6mm/204 Who had done one?

[Oso]

I am not a fan of rebated rim design... it is a critical failure point especially if going to use brass for multiple reloads. Nosler had to use the .224 head dimension in attempt to gain easier acceptance with AR15 community (no new bolt required).

 

[AWS]

Having built the 22-204, 6mm-204 and 25-204 and having shot them for more than a decade, I like them they are just about as much as you can get out of a .378 boltface and very easy to do. Any 223 is easy to ream to 22-204 if you have the mag length, same with the 6mm-204. For the 6mm 204 I ordered a prefit barrel in 6x47 Rem and just opened the chamber with my 22-204 reamer with a 6mm pilot on it as the neck and throat were already in place.

At 73 and happy with what I created I'm not going to do much wildcatting anymore, I do have a 20 Practical in the works. If I were going to play with the 224, 243 and 257 I'd really look hard at the 6.5 Grendel case and a Howa Mini, CZ 527 or Zastava 85 with a 7.62x39 Boltface, what a petite little shooter you could build. Most of the work has been done 224 LBC, 243 LBC are out there and I don't know if there would be enough difference between a .257 and .264 to make the effort worth while. I have a Howa Mini in 6.5 Grendel and it is a little much for coyotes(I save pelts) but would be a very nice deer rig with 100gr NBT's or Patitions. Even with the HB on mine it is a nice little rig to hunt with.

Howa Mini 20" HB, DIP bottom metal, bobbed mag, Meopta Artimes 1.5-6x42mm, 100gr Nosler Custom Competitions

 

[AckleymanII]

204 die modifications are easy for the 22 & 6/204. Using a 22/204 Reamer, PTG makes an adapter for the 22 cal reamer to accept the 6mm reamer bushings, then neck and throat reamers...piece of cake.

Question in my mind is if the primer pockets are going to hold up to get the potential out of the case.

Big win is no feeding issues out of a std Rem 700, remove the mag bock on the 223, use milled follower...done.