Some time ago I had this rifle apart and there was a delrin seal that corresponds to part #S610H. Rifle is the s510 x-tra FAC.

Thank for the reply, Rog.

I was concerned that my transfer port seal may need replacement. Looks like a fun job, but I have to order the delrin seal.

Lou

Hello, I just changed the barrel (breech) o-ring on the .177 caliber S510. This stopped the air blow by coming out through the magazine well, but there is a puff of air coming out of the rear holes on the shroud. Is this normal? Thanks for any replies.