It was quite obvious to me at this point that something was wrong. First the rotor drive spring was not strong enough to overcome internal friction of ammo and rotor together when firing on full auto. I made the assumption at that point that A/O had probably not tested one of these "C" drums under full auto live fire conditions.

The next day I wrote a nice long detailed letter to the Engineering Department at Auto-Ordnance West Hurley, New York. Smoke was coming from the letter. I explained in detail the difficulties I was experiencing with their new "C" drum magazine.

In late November I received a letter back from Mr. Tom Casey of A/O simply requesting I send my drum back for exchange. 

FURTHER ADJUSTMENTS:

I had plenty of time on this visit to Oregon, so I decided to investigate the drum a little further. I could see that the rotor drive spring was too weak. Next I inserted six dummy rounds between the drive arms, near the center of the rotor. With the Cover off and with the Key in place, I began to turn the rotor clockwise. The rounds traveled only a short way before they wedged. The guides were too tight. I found two more tight places. I adjusted the tight places between the guides until the rounds slid freely all the way to the feed lips.

I could also see that the ends of the driver arms on the rotor were not the same length. A couple of them touched the outer Body near the feed lips. The others did not. So I took a flat tip punch and through the feed port I rapped the ends of these driver arms that were touching. They now cleared. The rotor arms in general seemed rather rough as though the stamping equipment was very poor.

It was early December 1991, however I had enough time to do another test of the A/O "C" drum before I returned to southern California and to work.

I took my 1928A1 Thompson again to the range. Bear in mind, this thing only fires about 550 rounds per minute. I loaded one hundred rounds of factory ammo into the new A/0, West Hurley "C" drum. Suspecting a weak main spring, I wound the key eighteen clicks instead of fifteen. I fired in semiautomatic mode. Twenty five rounds went out perfect. This told me the rotor would keep up with a very slow rate of fire.

Then I moved the pivot to Full-Auto. It fired about thirty rounds and then again failed to pick up a round. I retracted the bolt and fired again. The same routine started again where it would fire one round and then five or six rounds. At each stoppage the bolt would fail to pick up and slam home on an empty chamber. Finally in frustration I removed the drum, wound it another seven clicks (making a total of 25), and reinstalled it. It gave several short busts with stoppages until it was finally empty.

My 28A1 does not fire fast. So the six round intervals told me that there was simply not enough strength in the spring to overcome the resistance of the rotor and ammo together, and move it fast enough to fire in full automatic. Too much mass for the spring. However it would work in semiautomatic mode.

These are my early conclusions. If Auto-Ordnance designed these "C" drums for use only in their new semiautomatic carbine, they will indeed work after a fashion and their advertising would not have been false. It is my opinion they should have been advertised as such, or even as static displays only. However, they continued to insist they would work in all full automatic Thompsons. This was to me false advertising.