While I have a couple .303's, an old #4 with a virtually new condition .315groove diameter 2-groove barrel that shoots into 1 1/2" at 100 meters, 174gr. Hornady's with it's metallics, along with the #3 that really isn't mine - yet.
I've never hunted with a .303.
Actually, I just mailed a box of 174's to a friend down in Castlegar, B.C. as he couldn't find any for his kid (I think).
So- I've no .303 bullets.
Were I to use it for moose, it would be with the 170gr. RN. in the #4. Might try the 180's instead, hoping for a tougher jacket.
Oh yeah- it's no longer chambered for the .303 Brit. It's now a .315 Express, I think Ken Waters called it .313 Express. Chambered for a necked down .350 Rem Mag. It easily does 2,840fps with that 174gr. bullet with the top load @ 2,940fps - and the 1 1/2" accuracy I noted.