Posted: 12/25/2011 7:55:17 PM EDT
| I need a lightweight rifle length barrel. Or hell, just a standard profiled rifle barrel. Preferrably without a fsb installed. I'm going to have it cut to 16 in, and the gas port opened up. Recontoured as necessary. Will go on a lightweight dissipator build. I was really excited by a Sabre rifle barrel assembly on closeout from midway, but they changed the price before I could buy it. Is a surplus A2 barrel going to be my best bet? Would like 1 in 8 or 1 in 7 twist. I can deal with whatever steel type or lining. Anyone have any leads? I don't want to spend a hell of a lot on a match grade barrel if I'm just going to cut it down. |
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I would go for an existing dissipator style barrel. Rifle length means rifle length gas tube, which is more finicky on a carbine length barrel. I'd definitely go midlength gas system on such a build. Yeah, that is very true. The point of using rifle gas is avoiding the weight of an extra gas block under the handguards, while still retaining the full rifle length sight radius. The plan is to drill the port out to .115, or maybe .120 (all the way). I'll be using an adjustable gas tube to regulate gas too. |
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What C-C said.
Why would you buy a 20" heavy bbl and cut it down/reprofile when you could get something like a DD LW 16" bbl, for just one example off the top of my head. |
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Quoted: What C-C said. Why would you buy a 20" heavy bbl and cut it down/reprofile when you could get something like a DD LW 16" bbl, for just one example off the top of my head. Sight radius. |
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I've had very good results with YHM barrels (Wilson mfg.).
Here's a Link. |
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Hmm, that could work. Anyone stock these other than YHM? |
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What C-C said. Why would you buy a 20" heavy bbl and cut it down/reprofile when you could get something like a DD LW 16" bbl, for just one example off the top of my head. Sight radius. Irrelevant. You can only put the FSB gas block so far forward regardless of configuration under the handguards/rails. |
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What C-C said. Why would you buy a 20" heavy bbl and cut it down/reprofile when you could get something like a DD LW 16" bbl, for just one example off the top of my head. Sight radius. Irrelevant. You can only put the FSB gas block so far forward regardless of configuration under the handguards/rails. Its been done before and worked. Colt 605 was the first incarnation, I believe. It worked but was iffy in cold weather. There are some posters in the retro forum that have made them work by opening the gas port up a little bit. I wanted to try it anyway. |
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I did a few of these and I always used lightly used or new Colt or FN gov't profile surplus barrels. http://i1191.photobucket.com/albums/z476/mongo0011/DSC02102.jpg http://i1191.photobucket.com/albums/z476/mongo0011/DSC01982.jpg Nice! Did you open up the gas port too? What diameter? |
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I did a few of these and I always used lightly used or new Colt or FN gov't profile surplus barrels. http://i1191.photobucket.com/albums/z476/mongo0011/DSC02102.jpg http://i1191.photobucket.com/albums/z476/mongo0011/DSC01982.jpg Nice! Did you open up the gas port too? What diameter? 0.102", IIRC. I'll have to look up some notes or threads here. It might have been 0.106", but 0.102" sounds correct. I think I did 3 or 4 of these. I tested them with all kinds of setups, meaning different bolt carriers and different buffers, going from the lightest setup to the heaviest. All ran fine with everything except the last one. For some reason it wouldn't run with an M16 carrier and a 9mm buffer, which is the heaviest setup I had at the time. I have more pics somewhere. The last one I did had a LaRue 12" rail. That's the one that wouldn't run the heavy moving mass setup. Found it: 
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I did a few of these and I always used lightly used or new Colt or FN gov't profile surplus barrels. http://i1191.photobucket.com/albums/z476/mongo0011/DSC02102.jpg http://i1191.photobucket.com/albums/z476/mongo0011/DSC01982.jpg Nice! Did you open up the gas port too? What diameter? 0.102", IIRC. I'll have to look up some notes or threads here. It might have been 0.106", but 0.102" sounds correct. I think I did 3 or 4 of these. I tested them with all kinds of setups, meaning different bolt carriers and different buffers, going from the lightest setup to the heaviest. All ran fine with everything except the last one. For some reason it wouldn't run with an M16 carrier and a 9mm buffer, which is the heaviest setup I had at the time. I have more pics somewhere. The last one I did had a LaRue 12" rail. That's the one that wouldn't run the heavy moving mass setup. Found it: http://i1191.photobucket.com/albums/z476/mongo0011/DSC02580.jpg Thanks for looking! Hmm...so it would seem the more mass behind the barrel, the more gas you need. I shouldn't have to open the gas port very much with my lightweight bolt carrier and standard carbine buffer. In theory. 
