Good choice!! I'm doing a 7 saum right now on a Defiance anTiX long action .220 FB, Bartlein #3, 8 twst, 22" finish. Hawkins hunter dbm with spacer kit and a Manners MCS-PH. I'm chomping at the bit to get it done.
You don’t think 2950 is attainable with 168s or that 2900 can be had with 175-180s? I don’t really care if I can’t hit 2900 with 180s I definitely think 2850-2875 is very realistic. I will take the SAUM’s inherit accuracy over 50-75fps.
It is my belief that 2950 with 168s and 2850-2875 with 180s is not a given. Your operating at the limits of the cartridge and don't have a lot of room to work with if something goes wrong. For example, you could get a slow barrel or the barrel might not like your projectile/powder combo of choice.
However, I see you have made a decision so I hope it all goes well for you.