6mm TCU same capacity as 6PPC

[bluetopper]

I was considering having a barrel made for my Thompson Encore in a 6mm caliber and was looking at data of several 6mm calibers with less capacity than the 243. I was utterly shocked when I discovered the lowly 6mm TCU had the same powder capacity as the 6PPC.
The 6TCU is just 223 brass necked out to .243 then fireformed. After fireforming, the body is blown out to nearly straight walled and it forms a steep shoulder. I've always heard it was a very efficient and accurate cartridge. I have a 7mm TCU in a 14" Contender handgun but I may just get me a 6TCU barrel also.

 

[someguy2800]

Interesting, didn't know that. I have a set of 6 tcu dies in my bench. I intend to get pawn shop pickup bolt action in 223 and rebarrel it to 6 tcu. I might just get one for my contender though.

Another interesting wildcat in 6mm is the 6mm BRM, which is basically a 30-30 AI necked down to 6mm. Eabco makes encore and contender barrels.

 

[adcoch1]

I wonder how much improvement the 6tcu is over 6x45? That one is 223 necked up to 6mm. It can't be very far behind...

 

[bluetopper]

I think the 6TCU will hold about about a grain and a half more powder than the 6x45. I haven’t found a picture comparing the two.