400 is correct,what ever he tells you you can take to the bank! Mono-block is not weaker than shoelump,in fact it is actually stronger, but the shoe lump simply "LOOKS" better, and both are more than strong enough. The mono-block if done properly, is exactly the same as the way a barrel is fitted to a bolt action rifle. The one piece MONO-BLOCK includs the reciever for both barrels, and the lumps as a solid peice of steel. This is fitted to the action exactly the same way all breach end of the barrels, and lumps are fitted to the action. with the hole drilled through the mono-block and threaded for about 1" while the rest of the hole is honed to a press fit for the barrel butts. The barrel portion that is not threaded, is fluxed, the barrel screwed into the mono-block, with about 1/4" of barrel sticking out of the breach end. The barrels are then brazed into the mono-block from the breach end. The barrel ends are then faced off to match the face of the breach end of the mono-block. I fail to see how that can be weaker than other methods. However, any method done sloppily is not acceptable.

You will not have to worry about punching a hole in a lion with the 450/400NE 3" That cartridge will "GET'ER DONE!"