Anyone have an experience with this little screamer...how hard to form, bullets used, powder, velocities, etc?

DB, Well I don't qualify as the expert on the mach4 yet but I am knee deep in the process. I'm breaking in a custom job and I'm not yet up to load development. I started with new 221 brass and the RCBS form set. Two form dies, one is also a trim die, so there is two operations. Full length and seater die is two more. I'm fireforming with 18.5gr of AA2520 and Hornady's 25gr HP. I haven't put it across the chronograph yet, but it should be about 3400fps. It takes some work, but I like the way it shoots. Quiet, no muzzle jump, watch the black dot appear on the paper. There is a pretty good rundown on loads in the Reloading Page, and quite a bit of info available here in the archives if you do a search.

Rick

the MK4 is a great round and hell of a shooter, like posted, little recoil

the brass is easy to form and easy to find a load for, it will run a 20 gr bullet near 4000 fps and 25 up to 3800 but there is no need to push this little round that hard to kill what ever you want

I form and sell MK4 brass if you would like to save money of dies drop me a line

JD

The Mach IV is a fun round . Effective on small varmints out to about 250 to 300 yds .

It is an easy to form (great introduction to)wildcat. As was stated above RCBS form die set (Redding also makes them) .
The big hint ,IMHO , is Imperial sizing die wax . Nothing else works as well period .

Lots of bullet makers with lots of weights and styles. Berger , Hornady ,Starke , Calhoon , come to mind .

Many medium fast powers work well . IMR4198/H4198 ,AA2015 , Reloader 7 , H322 , N133 , N135 , H335 , to name a few .

It is interesting to see what happens to an unopened can of pop hit with a 20 grain V-Max at 200 yds , mistify .

muck