Extending piston

[32:1]

As I’ve found decent changes with these SS nose jobs, I now want to try doing it the longer piston route to see if that longer spring room is any better as claimed.

Id like to ask if I could be pointed towards anyone who could cut and weld an extension to this 400 piston keeping it straight and safe, one thing I don’t have is anyone welding stuff. I wish I could load an image to show what’s needed, but it’s either a section of piston or just the latch pad

Chris

[TonyL]

Ah, yes, I think I can picture it. I hope you can find someone who might be able to assist.

[ashf9999]

For that type of welding, I’d suggest laser welding, as that can be used with precision and doesn’t cause excessive heating to one side and pulling things over. If both sections mated perfectly with a slight bevel on the outer edge, orbital welding is a possibility.

Carrs Welding in Kettering are excellent. They are also used to dealing with firearms welding repairs.

https://carrswelding.co.uk/services/

[Shed tuner]

are these rodless pistons ?

If so, might be easier to cut the piston in half thru the centre, and then weld in a tubular piece in the middle, retaining the "interesting" freatures front and rear. Then just machine out the cocking slot and smooth out the weld joints.

Much less to go wrong doing it that way...

[Waddy]

are these rodless pistons ?

If so, might be easier to cut the piston in half thru the centre, and then weld in a tubular piece in the middle, retaining the "interesting" freatures front and rear. Then just machine out the cocking slot and smooth out the weld joints.

Much less to go wrong doing it that way...

That's what I'd do too. The middle part of piston skirts tend to be a slightly smaller diameter than the front & rear. I think a decent welder could weld something like that, just needs spot welding at 12, 6, 3 & 9 o'clock to keep it straight. May need a quick spin in a lathe to take any excess weld off afterwards.

Adding another latch hole rear of the skirt would be the simplest solution, but would the metal used be hard enough not to wear extremely rapidly ?

.

[32:1]

Thanks lads

The piston has an extended latching pad which I thought I could just trim off and add another section to extend it, or cut piston inbetween the cocking slot end and the end of the piston so both welds were much bigger contact areas.

Cutting middle of piston would work too and need the cocking slot cut through added piece and the welded up so as cocking arm pushed piston back far enough to latch, my only issue there is trying to clean up the inside that far down ?

I’ve another piston to chop up if needed or just add the extra bit to existing latching pad so it’s just one small weld

[32:1]

For the experienced, is there a link between piston weight and diameters to counter bounce

[Shed tuner]

For the experienced, is there a link between piston weight and diameters to counter bounce

roughly yes, as the force fromt he air pressure building up is proportional to the surface area (ie to the square of the radius), assume the actual pressure is similar (for a given calibre / pellet).

Assuming the stroke and port are roughly optimised (if too long, you will need more weight, same if port too small), and extrapolating fom the sweet spot 200g for a 25mm gun - less well tuned guns will need more weight.

[Shed tuner]

[TonyL]

Brilliant information as ever, Jon.