stripping the 80...

[robthedog]

Got this last week, it looks like a sleeper guy has owned it a while & not been shot. Anyway i found the power was creeping up, so decided to strip it, never having done one before, fair bit of preload on it, & 3 weights in the piston, is this normal ?, gun doesn't seem to have been apart, everything was very tight. There is some slight play in the spring when in the piston should i make a sleeve & if so is an ally can ok to use ?

Thanks for looking,

Rob

[Rapidnick]

Got this last week, it looks like a sleeper guy has owned it a while & not been shot. Anyway i found the power was creeping up, so decided to strip it, never having done one before, fair bit of preload on it, & 3 weights in the piston, is this normal ?, gun doesn't seem to have been apart, everything was very tight. There is some slight play in the spring when in the piston should i make a sleeve & if so is an ally can ok to use ?

Thanks for looking,

Rob

There should be very little preload on an 80 spring. Also I'm puzzled by your description of 'weights' in the piston. Do you really mean weights or washers? A piston liner is often a good idea to tighten everything up and a lot of shooters use ally taken from a coke can. Be careful you don't cut yourself on the edge-it is very sharp!
Removal of the washers -I'm assuming you did mean washers-will certainly reduce power. The 80 is VERY easy to get over-I've chrono'ed quite few doing 18 ft lb especially older ones and especially .22. In .177 it is more difficult but the 80 is capable of 20+ ft lb in .22 so take care.

[robthedog]

Many thanks for the reply, washers is a better description, there are 3 in total, 2 are 5mm thick & one is 3mm, giving a total weight of 30 grams, so piston is 340g,+washers making the total weight 370g, i wasn't planning on putting them back in.
When i got the rifle it was doing 11.1 as an average of 10 shots with a high of 11.5. then after putting approx 200 pellets through it it now gives an ave over 10 shots of 11.7 with a high of 11.9. The rifle is in 177, & i was using aa express which weigh 7.8.
Think i will put it back together minus the washers & see what its like power & recoil wise. Thanks for the heads up re the cans being sharp.

Rob

[robs5230]

Got this last week, it looks like a sleeper guy has owned it a while & not been shot. Anyway i found the power was creeping up, so decided to strip it, never having done one before, fair bit of preload on it, & 3 weights in the piston, is this normal ?, gun doesn't seem to have been apart, everything was very tight. There is some slight play in the spring when in the piston should i make a sleeve & if so is an ally can ok to use ?

Thanks for looking,

Rob

Don't use an alloy can. Use steel if you must.
My preference is a HDPE plastic piston sleeve (Milk carton) as it make it quieter.
I'd suggest fitting a delrin kit and binning the weights. It will need the spring cutting and refinishing to be legal power

[maximus]

Don't use an alloy can. Use steel if you must.
My preference is a HDPE plastic piston sleeve (Milk carton) as it make it quieter.
I'd suggest fitting a delrin kit and binning the weights. It will need the spring cutting and refinishing to be legal power

Good advice above.

[robthedog]

Thanks for the advice, i have re finished the ends of the spring, but not cut any off it yet, it was legal prior to stripping it, but the power was creeping up

[Rapidnick]

Don't use an alloy can. Use steel if you must.
My preference is a HDPE plastic piston sleeve (Milk carton) as it make it quieter.
I'd suggest fitting a delrin kit and binning the weights. It will need the spring cutting and refinishing to be legal power

I agree with this but I know a number of shooters who do use coke can ally for piston sleeving. My experience with plastics is less than encouraging-it often just isn't strong enough . Even thin metal tears around the cocking shoe area on some rifles.
I think the OP is binning the weights as you suggest.

[robthedog]

Well couldn't compress it due to the preload, so took off 2 coils, now very easy to cock & smooth to shoot, but only doing 7.7 !, it must be the lowest powered 80 in the world !, should of left it to the experts...

So, tomorrow it can come apart again & i'll fit a couple of spacers & see how we go, at least there's not much chance of it creeping over 12 as it is !

[TonyL]

Sorry I couldn't join in earlier; a bit late now that you have shortened the spring.

I was going to suggest just using the 3mm washer that you had with the gun doing 11.9 with 13mm extra preload afforded by the three washers. It still may have been low on power, I'm guessing someone has shortened this spring beforehand. You could try, as you've said, to restore power by using extra spacers, but may not get there.

If you don't, ask Mr Tinners for one of his kits with the spring. That way you'll have a lovely top hat and guide tailor made for that spring and it should be lovely. Piston sleeve certainly a good idea.

Hope you get there.

[robs5230]

Sorry I couldn't join in earlier; a bit late now that you have shortened the spring.

I was going to suggest just using the 3mm washer that you had with the gun doing 11.9 with 13mm extra preload afforded by the three washers. It still may have been low on power, I'm guessing someone has shortened this spring beforehand. You could try, as you've said, to restore power by using extra spacers, but may not get there.

If you don't, ask Mr Tinners for one of his kits with the spring. That way you'll have a lovely top hat and guide tailor made for that spring and it should be lovely. Piston sleeve certainly a good idea.

Hope you get there.

Unfortunate.
My advice on cutting also advised installing a delrin kit and cutting to suit.

[where's it gone]

Don't use an alloy can. Use steel if you must.

Diet Pepsi is steel not ally.

[TonyL]

Unfortunate.
My advice on cutting also advised installing a delrin kit and cutting to suit.

Indeed you did, sir.

Also, and especially if going for a kit from a certain metallic bottomed person, it might be more than worthwhile contemplating a short stroke nose extension. Reducing the stroke and available swept volume will reduce its propensity to go over the limit and you can run "a little more spring" than you could with it at full stroke, making for a less lazy cycle?

[TonyL]

Diet Pepsi is steel not ally.

Off down to the supermarket with magnet in hand we go!

I'm sure I'd also seen that some Carling cans were steel?

[robthedog]

Once again gents thanks for your help & advice, you live & learn, & hopefully i can learn from my mistakes & your advice.

Regards,

Rob

[Shed tuner]

It's amost impossible to get an 80 down to 7 Fp unless there is something seriously wrong... any more than about 1/2" of preload and it'll be way over.

Check the transfer port - what size is it ? Clear ?
How tight/loose is the piston seal in the cylinder ?
Has the piston seal any nicks / splits ?
Is the breech seal leaking ?
What is the size of the spring, in terms of the wire thickness / length / number of coils ?

Also consider swapping to the new style "in the groove" cocking shoe - if you do fit a piston sleave (which you should; ally, steel or plastic), the new shoe will stop it being gouged up, and make cocking smoother.
Finally, as above, once it's sorted, a short stroke nose will make it much nicer to shoot at 12 FP