Bolt failures

[bkb0000]

Amazing thread, gents.

I was browsing the usual manufacturer's websites and noticed that Patriot Ordnance has a roller-cam-pin that I have not seen before. Could this roller cam pin (coupled with a slightly tighter fit) reduce the stress placed on the cam-pin hole in the bolt?

a shame this kind of thread doesn't happen anymore.

you do realize this thread is 200 years dead and buried right?

i've heard about POF's "advanced" BCGs, but never really investigated.. i'm guessing their cam pin is basically a big bearing? if you can reduce friction between bolt and cam pin, you can reduce erosion of the cam pin/hole (play), which will reduce bolt breakage at the hole, in theory.

bolt breakage at the hole can also be reduced by consistent proper hardening.. the studies ive read about bolt breakage have shown that it takes both play AND uneven tempering to prematurely break a bolt.. but "prematurely" is the key term.

[sinister]

You can buy a chromed cam pin a whole lot cheaper than a roller-gadget. It won't gall like a cheaper, commercial cam pin.

[BufordTJustice]

Here's the link to the POF page that has a pic of the roller cam pin:

http://www.pof-usa.com/slideshow/rollercampin.html

A pic is worth a thousand words.

Sinister, would a Hard chrome cam pin and hard chrome bolt be even better? Also, would a hard chrome bolt reduce the pitting that was spoken about?

And, yes I realize that this thread was a dinosaur, Bkb....I just couldn't help myself. Fountains of knowledge here on this forum, I tell ya!

[bkb0000]

You can buy a chromed cam pin a whole lot cheaper than a roller-gadget. It won't gall like a cheaper, commercial cam pin.

have/do you use them? how long does the chrome last on a cam pin? just a couple magazines starts to furrow out a regular cam pin..

[bkb0000]

Here's the link to the POF page that has a pic of the roller cam pin:

http://www.pof-usa.com/slideshow/rollercampin.html

A pic is worth a thousand words.

Sinister, would a Hard chrome cam pin and hard chrome bolt be even better? Also, would a hard chrome bolt reduce the pitting that was spoken about?

And, yes I realize that this thread was a dinosaur, Bkb....I just couldn't help myself. Fountains of knowledge here on this forum, I tell ya!

i wasn't ripping on you, just dissing on you.

i wish they'd show a shot of just the pin itself.. it looks like the only part that "rolls" is the top, which doesn't seem like its gonna help pin/bolt erosion much or even any.. also, that big ass bearing is gonna keep it from being used in DI carriers.

[sinister]

I put one in my National Match rifle when I went from cherry to Distinguished and President's Hundred. I got tired of changing out mil and commercial cam pins as they got all galled up.

bkb00 is right on that the POF roller is on the head and not the body of the pin that cams in the slot. Old school M60 machinegunners had to constantly check the cam area on the operating rod because of the galling. This got me inspecting the pin on M16s/M4s.

[Robb Jensen]

I replace my cam pins every 2-3K rounds. Doing this I notice bolt life seems to be a little longer.

[bkb0000]

answered my own question.. i have a little-used SDMR with a Y/M chrome BCG

this cam pin has exactly 90 rounds on it




the bolt hole erosion isn't through the chrome yet, but the carrier marks are definately all the way through

[Heavy Metal]

I use the LWRC cam pins. They are indexed and are well heat-treated. Mine look great after beaucoup rounds.

[Thomas M-4]

Here's the link to the POF page that has a pic of the roller cam pin:

http://www.pof-usa.com/slideshow/rollercampin.html

A pic is worth a thousand words.

Sinister, would a Hard chrome cam pin and hard chrome bolt be even better? Also, would a hard chrome bolt reduce the pitting that was spoken about?

And, yes I realize that this thread was a dinosaur, Bkb....I just couldn't help myself. Fountains of knowledge here on this forum, I tell ya!

The POF roller cam will not work in a DI gas system gas key is in the way.