Issue with new build

[32_d3gr33s]

Just finished an early wedding gift for the fiancee, and took it out shooting this weekend.

Its an ar15 in 5.56. Spent a good deal of time breaking it it while sighting it in, and had no issues (other than somehow i managed to put the hammer spring on backwards. Figured that out on the first round) I put about 30 or 40 rounds through it using the same p-mag the whole time. Decided to let the kids shoot it after my fiancee put a mag through it. My stepson started shooting, and it basically turned into a single shot - had to pull the charging handle after every shot, because it wouldn't pick up the next round. I tried again, with no issues. My stepdaughter shot a 1/2 mag through with no issues, and then i shot one final mag with no issues. The problem only occurred with my stepson. I'm assuming it was something in the way he was holding it, but I'm not sure. Id like to be able to correct him so it doesn't happen again, but i need to know why it happened first.

Any help?

 

[9mmepiphany]

I'm sure folks would be happy to help if you'd post a picture of how he was shooting it. Without that, we'd just be guessing

 

[32_d3gr33s]

He was holding it exactly the same way she is in the picture. The same as how I showed him how to hold it. That's why I'm confused. Nothing looked wrong to me. I'm thinking maybe it was something he was doing while pulling the trigger or something. Would flinching cause it not to pick up the next round?

 

[HammsBeer]

Sounds like the mag might not have been seated all the way into the magwell so the bolt was overrunning the mag follower.

What this means is if the mag is not fully seated, the bolt is juuuust barely able to strip the next round out of the mag by hand. But when shooting, the bolt is traveling back and forth so fast the mag spring can't push the next round up high enough, fast enough, to let the bolt strip off a round. Make sense? That's my guess.

 

[Jason248]

Could be the mag not seated.


Is it a set screw gas block? If it loosened up a little it could be causing a small gas leak making it short stroke allowing it to eject but not cycle back far enough to strip the next round.


Also if it's a new mag try only loading five rounds in at a time and see how it runs and or try a different mag after checking the gas block

 

[9mmepiphany]

I'm thinking maybe it was something he was doing while pulling the trigger or something. Would flinching cause it not to pick up the next round?

Nope flinching will cause a lot of bad things to happen when shooting, but FTFeed isn't one of them

He was holding it exactly the same way she is in the picture. The same as how I showed him how to hold it. That's why I'm confused. Nothing looked wrong to me.

Sometimes we see what we expect to see, that is why it is always easier for an objective observer, like an instructor, to see flaws in a shooter's technique. There are also differences in body build, arm length, hand size, and length of neck/head. But if you want to go with, "He was holding it exactly the same way she is in the picture", I can base an experienced guess off of an observation of her apparent technique.

Not surprisingly it falls much in line with the previous posters.

Seeing how she is using the magazine as a mono-pod, if he is the child in the background of the picture, he is noticeably smaller than she. The would mean he is applying more downward and rearward pressure on the magazine.

Depending on the tolerances maintained during your build, (is that a PMag?) I wouldn't be surprised that these pressures would cause the rear of the magazine lips to be pulled lower in the action, causing the bolt to override the rim of the case.

This is easy enough to test. Just have him shoot it while standing or have them shoot with a shorter magazine...I normally use a 20 round mag when shooting off a bench

 

[IndianaBoy]

I'm not saying it is impossible, but I have used an AR magazine as a monopod in a BUNCH of different scenarios that put tension both fore and aft on the magazine, and have never induced a malfunction that way.

And an AR should not be finicky the same way that you can limp wrist a pistol.

I suspect that the person who suggested that perhaps the magazine was not seated properly is on the right track.

 

[32_d3gr33s]

I had also thought it was the magazine not seated. I pulled the mag and re-seated it twice with me firing 2 shots after both times.

As for leaning on the mag like a monopod, I hadn't thought of that. He is quite a bit shorter and could have been leaning on the mag. I shot standing, and don't think my fiancée was actually leaning on the mag when she was shooting.

 

[kBob]

I am going with 9mme... on this one. I have seen this happen with M-16A1s and it is why we were taught to never use the mag for a mono pod.

It is great if you are someone this never happened to, but it does happen.

Also seen failures to feed when a 30 rounder was being used as a foregrip on older guns without M4 feed ramps, the tip of the bullet hitting just a hair low and stopping right there. If you just have to cramp up with your non firing hand use the front of the magwell and not the mag itself for a grip.

