I have a 6mm/06 Ack. Imp. and have killed three or four dozen deer with it( witnesses and papers on this)using a 55gr nosler going 4195 fps, it will make them do circus tricks.
The 243.Ack. will do about the same with less powder, real nice little cartridge.
Just got the reamer for a 6.5-08AI. Closest commerical cartridge would be a 260Rem AI. Should be fine for 800yd deer with 140gr class bullets out of a 26" pipe. Lighter bullets would work great for varmints.
You would be able to fireform commercial brass to form cases. Of course, the 6.5X284 Win would also work fine.
In the 7mm class, I would look at the 280 Rem. Friend is having great success with the 168gr MK out at 1km. They way it hits the plates, I would not hesitate to take a whitetail at 800yds.
For a 30cal, I would lean towards the 300WSM. Just gotta love these cases. You can always open the bolt face. I shoot a 30Gibbs which has very similar performance. Because this is a wildcat, no go for you. The 165gr SST or BT would be my first choice.
Jake, because you said G-dogs were the primary target with Whitetails secondary. Also you stated 800yds as max range. Last year I requested some information on a system for my girlfriend, S1 is a fan of the 243imp and it rubed off. Well after a couple months and a few hundred rounds I really like this chambering for shooting under 1000m. Its relatively cheap to shoot, VERY accurate, hardly recoils, and you can use regular 243 Winchester ammo if you need to. I say go with 1 in 8 inch twist medium weight barrel fineshed at 28 inches. Put a good scope on it and shoot 105gr A-MAX's, you'll be set. YMMV. [img]images/icons/smile.gif[/img]
Charles has done his home work, he is right on. I have seen several antelope and many whitetails flatened by a .243 and a 105 A-max. The wind deflection is great, and P-dogs past 1100 yards. More fun than a man deserves!
I think that the you should use whatever would inspire your confidence in a good hit. I have a hard time believing that a deer hit in the boiler room with a 243 will run off unless he was already full of adrenaline from being spooked before hand or a poor choice of bullets that don't expand properly.
I have used a 223 for most of the deer that I have shot and have yet to have one get away from this gun. I have had one get away from a bigger gun due to poor bullet choice where after someone else shot it on the run with a shotgun-His deer I guess-Oh well. I believe this though about small calibers that you have to be more proficient at shot placement and be more selective about the shots you take. I also believe that small caliber weapons with the lesser recoil inspire better proficiency in more shooters. Keep in mind a deers head isn't much smaller than a gopher heck with a 243 you might be head shootin' them out to 800yds.