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Posted: 1/30/2012 11:21:31 AM EDT
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I just finished my first 7.62 build and am having problems with the weapon cycling correctly.
The upper is DD, barrel is YHM (16" carbine), ASC 10 round mags, with AR Performance bolt and Model 1 firing pin. Ammo used is Silver Bear 125g SP and Golden Tiger 124g FMJ. The problem is every couple rounds fired, I end up with the fired case not being completely ejected and left in the gun, jammed on top of the next round from the magazine which has halfway feed into the weapon. The lower I used had an Enidine hydraulic buffer in it. I switched to an "H" buffer and got slightly better results. The Silver Bear SP runs a little better, but not reliable at all. Also, the bolt carrier often does not lock back after firing the last round in the magazine. After 40 rounds through it, it ran slightly better, but still fails to properly cycle every 3 or 4 rounds. I have learned so much on this website and hope one of you experts can provide some helpful advice...thanks in advance. -Steve |
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I'm willing to bet your ammo is under powered and switching to a carbine buffer would prove helpful. Also YHMs carbine barrels may need a slightly larger gas port if you want to cycle the cheap stuff.
Try those first and see where it gets you. My 16" carbine had a port of .079 and cycled Yugo milsurp M67 with a carbine buffer. Posted Via AR15.Com Mobile |
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Quoted:
I just finished my first 7.62 build and am having problems with the weapon cycling correctly. The upper is DD, barrel is YHM (16" carbine), ASC 10 round mags, with AR Performance bolt and Model 1 firing pin. Ammo used is Silver Bear 125g SP and Golden Tiger 124g FMJ. The problem is every couple rounds fired, I end up with the fired case not being completely ejected and left in the gun, jammed on top of the next round from the magazine which has halfway feed into the weapon. The lower I used had an Enidine hydraulic buffer in it. I switched to an "H" buffer and got slightly better results. The Silver Bear SP runs a little better, but not reliable at all. Also, the bolt carrier often does not lock back after firing the last round in the magazine. After 40 rounds through it, it ran slightly better, but still fails to properly cycle every 3 or 4 rounds. I have learned so much on this website and hope one of you experts can provide some helpful advice...thanks in advance. -Steve Sounds like short stroking. I doubt its an ammo problem. But you can rule that out by running Winchesters or Remington in it. Check gas rings. It could be a smaller than needed gas port (as everyone mentioned) or misaligned gas block. You might want to swap bolt carriers with another rifle and see if that works. If it does, then your problem is isolated. If it doesn't, gas port or gas block alignment is suspect. |
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I'm betting it's the Yankee Hill Machine barrels. I have an 18" midlength 7.62x39 upper (with a SS YHM barrel) from JSE surplus that I'm trying to break in, and I can't get the bolt to cycle. I was told to just polish the chamber but I'm thinking it's a gas port issue. |
| I called yankee hill when I was doing a 7.62x39 build and I asked the gas port size. I couldn't believe the size of the gas port size, I asked why so large and the guy said he had no idea why. Told them they made nice barrels but for my application it would make my rifle way overgassed and that even though they made nice barrels they would limit potential buyers from using them. |
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Guys,
Thanks so much for all the suggestions. Today I got it running like a sewing machine!! Sometimes it's just the simplest of things. Y'all were right about the ammo being underpowered. The lower I used (from a previous build) had a Wolf extra power spring and a Enidine hydraulic buffer in it. The weapon was short stoking every couple rounds. I simply switched to a more "stock" spring which felt slightly softer than the Wolf and a stock carbine buffer. Now she runs perfect. The YHM barrel looks great and it wasn't the problem. Also, using the ARP bolt with Model 1 pin results in primer strikes on Commie ammo that look very normal...I wouldn't want them to be any lighter. I have learned a ton of stuff here from you guys and hope I can give back something to another rookie builder: If you use cheap Commie ammo in your 7.62, start with a stock spring and buffer! Thanks again, Steve |
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Quoted:
Guys, Thanks so much for all the suggestions. Today I got it running like a sewing machine!! Sometimes it's just the simplest of things. Y'all were right about the ammo being underpowered. The lower I used (from a previous build) had a Wolf extra power spring and a Enidine hydraulic buffer in it. The weapon was short stoking every couple rounds. I simply switched to a more "stock" spring which felt slightly softer than the Wolf and a stock carbine buffer. Now she runs perfect. The YHM barrel looks great and it wasn't the problem. Also, using the ARP bolt with Model 1 pin results in primer strikes on Commie ammo that look very normal...I wouldn't want them to be any lighter. I have learned a ton of stuff here from you guys and hope I can give back something to another rookie builder: If you use cheap Commie ammo in your 7.62, start with a stock spring and buffer! Thanks again, Steve Steve have you run any quality hunting ammo through it, if so how do the primers look on them. The Commie primers are harder and usually set a little deeper, so I wouldn't worry about them. The quality american stuff is going to have softer flush set primers and that is where you could run into problems with over penetration. I run an ARP bolt and standard pin and usually get about 1 per 100 that don't go boom when running the Commie stuff, that I have always written off to <$4 box ammo. If you don't get over permeation on hunting ammo, it might be worth a try to try the model one our shave a couple thousandths of the blocking face of my standard pin? |
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Quoted:
Guys, Thanks so much for all the suggestions. Today I got it running like a sewing machine!! Sometimes it's just the simplest of things. Y'all were right about the ammo being underpowered. The lower I used (from a previous build) had a Wolf extra power spring and a Enidine hydraulic buffer in it. The weapon was short stoking every couple rounds. I simply switched to a more "stock" spring which felt slightly softer than the Wolf and a stock carbine buffer. Now she runs perfect. The YHM barrel looks great and it wasn't the problem. Also, using the ARP bolt with Model 1 pin results in primer strikes on Commie ammo that look very normal...I wouldn't want them to be any lighter. I have learned a ton of stuff here from you guys and hope I can give back something to another rookie builder: If you use cheap Commie ammo in your 7.62, start with a stock spring and buffer! Thanks again, Steve Thanks Steve! I learned something from you on the 'ol 7.62x39 set up. The whole time I was reading (given the H buffer, ARP bolt, and Model 1 firing pin too boot) I was betting it was a misaligned gas block or the gas port was too small. I stand corrected. Thanks for the report. As you stated before there is a ton of 7.62x39 AR knowledge on here and you just added to it and joined the club. Welcome 
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