HW77 cocking issue?

[Gecko]

Stripped my 77 to fit one preload washer but after putting back together to cock the gun i have to pull the lever very hard for it to engage.
Looks like the latch is going far enough back.

Ive shimmed the front stock screws to rule out the cocking arm catching the screws.

Edit - looks like the preload washer is slightly larger then the OD of the spring could the piston be catching the preload washer?

[Gecko]

Ok stripped the gun and removed the preload washer and it cocks fine.

[bhodge]

Was the washer particularly thick..i.e. more than about 1mm?
What kind of power was the '77 putting out before you tried the extra washer??

[Gecko]

Its was doing 9.3 with exacts.
The washer i fitted was 3mm but there was also a 2mm washer so 5mm total.

[MattyBoy]

Washers must not be more than 20.6mm diameter

Hth
Matty

[Gwylan]

Washers must not be more than 20.6mm diameter

Hth
Matty

Why's that Matty? does the piston go so far back it fouls the preload washer?
I assume the OP isn't putting the washer behind the spring guide, that would muck things up.
other things that could cause reduced power are a damaged or tight piston seal, or leaking breech seal.

Gus

[JLB]

Adjustment washers need to be roughly the same diameter as the spring if your putting them on the rear guide, if larger & you have too many, the rear of the piston will hit the washers before the piston rod engages the sear.

John

[bigtoe01]

Why's that Matty? does the piston go so far back it fouls the preload washer?
I assume the OP isn't putting the washer behind the spring guide, that would muck things up.
other things that could cause reduced power are a damaged or tight piston seal, or leaking breech seal.

Gus

the washers have to fit inside the piston regardless of whether they are fitted to the rear or front of the spring.

[Gecko]

I think the spring is quiet short as i dont have to put any pressure on the rear block to screw it in.
It needs a tophat as there isnt one fitted so i may just get a delrin tophat first before putting any preload washers in, as the 77 is an open sighter im happy if the power is 10.5ftlb.

[Gecko]

So currently its doing 9.3 with exacts and no tophat im aiming for 10.5 to 10.8 what thickness should the rim of the new delrin tophat be to roughly to get to the desired power levels?