I would build a 6-284 on a long action so you can seat the bullets out a bit. I shoot retumbo with a 28"bbl and 115 bergers and an 8 twist. It is a homewrecker. The 284 on a long really lets you do what you want. This aint your fathers 243 for sure. I havent chronoed it in ages but remember around 3050 with the 115 and lapua brass. 284 is hard to beat in a long action with long bullets and those 115s do some silly damage. Never seen a deer get away and it will shoot thru the front shoulder entering and out the hip bone leaving a huge hole on a big whitey.