My Ackley likes RL25 and a full case of it, light crunching if I don't pour it just right. I've never had a reason to try Retumbo but I will keep it in mind.
Last night I tried RL25 in a 6mm06 and it actually slowed down with higher powder charges. Leads me to believe its a bit to slow of burn rate. But it works so well in my Ackley I thought I'd give it a try.
If your looking for all our barrel burning velocites w/ the bigger slugs, the 6mm-06AI is the top dog here. Can push the 115's to 3400-3500fps. Also you can neck down/fireform lapua and nosler 30-06 brass! Everyone always has something to say about not having great brass available; however, there is uaually a great alternative. I am contemplating this build, although barrel life would be probably 1500+ max, BUMMER! However its the best, if you want more range, go w/ the 6.5mm or possibly the .257 catridges.
ALSO!!! the .243wssm is cathing on quite well, it's ideal in the 75-85gr range!
I have owned most of the ones listed ,Go with the 6mm remmy, if you reload it will run around 120-150 fps faster them the 243 and seams to last longer too.
RL-22 works great in it. has a long neck like the old trusty 222 remington.
Thanks guys, you have given me a ton of insight. At the moment after doing lots of reading and considering the suggestions I am leaning towards the 6X47 Lapua. I like the fact that I don't have to fireform, I can use Lapua Brass, Barrel life will be pretty decent, and it appears to be getting a good reputation for easy loading and accuracy. The 243AI is a close second right now.
So now here is two more questions. I am at 3500' in elevation, and want to know what twist rate to order. I know the 1-8 will stabilize the 105-107grn bullets, but will it work with the 115's running 3000-3100fps? It seems like a lot of guys are using 1-7.5" for the 115's. I am not dead set on the 115's, but it would be nice to have the option. My problem is I think all of the people that make pre-fit savage barrels only have 1-8 twist. Also finding one of these "pre-fit" makers with a 6X47 Lapua reamer is a little tough too.
Who should I order the barrel through and what twist if I get the 6X47 Lapua?
You still have the HUGE problem of sporting a long action.... the 6X47 isn't going to feed well because it's so short... why not sell it and buy and ADL from wal-mart.... then everything would fit correctly. If you're going to spend the moeny to build the rifle, you should at least have the appropriate action.
I love the 243 (from a match/tactical standpoint) and the 6X47 is a good choice too. Each in a short action of course.
I have at least 20 hot 6mm's. Have built all the hottest stuff out there through the years and all the stuff mentioned here except the lapua. The 240 gibbs is the hottest thing you can get with barrel life and accuracy before you get to diminishing returns. It is all you can get out of a blown out '06 case. Dies are easy to find and easy to fireform cases. 240 wby and 6mm-06 AI are next. It is really hard to beat the 243 AI but it is a little slower than the big '06 case stuff. You have a long action so you could do any of them. I have never built a 243 AI that didn't shoot like a dream. It is a fantastic round with easy to get components. I built a 240 wby with a Hart barrel for my wife and son to hunt with and it is a one hole rifle that is screaming fast, 1" groups at 300 yards are the norm. Super easy to load for but expensive brass. 1-8 twist will work fine. You really couldn't go wrong with any of them but considering your criteria I would do a 243 AI.
Predictions are difficult, especially when they involve the future