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Posted: 6/26/2014 10:32:16 AM EDT
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I just built two identical rifles (his and hers) both will not cycle wolf pmc or remington .223. They eject but will not pick up another round. No I havent tried xm193 etc as the cheap stuff is what I have a lot of.
Relevant parts list Ballistic Advantage 14.5 melonited mid length barrel. 5.56 1/7 twist .625 gas block diameter Rainer Arms RAC SLR rifle works clamp on gas block AIM BCG Aero precision upper/ lower Carbine buffer and spring. I made sure that the gas block and tube was centered and air flowed freely into the barrel from the gas tube. The gas key is tight and the gas rings seem to seal. Even with the gas block opened up all the way and all the weights removed from the carbine buffer the bolt will only come back far enough to eject a round. Im leaning towards a smallish gas port as its at .076 as near as I can measure. |
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If you're 100% sure the gas block is timed right with the barrel gas port, my guess is barrel gas port and/or gas block port is too small.
Cheap steel ammo could cause short stroking, but not if you've gone as far as removing weights from the buffer. You should have no issues with that light of a buffer. |
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The chamber is smooth and PMC brass comes out shiny too. Its just from what Ive read my gas port is fairly close to the right size. Not really sure. I'm fairly certain your gas port size is about right for a mid length barrel. Some go as big as .079-.082, but yours is certainly not small enough to be giving you the problems you're having I wouldn't think. Then again, it wouldn't take much size difference at all to see a big increase in gas pressure, so perhaps I'm wrong. Try measuring the gas block gas port size. |
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I'm fairly certain your gas port size is about right for a mid length barrel. Some go as big as .079-.082, but yours is certainly not small enough to be giving you the problems you're having I wouldn't think. Try measuring the gas block gas port size. Quoted:
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The chamber is smooth and PMC brass comes out shiny too. Its just from what Ive read my gas port is fairly close to the right size. Not really sure. I'm fairly certain your gas port size is about right for a mid length barrel. Some go as big as .079-.082, but yours is certainly not small enough to be giving you the problems you're having I wouldn't think. Try measuring the gas block gas port size. Id love to but its on a barrel with a pinned and welded brake :/ The exit diameter is larger by quite a bit judging by the carbon ring around the port. Internally though? |
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Id love to but its on a barrel with a pinned and welded brake :/ The exit diameter is larger by quite a bit judging by the carbon ring around the port. Internally though? Quoted:
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The chamber is smooth and PMC brass comes out shiny too. Its just from what Ive read my gas port is fairly close to the right size. Not really sure. I'm fairly certain your gas port size is about right for a mid length barrel. Some go as big as .079-.082, but yours is certainly not small enough to be giving you the problems you're having I wouldn't think. Try measuring the gas block gas port size. Id love to but its on a barrel with a pinned and welded brake :/ The exit diameter is larger by quite a bit judging by the carbon ring around the port. Internally though? Oh wow, that sucks. You'd have to drill the welded pin out to take the block off... I wasn't even thinking about that when you said 14.5". I would think the gas block port would be drilled the same size all the way though. |
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Throw a lot of lube on the moving parts and use some good stuff for the break in period. When it gets worn in a little it might work with the cheap stuff, it might not.
