I just checked the gap measurement at twenty thousandths. That is with a newly trimmed case.The hole in the sleeve measures .430". I think I used an 11mm drill to drill this hole and it is an easy fit over the case .
As far as using nylon for the sleeve goes , I thought the nylon would be tough enough to withstand repeated use and also provide a buffer between the two steel parts . As it happens only gentle tapping is needed to form the crimp and this shock absorbing function is not really necessary and I now believe steel or aluminium could be used if that is all that can be found .
I came up with this improvement while I was comparing ammunition loaded with a Lee Loader to ammunition loaded with a set of Lee dies . The caliber was 30-30 and all rounds fired in my 94 Winchester . All rounds were fed through the magazine and that is why they had to be crimped .
All documented on another forum . Here if anyone is interested .
http://garagegunsmithing.com/index.p...php&f=32&t=756