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Magazine Problems


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#1 DGinGA

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Posted 08 October 2019 - 08:54 AM

Last week, I ordered 10 shooter mags for &16.95 (30 round, some rust/pitting, worn finish) to take to the Creek this weekend. Took each one apart, cleaned with 3/0 steel wool, 400/600 sandpaper, solvent. At the range, 5 functioned perfectly. 4 others failed to feed. Failure was always the same: the bolt pushed the bullet nose above the chamber. Easy to clear, turn the gun 90 degrees ejection port down, and shake the cartridge out. Didnt matter whether semi or F A. But if I pushed up on the mag, failures stopped. No elongating of mag retention holes is visible. I am tempted to bend the mag lips up to raise the cartridges, but having been through this with Reising mags, know that can cause unforeseen problems. Read about a magazine anvil - are these being sold? Is it worth trying to fix these, or just buy new?
As a side issue, I used Sellier & Bellot ammo instead of Blazer brass. It was much hotter - louder and faster-firing.
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#2 gijive

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Posted 08 October 2019 - 09:20 AM

Last week, I ordered 10 shooter mags for &16.95 (30 round, some rust/pitting, worn finish) to take to the Creek this weekend. Took each one apart, cleaned with 3/0 steel wool, 400/600 sandpaper, solvent. At the range, 5 functioned perfectly. 4 others failed to feed. Failure was always the same: the bolt pushed the bullet nose above the chamber. Easy to clear, turn the gun 90 degrees ejection port down, and shake the cartridge out. Didnt matter whether semi or F A. But if I pushed up on the mag, failures stopped. No elongating of mag retention holes is visible. I am tempted to bend the mag lips up to raise the cartridges, but having been through this with Reising mags, know that can cause unforeseen problems. Read about a magazine anvil - are these being sold? Is it worth trying to fix these, or just buy new?
As a side issue, I used Sellier & Bellot ammo instead of Blazer brass. It was much hotter - louder and faster-firing.

Are you sure that some of the magazines haven't been modified for the semi-auto Thompsons?  The are easily distinguishable by the modification of the hole on the back of the magazine that has been ground from round to oval shape.  If they haven't been modified then you are correct you need an anvil to correct the feed lips that are likely out of spec.


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#3 Tiz

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Posted 12 October 2019 - 12:35 PM

As far as I can tell no one is currently making a "mag anvil" although there is talk on the form of giving it a shot with 3-D printing.

I have the mag specs courtesy of other members on the form.

There are several specs ( lip radius, lip gap and distance from the mag catch hole to the top of the lips ) for a Thompson mag to function perfectly. PK has all my mags at the present time and is gauging and correcting them to spec. Once I get them back I am going to attempt to fabricate a mag anvil similar, but improved, I hope based on Glen Whittenburg's original creation. I just need one of mine back to use a gauge in making the mag tool. I'm thinking all steel not 3-D.


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#4 Bridgeport28A1

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Posted 12 October 2019 - 02:44 PM

PM sent


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