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From the archives
On my first build I crept up on the gas port and got it to run fine at 0.105". Through my builds, I had one opened up to 0.110". IIRC, the last one, the one in the last pic with the LaRue rail, was opened up to 0.110". I used to spend WAAAAAAAAAAAAY too much time in the tech forums and WAAAAAAAAAAAAAAAAY too much money playing around with this or that. I've calmed down quite a bit in the last four or five years. I still feel the itch to mess with everything out there, but I get veto'd alot. |
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From the archives On my first build I crept up on the gas port and got it to run fine at 0.105". Through my builds, I had one opened up to 0.110". IIRC, the last one, the one in the last pic with the LaRue rail, was opened up to 0.110". I used to spend WAAAAAAAAAAAAY too much time in the tech forums and WAAAAAAAAAAAAAAAAY too much money playing around with this or that. I've calmed down quite a bit in the last four or five years. I still feel the itch to mess with everything out there, but I get veto'd alot. Mongo, Thanks for that link. In another thread, a few people came to that same spread, ie. .105-.110. I wanted to go to .115 with the MGI adjustable gas tube. By my very simple reasoning, I'd imagine this would put me almost overgassed with the 16 in barrel, lw carrier, carbine buffer, and extra power buffer spring. The idea is to achieve reliability with any ammo, wolf included, while still having the option to increase gas in cold weather, or in case of extreme fouling. I would think I could ttune down the gas to get that "sweet spot" for accuracy, or to make recoil almost nill. Unfortunately for my sake, I have noone to veto me.
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It is simply my opinion, but with the builds I did and the somewhat extensive testing I did, I don't see the need to go anything over 0.110" UNLESS you have problems. Even if you have issues, there are adjustments that can be done with the moving mass that might work.
On the flip side, let's say you over drill and get some crazy results. The fix is really easy. Drill and tap your gas port for a small setscrew, then drill the setscrew to the correct gas port size. ADD: I always kept my builds in the 16.5" range. I'm not sure if that extra 1/2" made any difference. |
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It is simply my opinion, but with the builds I did and the somewhat extensive testing I did, I don't see the need to go anything over 0.110" UNLESS you have problems. Even if you have issues, there are adjustments that can be done with the moving mass that might work. On the flip side, let's say you over drill and get some crazy results. The fix is really easy. Drill and tap your gas port for a small setscrew, then drill the setscrew to the correct gas port size. ADD: I always kept my builds in the 16.5" range. I'm not sure if that extra 1/2" made any difference. That's what I'm afraid of. I don't want to have to pull the fsb off and redrill from .110". I think I'll be ok with the relatively low mass I'll be working with. Are there weights inside a standard carbine buffer to swap out? |
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Have you thought about replicating the ADCO "cruiser" barrel? It's a mid-length gas 16in barrel with rifle length sights? I want to build a 605ish gun at some point and thought that would be the way to go... Yeah, that would be the sensible thing, but I wanted to avoid the added weight of the mid length gas block. |
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It is simply my opinion, but with the builds I did and the somewhat extensive testing I did, I don't see the need to go anything over 0.110" UNLESS you have problems. Even if you have issues, there are adjustments that can be done with the moving mass that might work. On the flip side, let's say you over drill and get some crazy results. The fix is really easy. Drill and tap your gas port for a small setscrew, then drill the setscrew to the correct gas port size. ADD: I always kept my builds in the 16.5" range. I'm not sure if that extra 1/2" made any difference. That's what I'm afraid of. I don't want to have to pull the fsb off and redrill from .110". I think I'll be ok with the relatively low mass I'll be working with. Are there weights inside a standard carbine buffer to swap out? To get something like this to run somewhat properly, you will have to pull the FSB at least once. Go to 0.110" and forget about it. If you find issues, play with the moving mass. I wouldn't mess with the buffer. Just get the standard carbine buffer - no H, H2, H3, etc. - and run that with whatever bolt carrier you have. |
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From the archives On my first build I crept up on the gas port and got it to run fine at 0.105". Through my builds, I had one opened up to 0.110". IIRC, the last one, the one in the last pic with the LaRue rail, was opened up to 0.110". I used to spend WAAAAAAAAAAAAY too much time in the tech forums and WAAAAAAAAAAAAAAAAY too much money playing around with this or that. I've calmed down quite a bit in the last four or five years. I still feel the itch to mess with everything out there, but I get veto'd alot. Mongo, I disagree, your time spent in the tech forum back in the day was some of my favorite posts. Especially when you were building your SPR. I still have your pics from your deck on my hdrive. I learned alot, get back in there, its been kinda lame as of late. |
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I have a couple of 16.5 inch rifles with rifle length gas tubes, they work just fine.