My guess is small gas port. Good luck. How loose is the gas block on the barrel? It might be leaking gas around the block which will seal with carbon in time. |
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Throw a lot of lube on the moving parts and use some good stuff for the break in period. When it gets worn in a little it might work with the cheap stuff, it might not. My guess is small gas port. Good luck. How loose is the gas block on the barrel? It might be leaking gas around the block which will seal with carbon in time. Lubed the snot out of it too :) I have to hand it to SLR the gas block seals absolutely tight on the barrel. Zero carbon around it. Guess im going to have to open up the port maybe 3 thou and get some 5.56 |
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Quoted: Im leaning towards a smallish gas port as its at .076 as near as I can measure. Just to be sure, how are you measuring? The best way is to use a pin gauge, and slide it all the way into the bore. Pin gauge sets aren't too expensive. Opening up the gas port is a good option. You can always compensate with a slightly heavier buffer, restrict the flow again with an adjustable gas block, or use that new gas key thingie from rubber city armory. btw, what is your buffer weight? 3.9 right? |
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Just to be sure, how are you measuring? The best way is to use a pin gauge, and slide it all the way into the bore. Pin gauge sets aren't too expensive. Opening up the gas port is a good option. You can always compensate with a slightly heavier buffer, restrict the flow again with an adjustable gas block, or use that new gas key thingie from rubber city armory. btw, what is your buffer weight? 3.9 right? Quoted:
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Im leaning towards a smallish gas port as its at .076 as near as I can measure. Just to be sure, how are you measuring? The best way is to use a pin gauge, and slide it all the way into the bore. Pin gauge sets aren't too expensive. Opening up the gas port is a good option. You can always compensate with a slightly heavier buffer, restrict the flow again with an adjustable gas block, or use that new gas key thingie from rubber city armory. btw, what is your buffer weight? 3.9 right? I measured several times with calipers. Id have pin gauges if I was at my old job ;) I tried with a carbine buffer with the weights removed no dice, I think I will go .080 as I have an adjustable gas block on them. |
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Make sure you do not have gas leaking from between the gas block and the gas tube (like the gas tube could be too small or the hole for it in the gas block too large).
After that you might have to resize gas port. Most gas port size charts I have seen do not include mid-length gas tube. so you might be having the same problem as the dissy's (not enough barrel after gas port). |
| 14.5+mid-length gas system = a pretty short dwell time. Combine that with cheap under powered ammo you're running through it, and it's really not at all surprising that it's short stroking. On top of that, you're saying you think your gas port may be on the small side. With all those combinations going, it's almost like you're begging it to short stroke. |
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I'd run at least 200 rounds of good brass cased ammo through it, clean the crap out of it, re-lube, then try the steel case again. If that doesn't work you can look at the gas port. Just really try to get it broken in before monkeying around too much. This. |
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This. Quoted:
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I'd run at least 200 rounds of good brass cased ammo through it, clean the crap out of it, re-lube, then try the steel case again. If that doesn't work you can look at the gas port. Just really try to get it broken in before monkeying around too much. This. Agreed. The only time I had OPs issue was with junk ammo. My Rainier won't do Tula with an H buffer. After the process above, it would do "some" weaker ammo like PMC Bronze, but Tula is still out. |
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Quoted: I'd run at least 200 rounds of good brass cased ammo through it, clean the crap out of it, re-lube, then try the steel case again. If that doesn't work you can look at the gas port. Just really try to get it broken in before monkeying around too much. you cannot make a gas port smaller |
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I would not consider PMC as junk or under pressure. I have never had an issues with it in my mid length. When all of your ammo doesn't work....problem is with the rifle. If it's PMC Bronze we're talking about, it IS under pressured. This is a verifiable fact by simply looking at the chrono numbers that come in around 300-400 fps under M193 clones. |
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I would not consider PMC as junk or under pressure. I have never had an issues with it in my mid length. When all of your ammo doesn't work....problem is with the rifle. Have you chrono'ed it recently? I know a couple years ago at Area 6 USPSA multigun several guys shooting PMC Brass got DQed because they weren't making powerfactor (ammo to slow). Irronicly the guys shooting Wolf made powerfactor. If I'm not mistaken they were all shooting 18-20" guns too. Anecdotal I know, but I wouldn't take "It's good ammo" without verifying it. |
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If it's PMC Bronze we're talking about, it IS under pressured. This is a verifiable fact by simply looking at the chrono numbers that come in around 300-400 fps under M193 clones. Quoted:
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I would not consider PMC as junk or under pressure. I have never had an issues with it in my mid length. When all of your ammo doesn't work....problem is with the rifle. If it's PMC Bronze we're talking about, it IS under pressured. This is a verifiable fact by simply looking at the chrono numbers that come in around 300-400 fps under M193 clones. Well...I stand corrected. Glad my rifle shoots everything....under pressurized or not. 
