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Posted: 10/2/2014 10:18:04 PM EDT
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A buddy of mine just built his first AR and it happened to be an AR-10 type in 260 Rem. All high quality parts and such but he has had a heck of a time getting it to cycle and the bolt won't lock back after the last round. Any thoughts or suggestions? He tried to check the gas system by using compressed air to see if he got anything to the bcg from the barrel. Seemed to work. His load is a hot load with 130 gr pill he uses in his bolt gun. The one thing that isn't store bought is the lower, made from an 80 percent block of aluminum. Any thoughts, tips or suggestions would be appreciated.
Thanks, Indy |
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A buddy of mine just built his first AR and it happened to be an AR-10 type in 260 Rem. All high quality parts and such but he has had a heck of a time getting it to cycle and the bolt won't lock back after the last round. Any thoughts or suggestions? He tried to check the gas system by using compressed air to see if he got anything to the bcg from the barrel. Seemed to work. His load is a hot load with 130 gr pill he uses in his bolt gun. The one thing that isn't store bought is the lower, made from an 80 percent block of aluminum. Any thoughts, tips or suggestions would be appreciated. Thanks, Indy If these are bolt gun loads he could be using powders that are to fast for a gas gun. Try a few factory loads. |
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I need way more info. Type of BCG Type of buffer and spring Barrel length Gas system length Type and amount of powder Over pressure can mimic under gassed malfunctions. Here are his specs: DPMS 20" barrel 260 DPMS Chrome bolt carrier Assy Syrac adj. gas block / rifle length tube DPMS buffer tube a1/a2 DPMS 308 rifle Buffer DPMS 308 rifle spring Load 43.5gr H4350 with 130 gr berger Hunting VLD |
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Here are his specs: DPMS 20" barrel 260 DPMS Chrome bolt carrier Assy Syrac adj. gas block / rifle length tube DPMS buffer tube a1/a2 DPMS 308 rifle Buffer DPMS 308 rifle spring Load 43.5gr H4350 with 130 gr berger Hunting VLD Quoted:
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I need way more info. Type of BCG Type of buffer and spring Barrel length Gas system length Type and amount of powder Over pressure can mimic under gassed malfunctions. Here are his specs: DPMS 20" barrel 260 DPMS Chrome bolt carrier Assy Syrac adj. gas block / rifle length tube DPMS buffer tube a1/a2 DPMS 308 rifle Buffer DPMS 308 rifle spring Load 43.5gr H4350 with 130 gr berger Hunting VLD The chamber may need to be polished. Are there any pics of the brass? |
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I'm assuming the gas block is open already. Check to make sure the gas block is centered over the gas port. If the block is partially blocking the gas port it will restrict gas flow. Check the gas rings to ensure they are in place and arent dragging inside the carrier. Check the carrier key to make sure it isn't loose or has broken screws. Check the gas tube to make sure it has the lip near the end that seals it inside the carrier key. If none of that helps then you might try a different powder, different powders have different pressure curves snd it's possible the load being used just won't work in an auto.
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Troubleshoot it like any other rifle, start at the start and move down the list.
the fact that it's a non standard caliber on a less than 100% lower may not be a problem. |
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Here are his specs: DPMS 20" barrel 260 DPMS Chrome bolt carrier Assy Syrac adj. gas block / rifle length tube DPMS buffer tube a1/a2 DPMS 308 rifle Buffer DPMS 308 rifle spring Load 43.5gr H4350 with 130 gr berger Hunting VLD Quoted:
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I need way more info. Type of BCG Type of buffer and spring Barrel length Gas system length Type and amount of powder Over pressure can mimic under gassed malfunctions. Here are his specs: DPMS 20" barrel 260 DPMS Chrome bolt carrier Assy Syrac adj. gas block / rifle length tube DPMS buffer tube a1/a2 DPMS 308 rifle Buffer DPMS 308 rifle spring Load 43.5gr H4350 with 130 gr berger Hunting VLD I have not run any 260’s, but H4350 sounds really slow burning for a 20” barrel gas operated weapon. |
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I have not run any 260’s, but H4350 sounds really slow burning for a 20” barrel gas operated weapon. Quoted:
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I need way more info. Type of BCG Type of buffer and spring Barrel length Gas system length Type and amount of powder Over pressure can mimic under gassed malfunctions. Here are his specs: DPMS 20" barrel 260 DPMS Chrome bolt carrier Assy Syrac adj. gas block / rifle length tube DPMS buffer tube a1/a2 DPMS 308 rifle Buffer DPMS 308 rifle spring Load 43.5gr H4350 with 130 gr berger Hunting VLD I have not run any 260’s, but H4350 sounds really slow burning for a 20” barrel gas operated weapon. It's not. In fact it's kind of fast for a 6.5. |
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Update: well he took a few things apart and the gas rings were ok, staggered etc. took off the gas block and measured the port in the barrel, it comes in at 0.075 inches. From what he read online it should be around 0.090"... Is that correct guys? If it needs to be opened up he can do that where he works (machine shop). Any advice for doing this gas port modification?
