Colt commando upper starting to get froggy

I had two guns start to act weird yesterday!

My recently SBR'd AR with Colt Commando Upper had two odd malfunctions yesterday. First, I had a failure to ignite. I didn't notice if it was out of battery. I just kicked it out. It worked on the second shot. The second malfunction was an empty case stuck above the bolt, oddly, with an unfired cartridge in the chamber (the empty case was sticking out of the ejection port.

Background,

I have had this upper for a long time (about 7 years), I have shot if with thousands of round of steel, 22, brass, etc. It has gone through many phases...

https://www.m4carbine.net/showthread...ars&highlight=


I don't clean it religiously, but I do clean it every few outings. It isn't disgusting right now.



I was running it with 55 grain Hornaday Frontier. That ammo has run perfectly in every gun. I was shooting it with my Surefire Socom as usual. I will say recently I have been shooting it with Tula steel without the suppressor and it was running fine. I wonder if it is finally over gassed?

So, AR masters....What say you? Give me your best diagnostic tips and I will do what I need to do. If I have to replace the barrel and gas system I will probably just buy a whole new assembly. I really dig the way I have it setup these days..


https://live.staticflickr.com/65535/...bf116e49_o.jpgIMG_2910 by stoiclawyer, on Flickr

Check your extractor, replace the extractor spring and maybe install the little rubber gasket thingy.

If all else fail, give it to me.

Could also be the old shooting brass after shooting steel thing. Clean the chamber thoroughly, try again.

You probably need a new barrel.

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Originally Posted by The Dumb Gun Collector

I was running it with 55 grain Hornaday Frontier.

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That's what we (in the high speed tactical community) call a "CLUE)!!

Is that not good ammo in your experience?

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Originally Posted by The Dumb Gun Collector

Is that not good ammo in your experience?

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There was quite a bit of chatter in another thread about it being poor quality. The accuracy is awful, but the stuff we have shot did run ok. The bottom line is the ammo would be my first guess.

Yes, give the extractor a good cleanjng and inspection.

If the extractor spring has over 6,000 rounds on it, replacing it with a new Gold spring would be a good idea.

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Originally Posted by Sam

Check your extractor, replace the extractor spring and maybe install the little rubber gasket thingy.

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Clean, lube, another known decent brass ammo. If a no go, I'd go with a quality extractor assembly replacement.

I cleaned it up paying particular attention to the extractor and chamber.. Replaced the buffer spring (which was visibly shorter) and fired 100 rounds of federal 55. Functioned fine but noticed it was ejecting around 1 o'clock. Might be time for a h3-4 buffer?

Quote:

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Originally Posted by The Dumb Gun Collector

I cleaned it up paying particular attention to the extractor and chamber.. Replaced the buffer spring (which was visibly shorter) and fired 100 rounds of federal 55. Functioned fine but noticed it was ejecting around 1 o'clock. Might be time for a h3-4 buffer?

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Try replacing the extractor spring first. If the buffer spring was done, there's a better than fair chance that the extractor spring is too. And it would explain the forward ejection.

That will be my next step then.

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Originally Posted by The Dumb Gun Collector

it was ejecting around 1 o'clock. Might be time for a h3-4 buffer?

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A BRT gas tube is a MUCH wiser purchase... assuming the 1 o'clock is indeed too much bolt speed. Heavy buffers as a fix suck royally compared to correct gassing.

I like it. I wouldn’t mind swapping it out but I have no idea what port is on the 11.5 commando.

Clint has a sizing question series to get you rolling. Current port is irrelevant.

Yes, if a new extractor spring doesn't bring it back to proper function, and it's still ejecting to 1:00, the next step would be to address gassing.

An EZTUNE is a great fix if the gas port is eroded but the barrel is otherwise fine.

^ Can confirm. Happy with both my older gas block insert and my gas tube. Used to think adjustable gas blocks were "cool" but the shiny wore off pretty quickly with the frequent tinkering and cleaning. Set it and forget it is the way to go if it works for your application.

Thanks so much for the help brothers. I went ahead and dropped in a Daniel defense bolt I had in my doomsday bag and it changed the ejection from 12:45 to 245 to 3. It’s also much more forceful. I swapped the old bolt back in and it went right back to pissing it out at 1 o’clock. Thanks very much. ! This Gun has run great for a long time, so I’m not gonna hold it against it that a little couple of springs got tired!

Nice. Glad it was an easy fix.

Glad to see it squared away. No concern abt brass ejection direction. That old ejection path "pie chart" is garbage.

Well! It's back. Now it is clearly over gassed. I can feel the bolt being more violent. And now if I run my surefire socom it will lock back with rounds still in the mag. The issue goes away if I remove my suppressor. I just ordered an EZ tune with the dedicated suppressor option for carbine gas.

Does it feel like the bolt catch spring is weak? Also, does it do this with different mags?

Quote:

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Originally Posted by The Dumb Gun Collector

The second malfunction was an empty case stuck above the bolt, oddly, with an unfired cartridge in the chamber (the empty case was sticking out of the ejection port.

I have had this upper for a long time (about 7 years), I have shot if with thousands of round of steel, 22, brass, etc. It has gone through many phases...

