What is the twist rate on that barrel? The reason I ask is that alot of the older 243's had twist rates designed for smaller/lighter bullets. A 100gr 243 will drop a deer as fast as a vw van, but if the barrel wont stabilize the bullet, then hitting it might present a problem...shoot a couple of groups for us and see which bullet weights work best for you...85gr and up will do the trick on deer...