I have a rock-ola M1 carbine... the barrel band has the bayonet mount on it, and the part were the screw tightens it is broken. I found an exact match to replace it with but I cant figure out how to put it on. I pulled the front sight off thinking it would slide right on..... but there is a notch that keeps the front sight centered that blocks it from slipping on. Is it possible to change this part out ??? any help would be great.