There are three things that you need to do to fix your flinch. Get a hold of an accurate .22, and carefully shoot a couple of bricks of ammo. The other two things have to do with what caused the flinch in the first place. I am always amazed at how many fellows seem to feel that their manhood would be called into question if they took adequate measures so that the sound of their rifles firing was reduced to the point where it was not a factor in their shooting. In short, you need to start using double protection, high db rated foam plugs, under your ear muffs. The second thing is to realize that there is no shame is using additional padding at the shoulder when shooting at the range. I never shoot anything that has any recoil without extra protection, because I have a lot of time and money invested in my benchrest hobby, and I do not want to mess that up with a flinch. For me, a strap on pad has worked well (magnum version). Lacking that, a sand bag of the appropriate size and shape. This idea that the pain and noise are things that require manly endurance is at the root of your flinch problem. When the sound of your rifle's discharge is sufficiently attenuated, and the sensation of its recoil reduced to a shove, you will be well on your way.