Rocker,
Try speedy metals if the scrap yard doesn\'t have what you are looking for. They cut to length and have most of the brass also. The prices are high everywhere on brass so don\'t freak out when you see the prices. Better yet, RG-G has material kits that are reasonable and contain everything that is needed for the project.
Is it difficult to obtain a right side plate for a 1919 in these times? How long was the waiting time for approval from the BATF? I have a friend in town that has several 30 cal 1919\'s, a 50 cal. and several tommy guns. Every 4th of July he takes a couple of them out to the desert with belts of nothing but tracers. Fun to watch.
I think you explained the broadwell drum correctly enough to get the picture. That o-ring is actually an extension spring looped together at the ends. You have to really zoom in on it to make it out.
I will probably make a broadwell drum after the .357 testing is done later on.
bruski