Different size cylinders and power.

[Shed tuner]

I just think it's one of those rifles that has just got to be left alone in its original form, I'll get my summer holiday over with and think about getting another new piston seal (I know how to fit them now so hopefully won't bugger it up like the one I just bought) and a pump and return it to it's former glory.

Pete

I told you so

(sorry, but the Theoben elves are a tricky lot to battle against)

[look no hands]

I told you so

(sorry, but the Theoben elves are a tricky lot to battle against)

If I'm honest Jon I've not actually put that much effort into it, I obtained a spring that was recommended on another conversion thread I read and got some guides made up, if I had a better spring compressor and could force the whole Titan no14 spring in (I had to chop off 3 coils) then it may have got to more acceptable power but 9.5ftp with a monster spring that I had to fight to get in, just isn't worth a piss in a bucket and I'm not risking an eye and a couple of fingers to try and get those circlips in and out everytime, at least I can say I had a go.

Pete

[TonyL]

If I'm honest Jon I've not actually put that much effort into it, I obtained a spring that was recommended on another conversion thread I read and got some guides made up, if I had a better spring compressor and could force the whole Titan no14 spring in (I had to chop off 3 coils) then it may have got to more acceptable power but 9.5ftp with a monster spring that I had to fight to get in, just isn't worth a piss in a bucket and I'm not risking an eye and a couple of fingers to try and get those circlips in and out everytime, at least I can say I had a go.

Pete

Wouldn't it be funny if it turned out that it was oversprung, Pete?

And this may well be the case and certainly wouldn't be the first time it's happened.

Maybe, just maybe, before you decide to convert back to rammer, it may just be worth trying cropping the spring a little? If this worked, it'd give you a nicer firing cycle and make stripping / reassembly easier and safer, too.

[look no hands]

Wouldn't it be funny if it turned out that it was oversprung, Pete?

And this may well be the case and certainly wouldn't be the first time it's happened.

Maybe, just maybe, before you decide to convert back to rammer, it may just be worth trying cropping the spring a little? If this worked, it'd give you a nicer firing cycle and make stripping / reassembly easier and safer, too.

That could be the case but most of the conversion threads I've read (and talking to Tony Bigtoe as well) have said they needed a lot of spring, Tony in particular said even he struggled with the spring and wouldn't ever do another one, the spring is only sticking out the back of the cylinder about 2 inches, so there isn't masses of preload, one of the threads I was reading is HERE, an interesting read.

Pete

[Shed tuner]

Heavy pistons need a lot of spring to accelerate up to speed to make the pressure. If the seal is a bit below par too, it's not a great combination.

[Hsing-ee]

Heavy pistons need a lot of spring to accelerate up to speed to make the pressure. If the seal is a bit below par too, it's not a great combination.

Why do they make 'em like that? To stop people converting them to spring?

[Shed tuner]

Why do they make 'em like that? To stop people converting them to spring?

Yup, cunning plan. More likely is that the gasram accelerates much faster than a spring initially, because the intial gas pressure (when cocked) is so high, and also due to not having to accelerate the mass of the spring itself.

[look no hands]

Heavy pistons need a lot of spring to accelerate up to speed to make the pressure. If the seal is a bit below par too, it's not a great combination.

So what you're saying is, make a lighter piston and put a better piston seal on it (as well as putting the spring back in) and it will be much nicer to shoot and probably make power?

Pete

[Hsing-ee]

So what you're saying is, make a lighter piston and put a better piston seal on it (as well as putting the spring back in) and it will be much nicer to shoot and probably make power?

Pete

No, he is saying sell it and get a Diana Mod 38 Commemorative.

[TonyL]

So what you're saying is, make a lighter piston and put a better piston seal on it (as well as putting the spring back in) and it will be much nicer to shoot and probably make power?

Pete

Better piston seal will always help, Pete.

Lighter piston in a wider bore gun will certainly give quicker piston acceleration, Pete, but might not make it nicer / any more accurate as, depending on other set-up parameters, you're more than likely to get greater piston bounce, which is much more detrimental to better accuracy / improved hold sensitivity.

I've sometimes wondered in this scenario, however, if we went for an aluminium piston to reduce overall weight, but a nice, heavy steel top hat (idea here thinking of increasing the cross sectional density) if this may help?

Any thoughts, JB?


Of course, going back to the original flavour of the thread, at our power level, narrow bore is always going to be best.