Have you tried using a different charging handle?

 

Not yet, but I am going to try a different one on my next outing. I did check the springs and the retention and all that is good. The machining on the receiver is good as well.

 

If the receiver cut looks good, definitely try a different charging handle. BCM makes good ones, and I'd default to Colt.

If they don't work, I'd look back to the receiver. Good luck man.

Either way, wear a mask

Edit to add: You could try different GI mags

I love Magpul as a company and their products...I just don't use their mags.

 

The charging handle is free floating, so I can't imagine why the bolt carrier group would grab it on the last round and give it a ride backwards. Take a look at the top of the BCG to see if there's anything that could grab the charging handle when the magazine follower is pushing up on the BCG. I don't think this is a charging handle issue.

 

Does the magazine follower somehow push up on the BCG at all?

 

I just gave it another once over and compared it to my 5.56 with a radon raptor charging handle, and it seems to be of the same mechanical functioning. I am going to have to make another range trip and swap the charging handles to see what happens. Might be a couple weeks though.

 

Take your BCG out and reseat the charging handle properly and that should fix it.

 

Nope... it did with the first mag I ran through it. I took it apart, cleaned and lubed, reassembled with the same result

 

I am speechless as to what is causing that. Do let us know if you find out what is causing it. It is possible that the latch that keeps it locked in place is too weak and it pops loose on the last round due to a empty mag, magazine catch and inertia. If a new charging handle doesn't fix the problem then you may need to ask a gunsmith about it and maybe even pay them to fix it. They may not tell you what the problem is unless they get paid for it.

 

There has to be some interference issue with the gas key on the top of the BCG and the charging handle. The magazine follower cannot do anything except push up on the BCG, and the only part of the BCG that could touch the charging handle is the gas key (where it passes through the hole on the front of the charging handle).

The only way that the charging handle can be unlatched and forced to the rear is if the BCG is grabbing / snagging it and pushing it rearward with enough force to make the latch pop off of its catch on the upper receiver. The only part of the BCG that could be doing this are the gas key. The rest of the BCG ride under the charging handle and should not be touching it at all. Once the BCG has traveled in recoil far enough that the gas key has passed rearward through the hole in the front end of the charging handle, it cannot have any contact with it.

Whatever is happening to force the charging handle rearward must be taking place in the first couple of inches of BCG recoil. If this is what is happening, there should be some indication by way of bare metal or some area exhibiting unusual wear.

Check to be sure that the gas key is properly screwed down and staked to the BCG. It could be slightly loose or misaligned on the BCG. If it's really loose, I suppose it could be pushed up by the BCG into the charging handle when the mag follower catches the front of the BCG to hold it open. This should be really obvious, though.

It is remotely possible that the BCG is recoiling too far to the rear and the gas key is hitting the closed charging handle at its inside rear. There should be evidence of this inside the charging handle. This could possibly happen if the rifle is way over-gassed (way too light buffer and / or recoil spring). If this was the case, though, I should imagine that the problem wouldn't just happen on the last round and an empty mag. (I suppose this could also happen if the inside of the gas key channel in the charging handle wasn't machined properly.)

When the BCG is locked to the rear by the empty mag, can the charging handle be returned forward and latched? If there's some interference with the BCG to the rear, this should manifest itself when trying to return the charging handle forward. It shouldn't touch anything other than the channel and grooves inside the upper receiver.

Other than this, the latch on the charging handle must be bouncing off its latching notch on the receiver, and the only way that can happen is if the spring is too weak, the spring is missing, the latch "tooth" is misshapen (rounded over, not deep enough, or something) or the latch notch on the upper receiver is misshapen (again, rounded edge, too shallow, or something).

Finally, check that the charging handle is actually straight and not bent somehow. A bend in the handle might be enough to cause an interference with the movement of the gas key during recoil.

I'm sure you've looked to be sure the charging handle latch notch on the receiver isn't fouled with something to prevent the latch tooth from engaging it.

 

Okay?
And how do the factors that be know to only do it on the last round?
Gun runs fine for 29rnds and then on the 30th one charging handle comes back? How do any of the parts know the difference between what round it is? That’s the mystery.

 

Just out of curiousity I checked my rifle (Ruger AR-556 - 8500)
Take the upper off.
Check bolt play while in battery - up and down.
Pop the bolt out of batter and check again.

First condition I see very little vertical motion.
The second maybe 10 thou?

How does that compare to you rifle?

 

All tolerances feel pretty tight. I just ordered a Radian Raptor SD-SL. I will put that on when I get it and compare. If it works just fine then I will do a warranty claim with Gieselle. If not, then I will further troubleshoot.

 

Even if the front of the charging handle is jacked up and catching gas instead of letting it pass through freely, shouldn't the rear latch still keep it closed at all times? I've heard about charging handles bouncing around before but that was with dirty latchless designs.

 

 

Comparison between the geiselle and the milspec CH from my M&P Sport. The geiselle has a flat top where the milspec is tapered

 

milspec CH from my M&P Sport

The milspec looks like it has a beefier latch.

