I recently read a magazine article on reloading the 310 Cadet cartridge and wrote this letter to the editor:

"I found Jeff Brown’s article on reloading the 310 Cadet very interesting but he doesn’t tackle the problem of crimping a heel base bullet into the case. I reload the 380 Rook cartridge and find that a crimp on the base of the bullet helps burning of the powder and improves accuracy. The normal methods of applying a crimp don’t work with a heel base bullet and the usual suggestions of using a blunt knife, wire strippers or drilled out pliers just seem a bit haphazard.

Fortunately I have a very bright pal. He reloads the 310 Cadet and uses a Lee 303 British collet crimp die to crimp in the heel base bullet. He achieves this by suspending the cartridge in through the top of the die. He has made up a two stage collar to hold the cartridge in place. The first stage sits in the top of the die and merely serves to centralise the cartridge, the second, wider stage has to be a precise depth as it controls the amount that the cartridge dangles into the die and hence where the crimp comes. All he does is place the cartridge in the collar, put the collar in the top of the die and apply firm thumb pressure to the base of the case while he raises the ram on the press. The result is a consistent and accurately placed crimp.

I have pinched his idea and use a Lee 35 Remington die to crimp my 380 Rook cartridges. I’ve extended the idea by crimping the bullet in place and then slipping a thick washer onto the cartridge before putting it back into the collar. This raises it in the die so I can then crimp a deeper grease groove into the bullet and hand lube it."

I found Trail Boss to be a very good powder for the 380 Rook.