HiPac striker springs.

June 25 2012 at 9:22 PM
robert  (Login gubb33ps)

New spring from Alex. Have to admit, he sent me this one as a freebie...but he knows I will call a turd a turd and can expect an honest testing. He happened to be considering this while I was playing with a shortened RWS 850 spring. We came out about at the same place and he offered to send one of the new springs for testing.

A new run of experimental greensprings.

Original Crosman spring: .03 wire thickness...... .10 coil spacing....1.92 OAL...135BAR
Old Green spring: .035 wire thickness.....065 coil spacing.... 2.20 OAL.....145BAR
New Green spring: .035 wire thickness......088 coil spacing....1.93 OAL....165BAR

Not really going to test the Red spring as it is too stiff to cock and too high a sweet spot pressure.
Red Spring: .046 wire thickness.....09 spacing....1.93OAL...210BAR

OK...here is the test gun. HiPac converted 5mm 2250. carbine (11.7 5mm LW barrel). About 44cc of air volume, so shot count isn't going to be long. Stock valve. All the same settings, just the spring replaced between tests. All using 13.5gr JSB) 5mm pellets.
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In case you like more numbers. On this carbine, the distance the striker travels from at rest on the valve stem to sear caught: is .55. That's all the stroke you're going to get with a stock valve, striker, and end cap.

Original Crosman spring:
135 90BAR
10 shots from 620 590fps = 605fps averqage / 11 foot pounds

old green spring:
145- 100BAR
10 shots from 650 620fps = 645fps average / 12.5 foot pounds

new green spring:
165 110BAR
10 shots from 675- 645fps = 660fps.average / 13 foot pounds

The good news:
With the wider coil spacing, is some room for pre-tension with the new spring and still get it cocked before becoming coil bound. The old green spring's narrow coil spacing would allow it to become coil bound faster. On an educated guess, believe enough pre-tension could be added to get the new green spring to run right at 170BAR (and a proportional increase in energy).

The EFFICENCY INCREADED with higher pressure. From 19.3bar/cc to 16.2bar/cc. There is room for better than this, and I hope to get it to about 12 or 13...but that would only be 2-3 shots more in a string.


1.Sweet spot pressure rose by about 20% and energy rose by about 20%. At least in the short run over a narrow range of pressure, it is staying proportional. Which means if I increase the sweet spot pressure to 184BAR (or about 15%) should see enery at about 15 foot pounds for about 10 shots.
2.Good shot count really didn't change. Will need to limit air use, reduce speed, in order to see a real increase in shot count. Easiest way to do that would be to restrict the transfer port slightly (so it would run at the same pressures, but spread the shot count wider at lower energy).

UNLESS you are really in love with the way you have your HiPac conversion tuned, give Alex a call. Try one of the new springs and let Alex know that the new green spring is an improvement on the old one. Could get close to the performance of the old green spring with the factory supplied spring. The red spring isn't going to work unless you find a way of increasing the distance by way of a longer end cap (or a shortened red spring). Either way. Using the red speing is like compressing a Jeep suspension spring by hand.

The new spring will gt your gun running right at something like 2400-2500psi without any major changes.

If I nncrease volume by about 50% (which can be done with HiPac extensions), then shot count would increase to something close to what the P Rod is getting. If I do that, would have all 3 carbines running on an even keel (different calibers and pellets, but the same basic shot count).

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