Mike:

I sent my .500 Merkel to JJ at Champlin's and he installed a recoil reducer and recoil pad. I loved the LOP, so I had him cut the stock to compensate for the recoil pad.

There is a noticable difference after installing this!

At the DRSS hunt, I held my .500 in one hand and jjs' .470 in the other and the .470 actually felt like it weighed more! In looking at the rifles next to each other, we guesstimated that Merkel uses the same exact barrels for both the .470 and .500 - with the .500 having more metal taken out of it for the bore diameter of the larger caliber. Because of this (the .470 having more metal in the barrels) the .470 weighed more. (This is just a human estimate and not based upon scale measurements.)

Also, 400NitroExpress at the DRSS hunt stated that he heard that the weight in the butt stock in some of Merkels came loose and could be heard jiggling around. I have not experienced this nor heard of it happening anywhere.