Question on stem bind


April 22, 2004, 10:55 AM
Can sombody tell me what stem bind is exactly? and what causes it?
I've read that it is given away by half moon shaped marks on the brass but thats it.

Thank ya

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April 22, 2004, 11:30 AM
I would say in a 1911-pattern pistol, it occurs in the feeding cycle where the aft end cartridge is designed to slide up the breechface under the extractor as it is stripped from the magazine. Meanwhile the forward end of the cartridge or bullet nose hits the top of the chamber and is supposed to deflect off and continue into battery. I would say at the point the bullet hits the chamber top it halts for a millisecond and causes the C- shaped ding on the cartridge case. Most times, I would guess that the round chambers anyway but it could halt right at that point.

My diagnosis is probably rough or dirty breech face that doesn't allow the cartridge to slide up, or rough grabby extractor, or nonstandard cartridge length or bullet profile (read that as reloads). HTH YMMV

April 22, 2004, 12:59 PM
Howdy andrew! Good to see ya again.

BigG nailed that one purty good. It's technically called a Three Point Jam,
and several things can cause it in addition to what The G-man said. In
a 1911, it should probably be called "Excessive Stem Bind" since even a
perfectly functioning pistol usually has SOME amount of stem bind. When
it stops the cycle, then it's a 3-point jam.

The first thing to look at is the top of the barrel throat. If there's a sharp
edge there, that may be all that's doin' it.

Too much extractor tension can mimic a stem bind, or contribute to it,
but won't be the sole cause of the condition.

Another possible cause is the barrel link itself. If the link holds the
slidestop pin too far away from the forward radius of the lower barrel lug,
the barrel pivots up toward vertical lockup on the link instead of the
lug correctly being cammed on the slidestop pin. The longer the link,
the faster the barrel rises, and the higher it will be in relation to the
slide's position. A steeper hill for the round to climb means more chance
of hangin' up before it can break over to horizontal and enter the chamber.

A SLIGHTLY shorter link may cure it, but can also bring on other problems with the linkdown timing, so don't rush out and buy a short link and stick it
in the gun without checkin' the timing. In any case, .003 inch shorter is about the limit.

Luck to ya, lad!


April 22, 2004, 03:25 PM
Thank you kind sirs.

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