Of the TCU cartridges the .257 is the rarest. There is more information and better component/supply availability for either the 6mm TCU (6-.223) or the 7mm TCU. I'd lean towards the 6TCU shooting 75-85 grain bullets. You're much more likely to find dies and appropriate bullets in 6-.223 than .25-.223 IMO. Good luck with your new rifle!

Hi guys can anybody shed any light on a 25 tcu - I need a round that is based on 223 but with more punch for model seven but with only a 20 inch barrel. Needed for a gun to shoot large varmits for my pest control business from my truck at night so it needs to be short and handy but with a bit of punch.

I have a pair of 6mm TCU contender barrels. One is a 14" pistol, the other in a Bullberry 20" carbine barrel. Both are sweet shooters. I also have a Kimber of Oregon M84 in 6x47 that I sometimes hunt blacktails with. All are more than adequate for game deer sized and smaller out to 200 yds.

Given the cost of screwing on a new barrel, you might be better off locating a Remington Seven in 243 or 260, and trading for it. Another option might be to purchase a synthetic 700 ADL in the caliber of your choice and have the barrel cut back to 20". If flat shooting varmint round isn't an absoulute requirement, a CZ 527 carbine in 7.62x39 might also meet your needs.