Spent the day zeroing an new AR and I had a horrible time with it. I used multiple mags, Okay Ind. and Magpul. All the mags functioned flawlessly on the 11.5 upper, as well as the 2 different ammos, LCm193 and Tula m193.

On the trouble gun, 13.9 unsuppressed, carbine gas system. 100 % of shots ejected. Aproximately 98% of all the shots didn't load the next round. I had to manually cycle the bolt and of all those (about 120) there were about 4 or 5 double feeds. I managed to get the gun zero'd but I was basically shooting a low quality bolt gun.

So, for the brain trust. The mags and ammo were flawless in the other gun. Assuming nothing wrong with the FCG and the receivers not being out of spec, nor the bcg would you lean towards the adjustable gas block( i had no tool to adjust it), buffer, buffer spring, or something else potentially causing the problem.

I have a pretty penny in this build and it bothers me that it doesn't perform like some of my other cheaper builds. Any advice or guidance is appreciated.

Cap'n Obvious says to inspect all components of the BCG assembly and the upper for any signs of scoring or friction that is unwanted.

And check the buffer tube and components for the same thing.

Is it picking up rounds and just not fully locking up, or what exactly?

If it is cycling rearward and extracting/ejecting, then it would appear to be enough gas pressure but sounds like it may be sluggish going into battery, and I would look at mechanical before changing gas setting, higher pressure might "fix" the "issue" without fixing a problem.

I dont think its picking up because 98% of the time I would manually cycle the bolt and no cartridge would eject, indicating it was ejected on fire but not stripping off the next round.

Five to seven times I would have to clear the gun because there would be two rounds fighting to enter battery, possibly one didnt make it all the way in on cycle and the second due to my manually cycling the bolt.

Also every time I shot the gun the trigger was reset and could be fired on the empty chamber.

OK.

If you insert a mag with the bolt locked back, then "paddle" the bolt release, will it feed correctly every time?

Or if you insert a mag with bolt closed and then "charge" the rifle, will it feed correctly every time?

Possible it might be short stroking, and the above would point to the rifle working correctly with the BCG starting fully rearward, but not always moving far enough back to strip the next round.

Where are the casings landing? (clocking)

I had something similar happen a while back when I bought a cheap case of steel cased ammo. It essentially turned by BCM into a single shot. The round would fire, eject the case, reset the trigger but did not have enough powder to send the bolt carrier back far enough to strip the next round and bring into the chamber. It was basically short stroking and it had me scratching my head for a few minutes. I switched to different brass cased ammo and it ran flawlessly. In short some steel cased ammo is junk.

I also tried the ammo in a different rifle and it would cycle properly but I noticed that the shots were key holing over half of the shots. The ammo was Sergeant Major which I believe is a rebranded Tula.

The barrel could be mis-clocked and out of time.

Over tightening the barrel nut can bend or shear the alignment pin.

If I’m reading this right, it ejects the round but doesn’t pick up the next round. I had the same issue on a rifle where the gas tube was installed with the port up in the gas block instead of down. Flipped the gas tube and it began running like a scalded ape. My rifle ejected the casings as well.

100% a gas issue. Check your gas key (should be properly torqued and staked; you'd be surprised how few do it properly) or swap in a known-good BCG to test. If you've got an adjustable block, that's your other likely culprit.

quote:

Originally posted by Nickelsig229:
would you lean towards the adjustable gas block( i had no tool to adjust it)

That's where I'd start, as the most likely culprit.

Adjust it all the way open. Take it back to the range, test fire it at full open, and gradually adjust it down while test firing until you start to get FTE/FTF issues again, then open it back up a click or two.

But if you still have issues even with the gas block all the way open, then you can rule that out and start looking elsewhere, like the BCG or gas tube.

I agree with Rogue. Everything else mentioned so far could be the problem, but if you have an adjustable gas block, the easiest place to start troubleshooting is opening it up all the way. If it doesn’t solve your issues, then you can start checking stuff like is it aligned correctly, is your gas tube upside down or blocked, bad gas key, burrs, etc, etc.

It's definitely short-stroking. Assuming your gas tube IS installed correctly, it sounds like the adj gas block is on the low setting. If you find that it's all the way open and you're still having issues, you could try a lighter weight buffer.

Here is a little update for you guys. Thanks for the input.

I cleaned the rifle and lubed it properly. It was dry so that didn't help with the issue. I didn't see any unusual rubbing marks or gouging anywhere. Gas tube aligns perfectly with the key. The orings and metal gas washers are installed correctly. H2 buffer should be fine with an 13.9 carbine.

I found the long allen key that comes with the superlative gas block and headed off to the range.

I was using that Sargent major rebranded tula that 06wrb Mentioned. So I brought out some LC 855 and and some RAUG m193 but did all my testing with the tula to be sure I fixed the problem.

I loaded the mags with one round and adjusted the gas until the bolt locked back on the empty mag consistantly. I ended up opening it up one more click to get the cases to eject at 3:30-4:30 and all the ammo functioned fine from there on out.

Once I got it cycling properly and on paper, I switched to the 855 and finished zeroing the gun for 50/200. I didn't feel like moving on to the other rifles, I switched around some new optics and they other optics get traded down the line so there will be a lot of range days ahead rezeroing.

This was an easy fix, but it was frustrating. People watching me use an AR like a bolt action at the range, I know they are laughing at me, and rightfully so.


Thanks again for the tips on the gas issues.

quote:

Originally posted by Nickelsig229:
Here is a little update for you guys. Thanks for the input.

This was an easy fix, but it was frustrating. People watching me use an AR like a bolt action at the range, I know they are laughing at me, and rightfully so .

Nope, they are just ignorant.
Gas issues are quite common and yes it can be a bit frustrating at times but all a part of the process.
You have nothing to apologize about.
Glad you are up and running.