I'm pretty sure they are the same lenght,both will handle 375H&H size rounds.

The 8400 long and short is pretty close in size to the M70 long and short. The little 84M is much more trim than a M70.

I have had problems with some of the Kimbers in the first couple of years of their production,but I have two now,one 338 mag and one 257 Roberts that are very nice.