The mainspring has plenty enough juice behind it to reach the firing pin, but either the firing pin is too short, or the firing pin stop is too thick. Without the gun in front of me, I cant' depth mike the distance between the back of the pin and the stop, but I can tell just by looking at it that there's not nearly as much protrusion as is found on just about every 1911 I've worked on. After poking around on Brownells for a bit, I haven't found any firing pin that's listed as being 'longer' than others. Any ideas?
Gunk build-up in the channel. Series 80 or Swartz system malfunction. Broken firing pin spring. Burr in the breech end of the firing pin port. Bent firing pin. Major headspace problem... unlikely, but?
Pictures of the rear of the firing pin and its relationship with the stop?
One picture shows a snap cap with masking tap on the back to show firing pin fall. It did dent the tape, which is .0035", but didn't go all the way through.
I'm wondering if I could just chuck up the firing pin and push the shoulder that sits up against the retaining plate back a few thou.
The first picture shows me pushing the firing pin flush with the back of the retaining plate. Obviously the pin travels further than that. The anvil on my depth mic is too wide to fit in the firing pin hole, so I'm not sure how far it is traveling.
Let me see. The M1911 firing pin is the inertial type, meaning that it is meant to be shorter than the firing pin tunnel. But the normal firing pin protrusion is 1/4" or more; the only thing that stop the firing pin is the primer or (if the chamber is empty) the spring going solid. (And that is true of the Series 80 as well.)
Why not compare the firing pin with a known good one?
The stop has a nominal thickness of 0.136 (-0.005) and th ehead of the firing pin to the collar is 0.165 (-0.004).
The nominal protrusion is thus only 0.029
The 1911 firing pin is shorter than the length of the firing pin tunnel in the slide so that even with the hammer down on the firing pin it does NOT protrude from the breech face.
Only when the pin is struck and driven forward does it briefly protrude from the breech face to hit the primer.
Try another firing pin. They're cheap enough.
Maybe I wasn't clear. When the firing pin of an M1911 is struck by the hammer, its front does not protrude only .029". It jumps forward, and if the chamber is empty will keep going until the firing pin spring goes solid, usually in about 1/4". If the chamber is loaded, the firing pin will be stopped in the primer.
Under some circumstances, when a cartridge is fired, the firing pin can move forward far enough that the back end is past the firing pin stop, allowing the stop to move down when the gun moves up in recoil. That does happen, rarely, and the gun hangs up.
With all guns, but with the 1911 in particular, you can't go by the nice neat book drawings of how the artist thinks things work, or how the gun appears to work when the action is operated slowly by hand.
Pin protrusion from the stop plate to the back of the pin is .022", but the stop thickness is only .1215". I hesitate to surface grind any more off the back, as it's already a bit looser than I'd like in the slide.
If anyone could mic the OAL of their firing pins for comparison, I'd appreciate it. Mine's at 2.391".
I was going to look in the books but to remove any doubt, I miked two firing pins, one a 1943 Colt and one a Norinco. The Colt ran 2.293, the Norinco 2.292. The part at the back that goes through the firing piin stop is .160, both pins. BTW, both guns are utterly reliable; 8500 logged rounds through the Norinco with no failures, no one knows how many through the Colt.
Let's start over. What brand of gun is involved? Does it have a firing pin block (Series 80 or other type)? If you don't know or won't tell us, I give up.
It's a STI frame with an unmarked slide, Series 70. I can mic the dimensions of the firing pin channel if that helps.
Had a burr/edge in a firing pin channel on a High Standard 22 lr pistol that kept the pin from hitting full force 100% of the time. Fired ok when up side down. Returned to factory, came back same way. Sold it.
Try an extended firing pin. Limcat, Millenium and dawson make them.
Are you in a position to compare your "unmarked slide" with one by Colt or another recognized maker? Some of those unmarked slides I have seen have been rejects or just cast junk. Either way, I wouldn't trust any dimensions.
With this parts gun, is it possible for the hammer to strike the FPS at an angle big enough to not allow the hammer to transfer fully its momentum (or force) to the firing pin? You can check that with a dab of modeling clay over the FPS and dropping the hammer.
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Pin protrusion from the stop plate to the back of the pin is .022", but the
stop thickness is only .1215". I hesitate to surface grind any more off the
back, as it's already a bit looser than I'd like in the slide.
The firing pin stop may be the problem if it is resting on the firing pin and causing some drag. Try this, with the pistol empty and held vertically, put a pencil, eraser end first, into the bore. Drop the hammer, the pencil should be easily ejected. Try this with the gun in it's normal firing position. The pencil should be ejected across the room.
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The pencil should be ejected across the room.
Boy howdy, did I ever get yelled at over that test.
Wifey really didn't care for No2's stuck in the ceiling. LOL