Hope he hurries up. My M&P 5" pro in .40 has a good day when getting a 5" group at 25 yds off a rest.There are a ton of posts on enos about the longslides throwing 4-6" groups at 25 yards and many even at 15. Never heard of that problem with a G17L or 34/35. Mine isn't that bad but I often wonder if the plate I just missed at 15 yards is me or the gun. I'm fairly good at calling my shots. This is mostly with the long slide versions ironically, the full size guns don't seem to have the issue as bad and neither do the .45s.
Randy Lee at APEX Tactical did his barrel specifically to address this. He claims if fitted perfectly 1.5" groups from a Ransom Rest at 50 yards are possible. It also sounds like he's pretty convinced it's because of loose tolerancing and modulus of elasticity of the barrel and slide steels. It's probably one of the reasons he's developing his own complete upper for the M&P line too.