I tried the steel breech for it bit,and if you're going to leave a scope on it,it's a rock solid setup. I went back to the plastic breech, just because, it only takes a minute or two to flip that rear sight to peep,and put the carbine stock on it.Pistol to carbine in minutes,or vice versa ...works for me.
Yes,the original rear sight can be flipped from notch to peep.(don't lose that tiny screw!)lol As my eyes have changed with time,I had read I could drill it out a bit bigger. It worked. Not much bigger, and it helped.