Well I answered part of my own question. Lyman, the company that owns Pachmayr, responded to my email about the weights of the grips. As I suspected they are HEAVY! Well the G10 ones are a little lighter than I thought, but still to heavy for the 13.5 ounce M&P 340 I want to put them on.
I will probably go with a set of laminates from Altamont. Most of them weigh just a touch over 1 ounce.
I will do the conversion for you since they used pounds in the email below:
G10 J Frame = 3 ounces
Renegade Laminates = 4.9 ounces!!!
It makes absolutely no sense to put a pair of 5 ounce grips on a gun that weighs 13.5 ounces WITH the factory grips! The factory grips are 1.1 ozs. So the gun weighs 12.4 ozs. With the Rengades the gun will weigh 17.3 ounces. That's a huge difference! The Rengades weigh over 40% of what the gun actually weighs. That's just silly.