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Posted: 7/23/2014 5:44:49 AM EDT
[#1]
#Class3Problems :)
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Posted: 7/23/2014 5:53:04 AM EDT
[#2]
Quoted:
So, A few months ago my 7.5" piston upper was running good, and surprisingly slow cyclic rate give it's a pistol gas system. It was averaging around 750-800 or so. Lately, I've begun to notice it's been creeping up, and now it's extremely high, somewhere around 1100 or so. An annoyance until recently. Now when shooting suppressed I'm getting jams (even on the suppressed gas setting). So, I can only presume my gas port is eroding. The barrel is still in good shape. I can't recall how many rounds I have through the upper, but I can't imagine more than 4k or so. What are my options here? Drill and tap it for a set screw and then drill that to the port size I want? It would seem to me a little easier to hit the gas port with a tig and then drill that. Anyone had to address this before? I made this barrel specifically for this upper, profiled it exactly the way I wanted it for the best balance with that heavy piston setup. Not ready to cut it loose yet, especially with it having so much life left. https://www.youtube.com/watch?v=4ZdfjFUWG9E You can see in this video how fast the cyclic rate is, that's a 20rd mag. What life left? Sounds shot. I can't imagine drilling and tappind a plug is good for the pressure involved. Welding would seem to have it's own problems also- i.e. changing the temper/heat treatment of the barrel. |
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Posted: 7/23/2014 6:01:30 AM EDT
[#3]
Quote HistoryQuoted:
What life left? Sounds shot. I can't imagine drilling and tappind a plug is good for the pressure involved. Welding would seem to have it's own problems also- i.e. changing the temper/heat treatment of the barrel. Quote HistoryQuoted:
Quoted:
So, A few months ago my 7.5" piston upper was running good, and surprisingly slow cyclic rate give it's a pistol gas system. It was averaging around 750-800 or so. Lately, I've begun to notice it's been creeping up, and now it's extremely high, somewhere around 1100 or so. An annoyance until recently. Now when shooting suppressed I'm getting jams (even on the suppressed gas setting). So, I can only presume my gas port is eroding. The barrel is still in good shape. I can't recall how many rounds I have through the upper, but I can't imagine more than 4k or so. What are my options here? Drill and tap it for a set screw and then drill that to the port size I want? It would seem to me a little easier to hit the gas port with a tig and then drill that. Anyone had to address this before? I made this barrel specifically for this upper, profiled it exactly the way I wanted it for the best balance with that heavy piston setup. Not ready to cut it loose yet, especially with it having so much life left. https://www.youtube.com/watch?v=4ZdfjFUWG9E You can see in this video how fast the cyclic rate is, that's a 20rd mag. What life left? Sounds shot. I can't imagine drilling and tappind a plug is good for the pressure involved. Welding would seem to have it's own problems also- i.e. changing the temper/heat treatment of the barrel. No, it isn't shot, still shoots sub moa, and the rifling is crisp and sharp. Both of those methods above are commonly accepted methods. I'd just like to hear from those who have experience with that, to hear how it went. |
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Posted: 7/23/2014 6:26:03 AM EDT
[#4]
Quoted:
So, A few months ago my 7.5" piston upper was running good, and surprisingly slow cyclic rate give it's a pistol gas system. It was averaging around 750-800 or so. Lately, I've begun to notice it's been creeping up, and now it's extremely high, somewhere around 1100 or so. An annoyance until recently. Now when shooting suppressed I'm getting jams (even on the suppressed gas setting). So, I can only presume my gas port is eroding. The barrel is still in good shape. I can't recall how many rounds I have through the upper, but I can't imagine more than 4k or so. What are my options here? Drill and tap it for a set screw and then drill that to the port size I want? It would seem to me a little easier to hit the gas port with a tig and then drill that. Anyone had to address this before? I made this barrel specifically for this upper, profiled it exactly the way I wanted it for the best balance with that heavy piston setup. Not ready to cut it loose yet, especially with it having so much life left. https://www.youtube.com/watch?v=4ZdfjFUWG9E You can see in this video how fast the cyclic rate is, that's a 20rd mag. You didn't say what buffer you are running, but you can always go heavier to slow it down. You can get all the way up to a Colt X buffer. |