... 55 grain Hornaday Frontier. That ammo has run perfectly in every gun. I was shooting it with my Surefire Socom as usual. I will say recently I have been shooting it with Tula steel without the suppressor and it was running fine. I wonder if it is finally over gassed?

So, AR masters....What say you? Give me your best diagnostic tips and I will do what I need to do.

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You need a new barrel. About thirty minutes work if you're doing it yourself.

You're addressing symptoms, not root cause.

Those EZ tunes work great at taming the old carbines with oversized ports. The guys at BRT know what they're doing.

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Originally Posted by sinister

You need a new barrel. About thirty minutes work if you're doing it yourself.

You're addressing symptoms, not root cause.

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I know you are right! I’m being a doofus

Quote:

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Originally Posted by The Dumb Gun Collector

I cleaned it up paying particular attention to the extractor and chamber.. Replaced the buffer spring (which was visibly shorter) and fired 100 rounds of federal 55. Functioned fine but noticed it was ejecting around 1 o'clock. Might be time for a h3-4 buffer?

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For your future reference, minimum length for a carbine buffer spring is 10-1/16 inches. Its an easy check when your round count is getting up there as it can be measured with a tape measure. I check them about every 6 months or so with the amount of shooting I do on personal guns. At work they get checked quarterly. As others have stated, probably time for a new barrel as it seems like you have some port errosion leading to overgassing.

Agreed.

Random lock backs point to an issue with the bolt catch assembly.

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Originally Posted by georgeib

Does it feel like the bolt catch spring is weak? Also, does it do this with different mags?

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Quote:

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Originally Posted by georgeib

Does it feel like the bolt catch spring is weak? Also, does it do this with different mags?

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It does it with mag and d&h. It only happens when suppressed at this point. If I remove my suppressor and shoot std pressure or steel the issue goes away. I will compare the bolt catch assembly tomorrow so I dont wake up the boss lady.

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Originally Posted by The Dumb Gun Collector

It does it with mag and d&h. It only happens when suppressed at this point. If I remove my suppressor and shoot std pressure or steel the issue goes away. I will compare the bolt catch assembly tomorrow so I dont wake up the boss lady.

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I can envision why a weak bolt catch spring, or possibly other worn components too, would prematurely cause the bolt to lock back when suppressed. I'm fairly sure the root of the issue is likely due to the increased bolt speed, which would be mitigated with one of Clint's gas tubes, but I still think it's quite possible that a weak spring may be contributing.

I'd be tempted to test it, in lieu of replacing the spring, by stretching the spring, and then trying it for a mag or two. Not sure if stretching the spring is a big no-no, even if you plan on replacing it in short order.

The whole bolt catch assembly needs to be looked at, not just the spring.

It's possible for the spring bore to become peened, which prevents movement of the detent and allows the catch to float without effective spring pressure.

Upon close inspection, it should be obvious whether the catch has enough spring tension.

Y’all are right! The bolt catch pin and spring are so badly peened it won’t fall out. I need to figure out how to get it out. Lol

OK, so I lightly filed the edge until the pin and spring popped out. What do you guys think I should do? just file it smooth? Swap the bolt catch? What causes that peening? My gun has a shitload of rounds and I do a lot of reload drills (lots of 7-10 round mags to maximize reloads. Just wear and tear or...?

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Originally Posted by The Dumb Gun Collector

OK, so I lightly filed the edge until the pin and spring popped out. What do you guys think I should do? just file it smooth? Swap the bolt catch? What causes that peening? My gun has a shitload of rounds and I do a lot of reload drills (lots of 7-10 round mags to maximize reloads. Just wear and tear or...?

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Do you grip the gun by the magazine well? I've seen severe peening on bolt catches caused by people inadvertantly having pressure on it while the gun is cycling. Can you post some some pictures of the bolt catch? Also, replace the bolt catch, spring and plunger. If the parts are peened then they need to be replaced.

Not typically. I have a little hands stop on the rail that keeps my hand near the tape switch. I will replace all the bits.

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Originally Posted by danieljmaunder

Do you grip the gun by the magazine well? I've seen severe peening on bolt catches caused by people inadvertantly having pressure on it while the gun is cycling. Can you post some some pictures of the bolt catch? Also, replace the bolt catch, spring and plunger. If the parts are peened then they need to be replaced.

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Well guys! Y'all fixed it. I took it out and ran 100 rounds of PMC and 16 rounds of 77gr. Did a bunch of reloads to maximize bolt catch engagement and everything ran great. Basically, the bolt catch spring pin hole was peened and no longer allowed it to put any tension on the bolt catch. Never had that issue in 25 years of AR shooting. I did order that special gas tube but I haven't installed it since everything is running well.

What did you do to fix it?

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Originally Posted by georgeib

What did you do to fix it?

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I knocked out the roll pin and removed the bolt catch. Then I took a small file and ran it along the perimeter of the pin/sping hole until the peened rim receded enough to release the pin and spring. Then I filed it back smooth. Then I replaced pin/spring and bolt catch. Works perfectly again.

Barrel replacement