bent cotter pin

[lowdrag]

For some reason my cotter pin that holds the firing pin in place in my AR is getting bent up everytime I fire about 100 plus rnds. Whats happening?:mad:

[JE3146]

how long is your barrel?

if its an SBR you could be having problems with too much gas causing havoc on your bolt carrier and internals..

if it isn't an SBR then what type of ammo are you using and is your chamber 5.56 or .223?..

uhh..... shoot.. i'm out of anyother ideas.... lets go from there..

[thedaledoe]

How old is your AR? Those do wear out fairly quick from what ive heard. You can try getting some replacements and change it out.

[lowdrag]

it has less than 1500 rnds through it. Makes me want to get somthing else. Like the Robinson Arms M96

[XHairs]

Try a search. The subject has been brought up a couple of times, related to firing pin contact with the hammer. ( I'm at work right now and can't get into it)

[thedaledoe]

Dont let a little 1mm thick piece of metal discourage you.. maybe if you rough it up a bit and give it a stern talking to it will start to cooperate. :D

[lowdrag]

ya, I tried talking nice to it, but it didn't listen. Stupid dummy metal thing.

[thedaledoe]

Of course it didnt listen. Cuz you were nice. I said get rough with it and scare it a little.. Little bastards like that only respond to aggresive behavior. :p

[JE3146]

shoving a firing pin into its side after every shot fired isn't agressive enough dale :)???


my advice would be prolly to search for a solid construction pin that replaces the cotter pin.. they make them... usually this is a peice that has to be replaced every so often.. especially if you clean your gun a lot and take apart your bolt..

[thedaledoe]

hell no its not aggressive enough.. no such thing as "enough" agression

[Krupski]

For some reason my cotter pin that holds the firing pin in place in my AR is getting bent up everytime I fire about 100 plus rnds. Whats happening?:mad:

Do you have a "real" AR cotter pin, or just a generic hardware store cotter pin?

The firing pin retainer CANNOT be an ordinary soft steel cotter pin, it must be a "real" AR cotter pin (harder steel - heat treated).

Roger

[lowdrag]

I think you are right. I bought the complete upper from Model 1 Sales, I think they use some shoddy stuff. I did fix it though, I traded it in for a Bushmaster, no more bent pins

Steve

[Krupski]

Dont let a little 1mm thick piece of metal discourage you.. maybe if you rough it up a bit and give it a stern talking to it will start to cooperate. :D

Cotter pin fails, firing pin falls out.

Firing pin falls out, carrier key falls out.

Carrier key falls out, bolt carrier comes out the back of the rifle.

Bolt carrier flies out of the rifle, shooter ends up in the hospital.

That little pin is, indeed, important.

Roger

[thedaledoe]

I dont see how that can happen. If the cotter pin fails and the firing pin slides back the action is most likely gonna jam and thats about it. None of that can "fly out" of the rifle unless the whole thing blows up.

[Krupski]

I dont see how that can happen. If the cotter pin fails and the firing pin slides back the action is most likely gonna jam and thats about it. None of that can "fly out" of the rifle unless the whole thing blows up.

Well I know of a person who got hurt when their bolt carrier blew out the rear of the stock.

Now, whether that was due to incorrect re-assembly or a part failure I don't know.

Because of this, I always double check my bolt carrier and make sure it's put together completely and correctly twice before I put it back into the rifle.

Both my eyes work, my skull is intact and I'd like to keep it that way! :D

Roger

[Circuits]

Without that pin, the firing pin is free to fly backwards into the face of the buffer, once the hammer's out of the way. More likely in that event that the pin would deflect and jam things up, or stay in place, but fall out and down into the FCG as the buffer pushes the carrier forward again on the counter-battery stroke.

Wanna break your AR firing pin? Reassemble your carrier with the firing pin retaining pin in front of the firing pin collar instead of behind it. Want to ask me how I know? ;)

[kamikazeak47]

For some reason my cotter pin that holds the firing pin in place in my AR is getting bent up everytime I fire about 100 plus rnds. Whats happening?:mad:
Try early M16 style pin..

[Epinephrine]

I got 10,000+ rounds on the same retaining pin and its still going strong. I would also suggest buying the same brand retaining pin as the brand of your rifle because either the ones I picked up at CMMG arnt true M16 retaining pins, or Bushmaster retaining pins and retaining pin holes in the carrier are machined smaller than everyone else. :letssee:

Oh and that solid retaining pin that you guys are talking about is called a Perma Pin and is supposidly what Eugene Stoner originaly designed but the military wanted to make the gun cost less so they opted for a heat treated cotter pin instead. How a $9 matters to the government I have no idea.

[Todd Smith]

It seems like I have had better luck with this part. I am still using the original pin that came with an Olympic Arms bolt carrier assembly I purchased back in 1988. It must have at least 12-15000 rounds through it at this point. Todd.

