Air Rifle Piston head Question

[ghostman01]

Hey guys,
I just upgraded my spring out of my air rifle and the piston looks like it could be replaced. So i took the old one off the top of the piston and saw that it had a sort of rivet shape to it, so i cut out some bike inner tube using a piece of pipe that is the same as the chamber and put it on the top of the piston and it went on in such a way that it was a cup shape. So i put it in the gun and then the spring and i put it back together and the power was just about the same as before ? Can some one please tell me an easy way to make a effective piston that has 100% seal and will work well !
the attached picture show what i have done
thanks

[Ragnarok]

In reality, the truth may be that it doesn't need replacing - they tend to get worn down a little, and because they slowly get worn to just the right size, it makes a very good seal. Their shape also tends to ensure that they get forces out against the walls to really give the best seal.

It's part of why spring air rifles need to get run in a bit to get to their peak power.

If you really need a new seal, consider buying a high quality one like from a brand like Maccari - it'll save you a lot of grief.

[ghostman01]

So with my new rubber thingo that i put on will work better than the old one ? or should the old one still work well?

[jackssmirkingrevenge]

That will wear out very quicky. Older spring piston rifles tend to have leather washers soaken in oil as a seal, while modern ones have a synthetic seal made of nylon, PTFE or similar. I suggest you buy a proper one, what make and model is your rifle?

Also, do you have a true scientific method of determining that the power is the same?

[Darkside 6ix]

Are you guys talking about a pump action pellet gun? Ive had mine for many years and the piston has never worn out on it.

[Ragnarok]

Are you guys talking about a pump action pellet gun? Ive had mine for many years and the piston has never worn out on it.

No, we're talking about spring piston air rifles.

or should the old one still work well?

The old one should still be working reasonably, although you might see a small improvement if you get an aftermarket seal.

Also, JSR has a point, how are you determining the power is the same?

[ghostman01]

lol by shooting a food can and seeing how far the dents go in its very scientific

JSR : its an old slavia 618. every were ive gone on the internet and in a car no ones stocks any parts for it. I had to go to a spring making company to get a new spring made up

[Gippeto]

Interesting! 8)

I have a couple of old Slavia's in the cabinet, a 622 and a 624. (.22 and .177)

Both use leather seals on the piston.

Possibly a cobbler might be able to help you make a new seal? Or at least provide some thick leather for you.

Edit: Soak your new leather seal in Neats Foot Oil overnight before you install it. This will make it "supple".

[ghostman01]

ok i might try to find some thick leather, ive only got thin stuff and ive tried layering it and that doesnt work. Today i sanded down a piece of rubber and put that in there, execpt i made it about 0.3mm to small so ill make another soon. Im also going to try and find some soft rubber or thick neoprene or something like that. Every where ive looked i cant find a single spare replacement part for it.

[ghostman01]

Well i made a piston head out of a solid piece of rubber and boy is this powerful !! I cant get an exact reading but using Ant's home made chrono method its saying im getting 800+ fps outta it ???? surely that cant be right. Every one else that ive seen on the internet that reconditioned their slavia 618 could only manage 300- 400 fps , oh well is powerful and accurate.

Another question is, can i make a piston outta dried sicaflex, you know the stuff you stick new windows in cars with. Ive got a big block of dried up stuff, That could work ?

double post i know !