Author Topic: AR15 Parts Failure/Breakage  (Read 3468 times)

les snyder

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Re: AR15 Parts Failure/Breakage
« Reply #10 on: November 01, 2020, 04:49:14 PM »
Rastus... don't know if you've ever changed out a set of gas rings on an AR bolt, but even brand new rings are not the same thickness between inner and outer circumferences... they look worn out, even when brand new...I would suggest a buna n O ring.... a 1/8" neoprene O ring will work if you don't have extreme cold... just slip it over the existing extractor spring

tombogan03884

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Re: AR15 Parts Failure/Breakage
« Reply #11 on: November 01, 2020, 06:30:29 PM »
The gas plug also backs out. That isn't so bad, the plug needs to be adjustable, a little extra safety never hurt.
Splitting receiver's cracking welds, and peened bolt heads are not acceptable.

bulldog75

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Re: AR15 Parts Failure/Breakage
« Reply #12 on: November 01, 2020, 08:10:10 PM »
tombogan03884. The m60 was what happened when a mg42 had a affair in a dark alley with American Machine guns.
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Rastus

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Re: AR15 Parts Failure/Breakage
« Reply #13 on: November 01, 2020, 08:26:33 PM »
I actually haven't changed out o-rings in any of my AR's.  5 to 6k rounds through 2 of them with no problems.  It sounds like time to replace O-rings though. 

I have actually changed out thousands of o-rings back in my pneumatic/hydraulic instrumentation days.  I'm very well acquainted with buna nitrile o-rings.  Are their any viton o-rings out there for AR's?  Viton handles a wider range of solvents and is good practically forever at 400 F....buna about 250 F.  Viton also wears better 

Two issues with viton...it swells in the presence of alcohol and hardens around 10 F.  I won't see either of those for my applications. 
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les snyder

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Re: AR15 Parts Failure/Breakage
« Reply #14 on: November 02, 2020, 08:13:37 AM »
Rastus... I think that Mike said that viton was what was currently used, I had a senior moment.,sorry

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Re: AR15 Parts Failure/Breakage
« Reply #15 on: Today at 02:07:31 PM »

tombogan03884

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Re: AR15 Parts Failure/Breakage
« Reply #15 on: November 02, 2020, 08:21:07 AM »
The fact that the AR uses gas rings proves it is not, and never was "direct impingement".
The bolt head acts as the piston.


alfsauve

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Re: AR15 Parts Failure/Breakage
« Reply #16 on: November 02, 2020, 09:31:41 AM »
The fact that the AR uses gas rings proves it is not, and never was "direct impingement".
The bolt head acts as the piston.

Others have said the same thing.  It's a variation.  I would say the BCG acts like a piston.
Will work for ammo
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tombogan03884

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Re: AR15 Parts Failure/Breakage
« Reply #17 on: November 03, 2020, 09:30:31 AM »
Yes, the bolt head acts as the piston driven by the gas chamber behind it.
That's why the gas tube continues through the bolt carrier.

Big Frank

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Re: AR15 Parts Failure/Breakage
« Reply #18 on: November 06, 2020, 09:09:11 AM »
The bolt carrier acts as a gas cylinder and the bolt acts as the piston. The piston stays there at first when the cylinder starts to move. It the opposite of most piston and cylinder arrangements. The only parts I recall actually wearing out on my AR15s are the gas rings, plus a couple of springs getting weak over the years. Always replace all 3 gas rings at the same time. I've heard that it doesn't actually matter if you stagger the rings or not but I still do (I can't for the upper with the McFarland one piece gas ring of course). When you put the bolt in the carrier it squeezes the end gap on the rings together, but even if it does close the gap I still like to stagger them about 120 degrees apart. When the rings wear and the gaps open up it will still work for a long time. I practically wore one end of one ring away before I changed them and it still worked.

And I've had a firing pin retaining pin or two break. The collar on the firing pin pounds on them until they're curved like a banana and eventually they break if you don't replace them first. I put the original type solid firing pin retaining pin in 2 of my uppers instead of another cotter pin type. They're a whole lot stronger. Mine ended up breaking near the end and the gun still functioned with the end of the pin floating around in there somewhere but I don't know how much longer it would have worked. I think it actually broke off a bit lower than where I drew the arrow. They can also break in half like in the picture I found and put your gun out of action. The solid pins when they do break will usually break one side off the tip where it's split, and you can still use the broken pin indefinitely if the other side doesn't break off too. When the new cotter pin type breaks you need to replace them ASAP and be prepared to replace them again when they break again.

