Top Hat Material

Aside from possible wear considerations, sometimes the shot cycle benefits from more weight in the piston, sometimes from less.  If all you want to do is center the spring, it doesn’t matter much which material.

I use delrin, it’s lightweight and really slick especially when used with krytox. It’s also a really tough durable marerial that doesn’t come apart or gall , it machines easily and finishes very nice.

I haven’t had a reason to try brass as a tophat, I suppose if you were wanting a heavier tophat   then it could work. It also machines easily and finishes very nice, but I could also see it being more abrasive and possibly leaving small pieces of brass inside the receiver and or wearing against the spring and breaking down.

TMurray ? 

I think the Delrin would wear better, and like Thomas said, can be nice and slick.  They seem to fair well with steel springs.  I have seen some steel top hats in kits.  Some will try to balance fpe/pellet weights with adding and removing weight in pistons.  Also, claims that adding more weight in favor of fat pellets, such as 10+ gr in .177 for example.

?

Jason G