Prosport preload

[charub]

Hi guys, my prosport is currently running at 740fps on its standard set up. I'm going to knock up a delrin top hat and guide. My question is how much preload should I be expecting to need to get it up to around the 780fps mark? I'm going to make the top hat the same length as standard.
Only after a ballpark idea, as I know it will be a case of trial and error.

I'm not really power hungry, just would like a slightly quicker lock time.

Thanks in advance.

[Murphy]

I think I put 5 or 6 thick ones in mine when I was experimenting while I waited for my Vmach spring.

But it shot better with the piston weight in rather than the spring pre loaded up IIRC.

[Phil Russell]

A bit of a guesstimate but if you keep the preload provided by the top hat and guide the same as you get with the standard parts ... try a washer at 2mm thickness first ... either over the top hat or on the guide.
Cheers, Phil

[PhatMan]

charub,

+1 on Phil's suggestion of ca. 2mm.

Have fun & a good Sunday

Best regards

Russ

[cooper_dan]

About 4 or 6mm (2 or 3 standard washers) made about that much difference in mine

[rapidresponse1]

4 in mine

[charub]

Thanks guys, i think I'm somewhere close now. The rifle is currently back on the bench awaiting the arrival of a new chrony - my little combro doesn't like this springer!!

[lensman57]

Give it about 4 mm to start with. Replacing the heavy steel top hat with light Delrin will also alter the behaviour of the gun with light and medium weight pellets.

A.G

[PhatMan]

charub,

Have you tried holding the Combro in place rather than rubber-banding it on ?

Holding the Combro onto the barrel this way turned my Combro from a useless piece to a useful chrono'.

Have fun !

Best regards

Russ