70g Hornady SP is the toughest 70g bullet on the market. Barnes used to make a 75g X bullet that would stabalize in a 14 twist.
I would start my hand loads off at 39.5g of IMR 4064 and go all the way to 41.5g in the 243 with the 70g Horandy Sp, velocity will be over 3400 fps when you hit the accuracy node, use a fed 210 or cci 200 primer in either Rem or Win brass.
Shoot the deer BEHIND the front legs in the lungs, you will be happy with the results.
I assume that your friend had a 1-14 twist installed on his gun, right? If he had a 1-12 twist installed, then the 85g Sierra BTHP or a Speer 85g BTSP would be an excellent choice, but they will not stabalize in a 1-14 twist.
Good luck!~