New AR build will not cycle open
- Thread starter Helka
- Start date
I personally would avoid MRA as they have shown they don't take care of their customers and the owner is a liar(YMMV).
OP, just want to get a clearer picture even though I might not have the answer. So your bolt locks open when you manually cycle it, right? What buffer spring are you using? Is it just a generic spring and do you know the weight? And can you confirm that you are using a mil spec tube with your H1 buffer? I'll reserve my opinion about the gas block for now. Seems like there are plenty of people chiming in on that.
I could have sworn odin works hadv the lock screw in the rear of the gas block. But maybe I'm wrong.
The noveske switchblock is a 2 or 3 position block rather than variable......i recall it being rather expensive but honestly i haven't pricechecked lately
Odin Works makes both types of adj block.
Lungorthin
Regular
- Location
- Calgary, AB
This was my problem
My first MRA barrel the gas port was not drilled all the way through. Was replaced and second barrel the hole was at 11 o'clock.
With my gas block mounted at 12 o'clock, there must have been some overlap of the port hole and the gasblock so I wasn't getting enough gas.
I switched to a carbine buffer and that worked until I finally exchanged the barrel for a properly aligned gas port and now I'm running the Geissele super 42 H1 buffer.
If I had to guess, its the alignment
2nd guess is bcg drag
I have never owned one personally(although I may try one) but, definitely no set screw as it uses a 20 click detent and says "no set screw needed" right in the description. This block is a bit on the heavy side but, other then that I think it is one of the better designs with its extremely heat resistant Inconel adjustment screw.
Yeah, the Switchblock is a pretty unique block and not great for many applications as it can't be covered by many HG's either. I just listed it as it is easy to adjust without tools. Everything Noveske is expensive lol.
Honest question, how do you figure so? Unless you’re recording the ejection port with a slow mo camera you’re not likely to see where and how far the bolt is moving rearwards.
That’s another option to gather some more info on the subject. If you have a smart phone with the slow motion camera you can record it and see exactly what’s going on.
When a rifle is over gassed the operating system is moving so fast that the magazine follower spring and the bolt catch spring can’t keep up and the BCG flys right over top of it all. Most often misdiagnosed as not enough gas, especially when you’re using an adjustable block, so you increase gas pressure in hopes of resolving the problem but in reality you’re just adding to the problem.
Again, not saying this is for sure the problem but it costs you nothing to go back out to the range and carefully dial the gas in, being conscious of over gassing, versus the other options listed in which you’re buying new parts that may or may not be correcting the issue you’re having in the first place.
Yes with all the info i’ve gained here I will make another trip to the range and dial the gas block in. The reason I think it didn’t have enough gas was that it originally wasn’t ejecting the cartridge. Then it got to the point where it would half eject it. (Stuck half open) then it finally ejected the round but wouldn’t stay open. I don’t think I jumped adjusted to over gassed. But will try the range next week if time permits.
OP I’m having same issue with a Stag 10.
Won’t lock open and won’t pick a end up on the way back.
This just started to happen when I installed a .308 commercial spec tube and stock.
It runs perfectly when I install a AR15 milspec tube and Stock.
AR 15 tube is about an inch shorter than AR308 tube.
Maybe it has something to do with your buffer or spring and nothing to do with your GB?
Won’t lock open and won’t pick a end up on the way back.
This just started to happen when I installed a .308 commercial spec tube and stock.
It runs perfectly when I install a AR15 milspec tube and Stock.
AR 15 tube is about an inch shorter than AR308 tube.
Maybe it has something to do with your buffer or spring and nothing to do with your GB?
My thought after the range was that the buffer H1 was too heavy for the lightweight BCG to fully reset. That’s why my initial post was concerning upgrading to a lighter buffer. Again I will try adjusting my gas block then go from there. I will also try and set up my phone to the slo-mo setting
So, there has been a lot of good info and advice shared so far. I get the feeling you're still a little uncertain.
My advice,
1. Remove your gas block and look for the carbon marks around the gas port which will tell you if it was aligned correctly. Reinstall making sure it's correctly aligned this time. Forget about measuring, the carbon marks will tell you exactly what needs to be done to line up the holes.
2. Adjust the gas block to 4.5 turns out from closed. This should give you maximum gas to the BCG according to the guys more familiar with your gas block.
3. Shoot it with one round in the magazine as you have been, feel the rifle when you shoot. Do you feel the carrier/buffer slamming into the back of the buffer tube or is it pretty light (easier if you're experienced with the AR).
If it's slamming into the back of the buffer tube you are overgassed, when set up correctly it will just gently touch the back of the tube which will result in a much more gentle recoil impulse.
4.1. If it cycles and locks back turn in the adjustment screw one click at a time and test again (repeat till it fails to lock back) then open back up one or two clicks to ensure reliability when the rifle gets a little dirtier.
4.2. If it fails to lock back (assuming it's severely overgassed) repeat the process above closing it one click at a time till it locks back but then keep going till it stops locking back then open one or two clicks as in 4.1 to ensure reliability as it gets dirty.
One method I use to ensure gas block alignment is to (open the gas block to 100%) plug the chamber (empty cartridge) and blow into the muzzle and adjust the gas block till the air flow through the gas tube is highest then tighten it down. No measuring needed and always works perfectly.
If the rifle still dosen't function correctly after trying the above you either have a barrel gas port size issue, gas tube is not long enough or cracked (unlikely), gas key is loose, the gas rings are worn out (unlikely), or your gas block is obstructed.
Without seeing the rifle it's hard to troubleshoot but if you still can't get it running after this I would either enlist the help of someone local who is experienced with AR's or take it to a smith.
Good luck.
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