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Member Section => Building America's Rifle => Topic started by: Rastus on October 31, 2020, 11:06:10 AM

Title: AR15 Parts Failure/Breakage
Post by: Rastus on October 31, 2020, 11:06:10 AM
Other than a broken lower (Mag Tactical...) I have never had a part fail on any of my AR's.  So, I was wondering....what have you guys had fail on one?  My lower was I think engineering on their part to get the lowest possible weight with an alloy that just did not hold up. 

Which brings up firing pins...ever have one fail?  How often do they fail?

What else?
Title: Re: AR15 Parts Failure/Breakage
Post by: bulldog75 on October 31, 2020, 12:25:23 PM
Parts fail. One when I first got to my unit and they had old A1s. The rear retaining pin would come out all the time. Brought that up to an armorer and it was fixed pronto.
Now malfunctions I have had a lot. Even the dreaded over bolt. Use to be a PMI instructor. I would give a class before I ran the range for my battalion. I would explain to new troops that they needed to fix their own malfunctions. No one is coming to fix your weapon during a real firefight. Never had a firing pin fail. I did see a troop put his weapon in the wrong place and a turret rotated and well that weapon could shoot around corners.
Title: Re: AR15 Parts Failure/Breakage
Post by: les snyder on October 31, 2020, 08:17:04 PM
my early AR was a Colt and the firing pin was not shrouded by the carrier, so the rim got beat up, now I use M16 carriers...

my good friend developed the SOCOM bolt upgrade, with high temp O ring to help the extractor, high temp ejector spring, and McFarland style continuous gas ring... I added the kit to my AR before my first big time 3 gun match in 1995 (North Carolina Tactical at Ft Bragg) at the end the the next year, I dis assembled the bolt, and found that the extractor spring had vanished, but was still operational with the O ring... the continuous ring was replaced with standard 3 ring set as I was shooting cheap Russian ammo for local matches, and it carboned the ring to the point of failure

a friend has a Class 3 M16, and doing a mag dump with a 7.5" barrel melted the gas tube (not sure of its pedigree), but I replaced it and roll pinned the gas block for him

not had a problem with 5.56 firing pins, but had a 9mm spring break at about 400 rounds... I rounded the strike end (as is the 5.56 pin) of an OEM Colt pin, so that the hammer strikes it closer to the center line and has over 7000 rounds in a couple of PCCs without a problem

minor gas cutting on the bolt face from leaking primers, but overall never really had a problem with a 5.56 ... the 9mm guns, on the other hand, have a different learning curve

one match embarrassment... assembled the bolt with the firing pin flange behind the cotter pin....

Les
Title: Re: AR15 Parts Failure/Breakage
Post by: tombogan03884 on October 31, 2020, 09:51:28 PM
Bulldog75
Ammo truck driver didn't need no stinking ground guide.
The only part they could salvage off the M 60 he didn't see was the trigger guard .
Got me a brand new Maremont .    The only M-60 I ever saw that wasn't a total piece of crap.
Title: Re: AR15 Parts Failure/Breakage
Post by: alfsauve on November 01, 2020, 07:42:31 AM
I had a bolt that was slightly out of tolerance around the gas rings.  The rings would jump out of the groove and jam inside the carrier.  When it happened on the second set of rings is when I figured it out.  Such a minor amount to be out of tolerance. 

