AR15 Suppressor problem

[sheetsp]

Just did a new build on Spikes Tact lower with KAK 5.56 kit. Function tested great breaking in barrel. Then screwed my can on and only fires 1st rnd. Seems the hammer wont stay in cocked position. Used factory PMC FMJ 55gr. just to get on paper. What can I do to rid this single shot problem? Ideas Anyone?

 

[vinson]

It's loading the next round though? Where does your ejected brass go (1-5 o'clock)? Do you have a full auto carrier (has extra material on it, thus heavier)? Is it a stock or aftermarket trigger?

Vinson

 

[left handed gun]

This was posted before, a few days ago?

If carbine length gas system (couldn't tell from your OP), maybe go to midlength or rifle length. Sounds like magazine is keeping up if it chambers next round.
If it functions OK without the can, that suggests the problem is added backpressure from the suppressor. See Feb 2014 article in Guns and Ammo, by Kyle Lamb on "A Case For Midlength" gas systems.

Assuming from description your gun is direct gas impingement. Seems to be agreement from fans and non-fans of piston guns that they work better with suppressors than direct gas guns, all else equal (bbl length, loads, etc.)

Are you shooting .223 or 5.56 MM? While pretty freely interchangeable, I believe there is a difference in chamber pressure, which could in turn aggravate the problem with backpressure from a suppressor. Superformance (spelling?) Hornady, however, is NOT recommended for carbines.

Maybe not what you want to hear, but if it were me, and the can caused the problem, I'd put the can on another gun. Or in the classifieds. Prairie dogs and coyote hear pretty good and would likely still be spooked by lower decibels. And if it is more of a personal defense gun than a hunter, I'd definitely lose the can.

If you have not shot it much yet, probably not an issue, but AR pukes where it feeds, craps where it eats, etc. Added backpressure from suppressor seems likely to make that worse, and necessitate more frequent cleaning.

 

[woodnut]

Have you looked into the adjustable gas block? I shoot suppressed,too. I have a 6.5 Grendel with an adj. gas block. At first, it was opened all the way and ran good ; but dirty and seemed to have too much pressure coming on the bolt. I just adjusted it in and not only does it run cleaner, but softer! Don't have trouble with my 260 or 6x47 Lupua suppressed, and they have a standard, non adj. block. I agree with the guy about the extra pressure from the suppressor; and I can only guess with too much back force, your bolt is running too fast and somehow messing things up. I do like the adjustable blocks! I may even look into more for my other ARs. I hope you resolve this as shooting suppressed is fantastic!

 

[sheetsp]

Thanks woodnut I will be checking gas port size on the barrel next to be sure it is .083" . Not sure I am impressed with this KAK built upper.

 

[woodnut]

There's a guy on here, I think, named "MSALM". He builds fine uppers. Knows ARs inside and out. If you'd like to get in touch with him, please PM me. We'll go from there.

 

[436]

Just did a new build on Spikes Tact lower with KAK 5.56 kit. Function tested great breaking in barrel. Then screwed my can on and only fires 1st rnd. Seems the hammer wont stay in cocked position. Used factory PMC FMJ 55gr. just to get on paper. What can I do to rid this single shot problem? Ideas Anyone?

Well with a can on it'.., it should work better as far as pressure, cans give you more back pressure. So I'd think you might also address the ammo, use M855 or M193 and see what happens. If you still have the problem then the next most logical place to look would be the gas tube.

Good luck.
436

 

[woodnut]

I've been told that with the can and already running a high pressure load, the added pressure will make the BCG run so fast it can (not on every trigger) over-run the triggers ability to reset. You may have a perfect spring without the can but then not with. Or a slow trigger (it's all about the disconnect), or something else. I seriously doubt the can is creating the problem... alone. Yes, it does create more back pressure/bolt thrust and can make a recoil spring run too fast and thereby over run the triggers ability to reset. I hope you solve the problem as shooting with a can is soooo much fun !

 

[436]

I guess the question(s) here might be.. what buffer and spring are you using? Is your upper and lower tightly fitting? The weight of the can on the end of the barrel thing. Only ting left as I might she it... would be the bolt carrier and the bolt, gas rings, that kinda stuff, along with the gas tube.
I go along with Woodnut on that it may be two or more things contributing when you put the can on.
Cheer's
436

 

[woodnut]

Thanks 436, sounds like you know about this. Sheetsp, we are all about trying to help you. 436 may have hit a salient point; the buffer and spring. If they are on the margin, putting the extra pressure from the can could cause it not to run at the proper speed. ARs are picky about gas pressures; set up without a can could be all wrong with it. The "fun" part is now I think you will need to "adjust" only one thing at a time til you find what works. It may not be hard, you could get lucky with the first change. I agree with 436 about the buffer/spring. Examine that first. Personally, I like the flat chrome silicon springs. It would be an in-expensive change and it's a good spring to use anyway. And don't grease it ! (Yeah, voice of experience.) May be the answer....or not. good luck and keep us posted, ok?

 

[ncwg2boatguy]

I've been told that with the can and already running a high pressure load, the added pressure will make the BCG run so fast it can (not on every trigger) over-run the triggers ability to reset. You may have a perfect spring without the can but then not with. Or a slow trigger (it's all about the disconnect), or something else. I seriously doubt the can is creating the problem... alone. Yes, it does create more back pressure/bolt thrust and can make a recoil spring run too fast and thereby over run the triggers ability to reset. I hope you solve the problem as shooting with a can is soooo much fun !

I had the same issue couple of years ago. Before you drill the gas port you may want to buy a pig tail gas tube and try it. Basically the length of a midlength tube but spiral to fit a carbine. 30$ Mine rock and rolled after that. Midlength is definatelythe best for cans. It should slow the bolt down enough to get a proper reset on the trigger/Hammer