Ballistics, ballistics... Given we are in the PNW, I would be pretty sure most of you who carry, use a "preferred" ammo for self defense. Given that the seasons around here vary fairly wildly, I would be pretty positive that most of us switch ammo from summer to winter. Winter ammo its a given to penetrate more layers of coats and/or clothing, and summer ammo, well. Not so much need for penetration of layers.. How many of you switch summer to winter, what do you use, and why?