How fast can a cast BTB in a .375 H&H bullet be ran?

It would be in a .375 H&H with a Lothar Walther barrel and a 1 in 12 twist. It would be a BTB and sized correctly for this rifle. Supposedly the LW barrels have a very smooth bore.

Can one be ran to 2700 to 2750 fps without leading, or what would be a practical limit?

Allen

A lot of things are possible in concept but not in practice. Normal cast bullet speed limits are around 2,000 fps. Smooth barrels with wide, deep grooves help.

Special alloys and methods can exceed that but it's hard to accomplish with acceptable accuracy. Accelerating bullets faster simply puts too much stress on the bullet during acceleration for it to hold the rifling. Faster bullets usually strip out of the grooves.

It was the introduction of harder copper jackets that allowed us to achieve todays velocities without stripping.

I've had no trouble achieving 2400 fps with a .30-'06 with relatively slow powders, gas checked bullets, NRA 50/50 lube, and a smooth barrel.

I intend to do some .375 H&H load development work this summer and fall. I have shot light loads in the 1200 fps range with the Lyman 375248 (~250gr plain base), but recently bought a 375449 (~270gr gas check).

There are a number of threads on the Cast Boolit board which describe velocities of 1800 and 2000 fps:

http://castboolits.gunloads.com/showthread.php?t=6281&highlight=375449
http://castboolits.gunloads.com/showthread.php?t=7008
http://castboolits.gunloads.com/showthread.php?t=6182
http://castboolits.gunloads.com/showthread.php?t=21385&highlight=375449
http://castboolits.gunloads.com/showthread.php?t=31743

CDD

I wouldn't hesitate to work up to 2700 fps with hardcast, gaschecked bullets. Oven treated wheelweights should come in at about 30 BHN and with gaschecks should be able to handle the pressure and velocity. Beartooth bullets are 22 BHN and could work as well. I've never driven them that fast, but Marshall has approached 2300 fps with some of his loads. I would guess that 2300-2400 fps is about the limit of a 22 BHN cast bullet.

To get hard bullets, I cast from wheelweights with a couple percent Tin added, and then drop the bullets from the mold into a 5-gallon bucket of water. This gets virtually all of the benefit of oven heat treating, with the benefit of aiding material handling: by the time the bullets reach the bottom of the bucket, they are slow enough and hard enough that they don't get any dings from hitting the other bullets.

CDD

Water-quenched wheelweights with a couple of percent added Tin is likely to be about 18-20 BHN. This hardness is fine to about 2200 fps, but if one is striving for 2700 fps it may not be hard enough. Oven-treated wheelweights with a couple of percent added Tin yields about 30-32 BHN which is needed to accommodate the forces exerted on the bullet at 2700 fps.

Call Marshall and ask him. I've been running his bullets at 2300fps in my .35 Rem, no problems at all, and other people are going faster than that. He can give you a definitive answer of how fast the Beartooth bullets can go.

I would not be surprised to hear that you could run full jacketed velocities in the .375 H&H.

One more neat article on the .375 H&H with cast bullets.

http://hgmould.gunloads.com/casting/castinthe375hh.htm

Over on the Cast Boolit board, there are people who talk about velocities up to 2700 fps. I have not shot bullets that fast. One lube that is highly spoken of for such high velocities is Carnauba Red available here:

http://www.lsstuff.com/lube/index.html

Added heat may be necessary to make the stuff flow through a machine.

CDD

water or oven hardened wheelweights are fine until the bullet hits a constriction like in a rifle barrel and then they revert to their old soft self
This is my experience yours might be different.