very nice Mark
So is the mechanism built into a 7mm tube and then into the cartridge or just direct into the cartridge and how do you judge the depth if so ?
There is a 'how to' in the file's pages by Les Elm which will help but I have adapted and modified over time...
I drill out a real bullet to take a cross refill after removing its lead and fit it into a case with a bullet reloading press. Then I drill the back of the case out with a 1/4" drill bit, I use the lathe and a collet chuck for this. Once I have a batch done and checked the swarf is out I put a flat bolt in my chuck and use it as a press to push the mech in. As I have done loads I know how far to insert the mech, if not its a little trial and error.
You can do this another way ......
Drill the cartridge with a 7mm hole, wrap one end of a std slimline tube with a little masking tape and glue this into the cartridges mouth. I don't glue the base! and then you can just use a std slimline nib in the front and push fit the mech the other end....
This works for .308.....303s are a little longer as are 30 06s, I hope this helps