M2HB.NET

King Bee · Loader Joined: 19 Jan 2009 Posts: 15

I was getting ready to change out my firing pin and noticed that the new pin was square shanked and not round, as is my old original pin. The OAL of the new pin is 3.813" and my old pin is 3.808" Any information on this new, square firing pin would be appreciated.

Thanks

BeltFedEd · Posted: Sun Jan 10, 2010 9:16 pm Post subject:

3.813" - 3.808" = 0.005"

That is just over the thickness of a sheet of Staples copier paper (0.004") that is sitting on my desk.

I'm no expert, but I'll go out on a limb and call it normal wear.

As for the square shank firing pins, I'm guessing a newer design. I have a bunch that are flat sided. Corners are rounded, not completly square. Probably just more room to allow junk and crud to pass and not cause a malfunction.

This is just all hear-say and rumor. Wink

King Bee · Loader Joined: 19 Jan 2009 Posts: 15

Thank you BeltFedEd,

I did find the answer. According to one of our old historians, he read from a 1944 TM that the round pins could have a problem of binding and so it was recommended that the shaft be taken down to .482" to overcome defects in manufacture. Firing pins of future manufacture will include these changes.

So, presumably, the "war time" pins were round and the later pins had the flat sides to prevent binding.

King Bee