ETA: What is the relation between barrel length and a mid gas system? Or, what lengths will/should function with a middy. |
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Agreed. The only time I had OPs issue was with junk ammo. My Rainier won't do Tula with an H buffer. After the process above, it would do "some" weaker ammo like PMC Bronze, but Tula is still out. Quoted:
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I'd run at least 200 rounds of good brass cased ammo through it, clean the crap out of it, re-lube, then try the steel case again. If that doesn't work you can look at the gas port. Just really try to get it broken in before monkeying around too much. This. Agreed. The only time I had OPs issue was with junk ammo. My Rainier won't do Tula with an H buffer. After the process above, it would do "some" weaker ammo like PMC Bronze, but Tula is still out. +1 to this. I would definitely fired some hotter ammo through it to see if it will cycle that first before you go messing with anything. My most recent BCM 14.5" Middy would not cyle steel case ammo right out of the box but, after about 1K of 5.56 XM193, it cycles it now. |
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I measured several times with calipers. Id have pin gauges if I was at my old job ;) I tried with a carbine buffer with the weights removed no dice, I think I will go .080 as I have an adjustable gas block on them. Quoted:
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Im leaning towards a smallish gas port as its at .076 as near as I can measure. Just to be sure, how are you measuring? The best way is to use a pin gauge, and slide it all the way into the bore. Pin gauge sets aren't too expensive. Opening up the gas port is a good option. You can always compensate with a slightly heavier buffer, restrict the flow again with an adjustable gas block, or use that new gas key thingie from rubber city armory. btw, what is your buffer weight? 3.9 right? I measured several times with calipers. Id have pin gauges if I was at my old job ;) I tried with a carbine buffer with the weights removed no dice, I think I will go .080 as I have an adjustable gas block on them. Are you certain the gasblock has no imperfections or burrs in it before you start opening up the barrel; that according to your measurements the barrel gas port is within spec??? Just a thought of course. You say your gas block is timed perfectly in relation to the barrel gas port, gas tube, and gas key. But if it won't cycle with the carbine weights removed then that is really odd. It should cycle with the weights removed, you'd think at least... Shoot full powered ammo out of it and then revisit Wolf ammo. PMC is good to go in all my 14.5's and 14.7's but it is underpowered. Now if we were talking about PMC X-Tac, that I know is NOT underpowered. But the Bronze, yes, yes it is and you need to shoot full powered brass for the first 200-300 rounds. |
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Have you chrono'ed it recently? I know a couple years ago at Area 6 USPSA multigun several guys shooting PMC Brass got DQed because they weren't making powerfactor (ammo to slow). Irronicly the guys shooting Wolf made powerfactor. If I'm not mistaken they were all shooting 18-20" guns too. Anecdotal I know, but I wouldn't take "It's good ammo" without verifying it. Quoted:
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I would not consider PMC as junk or under pressure. I have never had an issues with it in my mid length. When all of your ammo doesn't work....problem is with the rifle. Have you chrono'ed it recently? I know a couple years ago at Area 6 USPSA multigun several guys shooting PMC Brass got DQed because they weren't making powerfactor (ammo to slow). Irronicly the guys shooting Wolf made powerfactor. If I'm not mistaken they were all shooting 18-20" guns too. Anecdotal I know, but I wouldn't take "It's good ammo" without verifying it. When I was testing gas port sizes PMC Bronze was the weakest factory ammo I found, including Wolf. Sometimes on a new build after 100 rounds or so of full power ammo the gas rings get seated a bit and things smoothed out and then it will run fine on lower power stuff. There's no reason that it shouldn't run properly, there is nothing intrinsically ammo-sensitive about the configuration as long as everything is correctly put together and working. Would just double check that you don't have any gas system leaks, and that the gas block is aligned with the gas port (probably will be a gap between gas block and the shoulder on the barrel). |
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When I was testing gas port sizes PMC Bronze was the weakest factory ammo I found, including Wolf. Sometimes on a new build after 100 rounds or so of full power ammo the gas rings get seated a bit and things smoothed out and then it will run fine on lower power stuff. There's no reason that it shouldn't run properly, there is nothing intrinsically ammo-sensitive about the configuration as long as everything is correctly put together and working. Would just double check that you don't have any gas system leaks, and that the gas block is aligned with the gas port (probably will be a gap between gas block and the shoulder on the barrel). Quoted:
