Why does AR-15 which is proven to be reliable suddenly stop working?

[SC-Texas]

People should read and heed the Mike Pannone article.

This is like thge M4 Dust test that originally had the M4 failing misreably.

When done correctly the M4 performed at nearly the same level as teh SCAR and G36.

 

[Texas1911]

We had a Colt HBAR at work that has the lightweight SP1 carrier, the soft recoil spring, and was rented by any yahoo that walked in the door with virtually no cleaning maintenance. It got to the point where the gun lived with a solid cake of 2-3mm of sludge and carbon on every surface in the gun. The trigger mechanism even was caked with crap. You could watch the bolt skate back and forth it was so gummed up, BUT the gun ran flawlessly at all times with virtually no lubrication.

The AR being dirty and not working is yet another wives tale in the gun community. I've seen hundreds of thousands of rounds ran through every AR imaginable from self-builds to multi-thousand dollar cadillac builds. The most important things I've learned is the following:

1) Quality brass cased ammo. Some guns will eat the steel cased crap, but every gun will run brass cased ammo. If you are too cheap to buy quality brass cased ammo, then learn to reload ... it's the same cost or less, considerably more accurate, and fun to do.

2) Lubrication. It's a semi-auto gun ... it requires some lubrication to operate at it's peak efficiency. Synthetic motor oil simply works the best, hands down, for the ARs. Another option is grease on the rails.

3) Build quality. If you are the type of person that runs thousands of rounds through the gun, opt for quality components. What I've seen break the most in these guns is the bolt face itself. The Colts we've had generally last much longer than the Bushmasters, perhaps due to different materials used or the usage of HPT / MPI methods by Colt.

4) Magazines. Absolutely paramount to ANY semi-auto firearm's operation. I highly, highly, highly recommend the P-Mag, it is simply the most cost effective and most important upgrade you can make to any AR15.

 

[M. Sage]

The Big M4 Myth: “Fouling caused by the direct impingement gas system makes the M4/M4A1 Carbine unreliable.”

Cleaning Your AR-15 is Pretty Much a Waste of Time | Vuurwapen Blog

A piston AR will have just as much if not more problems due to additional moving parts. A properly staked gas key, like a properly staked castle nut, will hold till the next maintenance schedule and beyond.

Still a good thing to add, checking gas key to the AR's PMCS.

The conversion guns are actually harder on components because of carrier tilt. The AR set up as designed pushes off from the bolt, it shoves the carrier straight back. A "piston" (hate that term because the AR as designed is a piston rifle) gun pushes at the top of the carrier, and pushes hard. There aren't any rails in an AR like in something like the AK where the carrier rides on flat rails because it doesn't need them.

I'll keep my piston inside my bolt carrier, thanks. Smoother shooting, better accuracy potential and easy maintenance are worth the price of admission.

 

[SC-Texas]

I really dig the piston guns for barrels 10.5" and under

Over that and it's di.

 

[Sid]

An option to mitigate carrier tilt in piston ARs is this:
Firearm Ready Solutions

I love simple and ingenious solutions, especially if its by one of the little guys, so, since I was going to get a flat wire buffer spring anyways, I went ahead and bought one of these for my DI AR.

Tight bolt lock, no BCG bounce, smooth cycling and I don't hear the "sproiiiiing" on every shot. Ok, maybe the smooth cycling is just all in my head.

 

[M. Sage]

An option to mitigate carrier tilt in piston ARs is this:
Firearm Ready Solutions

I love simple and ingenious solutions, especially if its by one of the little guys, so, since I was going to get a flat wire buffer spring anyways, I went ahead and bought one of these for my DI AR.

Tight bolt lock, no BCG bounce, smooth cycling and I don't hear the "sproiiiiing" on every shot. Ok, maybe the smooth cycling is just all in my head.

I have to admit, I don't know what that is...

"Sproing!" doesn't bug me. I can hear when I reach the bottom of the magazine. "Sproing sproing sproing thunk", reload time!

I put an H3 buffer in my M4. Smooth? Yeah. Releasing the bolt doesn't give you a really quick slam forward. It still hits hard, but you can actually watch it close.

 

[OLDVET]

Just got to this thread.
I was shooting a several weeks ago and a young fellow a couple of bays down had the same problem as you originally described. He had a "parts gun". The upper was by Bushmaster. The lower was some off brand I had never heard of. The bolt assembly was also from Bushmaster. The stakes on the bolt carrier had loosened just as yours did. I let him use the bolt carrier out of my Rock River and his operated fine.
I notice in your picture that your bolt carrier has a lot of oil on it. The direct impingement ARs require only a thin film of oil. The young fellow I helped had also loaded his bolt carrier up with a lot of oil. Maybe this excess of oil is causing the staked bolts to loosen. Just a thought.