I am curently shooting bullets that are .003" to .005" smaller than the groove diameter of my 9.3x57. I puts those bullets into 2" approximately - that's 2 of each bullet weight - 270, 286 and 293gr. Each bullet weight 'group' has the holes touching or almost touching. I'm quite tickled with that accuracy.

I agree the grooved depth isn't the problem. Some rifles can be a mite finicky about ammo and more than one 'make' might have to be tried.

John Barnsenes did an article on the Ruger #1 .303 (August Handloader) and got splendid accurcy - sub inch with a few loads I think. Even the factory stuff was good.

The MOST interesting information - for me, was that Nosler .308" pattitions usualy shoot reasonably well in .303's due to base obturation. That is a bullet I need for serious hunting with my #4. It has a .315" groove depth - 2 groove in what basically looks like a brand new barrel.

180gr. @ 2,604fps, 150gr. at 2,804fps, 125gr. at 2,900fps, 220gr. Nosler at 2,170fps. No flies on the old girl.

Bastically .308 Win. factory-level loads.

He noted his Ruger barrel had 6 grooves - .302" bore and .313" groove & that it appeared to be lapped (bore scope used).