 

Since this is a Leggo Frankengun, I would assume that the assembler used brand new parts? The Geissele charging handle is a quality part. I have them on all of my AR15s and have never experienced any issues with them. If the parts are used, then maybe it's old and the springs are worn out? But, why would anyone use old parts on any assembly Leggo gun like this? Might need a new charging handle?

 

Everything is new... no used parts

 

The swapping of charging handle and or bcg test, has that happened yet?

The thing with follower pushing up on last round? The ammo pushes up on every round then, " just like that it's gone" .

The last charging handle I received needed replaced by manufacturer. I inspected and measured against other functional examples and could not find the defect.

The manufacturer said a replacement was on the way and "it happens, have a nice day".

Because it is from a top shelf vendor does not prevent a small error from slipping past qc.

It does imply that customer service will be swift and accommodating.

 

The rear latch is simply to keep it from falling back during handling. If the gas key is rubbing that thing, the latch isn't going to hold. This would amount to a significant fault in the service and the rifle would be sent up for repair/replacement.

 

The services teach people to put thier nose right up on the charging handle.

Looks like a trigger company will put thier name on anything for a cut?

 

"the charging handle flies back and hits me in the face"

Sorry, the visual on that made me LOL, like the Coyote's gun when he tries to ambush the Roadrunner.

Highest regard for those helping fix the anomaly, ahem, not just have fun with it.

 

We all seem to be fixated on the idea that the follower is pushing things UP in a way that for some reason the rest of the rounds in the mag aren't. What about the inverse of this idea? What if the empty mag's follower isn't pushing the BCG up enough vs. having a round in the mag? I'd advise the OP to look for problem areas on the bottom of the gas key and/or the underside of the charging handle. Remember that his rifle is chugging along fine with every round in the mag until the mag is empty. It has to be the difference between having another round and not having another round in the mag.

 

Correct. The only thing that's changed is the magazine condition. All other aspects of the gun are unchanged.

 

Ya sounds good.

 

Swapping a charging handle takes seconds...Before changing, I would take to the range as-is and safely hip-fire a few rounds and watch to see if the handle moves on every shot...I bet it does, and only has enough time to slap your snoot when the bolt locks to the rear on the last round in the mag...Then swap to a new charging handle and retest...If that doesn't fix it, I concur that the gas key may be misaligned and causing drag on the charging handle...Good luck! Let us know how it goes....Curious minds want to know....

 

Well, open 'er up and start taking some pics of the end of gas tube, and pics of gas key from various angles, post the pics here.

Charge round from magazine, drop the mag, does it fire and have the issue?

 

I received my Radian Raptor SD-SL charging handle in the mail today, and upon comparing the feel to the Geiselle charging handle, It is much tighter... It takes more pressure to release the latch, and it stays in more snug. I compared it to a standard mils-pec charging handle out of S&W as well. It seems like I may have just gotten a defective charging handle because it doesn't take much to get it to unlatch from my upper. I will confirm when I make it out to the range this weekend. I will try it with all three charging handles and different BCGs if need be.

 

The gas ports opposite of ejection port are kinda useless. Where does gas go on that side?

I might also argue that the gas ports ejection side actually causes a rearward force on the handle as some gas pushes through the holes and changes direction, and changing direction always involves a force.

I don't understand the "it happens on last round" part, but when the BCG key leaves the gas tube, a burst of gas still comes out the tube, which can shoot to the back of the handle and push on it a smidge.

Was the one round no magazine test done yet?

I have used the $19 CBC ambi handles on many different types of rifles, never had an issue.

Ambidextrous Charging Handle - CBC Precision AR's

A central component of your AR-15, the charging handle not only assists in chambering a round but is your main tool to clear a round that won’t eject cleanly. The aluminum design results in a rugged and capable charging handle for your AR-15. This ambidextrous charging handle features textured...

www.cbcpfa.com

 

UPDATE: I went to the range and tried different configurations of BCGs, charging handles, and buffer weights. Turns out the Geiselle charging handle is defective... it comes loose as I am firing and then pops me in the face on the last round in the mag. Geiselle has amazing customer service, and they have shipped me a replacement. There seems to be nothing wrong with my BCG or my upper receiver as everything performed flawlessly in every other configuration I tried.

 

That is great customer service.

What I would like to see is how that "defective" charge handle behaves in a different AR15.

 

Why only on last round? And when you say "last round", do you mean last round fired, or something other?

If the handle is defective, then explain why only on last round?

 

It was hitting me in the face after firing the last round in the mag and thus locking the bolt to the rear. It was most likely coming loose with every round but being slammed back forward before reaching my face.

 

Probably because of the bolt locking back and not smacking the charging handle back in place?
Or is that to technical?

 

Exactly!

 

I have a radian charging handle on my last build. Full function and has cut down on gas in my face when I ran suppressed.

They will be on my next build sheet along with thier handgaurd.