[kbhag]

That bent firing pin-retaining pin problem has to do with the type of bolt carrier you have. With an SP-1 type carrier the hammer can snag a bit on the firing pin shroud, that's what causes the retainer pin to bend. The only fix for it is to get a completly shrouded carrier (see M-16 type) RRA makes one that is fully shrouded but the rear is not long enough to allow FA parts to work. FYI: The pin is not likely to break. I've had many thousands or rounds through my compitition uppers with that type carrier and never had the pin break, I just replace the pin every couple of years just to be safe.

[Krupski]

That bent firing pin-retaining pin problem has to do with the type of bolt carrier you have. With an SP-1 type carrier the hammer can snag a bit on the firing pin shroud, that's what causes the retainer pin to bend.

If by that you mean the "C" shaped carrier with no closed "loop" in the rear... that's what I have. I also have the stock FCG and the hammer doesn't hit the retaining pin (i.e. I don't see any shiny polished steel where contact was made).

I think a LOT of AR-15 "upgrades" are just worthless hype, designed to solve a problem that doesn't exist.

The only worthwhile upgrades for the AR that I've found (so far) are the McFarland one piece gas ring (no worrying about staggering the ring gaps) and a Falcon A2 pistol grip with a built in trap door (storage for carbines that don't have a rear buttstock trapdoor).

Oh... one more... an Aimpoint M2 red-dot sight is an awfully nice upgrade! :D

Roger

[metroplex]

+1 on the MacFarland Gas ring. It's the same price as the 3 regular rings but it will never align.

Also, +1 on the Wolff XP Extractor spring.

[kbhag]

[QUOTE=krupski]If by that you mean the "C" shaped carrier with no closed "loop" in the rear... that's what I have. I also have the stock FCG and the hammer doesn't hit the retaining pin (i.e. I don't see any shiny polished steel where contact was made).

No, not the rear of the carrier, the area around the firing pin. On a SP-1 type carrier, some of the material will be removed around the firing pin shroud. You will need to compare your carrier with an M-16 carrier to see what I'm talking about.

It's not un-common to get that slightly bent firing pin-retaining pin with an un-shrouded carrier and a FCG with a notched hammer.

M-16s don't have this problem because the hammer does not have any notch in it and the firing pin is fully shrouded (by way of the M-16 type carrier)

Ken

[mnblaster]

I upgraded to a machined stainless pin that replaces the cotter pin, I bought it from DPMS. Look out when the bolt assembly is out of the gun, the stainless pin will fall out with little effort. (happened to me at the range in the snow) The gapless gas ring is very nice.

[lowdrag]

have you ever hada problem wth loss of gas pressure due to the gaps in the old gas rings? Can the gapless gas ring be changed in the field?

[XHairs]

1) McFarland one-piece rings can be installed in the field; it's configured like a coil spring instead of individual rings.

2) Here's a pic I found of the shrouded and non-shrouded carriers.

http://www.hunt101.com/img/228760.jpg

[lowdrag]

what is the purpose of manufacturing a non shrouded carrier. Who sells the McFarland gas ring? Can I order it on line. Can I go to CMMG

[denusn79]

brownells
100-001-257 punch in mcfarland in search about 3.00$

[Circuits]

The purpose of the non-shrouded carrier is to allow the step-faced AR-15 hammer to catch the firing pin, preventing attempts at full auto conversion via slamfire by simply removing or disabling the disconnector in the trigger group.

[Krupski]

(1) have you ever hada problem wth loss of gas pressure due to the gaps in the old gas rings?
(2) Can the gapless gas ring be changed in the field?

(1) No.
(2) Yes (tiny screwdriver or similar tool required).

Concerning (1)... I've never had a failure due to the gaps lining up, but I didn't like having to WORRY about it possibly happening (as well as staggering them after cleaning the bolt). So, I put in a McFarland ring and now I HAVE no worries. It should have been done this way from day #1...

Roger

1) McFarland one-piece rings can be installed in the field; it's configured like a coil spring instead of individual rings.

2) Here's a pic I found of the shrouded and non-shrouded carriers.

http://www.hunt101.com/img/228760.jpg

My bolt carrier looks like the one on the right.

Also, the cotter pin is ON TOP of the firing pin head - the hammer can't possibly hit the pin directly. And, the cotter pin merely keeps the firing pin from falling out... I would think a TOOTHPICK could do that job.

Why DO cotter pins bend and break? :confused:

Roger

The purpose of the non-shrouded carrier is to allow the step-faced AR-15 hammer to catch the firing pin, preventing attempts at full auto conversion via slamfire by simply removing or disabling the disconnector in the trigger group.

See picture below - is this what you mean (what I marked "small shiny spot")?



http://www.gunsnet.net/album/data//500/15750hammer_wear.jpg


(original hammer drawing courtesy of http://www.biggerhammer.net)

Roger

[Circuits]

Yep, that's the notch that will catch on the firing pin collar, if the carrier is not shrouded and the hammer is riding free of the disconnector or trigger sear.