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Discussion Starter · #1 ·
I shot my AR today and had 3 identical and strange failures. All 3 occurred with the same ammo (XM193) in the same magazine. All 3 were latter rounds in the same magazine (i.e., they were all loaded in the same magazine at the same time) - near the end.

In each occurrence, I pulled the trigger, heard an audible click, but no bang. I waited...nothing, then pulled the charging handle and the round ejected fine. I looked at the primer and it did not appear to have been struck??? 1 of the 3 had a very faint mark that I couldn't even tell whether it was a strike or a scratch. When I re-chambered the rounds and pulled the trigger, they all fired on the first try. I then put another 30rd magazine in, fired all 30 rounds, and no problems.

This one has me scratching my head. These failures occurred after ~ 200 rds. I wasn't rapid firing. The ammo was old, which is why I was purging it. So I'm stumped. :confused: My best guess is that the rounds before were somehow to blame. But even that, I'm not sure why or how. The rifle has never incurred any problems in the past and was quite clean prior to this range trip.

Any ideas?

I'll be tearing it down for a cleaning tonight or as late this weekend. I'm just not sure where to look or whether it's worth worrying about. As I say, the next 30 rds went through fine. Unfortunately it was a very short trip to the range and I ran out of time after those next 30 rds.
 
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Discussion Starter · #2 ·
Sounds like the bolt didn't lock into battery properly. Either dirty bolt or ammo, or magazine. If the cam pin and the channell gets real dirty they can cause the weapon to cycle slower. Sometimes this will keep the bolt from traveling far enough foward.

I've also seen one instance of some messed up lips on a magazine dragging on the bottom of the bolt. The bolt wouldn't lock into battery. He switched mags and it worked fine.

Next time you go out check out that magazine. Fire with it in the weapon again and if you get failures out of the same magazine it is probably the magazine.
 
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Discussion Starter · #3 ·
Sounds like the bolt didn't lock into battery properly.

An all too common malfunction with the AR15 rifles.


Is this the first time you ever blew through 200rds of ammo at the same time?
This wouldn't happen to be a match grade AR? I have a Bushmaster XM15E2 that does the exact same thing. I'm getting a different upper because the rifle is not combat worthy.
 
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Discussion Starter · #4 ·
how old is your recoil spring?
have you checked the firing pin and made sure it is still in one piece?
Is your FPRP intact?
have you cleaned the bolt face, lugs and chamber recently?
have you switched to a "match" trigger that may have a lighter hammer and hammer spring?
Have you modified the hammer spring recently (as in the 15 minute AR trigger job)?
Changed to a heavier buffer recently?
Is your gas tube centered properly?
is your gas key properly tightened and staked to the bolt carrier?
are there any burrs on the end of the gas tube or gas key that would indicate misalignment?
hard primers on the ammo? although even hard primers will have an indent from the FP

btw, if you need further explainations on how any of these factors can effect function, LMK.
 
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Discussion Starter · #6 ·
Jamie Young said:
An all too common malfunction with the AR15 rifles.


Is this the first time you ever blew through 200rds of ammo at the same time?
Oh no...I've shot it quite a bit...but I can't even guess how many rounds. I believe the last time I shot it, I went through 500 rounds with no problems.

Jamie Young said:
This wouldn't happen to be a match grade AR? I have a Bushmaster XM15E2 that does the exact same thing. I'm getting a different upper because the rifle is not combat worthy.
No match grade. It's an M4gery with a Del-Ton upper, no high-end match grade barrel, trigger, etc.
 
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Discussion Starter · #7 ·
ARin said:
how old is your recoil spring?
Probably 3 yrs...bought it new when I built the rifle.

ARin said:
have you checked the firing pin and made sure it is still in one piece?
I wondered that myself. I'll check when I get home.

ARin said:
Is your FPRP intact?
sorry, I don't recognize the abbreviation.

ARin said:
have you cleaned the bolt face, lugs and chamber recently?
yeah, actually gave it quite a good cleaning after the last use.

ARin said:
have you switched to a "match" trigger that may have a lighter hammer and hammer spring?
it's not match grade...but I plan on inspecting it tonight. The ammo was very dirty!!!

ARin said:
Have you modified the hammer spring recently (as in the 15 minute AR trigger job)?
Nope.
ARin said:
Changed to a heavier buffer recently?
nope
ARin said:
Is your gas tube centered properly? is your gas key properly tightened and staked to the bolt carrier?
should be centered & okay...I haven't played with the barrel nut and I don't have a vertical grip or anything on the handguards.


ARin said:
are there any burrs on the end of the gas tube or gas key that would indicate misalignment?
another thing to check for.

ARin said:
hard primers on the ammo? although even hard primers will have an indent from the FP
that was my first thought...but with no real distinguishable mark on the primer, it just seems like the firing pin never had a full distance to travel before the strike. I did check a lot of brass, since I picked it all up for reloads. And in every spent case, the primers showed a solid good strike.
 
