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Posted: 8/8/2015 10:40:37 PM EDT
| I have a new .300 blackout. It is a Spikes Tactical Lower with a CMMG parts kit. I have a black cat tactical upper with a Fail Zero BCG in Nickel Boron. I went to shoot it for the first time today and it fires fine. The problem is it will only load it once. Fire and then not cycle another round thru. If I pull the bolt back it will load, just not after firing. I'm using the Never Quit 147gr ammunition and Magpul 30 round Magazines. Anyone have any suggestions? |
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What size is your gas port?
Carbine or pistol gas? If carbine, your gas port will likely need to be around .108 or larger if your using FA carrier(semi carrier may work at around .105 gas port) and CAR buffer with collapsible buttstock and standard spring, If everything else is good. |
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Quoted:
I have a new .300 blackout. It is a Spikes Tactical Lower with a CMMG parts kit. I have a black cat tactical upper with a Fail Zero BCG in Nickel Boron. I went to shoot it for the first time today and it fires fine. The problem is it will only load it once. Fire and then not cycle another round thru. If I pull the bolt back it will load, just not after firing. I'm using the Never Quit 147gr ammunition and Magpul 30 round Magazines. Anyone have any suggestions? Never Quit147gr ammunition is training ammo, and is known to choke some 300 BLKs that are not running suppressed. Try running some 115 to 125 grain instead.... 
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Quoted:
What everyone has said already, but you probably have a gas issue. Check the gas block, tube, and carrier key. And if all that checks out, take a look at your gas rings to make sure they are there and in good shape. Have you looked to see if the BCG is moving at all upon firing? There is a big difference between short-stroking and no-stroking. |
| I'm having the same issue. My bolt is "short stroking" when I shoot Barnes Vor-TX .300 Blackout rnds. They are 110 gr and shoot at 2350 FPS but when I shoot PNW Arms Range ammo 147 gr. 2000 FPS my AR cycles perfectly. I have a stock DPMS Oracle that I first swapped barrels on but then got tired of swapping back and forth so I built a new upper. I had the issue both times when it was in the original upper and in the new upper. I can see on the next rnd where the bolt is scrapping as it tries to grab but the bolt doesnt carry far enough back to catch the next rnd and it just leaves a scratch then. Thoughts? |
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Quoted:
I'm having the same issue. My bolt is "short stroking" when I shoot Barnes Vor-TX .300 Blackout rnds. They are 110 gr and shoot at 2350 FPS but when I shoot PNW Arms Range ammo 147 gr. 2000 FPS my AR cycles perfectly. I have a stock DPMS Oracle that I first swapped barrels on but then got tired of swapping back and forth so I built a new upper. I had the issue both times when it was in the original upper and in the new upper. I can see on the next rnd where the bolt is scrapping as it tries to grab but the bolt doesnt carry far enough back to catch the next rnd and it just leaves a scratch then. Thoughts? From the sounds of it I do not think it is short stroking, but the opposite, the bcg is travelling too fast. What buffer/spring combo and what type of barrel, length and gas port size? |
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Quoted:
From the sounds of it I do not think it is short stroking, but the opposite, the bcg is travelling too fast. What buffer/spring combo and what type of barrel, length and gas port size? Quoted:
Quoted:
I'm having the same issue. My bolt is "short stroking" when I shoot Barnes Vor-TX .300 Blackout rnds. They are 110 gr and shoot at 2350 FPS but when I shoot PNW Arms Range ammo 147 gr. 2000 FPS my AR cycles perfectly. I have a stock DPMS Oracle that I first swapped barrels on but then got tired of swapping back and forth so I built a new upper. I had the issue both times when it was in the original upper and in the new upper. I can see on the next rnd where the bolt is scrapping as it tries to grab but the bolt doesnt carry far enough back to catch the next rnd and it just leaves a scratch then. Thoughts? From the sounds of it I do not think it is short stroking, but the opposite, the bcg is travelling too fast. What buffer/spring combo and what type of barrel, length and gas port size? It's a 16" barrel, .750 gas block, I believe the block rod is about 9.75". I honestly couldn't say on the buffer or spring, it can with the DPMS Oracle and I haven't modded that at all. |
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I'd say that using a heavy buffer in a new build of any caliber is not the wisest course. My 8" upper runs fine with a standard carbine spring and buffer running supersonic loads. I haven't put together any subs yet, but I have that in the planning stages.
It is possible that some barrels are made with odd-sized gas ports, anticipating that they will be suppressed, but I haven't seen any details about specific makers who do this. Keep in mind that a LOT of people think Blackout is ONLY useful with a short barrel and suppressed. If you build an upper with a barrel more than 9" long, or if you don't suppress it, or both, instead of blindly following AAC's lead (because they DO make short barrels with the expectation the upper will be suppressed) and using an H2 or heavier buffer, see what happens with a carbine buffer and spring. If it's too harsh, then think about going heavier. I think some uppers will benefit from using different buffers for different kinds of loads. Supers unsuppressed might need one buffer, subs suppressed may need another, and the inbetweens might need other buffers. |
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aac also makes 16 inch carbines . you should not need a different bufffer to go from subs to supers . A rule of thumb or starting point is carbine gas use a standard carbine buffer and spring . pistol gas use an h-2 buffer and spring.
I have a 16 inch carbine and an 8.5 inch pistol both run subs and supers suppressed or not and neither one are aac but i use their guidlines . |
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Quoted:
aac also makes 16 inch carbines . you should not need a different bufffer to go from subs to supers . A rule of thumb or starting point is carbine gas use a standard carbine buffer and spring . pistol gas use an h-2 buffer and spring. I have a 16 inch carbine and an 8.5 inch pistol both run subs and supers suppressed or not and neither one are aac but i use their guidlines . AAC's 16s have carbine gas systems, while their shorter uppers use pistol; that's where their different recommendations for buffers come from. MOST ARs benefit from matching the buffer and spring to the load you're shooting, but as long as you stick with a standard gas system they'll work with all but the wimpiest rounds. That's for .223/5.56mm guns, though. Since the amount of gas you get from 300 Blackout is highly dependent on whether you're running supers or subs, that makes for some "interesting" issues. In general, if you're suppressing a short upper in 300 Blackout, the lower gas pressure is offset by the silencer's higher back pressure. But maybe you aren't suppressing...you can probably get that short upper to run with subs if you use a lighter buffer. |
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