Ailing Airsporter

[Hsing-ee]

Cocking the gun with the loading tap open and then closing it produces a hiss as air is drawn into the vacuum created.

Suggesting to me the new replacement piston seal is doing its job.

As you say the swept volume alone should produce over 11ft/lbs.

Hell,I've got a couple of sixties Meteors,.22 and .177, both nudging 11.

The seal might be good but one Mercury I had was the same, a good seal but the friction of the O ring was slowing the piston down a great deal. The other thing is that sometimes they can be over-sprung, causing piston bounce which reduces power. It's a conundrum to be sure. The game is not helped by the unpleasantness of stripping them and building them, always found them the most difficult to re-spring due to the odd shaped back block and the amount of preload they have.

[mallyally]

my mk 2 does 100 fps less with jsb pellets than it does with superdomes its .177

[Shed tuner]

my mk 2 does 100 fps less with jsb pellets than it does with superdomes its .177

yup, seen that on an old HW35 too. Bore/tap fit is critical, especially on older guns...

I'd defo try supersomes as they are very much on the large side of .177 !

[piggy589]

yup, seen that on an old HW35 too. Bore/tap fit is critical, especially on older guns...

I'd defo try supersomes as they are very much on the large side of .177 !

Remind me to dig a tin out,and .177 superdomes weigh? .

[LESS THAN FORTUITOUS KENNETH]

Superdomes 8.3. Superfield 8.4.

[wints]

Reading this with interest...I bought my .22 Airsporter new in 1973. I doubt if 5000 pellets have been through it in all that time. About 6 months ago I re-discovered it (actually grandson found it in one of the bedroom cupboards along with my old HW35), so started a bit of target practice in the garden.
With the Airsporter I probably fired off about 200 pellets and noticed the piston sticking, pull the trigger then gun fires after a slight delay, but then it got worse and the piston apparently jammed in the bore. The piston does gradually let go but doesn't fire. Prior to this malfunction I hadn't noticed any lack of power etc.
So, how do I go about stripping the Airsporter to look for what's jamming the piston?
The HW35 is still working ok, buts seems 'agricultural' in comparison to the Airsporter..and it's heavier.

Allen

[piggy589]

Good luck,you'll find masses of good advice and hands on experience here.

[piggy589]

The seal might be good but one Mercury I had was the same, a good seal but the friction of the O ring was slowing the piston down a great deal. The other thing is that sometimes they can be over-sprung, causing piston bounce which reduces power. It's a conundrum to be sure. The game is not helped by the unpleasantness of stripping them and building them, always found them the most difficult to re-spring due to the odd shaped back block and the amount of preload they have.

A friend who seems to have some success tuning older guns thinks it's over sprung.

He suggested fitting a lower power spring,but also adding a piston weight.

Sounds good,that trigger block is indeed a swine to fit.