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Discussion Starter · #8 ·
tear down inspection didn't reveal much. Firing pin was intact. Lower trigger assembly didn't look too dirty. No signs of trouble around the gas tube. Buffer spring & pin looked fine.

The only real noticable thing...the bolt assembly was extremely dirty! I've shot many more rounds in one sitting and the assembly after this light use was more dirty.

With that said, one thing was obviously not good. It appears I may have been over zealous in my use of CLP in this assembly! The firing pin has a slick, mucky coating of residue and yes...CLP :( Normally I don't do that and I know better. But I actually cleaned it twice since shooting it last - once immediately following the range and I did a real quick, half-assed job. So I went back a second time and re-cleaned the whole rifle again.

I wonder whether or not that was the root cause...too much lubricant caused it to get way too dirty and subsequently gummed up the works a few times. Possible? Probable?
 
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Discussion Starter · #10 ·
a correct oiling of AR parts requires the parts to have a "BARELY VISIBLE" coating of oil.

too much collects crud and carbon. try a thin spray on oil such as REmoil, ive had good luck with that. sprays on thin, and evenly distributes itself..and dries to a protective film.

oh, and FPRP is Firing Pin retaining pin.

Oh, and as an afterthought, make sure you check that particular mag.....possibly a feed lip issue, dragging on the bolt carrier and preventing a full battery lockup.
 
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Discussion Starter · #11 ·
ARin said:
a correct oiling of AR parts requires the parts to have a "BARELY VISIBLE" coating of oil.

too much collects crud and carbon. try a thin spray on oil such as REmoil, ive had good luck with that. sprays on thin, and evenly distributes itself..and dries to a protective film.

oh, and FPRP is Firing Pin retaining pin.
Thank you! The FPRP looks fine. Sounds like it's back to cleaning 101 for me :( Hopefully that's it. I guess on the bright side...maybe my screw up will help prevent others from doing the same. Something good must come of it, right?
 
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Discussion Starter · #13 ·
einheit 13 said:
.....uh, nevermind.....;):p
alright smart @$$ - your "damn, you suck!" comment has been acknowledged:D Although, perhaps your comment is "buy an AK, because ARs suck", I bet that was it instead.
 
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Discussion Starter · #14 ·
one more quick Q, what brand of AR and what kind of chamber? is it a 556 nato chamber? 223 wylde? a 223 match chamber?
 
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Discussion Starter · #16 ·
ARin said:
one more quick Q, what brand of AR and what kind of chamber? is it a 556 nato chamber? 223 wylde? a 223 match chamber?
It's a Del-Ton upper assembly that is the mid-length chrome lined, flat top version - chambered for 5.56 NATO.
 
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Discussion Starter · #17 ·
ARin said:
i imagine he was gonna make an AK vs AR comment;)
Yep, I edited my reply once I saw who it was :D einheit's a good guy...and I've seen his opinion on ARs in the past.
 
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Discussion Starter · #18 ·
jdavionic said:
Yep, I edited my reply once I saw who it was :D einheit's a good guy...and I've seen his opinion on ARs in the past.
Nahh, not gonna start nothin, honest! Just remember, gas goes in the action full of nasties, and 'wet' lubes catch them after a while. Believe it or not, I use Slick 50 on my 180 and 180b, just a skim coat so it traps no nasties. On my AKs I use a 'dry' silicon lube on the carrier guides, firing pin and receiver rails.
 
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Discussion Starter · #19 ·
I use Remmington Dry Lube on my AK also.

Strange to see that happen on the last 3 rounds in that mag. It's probably just dirty. If it happens next time look at the bolt and see if it's all the way forward and engaged. Smack the forward assist a few times and see if the bolt moves if it does you need to clean it. If not it's probably something else.

Back in the good old days while in the Army when we had plenty of ammo to shoot at the range this would occur. Just lock the bolt back and spray a bunch of breakfree in the action and keep banging. The vapor burn off from the breakfree would sting and water your eyes but you were good for another 2,000 rnds at least. Those old M16's saw a lot of FA and cherry red barrels.
 
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Discussion Starter · #20 ·
Broadside said:
I use Remmington Dry Lube on my AK also.

Strange to see that happen on the last 3 rounds in that mag. It's probably just dirty. If it happens next time look at the bolt and see if it's all the way forward and engaged. Smack the forward assist a few times and see if the bolt moves if it does you need to clean it. If not it's probably something else.

Back in the good old days while in the Army when we had plenty of ammo to shoot at the range this would occur. Just lock the bolt back and spray a bunch of breakfree in the action and keep banging. The vapor burn off from the breakfree would sting and water your eyes but you were good for another 2,000 rnds at least. Those old M16's saw a lot of FA and cherry red barrels.
Thanks. I don't have a free float...so I can imagine how hot those handguards get after 2000 rounds.
 
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