port size-location. i'm thinking about a long barrel, long range one, saw that krieger makes a 26". anybody ever try it? Link to comment Share on other sites More sharing options...
THM7 Posted April 16, 2008 Author Share Posted April 16, 2008 (edited) Great...maybe it needs the mid-length gas to run....should have "left well enough" alone. Edited April 16, 2008 by THM7 Link to comment Share on other sites More sharing options...
mpeltier Posted April 16, 2008 Share Posted April 16, 2008 Dave, was that Sabre with Mid length gas??? I cant think of any good reason for mid length gas on a 20" bbl. 16" bbl with mid gas ok but on a 20" mid gas only maks sense cosmetically as you can hide a lo profile gas block under a full length handguard. To me though cosmetics is not a good reason though it may be to a company for marketing reasons. Link to comment Share on other sites More sharing options...
bigsaxdog Posted April 16, 2008 Share Posted April 16, 2008 yo mark....missed the last couple of matches, went to a couple of pistol matches, so...i'll be baaacckk!! that's what i was gettin' at, my saber barrel is a standard HBAR, 1-8, stainless, long gas system. i just think the gas hole is small. there's gotta be some design issues with that fact. i think they're designed with standard mil-spec 5.56 in mind, and i bet that stuff uses slower powders. paul the cop that always shoots w/us uses that XM198(i think that's the right #), and it ran mine great. he's got a naked muzzle 16"gun and in it the stuff is gawd-awful loud, huge flash. those gas holes were designed w/ammunition parameters in mind, i think. i'm sure the "army dogs" experimented with a few of these before they came up with 20" and 14.5". my 16" w/ the short gas system is nasty, bet it'd be better if you took 1.5" off the end to balance the gas a bit more.......just my .02, blah, blah.....see you soon..... Link to comment Share on other sites More sharing options...
scirocco38s Posted April 16, 2008 Share Posted April 16, 2008 Depending on the ammo you are using a 20 inch rifle system needs .080 at the gas port and some even run.100. You arent going to overgas a 20" like a 16 with a carbine gas system. If you have an adjustable gas block it is ok because you only have to adjust it once. The key for this isnt just gas pressure but volume as well, Lower pressures require more volume because the gas system is larger. All the cures to make the carbine gas system feel more like the rifle system are based around longer /larger gas tubes trying to slow down the gas impulse some. 16 inch midlengths are just a great comprimise and allow you some flexibility with ammo over the carbine. Generally, if a rifle length system wont run it is gas port size to small. Link to comment Share on other sites More sharing options...
THM7 Posted May 1, 2008 Author Share Posted May 1, 2008 I was told shorter gas tube (mid length) increases reliability and can reduce weight. Link to comment Share on other sites More sharing options...
Religious Shooter Posted May 1, 2008 Share Posted May 1, 2008 I was told shorter gas tube (mid length) increases reliability and can reduce weight. Did they say how it would reduce weight? Link to comment Share on other sites More sharing options...
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