AR pistol issue

[unicom]

Went to the range and finally put rounds through my ar pistol with a can on it. The bolt doesn’t lock back to rear on last round. I’m running 300 blk subs. Through a 8.5 “ barrel with a silencer Co omega can. I’m thinking the spring is to heavy. It will cycle the rounds just doesn’t go back far enough on last round to catch the follower part of the mag that holds it open after last round. Thus my reasoning about the spring being to heavy. Looking for input and help to fix issue.


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[gll]

Lighter buffer or weaker spring. Since it's probably a carbine buffer already, probably weaker spring.

 

[toddnjoyce]

If you have an adjustable gas port, you can open the port up.

 

[popper]

Factory ammo or your loads? Some powders just won't do it. Can should give more pressure, did it hold back without the can? Should be able to lock back with charge handle without scrunching the spring - all B tubes and springs aren't correct length. Bolt catch spring needs to be strong enough too. Mag problem is rare. Usually just not enough gas from short barrel - gas port can be opened up if needed. Also make sure to run BCG wet to start. Needs to break in.

 

[unicom]

To answer the questions. First, I don’t have an adjustable gas block. Second, it will lock back if I pull back on charging handle. Third, it will lock open without the can. And fourth, this time out was hand loaded ammo. The first time out was with factory sub loads, but I only shot maybe 3 or 4 to test functionality. I did use a load that was almost to max grain according to the Hornady load manual.


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[BeatTheTunaUp]

My ar10 did the same thing. Tried an adjustable gas block and even wide open no change. Turned out to be a magpul mag issue. Runs great with hex mags and half the gas. Try a different brand magazine.

 

[unicom]

My ar10 did the same thing. Tried an adjustable gas block and even wide open no change. Turned out to be a magpul mag issue. Runs great with hex mags and half the gas. Try a different brand magazine.

I’ll try different mags as well


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[unicom]

My ar10 did the same thing. Tried an adjustable gas block and even wide open no change. Turned out to be a magpul mag issue. Runs great with hex mags and half the gas. Try a different brand magazine.

My ar10 in 308 won’t even cycle rounds if there subs with a can on it. But supers are good to go


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[unicom]

Let me ask this. Is it possible for the bolt to go back far enough to load the next round just not far enough for the hold open to work?


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[BeatTheTunaUp]

yeah. In my case, the bolt was dragging on the feed lips and causing just enough energy loss to not retract fully

 

[SQLGeek]

If it’s only doing it with a suppressor on, that tells me that there’s possibly too much back pressure and the carrier is moving too fast to catch on the mag.

Might try a heavier buffer when running a suppressor. Or switch to an adjustable gas block.

 

[unicom]

If it’s only doing it with a suppressor on, that tells me that there’s possibly too much back pressure and the carrier is moving too fast to catch on the mag.

Might try a heavier buffer when running a suppressor. Or switch to an adjustable gas block.

Thanks for the info. I’ll up the buffer weight first. Easier then swapping out gas blocks


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[jjkukla]

Speaking of buffer weight, one common way you can tell if the buffer is too light is where the brass ejects. On my 5.56 pistol with a carbine buffer, brass was ejecting to my 5 o'clock (as a lefty this was even more troublesome). I put in a heavier buffer, it now ejects at 3:30 or so.

I never had an issue with bolt hold open, but food for thought.

Good luck... cheers.

 

[Renegade]

I would video action with a smart phone, and see how far back the bolt it going. my iPhone can do 240 fps and that is more than enough when I had similar issues.

 

[unicom]

I would video action with a smart phone, and see how far back the bolt it going. my iPhone can do 240 fps and that is more than enough when I had similar issues.

I like that idea. Had no clue the iPhone can record that slow. Thanks


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