I did try .308" Hornady 220gr. RN's in my 2-groove #4 as I thought they might flow out to fill, due to the exceptionally wide lands displacing metal. Didn't work - lousy accuracy. That barrel is .315", from one groove to the other one.

It does shoot 174gr. Hornady's into 1 1/2", though.100metrs, battle sights.

I had rechambered it to Ken Waters, .312 Express, although mine is .315".

Using necked down .350 Rem Mag or 6.5 Rem Mag necked up to hold .303 bullets, I drive those 174's (Re#19 - or is it Re#22?memory on some stuff sucks) at 2,960fps and they shoot quite well indeed.