I have been a bit quiet on this for the last month or so as I have been doing alot of research !
The 7mm Rem Mag was where I was headed until I re read all your comments !
The Mark V is a very nice hunting rifle. I have decided to keep it that way and not try to make it a crossover rife with a heavy barrel etc.
I am packing her up and posting it to Allan Swan gunsmithing. Allan specialises in barrel making and re-barrelling rifles.
Reading up on his work Allan seems to have a quite a few happy customers that have re-barrelled hunting rifles with excellent results. Fingers crossed I will get the same outcome with the .257.
I have asked for a 1 in 9 twist, as i would like to throw some heavier projectiles around - anyone have any experience with the .257 Wm in a 1 in 8 twist or 1 in 9 twist

it is currently a 1 in 10 twist.
Now to wait the 8 weeks for the job to be done !!!!