ETA: I forgot the pics.  :-[  I have the stainless steel pins. I think the originals were Parkerized but never saw anyone selling them before.
""It may be laid down as a primary position, and the basis of our system, that every Citizen who enjoys the protection of a free Government, owes not only a proportion of his property, but even his personal services to the defence of it, and consequently that the Citizens of America (with a few legal and official exceptions) from 18 to 50 Years of Age should be borne on the Militia Rolls, provided with uniform Arms, and so far accustomed to the use of them, that the Total strength of the Country might be called forth at a Short Notice on any very interesting Emergency." - George Washington. Letter to Alexander Hamilton, Friday, May 02, 1783

THE RIGHT TO BUY WEAPONS IS THE RIGHT TO BE FREE - A. E. van Vogt, The Weapon Shops of Isher

Big Frank

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Re: AR15 Parts Failure/Breakage
« Reply #19 on: November 08, 2020, 03:10:30 PM »
I already had a pic of the old and new style firing pin retainers side by side on my computer and simulated what they look like when the end breaks off. When my new style broke off it broke off a little bit higher than where the old style breaks, the whole pin was bent, the end that was left bent even farther, and it was weaker than an old-style retaining pin with a broken end. The new kind are flimsier but cheap to make. They're easier to pull out too. You have to push the old style out to get them started, but I still like them better. If you carry a spare firing pin, no problem. My drill sergeants always had a firing pin stuck in their pistol belt when we went to the range. They're a lot better than a bullet tip to make sight adjustments, plus you can push out pins with them, etc.

We didn't have much actual parts breakage on the M16A1s I worked on that wasn't caused by abuse. One of the things that happened multiple times was some grunt left his rifle laying in the open ramp of an M113 APC, the driver hopped in and closed the ramp, and they ended up with a barrel that was shaped kind of like ~. Straight line, 120 degree bend, an inch or two farther, another 120 degree bend back the other way.  If they were lucky, someone stopped the driver before he drove close to some trees. They weren't always lucky. Your parents may have told you not to stick your arm out of the car window or it will get torn off. Well, someone should have told those grunts not to stick your rifle out a 113 ramp. Then there was the time I heard the jingling of crap in a sack before a guy got to the shop door with a mysterious garbage bag. I already knew it wasn't the sound of sleigh-bells and jolly old Saint Nick with a bag full of goodies. Oh no. Crap in a sack was always a lot of paperwork. An M16 was run over by a company, or squadron or whatever it was of tanks, one right after another. I don't know whether the rest of the tracked and wheeled vehicles in the unit also ran it over, but at that point it didn't matter. What they found left of it pounded into the dust was FUBAR.

Once in awhile I had to replace a bolt carrier key. I don't know if people were dropping the bolt carriers on the floor or what, but the end of the keys were getting bent and sometimes a little piece broke off or it was bent so bad it cracked. Handy tip: if the hole in the key is whomped out of shape but everything is still intact, just put a punch in the hole and give it a couple of taps with a hammer. Most drift punches are way too long to get up to the shoulder but a short enough one is the perfect tool. Taper punches usually don't taper enough, but most of the time a center punch will do the trick. The original bolt carriers always had the keys staked in 3 places around the circumference of the screw heads. When we replaced them we didn't do anything like that. We used a cold chisel which wasn't the sharpest tool in the box, and staked it on an angle on the left and right sides of the screw heads. It looks like that's where everyone is staking them from the factory now. I've never had one come loose or heard of anyone else staking them that way having them come loose, and we made sure not to raise enough metal on top to rub in the upper. But if you don't want to use a dull chisel, "The MOACKS II is available only as a complete unit; $180 plus $10 shipping via Priority Mail." http://www.m-guns.com/tool_new.php?product=moacks
I can sell dull chisels all day long for a fraction of the cost if anyone is interested. ;)

Okay, I just dug out my M16A2 TM to see what it said about staking the key. They came out of the factory looking like the "field replacement staking", and when we replaced them in the field, they ended up looking like the revised staking where the factories are staking them. ??? The revised staking is just to the right of the "original staking" that I've never seen on an original. Lo and behold, on the facing page they're using a "key tool" to straighten out the opening on a key. It looks like a drift punch to me but it's one of the 7 tools in Appendix E that it tells you to make for yourself. I can post them all in another thread if anyone wants me to.

ETA: They never explain how to make your own tools when you aren't equipped with the tools to make them. I was never issued a lathe or mill or anything other than one tool box and what was in it. And some of that was just paper tags for each missing tool that was on order, but I was glad to have it. For the first 2 years I didn't even have a tool box. Between the 5 of us in my shop at Ft. Polk, 3 who actually worked, we had a bench grinder, about a 3' long screwdriver that would reach inside the length of the shock absorbers on 4.2" mortars that we constantly had to work on >:(, and the head of a sledgehammer that someone gave us. We never did get a handle for it. We had to borrow everything else off the tank turret repairmen, artillery repairman, wheeled vehicle repairmen...
""It may be laid down as a primary position, and the basis of our system, that every Citizen who enjoys the protection of a free Government, owes not only a proportion of his property, but even his personal services to the defence of it, and consequently that the Citizens of America (with a few legal and official exceptions) from 18 to 50 Years of Age should be borne on the Militia Rolls, provided with uniform Arms, and so far accustomed to the use of them, that the Total strength of the Country might be called forth at a Short Notice on any very interesting Emergency." - George Washington. Letter to Alexander Hamilton, Friday, May 02, 1783

THE RIGHT TO BUY WEAPONS IS THE RIGHT TO BE FREE - A. E. van Vogt, The Weapon Shops of Isher

 

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