Short Stroking - Power reduction?

[JayJay-2008]

I have fitted a hurricane M100 upgrade kit to my ICS MP5 including the spring and am now a little dubious as to wether it's going to be under my sites limits. I've read reports that this spring can achieve power levels of 400 fps!!??

This led me to wonder wether short stroking would be a viable option for reducing the power rather than changing the spring back out.

I know that changing the spring would be by far the easier option but there are several reasons for looking into short stroking and I'd be grateful if someone could either confirm my theories or point out if they are wrong.

Possible advantages -

Less Power
Less stress on gears during firing (Shorter stress period)
Faster ROF (though marginal)
Less degradation of the spring through compression within the G/Box

I'm kinda on the fence really which is why I'm asking the question so I'd be grateful for any advice at all.

Thanks

Jay

[sj_asc]

Re: Short Stroking - Power reduction??

None of the four points are wrong, but you should not need to worry about 2 and 4, the spring in particular, should not continuously degrade after being bedded in.

HurricanE springs are very much similar to Systema's in that they can be way off what they are rated, at least before they've worn in. I do however very much doubt that you will be nearing 400fps with that Spring in an MP5, you could resort to short stroking if you are in doubt, but it would be far easier to use a different spring.

Short stroking will reduce the muzzle energy, remember that the piston release tooth has to be the metal one, such modification would be easier done to a piston with the more than one release tooth. For sector gear teeth removal, remember to take from the initial pickup side, not the release side.

If it helps, these are some results i noted down in testing when building my setup last year,

Spring: Guarder SP100 (non linear)
Piston Assembly (16g): G&P Piston + Head + Viton #117 O-ring
Barrel: TM 247mm 6.08mm (stock)
Cylinder: Systema HS Teflon (Type 2 or 4/5 port)
Grease: G&P Cylinder Oil
Hop Bucking: KM RH45 w/RH65 spacer
All other air seal parts stock
Stock flat base spring guide
No Piston/Cylinder head spacers used

G&G 0.20g Tracers used
Guarder Chronograph used
Hop set to approx 30m
Approx 20 shots fired before 5 shots taken for averaging
Stock spring on full stroke averaged 291fps

SP100:
Full stroke: 391.2fps
-1 tooth: 376fps
-2 teeth: 358.6fps

[JayJay-2008]

Re: Short Stroking - Power reduction??

Thankyou for the quick reply.

I'd already suspected that it'd be easier with a piston such as the G & P Reinforced one with several metal teeth.

And yes it does help thanks, it means that I'm headed in at least the right direction.

Thanks again for the fast reply.

- Jay

[russelp]

Re: Short Stroking - Power reduction??

Sniperjesus, what kind of ROF increase did you see after removing 2 teeth?

[sj_asc]

Re: Short Stroking - Power reduction??

Sniperjesus, what kind of ROF increase did you see after removing 2 teeth?

I wasn't testing for ROF in that setup, but from what i can remember it wasn't a massive improvement, id say 100rpm at most, bear in mind that i was using an EG700 motor which