Seeing as Hudson's site is no longer there, here's a post based on their photos (plus a couple of mine) with some links to related posts on the Forum. I'm no expert so if I've missed something, please feel free to add your viewpoints!
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TUNING THE HUDSON M1A1 THOMPSON S.M.G.(Photos taken from their original web site – which has since been removed)
Problems, Problems! Problems, Problems! Problems, Problems!
There are two major areas to consider: the gun itself AND the MAGAZINE!
A) The M1A1 itself1. CHECK THE DETONATOR PIN:Check the detonator and make sure that it's retaining screw is tight! It is often loose.
CORRECTION: Remove and tighten the retaining screw.
2. CHECK THE PIN & CHAMBER:Ensure the detonator pit is not bent or off-centre and in good condition.
CORRECTION: remove the pin and re-align it, and gently smooth and remove any deformity with a small file.
3. CHECK THE FEED RAMP:The feed ramp must be smooth and free of any rough patches or dents.
CORRECTION: remove any imperfections using wet & dry sand-paper then polish or sand the bottom of the ramp smooth to eliminate any drag.
4. CHECK THE EXTRACTOR PIN:The extractor pin: The extractor is held in place in the bolt by a very long and small steel pin that is staked in place on the bottom due to an oversize hole. This oversize hole and the slight staking strikes sometimes allows the extractor pin to walk out of place and can lock-up the action. CORRECTION: The pin needs to be checked and re-staked in place to make sure it doesn't move.
OR replace the old-style pin with the newer threaded one. You will have to tap the thread in your old bolt, but being made of very soft zinc the new pin can be made to self-tap if you are careful.
5. CHECK THE EXTRACTOR:The extractor is hardened steel, and has a very small cross-section in the area where the claw tip is milled; as such it is prone to breakage. CORRECTION: Keep a spare on hand (if you can get one, or have one made (or make one yourself if you have the tools and the time).
NEW STYLE BOLTOLD STYLE BOLT6. ENSURE LUBRICATION OF THESE POINTS IN THE LOWER & UPPER RECEIVER:7. ENSURE THE BOLT IS SMOOTH & WELL LUBRICATEDThe underside of the cylindrical portion of the bolt is too rough and it causes drag on the cartridges in the magazine as it runs over them. CORRECTION: Polish or sand the bottom of the cylindrical section smooth to eliminate the drag. Ensure it’s well lubricated whenever you use it.
Likewise check this part of the upper receiver is smooth.
B. CHECK THE MAGAZINE FOR FEED PROBLEMSThis is a topic all on its own. Read this:
MAGAZINE FEEDING ISSUEShttps://mp40modelguns.forumotion.net/t1744-30rnd-thompson-mags?highlight=thompsonFinally please refer to these post for more details.
REVIEW BY 8ACEhttps://mp40modelguns.forumotion.net/t730-new-hudson-m1a1-thompson-8ace-s-review#5624REVIEW BY MARKhttps://mp40modelguns.forumotion.net/modelgun-reviews-f4/hudson-m1a1-thompson-mark-s-review-t231.htmSure it can take some work to get this modelgun firing smoothly, but it is worth the effort if you want to do so!
Kiwigunner
Thu May 07, 2009 7:10 pm
) what sort of a malfunction is that then 
