Fire Forming .222 Rem Mag Brass for .204 Ruger

This information has been graciously provided by Silverfox.

The Remington 222 Magnum brass is not very difficult to fire form. I take a 222 Mag casing and run it into my full-length sizing die just enough so it sizes a bit of the neck so when the casing is chambered, the donut crush fits against the .204 Ruger chamber (see illustration). The main reason for the crush fit is to avoid a headspace problem. The rest of the neck is left at the stock 222 Mag size.

On the first five casings I fire formed, I used the 40 gr. V-Max bullets and a load of 27.0 gr. of H4895.  The casings formed just great!! The average velocity was about 3,710 fps. The five-shot group was 1.375".

I then went to the 32 gr. V-Max and used 28.0 gr. of H4895 with that lighter bullet. No primer flattening and WAY BETTER accuracy. I fire formed 25 casings with that load and got an average velocity of 4,040 fps and the five 5-shot groups measured .770", .580", .580", .580", and .692"!!! I was pretty happy with that.

I have 40 of the Remington .222 Mag casings necked down for the crush fit and will load them up and take them to the prairie dog fields this summer. I also have another 60 casings sitting on the loading bench waiting to be necked down a wee bit for the crush fit. When I get those fire formed, that will give me about 150+ .204 Ruger casings that I will have fire formed from .222 Mag casings.

Subsequent testing with the fire formed casings with 32 gr. and 35 gr. bullets proved that the fire formed casings were every bit as accurate (even a wee bit better for the ones I neck turned with the K&M neck turner) as the factory Hornady brass.