I'm new to DA and just picked up a S&W PC 625. After two trips to the range, roughly 80-100 rounds fired, I am stymied. I am finding the firearm to be painful to fire. The pad between my thumb and index finger is sore... and then some, after just a few rounds.

I have medium to smaller hands. The frame is an N-Frame and I changed out the grips to the Miculek grips from JM's website. (the original were too colorful and very wide front to back) I am loading 200gn SWC with 5.2gn of W231. Not a light load, not a heavy load. (I had no problem with this load when used in a 1911 platform and have shot thousands of similarly loaded 45 colt rounds, 255gn SWC in a Ruger NV SA, and found both of those firearms pleasurable to shoot once technique was acceptable)

My suspicion is my grip technique is not proper, and doing the grip buy&try without focusing on technique first will not yield a happy hand or wallet. Any advice or links that show best grip form would be appreciated, I've googled around quite a bit and see lots of advice on which grips to buy, but little that talk about technique to solve this problem.