I bought a new AR15 on Black Friday, put a reflex sight on it and zeroed it at the range, firing 20 rounds from a single mag with no feeding or ejecting problems.

Fast forward 2 months.  I cleaned the rifle and installed 45 degree offset iron sights.  I wanted to check some of the other untested used USGI mags I had accumulated over the years while zeroing the new sights. I loaded 5 rounds from the same batch as before (62 grain British surplus green tips) in each of 4 mags and headed to the range for the second time.

I only fired 10 rounds total from the two mags, but this time every one of them failed to load after the initial, manually loaded round.  The round in the chamber fired and ejected normally, but the next round would not load automatically.  I had to manually chamber each round from each of the 2 mags.  

The mags look to be in good shape, with about 80% finish and no visible dings, dents or bent feed ramps.  I can't imagine how I could have messed anything up when I took the rifle apart last month to clean it.  30 round Mags should operate as well when they only have 5 rounds as when they're full.  Firing with the rifle rotated 45 degrees shouldn't affect anything.  So, what's your best guess as to why the rifle suddenly stopped loading rounds?

Did you take the trigger apart to clean? Is the BCG lubricated? Gas tube lined up?

First guess would be the disconnect is in wrong or left out.

WTH??? I've seen a LOT of things gone wrong with AR 15s. But I am really interested in learning HOW a missing or improperly installed  disconnector would cause the malfunction described by OP. Not being snarky either.
@Oldgold

OP, sounds to me like there is a glitch in the gas system. Loose or mis-aligned gas block. Maybe too small of a gas port in the barrel, leaking gas key, gas tube a little short. Oddly enough I've encountered incorrect dimensioned buffers that did not allow full travel of the bolt far enough to strip off the next round from the mag. Suggest you do a step by step troubleshoot of the gun. And please post an update when you figure out the problem.

This would be my guess also.  Is the gas block a clamp on or a set screw type?  If so, then it is quite possible that it has slipped because it was not tightened correctly at the initial install.  I'd check to make sure the gas block has not shifted.  If not that, then I'd be checking the carrier key screws to make sure one of them did not break.

It happened to a friend of mine. He left out the disconnect when assembling the trigger group.

@Oldgold

A missing disconnector would likely cause multiple slam fires. Still not seeing how a missing or improperly installed disco could prevent enough bolt travel to allow proper function. Going with my initial comments, and the one about underpowered ammo.

How about the basics...

Does it lock back on a single round?

How's the ejection pattern?

What does the brass look like? Any scratches, scuffs or weird marks?

Step one, check the FCG assembly.   Next check for loose, leaking, missing, or broken gas system parts.  

Next, lube properly, buy fresh name brand ammo, and use a quality brand name magazine.  As suggested, start with one round, check for lock-back, and determine ejection pattern.

"That British 62gr sounds a lot like the underpowered "SS109" for the SA 80.

Radway Green ( RG ) '89ish ?... pretty sure that stuff was underpowered."


You, Sir, are a genius.  Or at least smarter than the Average Bear-er.  The problem is indeed the British Ammo.  I erred when I said I used the same ammo on my two trips to the range.  The first trip I used Winchester white box 55 grain and all 20 performed flawlessly.  When I made my second trip I used 20 rounds of the British stuff and every one of them failed to load the next round.  That turned my AR into a high capacity bolt action rifle.  Yesterday I returned to the range, fired 10 rounds of Winchester and 10 of the British ammo.  All the Win loaded the following round, and all 10 of the Brits failed to load the next round.  And when firing a single round from an empty mag, the bolt locked back after the Win fired but wouldn't lock after the Brit.  

Looks like I need to either install an adjustable gas block and hope I can increase the gas enough to work with this ammo, or buy a good bullet puller and add another couple of grains of powder to each of the 200 or so remaining Brit rounds.  I'll solicit opinions as to which is the best path forward in a separate thread.  

For pointing me in the right direction!

Yes, I might try the Yellow spring.....cheaper than a Cam Lock bullet puller.

How light a buffer would you recommend?  My Radical Arms supposedly comes with a MilSpec 3 oz.

The Radway Green stuff has a different pressure curve powder that's optimized for their SA80 rifle, and tends to be... problematic... in carbine gas ARs. Longer gas system ARs like a midlength or KAC 16", or the old standby 20" rifle will usually work. I shot a bunch of it, mostly in 20" barrels.

Runs fine in 20's, I've run a couple K in A2's without issues. Some lots worked fine in carbines from what I heard, other lots, less so, I've shot a little in carbines [Colt 6721] and it worked OK but we are only talking about less then 200 rounds. [probably 150 or so] It does feel a little light but it worked OK. As someone said, it's the pressure curve of the powder burn.

"Runs fine in 20's, I've run a couple K in A2's without issues. Some lots worked fine in carbines from what I heard, other lots, less so"


Well, it seems to shoot OK as far as hitting the target downrange but not a single round of it will feed the following round in my 16".  Winchester white box ammo works flawlessly.  I plan to try a yellow Sprinco spring and possibly a buffer lighter than the 3 oz. one that came in my Radical.

If that solves the problem with Radway Green ammo, is there any downside to leaving the yellow spring in the rifle for other brands of ammo?

Original poster here with an UPDATE:

I bought the Yellow light spring and it fixed the problem.....Radway Green ammo is feeding perfectly now.  That's a big relief since on further inspection I found my Radway stash was 500 rounds.  Glad I don't need to pull the bullets and reload them to get enough gas to work the BCG properly.

My thanks to the learned members who correctly diagnosed my problem!

Is there any problem with leaving the lighter spring in the rifle when the Radway is gone and I resume firing normal-powered ammo?

An adjustable gas block is only capable of reducing gas, it can't increase it.