Hornady makes or at least used to make 6x45/6mm-223 dies that cost the same as their normal dies where as from anyone else the were listed as semi custom ($). The shoulder is easily set back so you have to seat and crimp in two steps. I shoot a lot of 223 so I use nickle cases for the 6mms so i don't get them mixed up.
Good choice. It is possible to get the barrel rebored to 6mm/.223. Dont know what it would cost but might be worthwhile to look into it. Might not work if your bore is chromed.
I am looking at doing an upper for my AR in 6x45. Heard lots of good stuff about this for varmit.
Your not going to get the "Original" barrel bored out to 6mm.
I have been shooting the 6x45mm for at least 30 years. It is an excellent wild cat for the .223/5.56mm platform.
You only have to get the dies which open the neck to 6mm. The best bullet I have found is the Sierra 85 gr. HPBT (#1530) it performs great out to 600 yards. And believe me I have tried many.
What is really great about the 6x45mm is there is less felt recoil than the 5.56mm. Yest, I know, but it's true. Also, another advantage is that the 6x45mm has less bore wear that the 5.56mm.
I got my High Master Card (NRA-High Power) using the 6x45mm.
However, with today’s bullets/barrels/powder I'm sure you can accomplish the same thing with a 5.56mm barrel in 1-7/1-8 twist.