the stock rear site doesn't fit the steel breech. but there are numerous peep, notch, red dot and scope options given that the breech is grooved. I think the breech makes the gun more accurate, because the barrel is more rigidly attached. I don't think it improves fps. I did flat top piston and valve mod and did get a significant fps per pump increase. I added a longer barrel with the steel breech. probably would not have attempted that with the plastic breech.