Magazines are for holding and feeding ammo not for a rest or a grip.

Might be a good idea to get a 20 rounder or one of the short commercial 5 or 10 rounders one occasionally sees for the young man to shoot and have him keep the magazine off the table.

-kBob

 

[wally]

I'm not saying it is impossible, but I have used an AR magazine as a monopod in a BUNCH of different scenarios that put tension both fore and aft on the magazine, and have never induced a malfunction that way.

You are correct that it shouldn't be possible to induce failure by using the magazine as a monopod. If you can there is something wrong with the mag-magwell-mag catch.

 

[TIMC]

I agree with check the gas block, since it was a build I would suspect it slipped, doesn't take much to turn it into a single shot.

 

[nastynatesfish]

Also check your gas key make sure the two Allen's are tight and or staked. It could be several things. Does the mag have any in out slop to it? I had that happen once.

 

[Jason248]

Any update? Figure it out?

 

[MistWolf]

Let's take this one step at a time. First, we can eliminate the mag being seating incorrectly. If it were seated incorrectly, the round would not feed when the charging handle was cycled

Second, a more complete description is needed of the malfunction. Did the spent case extract and eject? Or is the spent round still in the chamber?

My guess the spent case is extracted and ejected, but the next round failed to feed. The rifle functions fine when anyone but the stepson shoots it. It's possible the stepson is experiencing the rifle equivalent of "limp wristing". Get him to pull the rifle more firmly into his shoulder.

The rifle can also be tested for "limp wristing" by holding it loosely and firing it well away from the shoulder. A rifle could be at the edge of it's performance envelop and pushed into short stroking if it's "limp wristed"

 

[rcmodel]

How can you 'Limp Wrest' a gas operated firearm?

You can't.

I'm going with the mag as mono-pod guess.

If the mag seats too deep in the receiver, due to an out of spec mag catch hole in the lower, or a worn out mag?

It can rub on the bottom of the bolt carrier and slow it to the point it won't cycle fully.

rc

 

[jerkface11]

Could be an out of spec mag catch.

 

[MistWolf]

Any self loading weapon can be "limp wristed" by simply allowing the weapon to move with the recoil in a fashion that it causes short stroking. Don't forget, the gas only moves the BCG a very short distance. After that, it's running on momentum alone.

If the mag were seated too deeply, that would cause drag on the BCG but usually results in a bolt over with the round being pushed partially out of the mag.

I don't have much experience using a mag as a mono pod because I grew up in a time when that was strictly verboten. But there are many shooters that do with no trouble at all. It would easy to test though. Just have the stepson shoot the rifle again without using the mag as a monopod

 

[Caliper_Mi]

Any self loading weapon can be "limp wristed" by simply allowing the weapon to move with the recoil in a fashion that it causes short stroking. Don't forget, the gas only moves the BCG a very short distance. After that, it's running on momentum alone.

I agree with is. It is easy to notice a difference in ejection pattern when shooting my AR's standing vs prone. Standing allows your body to move much more and with it the receiver. Not holding the rifle firmly to your shoulder ("limp wristing") would be a more extreme version of this. With a new gun that may still be a bit stiff, I could see this resulting in failure to feed if the bolt carrier velocity relative to the receiver is reduced enough.

Clean the gun and then oil the bolt carrier throughly. At least one drop of oil on each of the four raised patches where it rides against the receiver, oil the back of the locking lugs, some oil on the sides of the gas key and a few drops through the gas vents on the side. Manually cycle it a few times to spread the oil and then re-try.

 

[mnrivrat]

Just a quick question - Did you change the butt stock position for him ? or was it left in the same position all the time.

 

[32_d3gr33s]

I haven't had a chance to take it back out yet. I can say that it wasn't a loose gas block. The mag is brand new, but could just be a bad mag. It doesn't seem like it has any more slop than any other mags. The stock was shortened down for him to use. The empty case was ejecting just fine and it would just fail to pick up the next round. Hopefully the weather clears up in the next couple days so I can go test it out some more.

 

[MartinS]

It's borderline functioning and the little tyke is not presenting enough mass, like limp wristing a Glock. You sure you have the right buffer and buffer spring? Gas port?

 

[M1key]

Try a 20-round mag and have him shoot off a rest...?

M