Those of you who own and use a 6.5-06 Improved....what do you find to be the best projectile weight and load for shooting out to the 300-400 yd mark?
Mine is a model 70 in 265 RCBS with a 24" barrel.

Roger

Subject to what you're shooting at, paper or game, I use 120 and 140 gr. bullets. Sierra bullets gave the best accuracy on paper. Nosler 125 and 140 gr. partitions worked well on game such as goats, sheep, and deer. I could not discern terminal performance difference of the 15 gr. differential of the Nosler bullets. All game taken was less than 200 yds. The game taken were on animal control hunts so there was a relatively fair sampling.

Almost any bullet will work well out to 400 yards.

I'll assume you're shooting big game with them??

The 140 Berger elite hunter shoots really well out of my rifle (6.5 x 280AI) but I'm not cracked up about the performance on game although I've never lost an animal with them.

The 124 Hammer Hunter looked good so I tried a few and found they measure more perfectly than any bullet I've ever used. They're a mono-metal bullet so they're long as most 140's. Velocity and terminal performance was great and accuracy is stellar.
It's now my go-to.

Fortunately there are tons of bullets from which to choose in the 6.5 diameter so you can have some fun and find what works for you.

Zeke

I use 120's in my dozen to fifteen different 6.5 cartridge rifles. That includes my Gibbs and 264 mag. Often a Rem corlok in the 260 size case, and Nosler solidbase ( if you can find them) in all the larger case 6'5's. Deer, pronghorn antelope and caribou for game taken with them.
I used to shoot some 129 Hornady, but they were never as accurate as the various 120's I used, and never did any better on game.

For target work mine has done the best with Hornady ELD 140 and 147 gr. The 147 seems to edge out the 140 by a little in accuracy out to 700 yds. As far as a game bullet I use the 140 Partition it gives good hunting accuracy out to 400 or so. My rifle seems to like H4831 for best accuracy but I don't push it too hard everything seems to like to run at about 3000 fps.