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Posted: 7/23/2014 6:34:43 AM EDT
[#5]
Quote HistoryQuoted:
No, it isn't shot, still shoots sub moa, and the rifling is crisp and sharp. Both of those methods above are commonly accepted methods. I'd just like to hear from those who have experience with that, to hear how it went. Quote HistoryQuoted:
Quoted:
Quoted:
So, A few months ago my 7.5" piston upper was running good, and surprisingly slow cyclic rate give it's a pistol gas system. It was averaging around 750-800 or so. Lately, I've begun to notice it's been creeping up, and now it's extremely high, somewhere around 1100 or so. An annoyance until recently. Now when shooting suppressed I'm getting jams (even on the suppressed gas setting). So, I can only presume my gas port is eroding. The barrel is still in good shape. I can't recall how many rounds I have through the upper, but I can't imagine more than 4k or so. What are my options here? Drill and tap it for a set screw and then drill that to the port size I want? It would seem to me a little easier to hit the gas port with a tig and then drill that. Anyone had to address this before? I made this barrel specifically for this upper, profiled it exactly the way I wanted it for the best balance with that heavy piston setup. Not ready to cut it loose yet, especially with it having so much life left. https://www.youtube.com/watch?v=4ZdfjFUWG9E You can see in this video how fast the cyclic rate is, that's a 20rd mag. What life left? Sounds shot. I can't imagine drilling and tappind a plug is good for the pressure involved. Welding would seem to have it's own problems also- i.e. changing the temper/heat treatment of the barrel. No, it isn't shot, still shoots sub moa, and the rifling is crisp and sharp. Both of those methods above are commonly accepted methods. I'd just like to hear from those who have experience with that, to hear how it went. OK. Not my area of expertise. Just thinking out loud. Good Luck! |
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Posted: 7/23/2014 6:47:40 AM EDT
[#6]
Quote HistoryQuoted:
You didn't say what buffer you are running, but you can always go heavier to slow it down. You can get all the way up to a Colt X buffer. Quote HistoryQuoted:
Quoted:
So, A few months ago my 7.5" piston upper was running good, and surprisingly slow cyclic rate give it's a pistol gas system. It was averaging around 750-800 or so. Lately, I've begun to notice it's been creeping up, and now it's extremely high, somewhere around 1100 or so. An annoyance until recently. Now when shooting suppressed I'm getting jams (even on the suppressed gas setting). So, I can only presume my gas port is eroding. The barrel is still in good shape. I can't recall how many rounds I have through the upper, but I can't imagine more than 4k or so. What are my options here? Drill and tap it for a set screw and then drill that to the port size I want? It would seem to me a little easier to hit the gas port with a tig and then drill that. Anyone had to address this before? I made this barrel specifically for this upper, profiled it exactly the way I wanted it for the best balance with that heavy piston setup. Not ready to cut it loose yet, especially with it having so much life left. https://www.youtube.com/watch?v=4ZdfjFUWG9E You can see in this video how fast the cyclic rate is, that's a 20rd mag. You didn't say what buffer you are running, but you can always go heavier to slow it down. You can get all the way up to a Colt X buffer. That's true, but honestly I have not had much luck with a piston setup using heavier buffers. It seems to like one buffer and that's it. I'm running an H2 buffer. H1 bolt bounces, H3 doesn't get a full stroke. I've tried an ST:T2 spikes and it bolt bounced as well. Anyone in here have a piston 7.5". |
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Posted: 7/23/2014 6:50:10 AM EDT
