While at class all week this week: even though these are AR15-centric, students and staff will sometimes bring me something that that “needs attention”—and I’m happy to do it because I’m there anyway, on the clock so to speak. I can sweat while helping out with range duties, or stand around and sweat while doing nothing, or sweat while working on someone’s gun, hopefully making some improvements. I love doing that for the guys and gals.
This old beauty came my way. A pin gun from the ‘80’s, said to have been done up by Al Greco and/or Randy Hollowbush, two familiar names from the Second Chance days of pin shooting, and from the biz of 1911 pistolsmithing in the eastern states area. As best I know both are still involved in the firearms biz.
It’s had a lot of pinloads through it. Let’s talk power factors for a minute—standard 230 ball at 825-850 FPS, PF’s at 190/196. The USPSA power floor for making Major is still 175, often done with a 200 grain H&G 68 at (minimum) 875. The owner complained of feed stoppages at a rate of maybe 1 in 50, with his pin loads—the bulbous 250-grain Long Colt bullet favored by many pin shooters. These will typically be loaded to a PF of, at the very, very least, 205 (820 FPS) and some will push it up to 215-plus, running maybe 860-875 FPS. This is not necessarily the best feeding bullet but better than some of the other popular ones like the 255 Keith wadcutter. The stoppage was described as being something akin to too much extractor tension. I found extractor shape and tension to be pretty close to textbook perfect, but noticed that in the breechface wear pattern, there was something I don’t believe I’ve noticed before—a semicircular wear area that surely was caused by up-feeding rounds. In other words, as a case rim’s edge slides up the breechface in feeding, it is doing so with a fair amount of rearward pressure against it, caused by all the things that a feeding round has to do that it would rather not do, like come out of the magazine, tip up and slide up the feedramp, and slide the bullet ogive against the top of the chamber. Meanwhile the edge of the case head is sliding up the breechface and bumpitty-bumping over that breechface topography. It falls into the ring-shaped depression made over the years by the case head and then encounters the unworn spot circling the firing pin hole—so now in addition to the normal upward drag, it has a slight bump to get over. This eventually wore the semi-circular divot, which made the feeding worse and worse as the divot progressed, given that the area of contact got wider and wider.
Having noticed it on this gun, I now see that the divot is starting on the above high-mileage Colt too (a few posts up).
The breechface, “before”:
And, “after”. I started with pillaring file; a couple swipes with it and then to a stone. I wasn’t going for 100% cleanup or perfection, just to get rid of the divot. Of course as this was done “in the field”, I didn’t get a chance to put an indicator on the topography of the breechface, but I’d guess it was more than .0025 and less than .005. I was not worried about increasing headspace too much as it appeared to be on the short side, and anyway, I did not go beyond existing wear.
How many rounds is a lot of rounds? This gun is on its second pin shooter, there’s no telling. By attempting to “read” the wear on it I would say we’re in the tens of thousands. Maybe 50K but maybe not yet 75K. Remembering that I’m still trying to teach myself to estimate round counts with some accuracy, perhaps +/- 20%..... with the many variables in play I may never get there but I’ve made a few calls that turned out to be close. Are pin loads harder on a 1911 than USPSA Major loads? Certainly. Another indicator on this old girl is that the frame is cracked, where they crack, especially on pin guns-- at the root of the dust cover where the slide bangs the frame each shot.
Here’s another interesting indicator: it’s been shot to slide lock enough that the slide stop, being pressed upward by the mag follower and spring, has worn a groove on the bottom of the slide rail. I have to think that would take well over 5000 reps to wear that much steel off—which would be 5000, 7-round mags, or 35,000 rounds. A guess, certainly…… “educated”, hopefully.
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