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I would not consider PMC as junk or under pressure. I have never had an issues with it in my mid length. When all of your ammo doesn't work....problem is with the rifle. Have you chrono'ed it recently? I know a couple years ago at Area 6 USPSA multigun several guys shooting PMC Brass got DQed because they weren't making powerfactor (ammo to slow). Irronicly the guys shooting Wolf made powerfactor. If I'm not mistaken they were all shooting 18-20" guns too. Anecdotal I know, but I wouldn't take "It's good ammo" without verifying it. When I was testing gas port sizes PMC Bronze was the weakest factory ammo I found, including Wolf. Sometimes on a new build after 100 rounds or so of full power ammo the gas rings get seated a bit and things smoothed out and then it will run fine on lower power stuff. There's no reason that it shouldn't run properly, there is nothing intrinsically ammo-sensitive about the configuration as long as everything is correctly put together and working. Would just double check that you don't have any gas system leaks, and that the gas block is aligned with the gas port (probably will be a gap between gas block and the shoulder on the barrel). Ok...so what does all this say about a new rifle/build that does shoot crappy under pressurized ammo plus full power good quality ammo right out of the gate? Was it assembled better and/or better quality components? |
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Well...I stand corrected. Glad my rifle shoots everything....under pressurized or not.
ETA: What is the relation between barrel length and a mid gas system? Or, what lengths will/should function with a middy. Quoted:
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I would not consider PMC as junk or under pressure. I have never had an issues with it in my mid length. When all of your ammo doesn't work....problem is with the rifle. If it's PMC Bronze we're talking about, it IS under pressured. This is a verifiable fact by simply looking at the chrono numbers that come in around 300-400 fps under M193 clones. Well...I stand corrected. Glad my rifle shoots everything....under pressurized or not.
ETA: What is the relation between barrel length and a mid gas system? Or, what lengths will/should function with a middy. A mid-length gas system has the gas port further up the barrel and doesn't send pressure back to the BCG until the bullet passes it (as with any gas system of course) and once the bullet exists, no more pressure. Because it's further up, the amount of time pressure is being pushed back into the BCG (dwell time) is lessened, and having a shorter barrel, lessens the dwell time even further. You combine that with under-pressured ammo and potentially a smallish gas port and you pretty much have done almost everything possible to encourage short stroking. |
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A mid-length gas system has the gas port further up the barrel and doesn't send pressure back to the BCG until the bullet passes it (as with any gas system of course) and once the bullet exists, no more pressure. Because it's further up, the amount of time pressure is being pushed back into the BCG (dwell time) is lessened, and having a shorter barrel, lessens the dwell time even further. You combine that with under-pressured ammo and potentially a smallish gas port and you pretty much have done almost everything possible to encourage short stroking. Quoted:
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I would not consider PMC as junk or under pressure. I have never had an issues with it in my mid length. When all of your ammo doesn't work....problem is with the rifle. If it's PMC Bronze we're talking about, it IS under pressured. This is a verifiable fact by simply looking at the chrono numbers that come in around 300-400 fps under M193 clones. Well...I stand corrected. Glad my rifle shoots everything....under pressurized or not.
ETA: What is the relation between barrel length and a mid gas system? Or, what lengths will/should function with a middy. A mid-length gas system has the gas port further up the barrel and doesn't send pressure back to the BCG until the bullet passes it (as with any gas system of course) and once the bullet exists, no more pressure. Because it's further up, the amount of time pressure is being pushed back into the BCG (dwell time) is lessened, and having a shorter barrel, lessens the dwell time even further. You combine that with under-pressured ammo and potentially a smallish gas port and you pretty much have done almost everything possible to encourage short stroking. Thank you. I actually understood that. 