[#7]
Quote HistoryQuoted:
That's true, but honestly I have not had much luck with a piston setup using heavier buffers. It seems to like one buffer and that's it. I'm running an H2 buffer. H1 bolt bounces, H3 doesn't get a full stroke. I've tried an ST:T2 spikes and it bolt bounced as well. Anyone in here have a piston 7.5". Quote HistoryQuoted:
Quoted:
Quoted:
So, A few months ago my 7.5" piston upper was running good, and surprisingly slow cyclic rate give it's a pistol gas system. It was averaging around 750-800 or so. Lately, I've begun to notice it's been creeping up, and now it's extremely high, somewhere around 1100 or so. An annoyance until recently. Now when shooting suppressed I'm getting jams (even on the suppressed gas setting). So, I can only presume my gas port is eroding. The barrel is still in good shape. I can't recall how many rounds I have through the upper, but I can't imagine more than 4k or so. What are my options here? Drill and tap it for a set screw and then drill that to the port size I want? It would seem to me a little easier to hit the gas port with a tig and then drill that. Anyone had to address this before? I made this barrel specifically for this upper, profiled it exactly the way I wanted it for the best balance with that heavy piston setup. Not ready to cut it loose yet, especially with it having so much life left. https://www.youtube.com/watch?v=4ZdfjFUWG9E You can see in this video how fast the cyclic rate is, that's a 20rd mag. You didn't say what buffer you are running, but you can always go heavier to slow it down. You can get all the way up to a Colt X buffer. That's true, but honestly I have not had much luck with a piston setup using heavier buffers. It seems to like one buffer and that's it. I'm running an H2 buffer. H1 bolt bounces, H3 doesn't get a full stroke. I've tried an ST:T2 spikes and it bolt bounced as well. Anyone in here have a piston 7.5". Have you tried the heavier buffers since you noticed the over gassing problem? |
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Posted: 7/23/2014 6:59:19 AM EDT
[#8]
Quote HistoryQuoted:
Have you tried the heavier buffers since you noticed the over gassing problem? Quote HistoryQuoted:
Quoted:
Quoted:
Quoted:
So, A few months ago my 7.5" piston upper was running good, and surprisingly slow cyclic rate give it's a pistol gas system. It was averaging around 750-800 or so. Lately, I've begun to notice it's been creeping up, and now it's extremely high, somewhere around 1100 or so. An annoyance until recently. Now when shooting suppressed I'm getting jams (even on the suppressed gas setting). So, I can only presume my gas port is eroding. The barrel is still in good shape. I can't recall how many rounds I have through the upper, but I can't imagine more than 4k or so. What are my options here? Drill and tap it for a set screw and then drill that to the port size I want? It would seem to me a little easier to hit the gas port with a tig and then drill that. Anyone had to address this before? I made this barrel specifically for this upper, profiled it exactly the way I wanted it for the best balance with that heavy piston setup. Not ready to cut it loose yet, especially with it having so much life left. https://www.youtube.com/watch?v=4ZdfjFUWG9E You can see in this video how fast the cyclic rate is, that's a 20rd mag. You didn't say what buffer you are running, but you can always go heavier to slow it down. You can get all the way up to a Colt X buffer. That's true, but honestly I have not had much luck with a piston setup using heavier buffers. It seems to like one buffer and that's it. I'm running an H2 buffer. H1 bolt bounces, H3 doesn't get a full stroke. I've tried an ST:T2 spikes and it bolt bounced as well. Anyone in here have a piston 7.5". Have you tried the heavier buffers since you noticed the over gassing problem? I can give it a shot, but it sounds like a bandaid on the real problem. From my experience, buffers only pull off a very small amount of cyclic rate, like 50rpm or so, I'm nearly 400rpm too high right now. |
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Posted: 7/23/2014 7:11:55 AM EDT
[#9]
I would try a new action spring before i suspected that much gas port errosion. 4000 rounds isnt really much at all unless it was all in a single day.