But these failures, assuming they happen in practice not combat, help make you a better armorer.
Title: Re: AR15 Parts Failure/Breakage
Post by: les snyder on November 01, 2020, 08:20:18 AM
Alf... yeah... I'll never install a firing pin incorrectly again
Title: Re: AR15 Parts Failure/Breakage
Post by: bulldog75 on November 01, 2020, 09:40:00 AM
tombogan03884 was a pig gunner also. They broke all the time. Finally the we got m240s. I had one of the few that worked correctly. For awhile. A gunner and I fired our first round on qualification and I sat the pile of crap down and the range safety started screaming at us. I started grabbing for my hearing protection and the range safety started laughing and walked away. That was the qualification that they fired 155s over head. I thought a M60 was impressive. Nope 155s are impressive.
Title: Re: AR15 Parts Failure/Breakage
Post by: tombogan03884 on November 01, 2020, 10:36:55 AM
When I was in the Guard they fired a night mission 50 yards from me and I slept through it   ;D
The guys that got NEW M60's liked them OK, but it is an inherently bad design that beats itself to death.
Having safety wire on the gas plug is something some guns have just for luck.
A trigger group that can fall off during odd moments, including while firing is not.
The only part on that POS not prone to breakage is the Trunnion.
It's like they took the best ideas of WWII machine guns and worked to f#ck them up as much as possible.
OOOW, Quick change barrel ? Yeah, yeah, yeah, but lets hang an extra 15 pounds of bipod on every barrel so the gunner still has to work his ass off.
Between that and 7.62X51 I don't really blame McNamara for canning those jack asses.
Title: Re: AR15 Parts Failure/Breakage
Post by: Rastus on November 01, 2020, 11:52:12 AM
Thanks for the feedback guys.

gas rings and springs...
Title: Re: AR15 Parts Failure/Breakage
Post by: bulldog75 on November 01, 2020, 03:13:42 PM
tombogan03884. The reason they put a safety wire on the gas block was because you could put it in backwards. If you did it turned the pig into a single shot.
Title: Re: AR15 Parts Failure/Breakage
Post by: les snyder 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
Title: Re: AR15 Parts Failure/Breakage
Post by: tombogan03884 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.
Title: Re: AR15 Parts Failure/Breakage
Post by: bulldog75 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.
Title: Re: AR15 Parts Failure/Breakage
Post by: Rastus 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. 
Title: Re: AR15 Parts Failure/Breakage
Post by: les snyder 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
Title: Re: AR15 Parts Failure/Breakage
Post by: tombogan03884 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.

Title: Re: AR15 Parts Failure/Breakage
Post by: alfsauve 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.
Title: Re: AR15 Parts Failure/Breakage
Post by: tombogan03884 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.
Title: Re: AR15 Parts Failure/Breakage
Post by: Big Frank 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.
Title: Re: AR15 Parts Failure/Breakage
Post by: Big Frank 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...
Title: Re: AR15 Parts Failure/Breakage
Post by: les snyder on June 18, 2021, 08:51:55 PM
kinda, sorta AR failures... my Atchisson style .22lr conversion in my SBR broke a firing pin the other day, and I replaced it with one from Bore Buddy...the Bore Buddy pin is designed well, with a radius at the front step transition, strike end cone shaped to allow hammer to strike closer to the center line, and the actual point is not a typical chisel strike, but a flat not rounded circular impact just under the rim where it does not need to indent the double thickness of brass at the rim, but hits where the priming compound it located... really smacks the case

 stuck a Volquartsen trigger, hammer, sear into the MK IV couple of weeks ago... VQ firing pin installed today... I think I'm about done with the Steel Challenge pair....
Title: Re: AR15 Parts Failure/Breakage
Post by: Rastus on June 19, 2021, 07:14:41 AM
Atchisson style?  OK.  Educate me.  I have a couple of CMMG conversion devices.  How do they differ?
Title: Re: AR15 Parts Failure/Breakage
Post by: les snyder on June 19, 2021, 09:33:03 AM
I use the term Atchisson as a generic for the drop in units that replace an AR bolt and carrier... I think it was the original producer used in the USAF .22lr conversion units...my two conversion units are CMMG B (stainless)... Ive had exceptional warranty service from CMMG... they went out of their way to replace an old Parkerized type A unit...

I'm shooting a little over 1000 rounds a month now that ammo is available, even though it is expensive, so reliability is becoming a concern...you get to throw out only one bad string per course of fire in Steel Challenge... I switched to the CMMG unit in my SBR as the modular 10/22 based unit I built didn't give the reliability with the new production rotary magazines compared to what I had with those in the mid 90's... full disclosure the receiver for that build was not a factory Ruger product

gratuitous picture from Rimfire Central site

https://www.rimfirecentral.com/forums/showthread.php?t=1222633

Title: Re: AR15 Parts Failure/Breakage
Post by: Big Frank on August 30, 2022, 05:51:53 AM
Jonathan Arthur Ciener used to make Atchisson conversion devices back in the day, up to at least a MKIII. They were just like the military versions as far as I know. If I recall correctly they also sold silencers. Here are a couple of pics of vintage Atchisson devices that still come up for sale or auction sometimes.
Title: Re: AR15 Parts Failure/Breakage
Post by: Rastus on August 31, 2022, 06:10:38 AM
Thanks Frank.  It looks a lot like the CMMG unit...or vice versa.

