Frustrating range day... crazy Fails to Feed on 2 of my rifles.

Silverado

Silverado

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My AR was giving me fits today. Almost every mag (I had 30 or so on hand) I experienced a fail to feed on the first round. Perhaps fail to go into battery is more accurate.

The bolt would strip a round out of the mag, but wouldn't go completely into battery. Pressing and/or hitting the FA didn't help. On remedial action, the round was left in the chamber... the extractor hadn't grabbed the rim. The round fell free of the chamber easily though.

The odd part is that on every round, there is a scratch on the bullet as if it's catching on something. That something isn't the mag, as it happens with PMags too. I was shooting mostly Norc ammo, but this happened with AE and PMC too. It also re-occured several times even if I didn't reload that same round, but went for the second round in the mag.

I looked at and felt around the chamber mouth and feed ramps, and couldn't find anything amiss.

Next I lubed the bolt and carrier, even though they weren't dry. It didn't help, so I then SOAKED the bolt in G96 spray and re-assembled.

That helped somewhat, but didn't completely eliminate the problem.

WTF? Somebody must know what I should look for here?

Then there was my M305 failing to feed the first round... but that's for another forum.
 
Just the first round? I can't tell if your comment regarding the second round applied to the fail to feed or the scratch.

Your description of the forward assist not being effective, the round being easy to remove, and the extractor not latching onto the rim allsuggest the bolt is binding, not the cartridge. But if it's not happening to all the rounds, then that doesn't add up.

I don't think the scratch is meaningful. Lots of semis scratch cartridges as they strip them.
 
What I meant was that if I remove the failed first round from the chamber, reinsert the magazine with only the 4 remaining rounds, and have another go, the top round will again fail to feed, just like the first.

The scratch is on the bullet itself, not the casing. I was just wondering if it's catching on something like a burr or nick which is stopping it.

On an AR, when does the extractor engage the cartridge rim; when it's stripped from the mag, or when the cartridge stops in the chamber and the bolt rotates into battery?
 
I have an identical spare M16 BCG... can I throw that in and see if there's an improvement, or do I need to headspace it first?
 
Perhaps the magazine might be pinned too tight?

Does the problem persist if you load the mag with 4?
 
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Since this is happening with ALL of your mags, it's not a particular magazine issue.

Try checking how tight your mag catch is. If it's loose, it may not be holding the magazine up high enough for the bolt to catch the round properly.
 
The bolt catches the mag fine. The round strips off the mag and goes all the way into the chamber, but the extractor doesn't slide over and engage the case rim. This prevents the bolt from camming into battery. It's the last 1/4" of action travel that's the problem.

I disassembled my bolt just now, and didn't find anything odd with it that I can see. It wasn't particularly dirty, and is well lubed. I can make the extractor pivot on it's pin if I press hard with my thumb. No burrs or nicks in the extractor. I blasted it with crud cutter and then basted the works with G96 and put it back together.

Examined the chamber, throat and barrel extension as well as I could with a light but without a bore scope; nothing odd looking there either.

The whole BCG is nice and wet with lube. I'm going to have at 'er at the range again this afternoon and see what I can make of it.
 
I got some questions, what type of AR are you using? Did you modify your AR as of late? Something random but what was the weather like? Have you considered that maybe something was wrong with the buffer? We could use some pictures to help us help you.
 
Stag 2T. The only mod that could affect this might be the Magpul BAD lever, but I don't think so. It seems to function fine, and doesn't cause the bolt catch to ride the bolt that I can tell. When I release the bolt, it heads forward enthusiastically, just won't close on that first round.

It runs fine once a round is chambered.

Rifle was new at Christmas. Has maybe 50-600 rounds through it.

Chamber is clean enough.

Like I said, this is the last bit of travel of the action; that's why I think it's in the bolt, or the barrel/barrel extension maybe.

Will report back.
 
Um, yeah. So my range report is that I got to the range and the keys for my restricteds were at home on the counter. FML
 
Silverado said:
Um, yeah. So my range report is that I got to the range and the keys for my restricteds were at home on the counter. FML
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I switched to combo locks a few months ago. I got tired of having to pick them open with a screwdriver, though I did get really good at it!
 
Also, scratches on bullets after extracting a live round are common to the AR15. The extractor pulls the bullet to the right and over the sharp inner corner edge of the barrel extensions at hand speed. Not a fault and probably shouldn't be rectified (by filling the inside of the barrel extension lugs), those corners will wear somewhat on their own through the barrel's life.
 
Another thing that could be is the gas tube and gas key fit. during one of my builds the gas key wouldn't allow the gas tube to insert far enough and stop the bolt from traveling all the way, not even the FA would push it. alittle 600 grit sand paper on the gas tube fixed this.

the extractor claw engages the rim when in full battery.

has this happened before?

like danger tree said the bullets are gonna get scratched no matter what, the rounds will run along the locking lugs and ramps, they aren't cut smooth as you can tell by looking at them and have small sharp edges.
 
Well, BAD lever off, 150 or so rounds downrange, and I had exactly 1 failure of this type. Ran both PMags and OKAY USGI mags.

Interestingly, after you guys mentioned the lever, my 'Drunken Carpenter Google-Fu' turned up lots of mentions on different forums, but all that I saw were of failure to lock open on last round. I never had that happen once?

Anyway, I'm going to see if I can thin out the back of that lever to make it work - it contacts the upper, and I can see how that would cause the bolt catch to drag on the bottom of the carrier. If not, it's not a particularly expensive lesson.

Thanks for the help all.
 
Silverado said:
Well, BAD lever off, 150 or so rounds downrange, and I had exactly 1 failure of this type. Ran both PMags and OKAY USGI mags.

Interestingly, after you guys mentioned the lever, my 'Drunken Carpenter Google-Fu' turned up lots of mentions on different forums, but all that I saw were of failure to lock open on last round. I never had that happen once?

Anyway, I'm going to see if I can thin out the back of that lever to make it work - it contacts the upper, and I can see how that would cause the bolt catch to drag on the bottom of the carrier. If not, it's not a particularly expensive lesson.

Thanks for the help all.
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good to hear is was somthing simple, not make sure you pass to other people!! the BAD is BAD ! :)
bbb
 
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