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Posted: 7/23/2014 7:39:14 AM EDT
[#10]
Quote HistoryQuoted:
I would try a new action spring before i suspected that much gas port errosion. 4000 rounds isnt really much at all unless it was all in a single day. The spring in the gun was recently replaced, it has about 1000rds on it. It's about a month old. I don't think that's the issue. I'll pull the block off the gun tonight and measure the gas port. |
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Posted: 7/23/2014 9:21:33 AM EDT
[#11]
Quote HistoryQuoted:
That's true, but honestly I have not had much luck with a piston setup using heavier buffers. It seems to like one buffer and that's it. I'm running an H2 buffer. H1 bolt bounces, H3 doesn't get a full stroke. I've tried an ST:T2 spikes and it bolt bounced as well. Anyone in here have a piston 7.5". Quote HistoryQuoted:
Quoted:
Quoted:
So, A few months ago my 7.5" piston upper was running good, and surprisingly slow cyclic rate give it's a pistol gas system. It was averaging around 750-800 or so. Lately, I've begun to notice it's been creeping up, and now it's extremely high, somewhere around 1100 or so. An annoyance until recently. Now when shooting suppressed I'm getting jams (even on the suppressed gas setting). So, I can only presume my gas port is eroding. The barrel is still in good shape. I can't recall how many rounds I have through the upper, but I can't imagine more than 4k or so. What are my options here? Drill and tap it for a set screw and then drill that to the port size I want? It would seem to me a little easier to hit the gas port with a tig and then drill that. Anyone had to address this before? I made this barrel specifically for this upper, profiled it exactly the way I wanted it for the best balance with that heavy piston setup. Not ready to cut it loose yet, especially with it having so much life left. https://www.youtube.com/watch?v=4ZdfjFUWG9E You can see in this video how fast the cyclic rate is, that's a 20rd mag. You didn't say what buffer you are running, but you can always go heavier to slow it down. You can get all the way up to a Colt X buffer. That's true, but honestly I have not had much luck with a piston setup using heavier buffers. It seems to like one buffer and that's it. I'm running an H2 buffer. H1 bolt bounces, H3 doesn't get a full stroke. I've tried an ST:T2 spikes and it bolt bounced as well. Anyone in here have a piston 7.5". I have an AA 7.5 PDW kit that required a colt B buffer to quit bouncing and slow down. Short stroked with X buffer. |
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Posted: 7/23/2014 9:33:23 AM EDT
[#12]
Pistol gas ports do have pretty severe erosion since they are in such a high temperature & high pressure part of the barrel. Plus the port diameter is relatively small, so erosion makes a proportionally larger difference in energy.
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Posted: 7/23/2014 9:52:58 AM EDT
[#13]
Quote HistoryQuoted:
Pistol gas ports do have pretty severe erosion since they are in such a high temperature & high pressure part of the barrel. Plus the port diameter is relatively small, so erosion makes a proportionally larger difference in energy. Sounds like I'll weld it up and redrill, I just need to see what the diameter needs to be, I don't recall. I know it was quite small. 
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Posted: 7/23/2014 10:22:22 AM EDT
[#14]
What is your estimate of # rounds fired, and the relative percentage full-auto?
Before doing surgery I would at least try a ring to deal with extraction, plus the MGI buffer to see whether I could get enough reduction in ROF. I suspect your pessimism is warranted, though. Sam |
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Posted: 7/23/2014 11:28:55 AM EDT
[#15]
Quote HistoryQuoted:
What is your estimate of # rounds fired, and the relative percentage full-auto? Before doing surgery I would at least try a ring to deal with extraction, plus the MGI buffer to see whether I could get enough reduction in ROF. I suspect your pessimism is warranted, though. Sam I'd say 1500 round full auto, 2500 semi. |
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Posted: 7/23/2014 11:31:05 AM EDT
[#16]
deleted
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Posted: 7/23/2014 11:52:11 AM EDT
[#17]
That is not very much. I would try to repair it, then. Is bbl chromed?
Sam |
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Posted: 7/23/2014 12:00:37 PM EDT
[#18]
Quote HistoryQuoted:
That is not very much. I would try to repair it, then. Is bbl chromed? Sam It's a stainless barrel, so no chroming. |
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Posted: 7/23/2014 3:29:01 PM EDT
[#19]
Quote HistoryQuoted:
It's a stainless barrel, so no chroming. Quote HistoryQuoted:
Quoted:
That is not very much. I would try to repair it, then. Is bbl chromed? Sam It's a stainless barrel, so no chroming. Stainless erodes much more than CM/CMV steels, personally I think a stainless pistol gas barrel is a bad idea. I've read about but never seen where the gas port was partially drilled to a larger diameter (not going into the bore) and an insert of more erosion resistant material with correct size gas port was installed into the barrel. |
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Posted: 7/23/2014 8:53:13 PM EDT
[#20]
If you're sure it's a gas problem, get an adjustable gas block and keep shooting. No need to redo the hole if you can adjust on the fly.
