Help Diagnose Problem

[Jay Baker]

Took the '28 out to test fit with a new drum and discovered a little problem. With no magazine, the trigger and bolt seemed to operate normally. Upon inserting a magazine, the trigger became stiff and the bolt would not release. Closer examination revealed a trip which has a projection into the channel for the magazine rib was loose. I have never looked at this before, but presume it should have been sprung. I looked up a parts list on the lower internals and it appears that a disconnector spring should be maintaining pressure on this trip. To me it appears to be a broken spring.

 

Using a drum which does not contact this trip in the channel, trigger and bolt seem to be working normally. Insert a box mag, and it will not function. Anyone seen this problem before, recommend repair procedure, and advise possible cause? Maybe I inserted a box mag with bolt closed causing damge to the disconnector spring? Your help and advice is most welcomed. Thanks.

[PK.]

Everything you describe is absolutely normal.

 

With an empty box magazine in the gun, the tab on the back of the mag follower engages the Trip (which has no spring) which depresses the disconnecter preventing the bolt from being released. It does this on the last shot so you have only to insert a fresh magazine in order to continue shooting. The drum has no provision for this function and the bolt will go home on an empty chamber when the drum is exhausted.

 

 

[Jay Baker]

Thanks PK, I knew you would spot my mistake. I don't usually leave an empty mag in the Thompson, and totally forgot about the hold open feature. Its a relief just to know I didn't screw something up.

[JimFromFL]

Its a good think PK replied when he did, because I was under the assumption that you were using a loaded magazine. If it were the case, I was all set to type a long paragraph of things to check and what it could be. http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/tongue.gif