Here's an email I sent to Charlie and thought I'd put it on this thread as it might be of interest to others and I'm sure he won't mind.
Here's what I wrote:
I just checked some Hornady and Sierra gas checks I have and
both have metal thickness of about .010-.011, or about the same as I'm using
with yours, the inside ID's on the bottm end are about the same as your's, maybe a few
thousands smaller. but the outside high end dia's on the mouth for the
Hornady's is .317 and the Seirra's is .312 with the bottom OD dia still the
same as yours. It looks like those cups are flared out to the larger dia. by
a forming mandrel with the bottom OD remaining the same.
I did notice that when running the cast bullets with the commerical checks
on. The only area of the check touched/crimped by the sizing die. is at the
mouth/top of the check.
This is interesting as instead of opening up the anvil as I was thinking
about doing, I experimented and used the rounded head of a machine screw
just to flare the OD to a larger .312-314 dia. which should work/seal in the
Enfield bore, .314.
The only problem that I could invision is the copper/brass checks of the
commerical ones would maintain that larger form better when fired then the
alum. ones. Don't know if that would make any difference or affect the
firing any though.
I won't be able to try them at the range for a week or two. But if they work
well, you might include the info that the checks could be enlarged/altered
for folks that need a larger OD for their checks. Ray End email.
Charlies 30 cal checks mike out at about .309 OD, bottom of cup to top, which work well as made for 30 cal but are undersize for 7.7. or .303 bullets that need bullets and checks that can be sized to .312-.314 OD in order to better gas seal. Flaring Charlies checks to those OD dia's like the commerical ones are would do it. Most of these .312-14 moulds have the same dia gas check shanks as the 30 cal bullets and are designed to use 30 cal gas checks and as I found out, the commerical GC's are just flared out so that can be used with larger dia bullets also. Ray