I never went to the Rimfire Central website link.  Les is that you with the short little Ruger?
Title: Re: AR15 Parts Failure/Breakage
Post by: les snyder on August 31, 2022, 09:48:23 PM
Rastus... I built a 10/22 Charger with a PMACA chassis for a proof of concept, but my Steel Challenge rim fire optic rifle (a couple of pictures probably on the Rimfire Central site) is my registered SBR, an AR lower with LaRue MBT trigger, and  a CMMG stainless collar conversion unit with a CMMG 9" dedicated barrel... generic hand guard with a home made flash can to get a little more muzzle away from my hand (and it doesn't clog with lead)... I use Black Dog sonic welded magazines with stainless feed lips... currently a Holosun 510cg (I really like the green circle dot combo for the reticle)... runs on CCI standard velocity

I cut a 16" CMMG barrel down to around 10", and use a longer fore end with 1913 rail for rimfire irons division... a Striplin flip up fiber optic (pricey) and carry handle rear sight with the small aperture opened up to about .153"... I'm trying to squeek into A class with the optic gun (.11 seconds out)... 
Title: Re: AR15 Parts Failure/Breakage
Post by: Rastus on September 01, 2022, 12:22:48 AM
So you like this Holosun 510 https://www.midwayusa.com/product/1019944962?pid=939932 (https://www.midwayusa.com/product/1019944962?pid=939932) over the Holosun 507 https://www.midwayusa.com/product/1022945810?pid=706100
 (https://www.midwayusa.com/product/1022945810?pid=706100)  . 

Is it the field of view you like better or ?????  I'm not up on these sights at all but methinks I should have one.

Edit:  Oops.  I got it.  One for a pistol the other rifle/carbine.
Title: Re: AR15 Parts Failure/Breakage
Post by: les snyder on September 02, 2022, 04:21:22 PM
Rastus... the 510c has a very large view area and I don't have to search for the dot as I do on smaller lens red dots...the large slanted concave lens keeps the dot centered... I have 3... two red and the newer one is a green... the solar cell adjusts for the brightness of the Fla sun, and the "shake awake" function turns the dot off after about 10min of non use, .. I use the quick detachable mount...green light is close to the center of the visible light spectrum, and I think that is why I am liking it more every time I shoot it...on the closer eye relief of the rifle, I adjust the intensity down a little and make the reticle's image slightly transparent

the 510 looks funny on the Ruger MK IV pistol, but it works for the same reason... I can pick up the dot quicker...

I use the circle+dot reticle for the rifle, but dot only for the pistol... I perceive that with the extended eye relief using the pistol with extended arms, I loose the distinction of a precise aiming point as the circle+dot tends to look like a large dot

if I want a larger dot, I turn the intensity up and the 2moa dot blooms... I get a year's use out of a 2032 cell... time to change in October... regards Les
Title: Re: AR15 Parts Failure/Breakage
Post by: les snyder on October 11, 2022, 02:43:45 PM
short comment... shot an 8 stage Steel Challenge match Sunday... most likely my last as it makes for a long day, and I've developed a weird sleep pattern.. did manage to cut 1.1s off my Outer Limits time, which gets me an A card in Rimfire Rifle Optics... think I'll shoot the Ruger MKIV in Irons for practice Friday... regards
Title: Re: AR15 Parts Failure/Breakage
Post by: alfsauve on October 11, 2022, 04:18:33 PM
My 10/22s have done well and felt no need to use an AR platform for .22lr.

Les, I shot all 8 stages SC at River Bend Sunday.  It does make a long day.