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Posted: 7/24/2014 5:16:29 AM EDT
[#21]
Quote HistoryQuoted:
If you're sure it's a gas problem, get an adjustable gas block and keep shooting. No need to redo the hole if you can adjust on the fly. It's a piston gun, so my options are limited or extremely expensive (more expensive than a barrel). |
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Posted: 7/24/2014 6:21:02 AM EDT
[#22]
My 7.5 AA piston upper ran stupid fast out of the box with an H3 buffer. H and H2 would bounce and cause stoppages after 2 or 3 rounds. B buffer slowed it down below 1000rpm, and x buffer caused some short stroking.
The only problem with the B/X buffers is they are colt only expensive things. Slash offers his stuff as well. Try them too. Really, buffers are cheaper than new barrels and are useful when tuning other guns later if you have them laying around. |
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Posted: 7/24/2014 8:52:15 AM EDT
[#23]
Quote HistoryQuoted:
My 7.5 AA piston upper ran stupid fast out of the box with an H3 buffer. H and H2 would bounce and cause stoppages after 2 or 3 rounds. B buffer slowed it down below 1000rpm, and x buffer caused some short stroking. The only problem with the B/X buffers is they are colt only expensive things. Slash offers his stuff as well. Try them too. Really, buffers are cheaper than new barrels and are useful when tuning other guns later if you have them laying around. In mine the H3 short stroke, H bounced, and ST:T2 bounced. I settled on the H2. I'm not familiar with the "B" buffer? I'll give it a shot if you can point me in the right direction. |
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Posted: 7/24/2014 9:16:50 AM EDT
[#24]
Okay, I found some info, looks like a 7.1oz (!) 9mm buffer. I'm really surprised it cycles this, I was getting short strokes with a 5.4oz buffer. I wish someone had a buffer rental company, haha, so I could try them out and decide which one I needed.
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Posted: 7/24/2014 9:57:58 AM EDT
[#25]
Quote HistoryQuoted:
Okay, I found some info, looks like a 7.1oz (!) 9mm buffer. I'm really surprised it cycles this, I was getting short strokes with a 5.4oz buffer. I wish someone had a buffer rental company, haha, so I could try them out and decide which one I needed. Yeah or sell a whole sampler pack! 
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Posted: 7/24/2014 12:15:12 PM EDT
[#26]
Quote HistoryQuoted:
In mine the H3 short stroke, H bounced, and ST:T2 bounced. I settled on the H2. I'm not familiar with the "B" buffer? I'll give it a shot if you can point me in the right direction. Quote HistoryQuoted:
Quoted:
My 7.5 AA piston upper ran stupid fast out of the box with an H3 buffer. H and H2 would bounce and cause stoppages after 2 or 3 rounds. B buffer slowed it down below 1000rpm, and x buffer caused some short stroking. The only problem with the B/X buffers is they are colt only expensive things. Slash offers his stuff as well. Try them too. Really, buffers are cheaper than new barrels and are useful when tuning other guns later if you have them laying around. In mine the H3 short stroke, H bounced, and ST:T2 bounced. I settled on the H2. I'm not familiar with the "B" buffer? I'll give it a shot if you can point me in the right direction. The Colt letter buffers are the steel body counterparts to the normal Aluminum bodied buffers most folks are used to dealing with. There is the H, H2, & H3. All of which are aluminum bodied and have three sliding weights inside. The H = 2 x Steel & 1 x Tungsten, the H2 = 1 X Steel & 2 x Tungsten, and the H3 = 3 x Tungsten. The A, B, & X buffers are the same setup but have an overall higher weight due to the oversized steel body but have the same reciprocating mass as the H, H2, & H3 with the A = 2 x Steel & 1 x Tungsten, the B = 1 X Steel & 2 x Tungsten, and the X = 3 x Tungsten. The letter series were generally designed for the 9MM M16 but I own both the B and X which are great for troubleshooting bolt bounce and ROF issues in DI or piston guns. I have a B buffer that permanently lives in my 9MM LRM Integrally Suppressed M16. I usually tune the gas port on my DI guns to run with an H3 though but have run DI guns in the past with an X when I wanted a really reduced ROF. Ken Elmore at Specialized Armament Warehouse has all of them for sale and they are usually ~$100 each. Hope this helps |
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