This new load is designed ONLY for certain firearms. They are as follows; Ruger Red Hawk, Ruger Super Red Hawk, Ruger Super Blackhawk or Vaquero, Freedom Arms Model 83, Taurus Raging Bull, Colt Anaconda and Dan Wesson Revolvers.
From the Buffalo Bore site regarding 44 Mag +P+ 340 Grain. I know at one time Buffalo Bore used Hornady for their pressure testing. With the demand of ammo these days I'm not sure that is still the case. I have used this and had no problems. It also states that this WILL NOT work in SMITHS. I use this in Redhawks, and Super blackhawks. I've had no problems. Having said that outside of Alaska and some places in Canada and Montana, Idaho etc, I see no purpose to use that heavy a load. Years ago I used a lighter 328 grain Hard cast lead bullet in my 44 and it would shoot through both shoulders of a moose. Not nearly as hot as the 340 grain. Even in Idaho I doubt I will use that round, although I still have some. People leave the extra time a heavy load takes to recover and get back on sight, and deliver another round as part of the whole self defense question. Good bullets (hard casts) do not require high velocity to perform. IMO