If you want to do your own FSB, how about a 41V50 chrome lined barrel with no sight: 1:7 20" AR barrel . |
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I have a couple of 16.5 inch rifles with rifle length gas tubes, they work just fine. If you want to do your own FSB, how about a 41V50 chrome lined barrel with no sight: 1:7 20" AR barrel . That's essentially what I used. I just have a thing for Colt barrels. The FN barrels are equal. I even made two from EMCO barrels. All military surplus. And I wanted 1/7 twist. |
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I have a couple of 16.5 inch rifles with rifle length gas tubes, they work just fine. If you want to do your own FSB, how about a 41V50 chrome lined barrel with no sight: 1:7 20" AR barrel . That's essentially what I used. I just have a thing for Colt barrels. The FN barrels are equal. I even made two from EMCO barrels. All military surplus. And I wanted 1/7 twist. ? |
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I have a couple of 16.5 inch rifles with rifle length gas tubes, they work just fine. If you want to do your own FSB, how about a 41V50 chrome lined barrel with no sight: 1:7 20" AR barrel . That's another option for retro builders to start from. Cool. |
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I have a couple of 16.5 inch rifles with rifle length gas tubes, they work just fine. If you want to do your own FSB, how about a 41V50 chrome lined barrel with no sight: 1:7 20" AR barrel . That's essentially what I used. I just have a thing for Colt barrels. The FN barrels are equal. I even made two from EMCO barrels. All military surplus. And I wanted 1/7 twist. ? EMCO had a contract to make A2 upper receiver assemblies some time in the past. You will occasionally see a gov't barrel stamped "E MP 1/7 NATO". They had a bad run of barrels with rough chambers, which essentially put them out of supplying uppers in the future. Or the story goes. |
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I have a couple of 16.5 inch rifles with rifle length gas tubes, they work just fine. If you want to do your own FSB, how about a 41V50 chrome lined barrel with no sight: 1:7 20" AR barrel . That's essentially what I used. I just have a thing for Colt barrels. The FN barrels are equal. I even made two from EMCO barrels. All military surplus. And I wanted 1/7 twist. ? EMCO had a contract to make A2 upper receiver assemblies some time in the past. You will occasionally see a gov't barrel stamped "E MP 1/7 NATO". They had a bad run of barrels with rough chambers, which essentially put them out of supplying uppers in the future. Or the story goes. I had several of those bad barrels that I picked up without checking them well. I bought about a half dozen or so cheaply at a local gun show and about half of them were unusable due to bad chambers. They looked like they had been cut with a hand drill and I was told by someone with machining experience that they probably tried to use their reamers longer than they should have before switching them out. Oh well, live and learn.
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I have a couple of 16.5 inch rifles with rifle length gas tubes, they work just fine. If you want to do your own FSB, how about a 41V50 chrome lined barrel with no sight: 1:7 20" AR barrel . That's essentially what I used. I just have a thing for Colt barrels. The FN barrels are equal. I even made two from EMCO barrels. All military surplus. And I wanted 1/7 twist. ? EMCO had a contract to make A2 upper receiver assemblies some time in the past. You will occasionally see a gov't barrel stamped "E MP 1/7 NATO". They had a bad run of barrels with rough chambers, which essentially put them out of supplying uppers in the future. Or the story goes. Where do you usually find your surplus barrels at? EE? Some special magic secret source? |
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There's always a couple on the EE. Often they show up in some of the surplus vendor's hands. When I wanted one, I could almost always find one at a reasonable price. I'm sure there's fewer now than there were then, but I wouldn't expect to have too much trouble.
Many vendors even manufacture new barrels to the same spec. - length, profile, twist, etc. Bushmaster sells an M16A2 profile barrel, but it would likely be 1/9 twist. While not an issue for most, I only use 1/7 barrels, unless I have a specific need otherwise. |
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There's always a couple on the EE. Often they show up in some of the surplus vendor's hands. When I wanted one, I could almost always find one at a reasonable price. I'm sure there's fewer now than there were then, but I wouldn't expect to have too much trouble. Many vendors even manufacture new barrels to the same spec. - length, profile, twist, etc. Bushmaster sells an M16A2 profile barrel, but it would likely be 1/9 twist. While not an issue for most, I only use 1/7 barrels, unless I have a specific need otherwise. Yeah, PSA is supposed to be the commercial variant of FN. I have yet to shoot any of their barreled rifles. |