AR pistol won’t cycle

T/C Encore in 450b anyone?

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AR pistol won’t cycle

Postby Smithjdsr » Mon Aug 16, 2021 1:42 pm

So, I built a Bushy upper for my pistol lower. It’s a 10.5” barrel with an adjustable gas block adjusted wide open. I shot it with two kinds of factory ammo; Hornady Black and Winchester Deer Season. It just won’t cycle. It’s a single shot. If I manually work the operating handle, the empty ejects and another round chambers- for another single shot. Watching g from the side, my son says the bolt is going, maybe, 1/4 of the way back. I took it home, made sure the gas block was wide open, and re-lubed the BCG. Same thing on the second trip to the range.

Is the gas port too small? What size should it be? Is it the spring and buffer? I wouldn’t think so, as they’re both standard and the lower works perfectly with a .300 AAC upper.

Please send advice!
John

“Remember; No matter where you go, there you are.” -Buckaroo Banzai
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Re: AR pistol won’t cycle

Postby Hoot » Mon Aug 16, 2021 5:27 pm

Smithjdsr wrote:...snip...
Is the gas port too small?...snip...


Define too small. IE what is the diameter? When you remove the gas block to measure it, see if there's a soot ring around the hole, confirming that the block is placed properly. If you have a set of numerical drill bits, they can be used to see what passes vs what doesn't. If not, see which fractional bit you can get through as close as possible.

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Re: AR pistol won’t cycle

Postby s4s4u » Tue Aug 17, 2021 8:58 am

Port could be small. What buffer and spring are you using?
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Re: AR pistol won’t cycle

Postby Smithjdsr » Wed Aug 18, 2021 8:18 pm

I will have to check the gas port size. I don’t have time for the next few days to pull the handguard and gas block off (first week of school…) I don’t have a set of numbered drills, so I’ll
Either have to get some or measure some other way.

I don’t remember exactly where I got the buffer tube, spring, and buffer. But they’re standard. “Mil spec”
John

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Re: AR pistol won’t cycle

Postby coyote wacker » Thu Aug 19, 2021 10:08 am

Before next time you go to the range get a number drill index and take a cordless drill motor with some oil to open up the gas hole....
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Re: AR pistol won’t cycle

Postby Hoot » Fri Aug 20, 2021 3:11 am

coyote wacker wrote:Before next time you go to the range get a number drill index and take a cordless drill motor with some oil to open up the gas hole....


That's what I wound up doing in the name of expedience, with a Rifle length as system barrel that I had. Once I found the magic port size, it has run reliably ever since.
Barrel manufacturers need to test their barrels before passing them into the customer stream. Clearly, that is not happening as we keep seeing threads along this line. That having been said. With new systems that simply need to be run in, in order to slick up their mating surfaces, gas port enlargement should not automatically be the first stop in ensuring proper cycling. This is especially important in systems where the majority of components are simply phosphated. Systems that are NiB plated or which use some other slick technology, don't need as much or any run in to get them into a reliable state of operation. With my original first Bushy upper, which had a matte, manganese phosphate finish, I rubbed MoS2 powder into the pores of the mating surfaces a couple of times and its characteristic changed from scrapy, scratchy, grindy, to slippery smooth cycling after doing so. That was before components were readily available with more slick finishes. Bottom line is: Don't mistake the need for running in with an inadequate gas system or poorly conceived buffer and spring combination. Save those diagnoses until after the system has been smoothed up. That can help save from the need to go with an adjustable gas block later. More importantly though is the fact that manufacturers need to test what they sell. The consumer should not be their Quality Control department.

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Re: AR pistol won’t cycle

Postby plant_one » Tue Aug 24, 2021 11:39 am

carbine gas port location or pistol gas port location?
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Re: AR pistol won’t cycle

Postby Smithjdsr » Tue Aug 24, 2021 3:50 pm

I think carbine length gas tube.
John

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Re: AR pistol won’t cycle

Postby Smithjdsr » Thu Sep 09, 2021 9:43 pm

So, a late post on a situation finally resolved. 

The thing is, I don’t really intend to shoot the beast all that much. It’s just a stop-gap that will let me shoot a modern arm during the late muzzle-loader season, since it’s a pistol. I have several .50 cal rifles, but I have stopped enjoying the challenge of a smoke-pole when I’m just trying to put venison in the freezer.

Long story short: now it works. And with a 10.5” barrel it’s still really accurate (who knew?). And it kicks like a $40 mule. It seems that adjustable gas blocks have four screws: 1 in the detent for alignment, 1 to secure the block to the barrel, 1 to adjust the gas passage bore, and 1 set screw to lock the adjustment screw in place. Well, it appears that if all you do is loosen the set screw with the adjustment screw fully closed, no gas goes through the tube and the action doesn’t cycle. If you actually open the adjustment screw first and then tighten the set screw down it, it cycles. :oops:
Last edited by Smithjdsr on Fri Sep 10, 2021 4:55 am, edited 1 time in total.
John

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Re: AR pistol won’t cycle

Postby Hoot » Thu Sep 09, 2021 10:43 pm

Image
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