Shooting left and I don't understand why

[Redhat]

If you can call your shots, I would consider changing the back strap to a different size. Also might try shooting with thumbs off the gun.

I think what's really going on is for some reason you are pushing left with your trigger finger or the fingers on your strong hand. Could be affected by trigger reach / finger placement.

[jwperry]

I had this same problem for a while; but it didn't matter what I shot, Sig, Glock, Hk, M&P..
Finally spent some one on one time with an instructor after a match. We found that my support hand was torquing the pistol too much. We remedied this by a)changing to a larger backstrap on my M&P b)raising my support hand a little higher on the pistol c)using my support hand thumb to place a little pressure where it was contacting the frame.
I then placed some skateboard tape onto the pistol(under the trigger guard and above the forward rail) to make sure I always gripped the same points.

I also found that I gripped the pistol differently coming out of a holster than I do when I pick it up off a table. The fixed, textured index points really helped for consistency.