Thread: Best projectile type for metford rifling?

I'm reloading for 7.7 x 58mm Jap, trying to develop a good load for one of my Arisaka's, which has metford (polygonal) rifling. Does anyone know the best projectiles to utilise for this sort of rifling? Barrel length is 25.9" with 1:9 1/2" twist.

I've tried the Hornady 150gr SP and Sierra 174gr HPBT match with average results.

Cheers,

D

Slug the barrel and see what size groove and bore diameters you are dealing with, nothing will shoot well if the barrel dimensions a over sized

All my metford barrels are worn so I have found slightly oversized gas checked cast 200gn projectiles to shoot the best.
All on lee's though if that affects anything

Avoid boat tails, flat base bullets set up best. I would be suprised if the rifling pattern is true metford as that was designed to minimise sharp edges that would trap black powder residue and was quite shallow and couldnt stand the heat of cordite so soon wore out. Anyhow slugging it is excellent advice, Ive heard that later production had quite generous tolerences.

yes slug it and show us the result... very interesting. My mate had a lee-metford and I thought the rifling was just plain buggerd BUT maybe it was polyagonal. I think the old style round nose flat base bullets shot best out of it.

Is it true polygonal rifling fouls easier with straight lead projectiles?

I think I read somewhere this is why you can't use cast lead projectiles in a glock?