6BR vs 243 vs 243AI

[MattR]

I'm going to rebarrel a Savage target action in something in a 6mm, the BR looks pretty cool but is it really any better than the 243's? I guess is there enough of a difference between the 3 to justify the added expense of the BR?

[Colorado Osprey]

The BR is the slowest of the three.
All within a about 100ft/sec of each other with the 243 in the middle and the AI as the speed demon of the ones mentioned.

At 1-200 yard ranges the difference is minor. Get out to 300 yards and the bullet drop difference with the same bullet is about 3" between the 3 cartridges mentioned.
Stretch that out to 600 and the bullet drop difference gets up to 16" and at 1000 yards jumps to almost 70"!! (Berger 105VLD)

Being slower as well as a steep shoulder the BR should get you the best barrel life with the most accuracy potential from pure case design.

Obviously is using high quality Norma or Lapua brass all 3 can have excellent cases.
If you go the BR route make sure your gunsmith chambers it for the brass you intend to use. Remington and Norma are different than Lapua in chamber specs.

Personally I went with a 243 because even though Lapua brass is more expensive than 6BR Lapua brass, the precise case dimensions does not seem as finicky in the 243. The short fat cases with the steep shoulders seem to need higher quality brass. Factory ammo availability is also much greater in the 243.

Another one you might consider is the 243 WSSM. It will out perform both the 243 and AI, same length as the BR.

[Hoser]

Take a look at the 6CM.

It is a long 6BR or a 243 Ackley with a 30' shoulder.

The nice thing is you can use real slow powders like H1000 to save the barrels throat, the 30' shoulder still feeds through mags and the 30' shoulder keeps brass growth down to a dull roar compared to a normal 243.

And 115 gn bullets are cheap and dont recoil much when compared to the 6.5 142s.