Hi, I'm planning on buying a rifle chambered to one of the 7mm mag. cartidges. Currently I've narrowed it down to the STW, Ultra Mag. or Lazzeroni. Do any of you have any experience with these guns. I can't find a good model in 7 STW but might get a custom gun. Can someone tell me what the practical, in the field differences are between these cartidges when using a 140 grain bullet.