ar-15 failure to feed(first time)

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JR Hartman

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today, I had a few failure to feeds. 3 or 4 different mags, same rifle. Not that old, 1000 -1500 rounds maybe? absolutely NEVER had any kind of issue at all that I didn't directly cause by being new.(not fully inserted mag etc)

I would drop the bolt and it would not go all the way forward. I could see the round angling upwards. of course the mag wouldn't drop, unless I helped it. pull the offending round out, slap the mag back in and it was usually good to go.

I found it more prevalent on a full mag. you could tell that the bolt didn't have enough force to strip a round and fully close the bolt. a few times it was almost closed and some forward assist got it working. A couple of times it barely got the tip of the round out of the mag.

any ideas what needs to be looked at?

thanks!
 
My friend was having this issue and he couldn't figure it out.

This may or may not be the problem, but if it is it's an easy fix.

-Take the bolt carrier assembly out of your gun
-Grab a decent quality lube (I like Breakfree CLP, but there are lots to choose from. avoid bottles that simply say 'gun-oil')
-Put a few drops through the vent holes on your carrier to wet the gas rings, a couple on your cam pin, and some on the 'rails' of the carrier (just lubing the body where it doesn't touch the receiver won't help)
-Return carrier to upper, cycle by hand a few times

You don't have to dip it in a bucket of oil, but a little lube goes a long way, especially if your carrier is dry and chalky from carbon

Try that and report back.

If it works, I will mail you an invoice for my consulting fee ;)
 
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it certainly could be a dirty gun issue. I did clean it after last weekends black rifle competition, but I didn't take the bolt apart or anything like that, just oiled it up and wiped a few things down.

I also have tried out a new lube, and I am not sure the rifle is in love with it. Its called M-pro 7 or something like that. I had some Hoppes #9 in the range bag and I hit the bolt and carrier with a bit of it and it was better. still did one misfeed after.
 
Strip and lubricate the girl is what I say. Alternatively, since you mentioned it seems more prevalent on a fully loaded mag, are the mags being very tight when fully loaded? If you need to strain yourself to get the last round or two in, a bad riveting job could be contributing to your problems. Just an idea.
 
Stevebot-7 said:
Strip and lubricate the girl is what I say. Alternatively, since you mentioned it seems more prevalent on a fully loaded mag, are the mags being very tight when fully loaded? If you need to strain yourself to get the last round or two in, a bad riveting job could be contributing to your problems. Just an idea.
Click to expand...

I would agree, except for that he just started having the problem after 1000-1500 rounds (or so he says). A bad rivet job would have showed up long before that.
 
yea, this is a new problem for sure. never any hints of problems before. the mag rivets are nice.

Now, recently I did change two of the mags over to Magpul anti-tilt followers. However this feed issue happened on a mag that I have not touched and one that I did. It also didn't happen on another one that I did put a new follower in.

also, these are 10 round pistol mags(two manufacturers of LAR15 mags)

again tho, the only thing I have ever used in my rifle, except for the first day, I only had the one that came with it.

The last 2 rounds are tight, but they have always been tight.
 
Lube.

It works for women, it will work for your gun ;)



One more thing to inspect (I still think it's the lube issue):

1) Use a pencil and feel the leading edge of the pistol mag lips for a slight burr or catch. ASC had a few batches that were burred and would drag on the rounds.

2) Load 10 rounds in the pistol mags and insert them in the gun on a closed bolt. If they are difficult to seat, you might have to adjust the follower slightly so that they hold 10.5 rounds. If they seat easily, that's likely not the problem

Again, I don't think this is the problem, though, because you state that the issue is the same with a mag that you didn't touch and you haven't had this problem until after 1000 rounds
 
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see, I have never had to use lube with women either, so that might be my problem !! :D

I have just torn it down. I didn't unstake the gas key and I didn't take the rings out, but the bolt and carrier are right apart.

I found tons of really hard scaly carbon inside the carrier and on the end of the bolt. The part of the bolt where its like an inverse cone shape. the tapered part. and inside the carrier on that ledge down where the gas comes into it. Really hard carbon. carb spray didn't really soften it up. I had to pick it off like they do at the dentist with hard plaque. it was nasty.

as bad as that was, I am not sure how that would make it fail to fee on a fresh mag tho. No problems when firing(or maybe once?)

it will go back togeather soon. I will try it out with dummy rounds as the range is closed now and its a bit of a drive.

I am using this stuff called M Pro 7. anyone hear of it?
 
Ya, don't unstake the gas key or remove the gas rings.

Potentially, the reason it's hanging up is because the bolt has to rotate as it's chambering a round. If it's having a hard time rotating, it could slow down the forward momentum of the carrier which will cause the round to hang up. But that's when the carrier is closer to being closed/in battery.
If it's slow right out of mag/when releasing the bolt stop, your carrier rails or the inside of the upper being 'caked' with dry carbon is also going to potentially slow down the carrier.
There is more force on cycling backward so that's probably why it still cycles fine.

I have heard of Mpro7, but I have only ever used their 'copper remover'. I've also heard it's similar to Breakfree, but I don't know that for sure.

You gun doesn't need to be dripping/spraying oil, but a generous application won't really hurt it.

see, I have never had to use lube with women either, so that might be my problem !!
Click to expand...

Don't be a show-off. ;) That's T870's job
 
hehe, as a liscenced mechanic I have used atf and synthetic engine oil. also synthetic gear oil. seemed to work fine? heheh. This Mpro7 stuff was only a few bucks and I knew I was outta Hoppes.

I used the diagram for what takes oil and what takes grease. I used a quality high heat silicone based grease in those areas and a little oil in the others. I was generous with the oil tho, then wiped off the really excessive stuff. its not dripping on the table :)
 
and, on another note, I found what I think might have been the problem. It has had a few times of slow bolt movement forward into battery. it has always gone in, but sometimes it was slow to iffy.

I loaded a mag up and tried to strip the rounds off with my thumb. I found that on a few of the mags, the rim of the cartridge would catch on the little vertical slot in the follower. not sure what its for or what its called, but its about 2/3rds the way back, cut in the top of the follower and goes all the way thru, you can see spring below it.

now, this on some followers is slightly slanted forwards and upwards. others it is just straight and flat. the straight ones catch the rim really easily. like, you couldn't design something to catch one better if you wanted to! it would catch in there every time. So, with a small sharp blade I chamfered that forward edge. noticeable improvement every time. Slightly more chamfer and a secondary angle, now its much better. so I looked at how the cartridge case fits onto that spot on the follower and on the case of the magazine itself and all I could find catching it now was a small spot where the axial cut intersects the radial cut. a little more work there, and its buttah!! I can load a mag to full capacity and strip em all off easily by hand.

next I loaded 8 real rounds in and then 2 dummies(that's all I have for dummies). closed the bolt, inserted the mag, and cycled the bolt(with some authority). it stripped a dummy, and chambered it really forcefully. no slow draggy bolt lockup. cycled it again, ejected really good, stripped off another dummy and chambered it nicely. Pretty much as fast as with no ammo in it. Dropped the mag, cycled the action again and ejected the second dummy. NO LIVE ROUNDS WERE CHAMBERED.

tried another mag like this, got jams just like at the range today, intermittently.

Tweaked each mag in turn. some just a minor smoothing, others like the first one.

all work perfectly now, rifle cycles so smoothly.

I want to go shoot it now, but the range is closed. boo

:)

thanks for all the help.

I hope its fixed when actual ammo is cycling thru the rifle tho.
 
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