I'm planning on screwing together a rifle (or two) based on a necked up 204 Ruger with no changes to body taper or shoulder angle. Case capacity will be 34.7 gr of water by my calcs and nearly identical to the old 257 Kimber round. Can somebody estimate my velocity with a 20" bbl with 75gr bullet? Also, couldn't a 204 Ruger bushing die be used by swapping in the appropriate 25-cal bushing (ala Redding)? Any input appreciated!
http://www.hunt101.com/img/215671.JPG

Would this be any better than the 25TCU ? Its not popular as the 7mmTCU but would the exter length of the 223 mag. case increase the power that much.

I get 3030 fps with 29.8 grains of 3031 on my old Powley computer, IF I did it right.

Bye
Jack

Thanks for crunching the numbers, Jack. They seem reasonable. My goal is at least 3000 fps. I wonder how the old Powley compares to the new software programs. The plan is to build one on a Mini Mauser action, then if it works out rebarrel my Mini 14.

Bamajohn, there will be very little gain over the TCU case, less than a grain by my calcs. I just think this would be an easier wildcat, requiring a single pass thru an off-the-shelf die (hopefully). The drawback of course is brass will cost more than 223, but I won't have to spend a lot of time (and powder, primers and bullets) fireforming before loading full power loads, just neck up and go.

Uh, wait a sec, guys. The 204 is based on the 222 magnum case- important for 2 reasons.
1) the parent case is slightly larger than the 223 case, not smaller. So, you should be able to slightly exceed TCU performance, since the TCU's are based on the 223.
2) If you do some digging, you'll find data for wildcats based on the 222 magnum case. Heck, Hodgdon has data for the 6x47 (6mm-222 magnum) in their manual. I bet P.O. Ackley's Handbook for Shooters and Reloaders would be a resource, too.
Kinda shows you there's nothing really new....

Yup, .25-222 Remington Magnum, RCBS #56150 and CH-4D, 3 variants.
http://www.ch4d.com/

Bye
Jack

Anybody got any loading/velocity data for the 25 TCU / 257 Ugalde, especially from a carbine barrel?
Thanks!

You should remember a little thing called the .25 copperhead on the .222 case. Pretty close also.

You should remember a little thing called the .25 copperhead on the .222 case. Pretty close also.
Actually Swany, from the data I've seen the Copperhead would be quite a bit slower, with over 5 grains less case capacity. That's a pretty big difference in a case this small (>15%).