The rifle has more to do with accuracy but the 308 and the old 222 were two of the best. All other things being equal the 308 is about as good as it gets. The 6.5x55 is another round that more than holds its own. Again with all other things equal. The Swedish mauser rifles had a lot to do with that cartridge being as accurate as it is. No other caliber of its size that I know of can equal the 6.5x55 when it comes to taking down Game. It kills way beyond what its ballistics say on paper.

I agree with the 308 Win. Very accurate and reliable with substantial knock down powder.

I will vote on the 308, but i have seen many different calibers in many different rifls shoot absolutely awesome, on the other hand i have seen much of the opposite too.

Sure I think there are many inherently accurate cartridges out there but you won't see the difference unless your comparing identical rifles and even making identical rifles is pretty much impossible. I think pretty much anything made on the 308 case the 250 savage case, 270 win,300 win mag,300wsm, the ultramags can be extremely accurate and shouldn't be too hard to work up loads for. I am not getting into benchrest cartridges because I know nothing about them other then stubby cartridges do very well.

I think the PPC's are more accurate overall than the .308, but there is no such thing as THE most accurate cartridge. There are a lot of other factors involved besides just cartridge design.

how does expansion ratio fall into all of this. You know the ratio of case capacity to bore diameter.

I have no idea on the accuracy of the statement, but someone once told me that the 222 rem, 308 win, and 458 win mag all had similar ratios.
Don't holdme to the truth in that, I don't know.

There is something to be said about larger diameter bullets being more accurate due to flaws of the same size having less of an effect on the overall performance due to less of a percentage of overall size.

The 270 seems to be one of the more easy guns to get to group really tight..but it is a long action. I been shooting the 7mm-08..love the recoil and the groups....its hard to go wrong with the 308 family. Have shot a 7mm mag that grouped extremely well all day also. I think its more gun and shooter than caliber. Although some will always stand out. I can also vouch for 222 accuracy....will shoot same hole almost all day.

the 308 is the most accurate cartridge. if you want more power i think you should go with 338 winchester mag or the 300 winchester short magnum.

if your talking any cartridge i would have to go 17hmr. it can shoot the tightest groups Ive ever seen. big bore i would say 308 338 lapua mag

I wonder if there isn't something to the dimensions of the .284 winchester case... I don't know about the accuracy potential of a .284 winchester rifle, in fact I've never seen one, but the 6.5/284 seems to be a big hit, and the 7.5x55 Swiss cartridge is a very accurate cartridge, (or maybe its just the rifles or a combination of both?) is pretty much the same case dimensions with a .308 bullet. (You make 7.5 Swiss brass by necking up a .284 case.)