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It's not rare for mid length 14.5'' barrels to not cycle under powered ammo. Lighter buffer/spring or opening the gas port are pretty much your only two options. Or hoping that it wears in and fire 5.56 through it for the time being. I agree, one of mine runs anything, another I drilled out the port to .90 and the other I'm running a reduced power Wolff spring. |
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A mid-length gas system has the gas port further up the barrel and doesn't send pressure back to the BCG until the bullet passes it (as with any gas system of course) and once the bullet exists, no more pressure. Because it's further up, the amount of time pressure is being pushed back into the BCG (dwell time) is lessened, and having a shorter barrel, lessens the dwell time even further. You combine that with under-pressured ammo and potentially a smallish gas port and you pretty much have done almost everything possible to encourage short stroking. Quoted:
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I would not consider PMC as junk or under pressure. I have never had an issues with it in my mid length. When all of your ammo doesn't work....problem is with the rifle. If it's PMC Bronze we're talking about, it IS under pressured. This is a verifiable fact by simply looking at the chrono numbers that come in around 300-400 fps under M193 clones. Well...I stand corrected. Glad my rifle shoots everything....under pressurized or not.
ETA: What is the relation between barrel length and a mid gas system? Or, what lengths will/should function with a middy. A mid-length gas system has the gas port further up the barrel and doesn't send pressure back to the BCG until the bullet passes it (as with any gas system of course) and once the bullet exists, no more pressure. Because it's further up, the amount of time pressure is being pushed back into the BCG (dwell time) is lessened, and having a shorter barrel, lessens the dwell time even further. You combine that with under-pressured ammo and potentially a smallish gas port and you pretty much have done almost everything possible to encourage short stroking. You say that like greater dwell is always better. It's not. Increased dwell means shorter timing - the gun starts trying to unlock sooner. It also means higher pressure in the gas system. Proper operation needs to balance dwell, timing, and gas volume & pressure to get the correct amount of energy, at the right time, into the operating system. |
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You say that like greater dwell is always better. It's not. Increased dwell means shorter timing - the gun starts trying to unlock sooner. It also means higher pressure in the gas system. Proper operation needs to balance dwell, timing, and gas volume & pressure to get the correct amount of energy, at the right time, into the operating system. Quoted:
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I would not consider PMC as junk or under pressure. I have never had an issues with it in my mid length. When all of your ammo doesn't work....problem is with the rifle. If it's PMC Bronze we're talking about, it IS under pressured. This is a verifiable fact by simply looking at the chrono numbers that come in around 300-400 fps under M193 clones. Well...I stand corrected. Glad my rifle shoots everything....under pressurized or not.
ETA: What is the relation between barrel length and a mid gas system? Or, what lengths will/should function with a middy. A mid-length gas system has the gas port further up the barrel and doesn't send pressure back to the BCG until the bullet passes it (as with any gas system of course) and once the bullet exists, no more pressure. Because it's further up, the amount of time pressure is being pushed back into the BCG (dwell time) is lessened, and having a shorter barrel, lessens the dwell time even further. You combine that with under-pressured ammo and potentially a smallish gas port and you pretty much have done almost everything possible to encourage short stroking. You say that like greater dwell is always better. It's not. Increased dwell means shorter timing - the gun starts trying to unlock sooner. It also means higher pressure in the gas system. Proper operation needs to balance dwell, timing, and gas volume & pressure to get the correct amount of energy, at the right time, into the operating system. I said, nor implied nothing of the sort. The question asked was the relation between mid-length gas systems with a shorter barrel and functionality and that's what I answered. Your interpretation is the issue here. |
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You say that like greater dwell is always better. It's not. Increased dwell means shorter timing - the gun starts trying to unlock sooner. It also means higher pressure in the gas system. Proper operation needs to balance dwell, timing, and gas volume & pressure to get the correct amount of energy, at the right time, into the operating system. Quoted:
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I would not consider PMC as junk or under pressure. I have never had an issues with it in my mid length. When all of your ammo doesn't work....problem is with the rifle. If it's PMC Bronze we're talking about, it IS under pressured. This is a verifiable fact by simply looking at the chrono numbers that come in around 300-400 fps under M193 clones. Well...I stand corrected. Glad my rifle shoots everything....under pressurized or not.
