Hello everyone,
A few years ago the brass case on my breechseater sustained some damage to the mouth of the case. I replaced it with one of the extras that Russ Weber made for me when I bought the breechseater, with the intention of making another spare. I just discovered that I never did make that spare. 
Before I go down a rabbit hole, maybe you can help me out. 

1)Is there any reason I cannot use the damaged case?  I think it is perfectly functional but maybe there is a reason out there that I am not aware of. 
2) Is there any reason I could not use the damaged case if I trimmed it down to eliminate the damaged portion of the case mouth?
3) If I decide to make a new case, does anyone know what thread size Russ Weber would have used for a 38-55 breechseater? I tried all the machine screws that I have and none fit. A friend of mine says 8mm x 1 works. It seems a little odd that Russ would have used a metric thread but maybe he did . I would prefer to not have to dissassemble the tool to find out, since it isnt broke right now, so if someone knows the answer I would appreciate it if you could help me out. 

thanks!
Joe

If push comes to shove I can check the threads on mine too, but can't be until Monday. I have the tap also (but it's located where my seater is). You're welcome to use it. It is indeed an uncommon thread size - my apologies for not remembering off the top of my head.

5/16-24 is very close to 8mm-1 metric.