Lee mold for a .375 H&H?

slug your bore to find what sizer u need, one tho over is most common. I would powder coat them, i that possible for you.what's the rifle you have, i am really thinking off getting a 375.

if it were me i would do .376

The Lee bullet isn’t ideal for the H&H or .375Ruger. It was designed primarily for the .38-55, a straight wall case with a short throat.

However, I’ve seen good results with it from my .375Ruger.
Seating it requires placing the base of the bullet below the neck exposing the lowest lube groove to the powder.
I lubed with SPG, and only loaded Unique. I started with 12gr and worked up to 16gr. I’m sure more would have been safe, but accuracy began to deteriorate so I stopped. I was just plinking and forming brass, so velocity wasn’t a consideration. I guesstimate 1,500fps at top loading.
Without a gas check, greater velocity with adequate accuracy is unlikely.

For just plinking or case forming, ect, the Lee bullet will work. However for optimum performance at velocities stipulated by OP, I’d suggest getting a NOE mold better suited to the modest necks of the Ruger or H&H.
I’m sizing .378”. As long as a loaded cartridge easily chambers, oversized is infinitely better than undersized.

But, a 255gr .375” bullet at 1,500fps will completely penetrate any deer. Shot placement is most important consideration.