ETA: What is the relation between barrel length and a mid gas system? Or, what lengths will/should function with a middy. A mid-length gas system has the gas port further up the barrel and doesn't send pressure back to the BCG until the bullet passes it (as with any gas system of course) and once the bullet exists, no more pressure. Because it's further up, the amount of time pressure is being pushed back into the BCG (dwell time) is lessened, and having a shorter barrel, lessens the dwell time even further. You combine that with under-pressured ammo and potentially a smallish gas port and you pretty much have done almost everything possible to encourage short stroking. You say that like greater dwell is always better. It's not. Increased dwell means shorter timing - the gun starts trying to unlock sooner. It also means higher pressure in the gas system. Proper operation needs to balance dwell, timing, and gas volume & pressure to get the correct amount of energy, at the right time, into the operating system. You're both correct. 2IS's explanation was just a very brief and simple description that was easily understandable. |
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Quoted: Didn't see anyone ask this can you lock the bolt open on an empty mag using the CH with not a lot of resistance? |
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A mid-length gas system has the gas port further up the barrel and doesn't send pressure back to the BCG until the bullet passes it (as with any gas system of course) and once the bullet exists, no more pressure. Because it's further up, the amount of time pressure is being pushed back into the BCG (dwell time) is lessened, and having a shorter barrel, lessens the dwell time even further. You combine that with under-pressured ammo and potentially a smallish gas port and you pretty much have done almost everything possible to encourage short stroking. Quoted:
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I would not consider PMC as junk or under pressure. I have never had an issues with it in my mid length. When all of your ammo doesn't work....problem is with the rifle. If it's PMC Bronze we're talking about, it IS under pressured. This is a verifiable fact by simply looking at the chrono numbers that come in around 300-400 fps under M193 clones. Well...I stand corrected. Glad my rifle shoots everything....under pressurized or not.
ETA: What is the relation between barrel length and a mid gas system? Or, what lengths will/should function with a middy. A mid-length gas system has the gas port further up the barrel and doesn't send pressure back to the BCG until the bullet passes it (as with any gas system of course) and once the bullet exists, no more pressure. Because it's further up, the amount of time pressure is being pushed back into the BCG (dwell time) is lessened, and having a shorter barrel, lessens the dwell time even further. You combine that with under-pressured ammo and potentially a smallish gas port and you pretty much have done almost everything possible to encourage short stroking. Very good short and to the point version on explaining how a middy gas system, or any DI gas system works in the platform. Very useful post... ETA: Not bad for a 14er..., 
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Got them to run finally. XM193 didn't do it. I had to open the gas port to. 080. They both run well and eat everything. The gas blocks are adjusted about half way out for wolf. PMC bronze is actually more powerful. I can run it 4 clicks in from wolf. Milspec is in from there. Most importantly the wife is happy
p.s those RAC brakes will blow everything off the bench lol. |
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Very good short and to the point version on explaining how a middy gas system, or any DI gas system works in the platform. Very useful post... ETA: Not bad for a 14er..., Quoted:
Very good short and to the point version on explaining how a middy gas system, or any DI gas system works in the platform. Very useful post... ETA: Not bad for a 14er..., Why thank you kindly. Lots of reading and googling foreign terms like "dwell time" because I had no clue what it meant when seeing it, lots of youtube vids, and a little bit of sifting through bad info is all it took lol Got them to run finally. XM193 didn't do it. I had to open the gas port to. 080. They both run well and eat everything. The gas blocks are adjusted about half way out for wolf. PMC bronze is actually more powerful. I can run it 4 clicks in from wolf. Milspec is in from there. Most importantly the wife is happy
p.s those RAC brakes will blow everything off the bench lol. That's good to hear. If you can shoot Wolf reliably, you should pretty much be able to shoot anything... Except for may be Tula |
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