Hi all I have two questions

1.
I'm in the process of customizing my 2240 and was wondering if there is a way of leaving my front sight on and still adding a silencer, as to put the UNF adapter on I had to remove the front sight.

2.
I have a Aimpoint red dot sight CompM2 4MOA 10338 240944 that I got when I bought a airgun and I would like to sell it, can anyone tell me what they go for second hand.

Cheers
Luke