Well, if you want to blow them up - go 70NBT or even that 80 Sierra SBT/Blitz bullet that someone was recommending earlier. So far in my 243, the 70NBT's with Reloader 19 and CCI BR-2's @ 2.620" have been the most accurate of anything I've tried. Start about 47.5 and work your way up to say 48 or 48.5. This is not a hot load at all, in fact I've heard of people pressing it all the way to 49.0 of RL19, but for me the sweet spot was 48.1 and I had a full case and didn't want to go compressed. 3,250 fps or right around there is where I was with 48.1 when I chrono'd this load long, long ago.
I've shot the 80 SBT HOT HOT HOT! 40.7 of IMR-4064 @ 2.695 using Fed210GM match primers. 48.5 of Reloader 19. 45.2 of H414.
I shot the 75 V-MAX HOT too, at 42.3 (or maybe it was 43.2 ?) of Reloader 15.
All of the above 80 loads, and that 75 V-MAX recipe, will get you up over 3,400fps. But I can tell you with certainty, the 75 V-MAX doesn't explode anywhere near as bad as the 80 SBT, and I don't think it makes as big a mess as even the 70NBT does driven considerably slower.
So I'm going back to try and work up a load with the 80 SBT again using IMR-4350 this time around. So far though, I'm having a hard time finding load data. I've seen people using everything from 42.0, all the way up to 47 and one fella even pushing it to 48.0 !! 42.2 with an 85HPBT was "MAX LOAD" in one of the manuals I looked at for IMR-4350, so I'll probably start about 42 and just take my time. RL17 is pretty close to IMR-4350 and Nosler's reloading site says 44.4 with an 80, so I'm hoping to find something good in the 43-44.5 range. I definitely want to get back up over 3,400fps again with this bullet though. And if this works, I'll probably try IMR-4350 with the 70's this year too (70 TNT, 70BK, and 70NBT), where I want to get back up to 3500 or so with these, like I had been with Varget initially shooting about 42.7 or 42.8 with a 70NBT and CCI-BR2's.
New guns are great. Just start well below "book max" and work up. I usually don't go in more than .2 or .3 grain increments, going to .1's if I really think I'm pushing it. Better to push 'em in high heat & humidity too to avoid any nasty surprises.
70-80gr is ideal though I think for the 243. Better wind resistence, still fast & flat, and plenty of energy when the package arrives!!
Stephen