question for M-4 folks

[frezrbrn]

looking for info on more durable cam pins. does anybody make them from titanium?

[mxwelch]

looking for info on more durable cam pins. does anybody make them from titanium?

You don't need titanium pins. These are not really any stronger than good quality steel anyway, just lighter. A pin in an AR reciever doesn't face that much stress anyway. The majority of problems result from the aluminum reciever egging causing the pin to loosen. A good quality receiver is made from 7075-T6 aluminum with an anodized finish. Even though it's a high quality aluminum with a harness coating it's still weaker than the weakest of steels.

I've seen a couple of AR owners who had their receiver pin hole bored out and a bushing installed when this problem arose which isn't that often from what I've seen.

Nevertheless, if you must have them and can't find a dealer that sells them let me know and I'll quote it for you. I can tell you now it won't be cost effective.

[frezrbrn]

maybe i'm just a nervous nellie, but my bushmaster m4a3 seems to cause a lot of wear on the cam pin. there is a specific galling pattern where the pin rotates in the carrier, also, i've heard that cam pin failure is pretty catastrophic and often requires replacement of the bolt carrier. have you had anything like this?

[frezrbrn]

"I've seen a couple of AR owners who had their receiver pin hole bored out and a bushing installed when this problem arose which isn't that often from what I've seen."

? never heard of it, is there someplace i can see pictures?

p.s. thanks for the info

[mxwelch]

maybe i'm just a nervous nellie, but my bushmaster m4a3 seems to cause a lot of wear on the cam pin. there is a specific galling pattern where the pin rotates in the carrier, also, i've heard that cam pin failure is pretty catastrophic and often requires replacement of the bolt carrier. have you had anything like this?

Sorry, got my wires crossed. Somehow I saw only "pin" and missed the cam part. (I've got to stay off of here when I'm tired.)


Are you sure it's galling or is it just the finish worn off? Is it rough to the touch or just no longer black?

If it is galling:

Sometimes when galling occurs it's due to an incorrect heat treat. Two mating parts are an identical hardness and neither part will "break in" like they should. Springfield had problems like this years ago with slides on some of their 1911s. The fix was to heat treat one component harder than the other. Presto, no galling.

I really doubt this is the cause of your problems however. I'd be willing to bet that you have too much oil on the bolt and pin and it's trapped an excessive amount of carbon residue between the two surfaces. You must put ALOT of rounds thru it for this to occur however. Carbon is very abrasive but it would still take many rounds.

It could also be due to an pin that's oversize in the carrier. Can you feel resistance when manually charging the bolt? Do you find yourself using the forward assist often even when you've jacked a round in the chamber? Bushmaster has good quality control so I doubt this would be a problem.

These things are extremely hard (about 55 Rockwell) and can be polished if galled. Can you post some good pics of it? That would help me to see what's going on.

[frezrbrn]

definate delineation, agroove all the way around the pin you could catch your fingernail on, starts after 100 or 200 rounds. have been replacing every 1500 rounds to prevent "DOH".

might be too much oil...usually i'm not an overoiler, but will reduce to see

probably not oversized. is a standard m4a3patrolcarbine, get new cams from bushmaster pretty regular

no unusual resistance, almost never need foward assist with it, don't have digital cam, but will see if i can find similar photo on web

thanx

[mxwelch]

definate delineation, agroove all the way around the pin you could catch your fingernail on, starts after 100 or 200 rounds. have been replacing every 1500 rounds to prevent "DOH".

might be too much oil...usually i'm not an overoiler, but will reduce to see

probably not oversized. is a standard m4a3patrolcarbine, get new cams from bushmaster pretty regular

no unusual resistance, almost never need foward assist with it, don't have digital cam, but will see if i can find similar photo on web

thanx

If you're getting a groove then it's not abrasives causing the problem. Something's out of spec with the bolt. I'm guessing the groove is exactly even with the body of the bolt. Does the pin have any lateral movement when assembled? Sounds like it's cocking to one side while in rotation giving you a sharp contact point on the pin against the body of the bolt. Just a guess. 100 -200 rounds should be nothing as far as wear goes. I'd have Bushmaster swap you bolts. The headspacing shouldn't be an issue with a new bolt on an M4. Even more so if it's chambered for 5.56mm instead of .223. I bet the problem would disappear.

[Johninaustin]

Sounds like an out of spec bolt/carrier. There should not be ANY wear other than cosmetic. My M4 has over 10K rounds thru it and there is no wear on the cam pin.

[frezrbrn]

thats just plain spooky welch....its like you can see it from there. will definately try switching out carrier! thx

[mxwelch]

thats just plain spooky welch....its like you can see it from there. will definately try switching out carrier! thx

Even a blind squirrel finds a nut now and then.:D

[frezrbrn]

sometimes two:D, hey have you got a chance to shoot the DPMS Panther yet?

[mxwelch]

sometimes two:D, hey have you got a chance to shoot the DPMS Panther yet?

Yep, very nice weapon. I'm in the process of building a match AR. DPMS lower, White Oak match upper complete with Kreiger 1-7" twist, Wylde chamber, free float tube, .047 sights, etc...

Hopefully I'll shoot my first serious match with it at Camp Perry this year if funds are available.

[frezrbrn]

you lost me somewhere in the modifications. i'm not a smith. i got one on layaway (400.00 left to go), so by the time i pay it off i'll have to wait a month to buy ammo!!!lol...can't wait to shoot it