I have 1928 Thompson post sample. The 50 drum I bought for it was I believe out of spec. from the beginning. First you had to pretty much bang/beat it on with your hand. Which I had read tht they could be tight at first but this was extream. After some sanding and fileing it will slip on and off but still not with ease. The mounting plate openings are out of alignment with the openings in the drum. At first the gun would not strip off any rounds and sometime the bolt would even catch on the drum. I have done some filing on the sides of the drum and got it to feed every now and then even a few bursts. should I keep keep filing or does someone have other suggestions. Thanks

Every issue I've had with aftermarket Thompson drums has been due to burrs on the back side of the rotor "fingers", resulting in a tenancy to catch the rim of the case when feeding ....... clean them up, and see what happens.

If that doesn't work, get a Taiwan "Crosby" L drum ....... they run out of the box ......you just need to grease them eventually

The Taiwan drums are great. I see them listed as GPC at Numrich. I have a few and all run great.

If you need to grease the rotor, I sell the greaser for it.

Regarding greasing the drum. I found a video and it showed that you had to make a grease fitting. Then clamp it on ect. Is this correct and if you sell grease do you sell a fitting also? Thanks Tom

I sell the fittings with the greaser nozzle. All you need is a standard greaser gun used for automotive and such.

Just note that I don't think that missing grease would be your original issue.

I think that I might be better off to buy another drum from the supplier suggested Numrich. Maybe having another drum to compare will help me get my original one back into spec Right now I can only get about a 4-5 round burst before getting a light strike. You would not think that a new drum would ship without enough grease to function.

Greasing Thompson drum rotor shafts appears to be an internet forum driven concept that originated about ten years ago.  I am not aware of any authoritative documentation that mandates such greasing.  In fact, an older article on Thompson drums by Tracie Hill merely notes oiling the rotor shaft when reassembling a drum after cleaning. Further, unless I misread them, none of the Auto Ordnance or U.S. Military manuals that I have seen mention greasing Thompson drums.  I have a couple of pre-WWII Thompson 50 round drums; and neither has any sign of ever having been greased.  And I used to have a WWII era ("Bridgeport") 50 round drum that likewise did not show any sign of ever having been greased.  The 50 round drum that came with the 2012 Kahr 27A1 Thompson that I have did not have any grease.  I have not, and I do not intend to grease any of the Thompson drums that I have.  I believe that oiling the rotor shaft is sufficient lubrication.

That said, I don't think that there's much, if any, harm to including a discrete amount of grease to the rotor shaft if one wishes to do so.  Excess grease would just be a contamination trap.

MHO, YMMV, etc.  Be well.

ETA: I am not aware of any recommendation ever being presented for greasing the rotor of Suomi drums.

I agree that you would be better off getting the Taiwanese drum.