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Well, I received my new Thompson 1927A-1 back from the factory in Wooster MA. They changed out the ill-fitting rear grip for one that fits properly, gave the 10-round drum mag a trip thru the vice so that the stampings would fit into the grooves on the receiver, and test fired it. The rattle evident between the frame and upper they deemed "within spec" and did nothing; the failure to set the f.p. during my initial test firinG (first shot!) did not reoccur. It would seem that that's the best I can extract from them, under the circumstances. The drum mag now actually fits, and it feeds fine.
My new problem is with how the 30 shot stick mag fits and feeds--rather, is deficient in these respects. The mag in question is pre-ban vintage, supplied by the factory as part of my original order. It tended to hang up on the rounds presented on the left side of their zig-zag stack. The sharp lower edge of the funnel-shaped feed area behind the chamber caught a handful of rounds on their way to the chamber, digging into the copper jacket to start shaving off a piece of the bullet, or caught the tiny step in dimension presented by the end of the casing. With the front end of the round hung up in this way, it'd jam right up.
Examination of the feed lips of the mag yielded the observation that the left side appeared to have been hit by the bolt at some point, resulting in a dent about halfway along its upper edge. The symmetry was way off, too, with the left and right hand profiles of different radii and angles. I clamped a 1/2" steel rod in the vice and used it as a mandrel to make the left side lips look more like the right. Fine tuning was necessary to influence the top rounds to come off straight and smoothly--and controlled--by hand, about the same way both sides. The right side was the benchmark, as rounds exiting from this side came out straight and smoothly already. With a little patience I was able to improve the feed considerably by doing this.
The mag rattled all around when clicked into position, as was. The displacement was evident in all directions, even rotational, and I figured that anything I did to effectively jack the front of the mag up and prevent it from twisting all around would help. Between the back of the mag and the front surface of the back side of the "well", about 3/64" space was evident on either side of the back "T" form of the mag. So I tried a good, ol' shim on either side to snug things up and kick the lower end of the mag forward, which also eliminated most twisting on its vertical axis. I accomplished this by applying a ramp constructed of successively longer strips of self-adhesive stainless steel tape to the flats, tucked under either side of, and parallel to, the "T" shape, or spine. (Sorry, someone correct my terminology, if necessary. Thanks) The result is that the mag clicks in snug and moves around way less. The arrangement (cob job) is not visible when the stick is in place.
Something I noticed about the current Thompson is that the journey from stick mag to chamber is sort of perilous for a round to make without going somewhat astray. That ~1/4" gap between the front of the mag lips and the back edge of the feed ramp/structure was where the rounds had screwed up; the lips seemed to ride a hair low in this arrangement, allowing the sharp lower edge of the ramp to catch the side of the round's jacket and dig right in. This was fixed by the shims. I tried about a dozen rounds thru it, post adjustment. The first round needed help to be picked up by the bolt, but once I had it chambered, the rest all made it, except two rounds that hung up with the action not quite back in battery.
I thought my 1911 was a dirty gun to shoot, but the condensed crud and residue from just a few shots made the formerly shiny inside of the 1927's feed area look as if I'd blacked it with a candle flame! I think that the offending rounds merely hung up in the gritty dirt on the way in. But this is where the expertise of the forum comes in handy. Does anyone have any comments about my approach, or suggestions how to further improve the dependability of feed?
David Parker
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"... Liberty is the seed and soil, the air and light, the dew and rain of progress, love and joy."-- Robert Greene Ingersoll 1894
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