Old Cop,
The cheapest LE discount I have seen on the M&P 340 Model# 103072 ( No Lock ) is $615. The bullet pull was only on the AirLight with the Scandium Frame and Titanium cylinder. S&W advised using 125gr or heavier bullets, if I remember correctly they also said no lead bullets, jacketed only. The problem occurred mostly with the lead bullets and the lighter 110gr ammo.
The weight for the 340PD 11oz, the M&P340 13.5oz and the 442/642 at15oz.
Speer GD makes a 135gr Short Barrel in 357 magnum that is pretty mild to shoot compared to the 125 or 158gr loads. They also make a 135gr Short barrel in 38+P.