Thanks guys. |
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Update: well he took a few things apart and the gas rings were ok, staggered etc. took off the gas block and measured the port in the barrel, it comes in at 0.075 inches. From what he read online it should be around 0.090"... Is that correct guys? If it needs to be opened up he can do that where he works (machine shop). Any advice for doing this gas port modification? Thanks guys. DO NOT GO IMMEDIATELY TO .090"! Step it up. The last 6.5 barrel I made worked perfect at .075" and that was 2" past normal rifle port location. If you've polished the chamber, and checked absolutely everything else, then go ahead and open the port. |
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DO NOT GO IMMEDIATELY TO .090"! Step it up. The last 6.5 barrel I made worked perfect at .075" and that was 2" past normal rifle port location. If you've polished the chamber, and checked absolutely everything else, then go ahead and open the port. Quoted:
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Update: well he took a few things apart and the gas rings were ok, staggered etc. took off the gas block and measured the port in the barrel, it comes in at 0.075 inches. From what he read online it should be around 0.090"... Is that correct guys? If it needs to be opened up he can do that where he works (machine shop). Any advice for doing this gas port modification? Thanks guys. DO NOT GO IMMEDIATELY TO .090"! Step it up. The last 6.5 barrel I made worked perfect at .075" and that was 2" past normal rifle port location. If you've polished the chamber, and checked absolutely everything else, then go ahead and open the port. Why not if he has an adjustable gas block? Fuck taking the thing apart a half dozen time to drill tiny bits out. |
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Why not if he has an adjustable gas block? Fuck taking the thing apart a half dozen time to drill tiny bits out. Quoted:
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Update: well he took a few things apart and the gas rings were ok, staggered etc. took off the gas block and measured the port in the barrel, it comes in at 0.075 inches. From what he read online it should be around 0.090"... Is that correct guys? If it needs to be opened up he can do that where he works (machine shop). Any advice for doing this gas port modification? Thanks guys. DO NOT GO IMMEDIATELY TO .090"! Step it up. The last 6.5 barrel I made worked perfect at .075" and that was 2" past normal rifle port location. If you've polished the chamber, and checked absolutely everything else, then go ahead and open the port. Why not if he has an adjustable gas block? Fuck taking the thing apart a half dozen time to drill tiny bits out. Yeah you're right, just drill it to .150 and drive on. What the hell do I know. |
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Yeah you're right, just drill it to .150 and drive on. What the hell do I know. Quoted:
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Update: well he took a few things apart and the gas rings were ok, staggered etc. took off the gas block and measured the port in the barrel, it comes in at 0.075 inches. From what he read online it should be around 0.090"... Is that correct guys? If it needs to be opened up he can do that where he works (machine shop). Any advice for doing this gas port modification? Thanks guys. DO NOT GO IMMEDIATELY TO .090"! Step it up. The last 6.5 barrel I made worked perfect at .075" and that was 2" past normal rifle port location. If you've polished the chamber, and checked absolutely everything else, then go ahead and open the port. Why not if he has an adjustable gas block? Fuck taking the thing apart a half dozen time to drill tiny bits out. Yeah you're right, just drill it to .150 and drive on. What the hell do I know.  
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Update: well he took a few things apart and the gas rings were ok, staggered etc. took off the gas block and measured the port in the barrel, it comes in at 0.075 inches. From what he read online it should be around 0.090"... Is that correct guys? If it needs to be opened up he can do that where he works (machine shop). Any advice for doing this gas port modification? Thanks guys. DO NOT GO IMMEDIATELY TO .090"! Step it up. The last 6.5 barrel I made worked perfect at .075" and that was 2" past normal rifle port location. If you've polished the chamber, and checked absolutely everything else, then go ahead and open the port. Why not if he has an adjustable gas block? Fuck taking the thing apart a half dozen time to drill tiny bits out. Yeah you're right, just drill it to .150 and drive on. What the hell do I know.
In all fairness he did state .090". This doesn't sound out of the realm coupled with an adjustable block. |
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DO NOT GO IMMEDIATELY TO .090"! Step it up. The last 6.5 barrel I made worked perfect at .075" and that was 2" past normal rifle port location. If you've polished the chamber, and checked absolutely everything else, then go ahead and open the port. Quoted:
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Update: well he took a few things apart and the gas rings were ok, staggered etc. took off the gas block and measured the port in the barrel, it comes in at 0.075 inches. From what he read online it should be around 0.090"... Is that correct guys? If it needs to be opened up he can do that where he works (machine shop). Any advice for doing this gas port modification? Thanks guys. DO NOT GO IMMEDIATELY TO .090"! Step it up. The last 6.5 barrel I made worked perfect at .075" and that was 2" past normal rifle port location. If you've polished the chamber, and checked absolutely everything else, then go ahead and open the port. Update: he took the upper partially apart and set it up on a drill press i. The shop where he works and drilled out the port yesterday. It was .075 and he went right to .150! Just kidding, he stopped at .085. Just fired two rounds from two different magpul mags and they worked fine. Action cycled, brass ejected, all is good. Now to work up a load that is accurate in that rifle. Thanks guys! |
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