I built an AR in 6mm Mongoose which is basically the same as the as a TCU (223 AI necked to 6mm) but made a little shorter to work better within the COAL restrictions of an AR mag. It was a pretty impressive cartridge. If I recall correctly ( I sold it a couple of years ago) I was around 2750 out of a 16” suppressed barrel with 90gr bullets. I remember using H335.
Info on what you used for dies?
I was thinking of doing a 6x45 AI (reamer can be rented). Dies is where I stopped. Can I just set up a 223ai die set with a 6mm bushing instead of the 223?
A custom die set doesn’t make sense with 6ARC and others out there now. But if it’s just a little tinkering, the extra 10% of case fill becomes pretty interesting.
I have a 6 TCU and a 6x45, both bolt action. I have built over a dozen rifles chambered in 6x45. I promise you, you won’t gain more than 50fps going TCU over straight 6x45. Have your gunsmith cut the chamber with a longer freebore and you’ll gain a lot more than “improved” can gain you. Also, the TCU doesn’t feed nearly as nice as the 6x45.
My friend’s son shot his first deer with my 6x45 yesterday.
Hornady 87 V-max, hands down. It’s an undisputed killer! I’ve literally seen hundreds of deer taken with that bullet.
I have my gunsmith do all the chamber work when doing the initial build. He uses a floating pilot reamer and uses a tool to set freebore based on a dummy round that I provided.
Definitely gonna need more details on this one...