Tazman, There are many many indoor ranges that employee plate steel deflection. With a 22 short you can get by with quality 1/8 plate steel but I recommend 1/4 inch which is what I use in my job as a gunsmith. You will never dent 1/4 in with a 22. You can get by with a little less than 45 degree but I recommend to stay at 45. To be the safest use sides on the backstop and you won't have to worry. Good luck Taz.