Spring gun tuning

[darren m]

At 11.8 FT.lbs, Darren, it's a bit too close for comfort.

What pellets are you using?

If you were using 8.44 gr pellets, just 7 feet per second will have you at 12.0.

Now, you can make the '80 much sweeter, depending on how far you want to go.

The '80, at 30mm bore, has a pretty hefty piston. If you reduced piston weight that would help. And if you were to reduce the stroke, that would also help.

However, if you generally like it the way it is, and just want to make it a little more refined, I'd be stripping it. Degrease, de-burr and polish. Fit a top hat. If the standard guide is a snug fit on the spring, you could stick with that. If not, an aftermarket guide that fits your spring nicely will help quieten things down. If there's room and if there isn't one already fitted, a piston sleeve will also help towards refining the firing cycle.

Then I'd be removing or collapsing a coil from the spring to get the power down. If keeping the piston weight and stroke standard, this may make the firing cycle feel a little lazier. But many prefer them like that anyway and the result will be a more refined shooting rifle that's safely below the limit.

Hi Tony -- yep I get your drift , using AA field 8.44 , strange 2 separate tins of same pellets gave different fps , one tin was about 5 yrs old and faster by 20fps , putting it even higher , but the second tin a new unopened tin of same pellet kept it at 11.8 level , both ran very well over 20 shots each tin.

cocks nice and easy , maybe a little bit lazy on firing ... going take it apart and look at the spring guide , just wondering now if its got hw77 internals like in a early forum post I read over the weekend.

just for reference how tight does the fit of the spring guide need to be when slipped into the spring , should the spring spin on the guide or should the whole lot spin on the block.

lastly re reducing the stroke , is it as simple as putting a tbt piston extension on to existing piston .

Thanks

[TonyL]

Hi Tony -- yep I get your drift , using AA field 8.44 , strange 2 separate tins of same pellets gave different fps , one tin was about 5 yrs old and faster by 20fps , putting it even higher , but the second tin a new unopened tin of same pellet kept it at 11.8 level , both ran very well over 20 shots each tin.

cocks nice and easy , maybe a little bit lazy on firing ... going take it apart and look at the spring guide , just wondering now if its got hw77 internals like in a early forum post I read over the weekend.

just for reference how tight does the fit of the spring guide need to be when slipped into the spring , should the spring spin on the guide or should the whole lot spin on the block.

lastly re reducing the stroke , is it as simple as putting a tbt piston extension on to existing piston .

Thanks

Hi Darren,

Re spring guide fit, opinions do seem to vary, but I like them to be a snug "friction fit". So, no slop. But not that tight that you have to virtually hammer the thing in! When the spring compresses, the ID does increase fractionally.

Re reducing the stroke, the two very easy methods would be to either fit the TBT extension or fit one of the Aussie seals, which are much deeper and also reduce the stroke. I haven't tried either, personally. The more involved way would be to have a longer piston rod made up, but you'll need to be knowing what it's made from and that it's properly heat treated, as you wouldn't want that to let go! ISP supply them for some guns, like the TX. Don't know if they supply HW ones? The other person to ask if you wanted to go down the longer rod route would be NickG on here.