Advice on decreasing FPS

[callum89]

Hey people

currently looking at getting myself a GSG-552 RIS MP5 blowback

But from the information I can find on it, the FPS runs around 400 and i'm curious if there was a simple way to lower it below 350 or if I am going to have to find another gun.

Help much appreciated.

[Fizzy]

Re: Advice on decreasing FPS

If i's firing at 400fps it will need the spring changing

[Sir Stephen]

Re: Advice on decreasing FPS

advertised FPS is more of a guideline anyway. only way to know what you need is to buy the gun, then test THAT gun.

once you know what fps it is, you can work from there. it might already be under 350.

if not an m90 or m100 spring and good airseal will be all you need.

[JCheeseright]

Re: Advice on decreasing FPS

buy it, chrono it, if it needs a new spring put one in.

Or, if you're buying from Z1 (who are of course the only retailer) ask them to put a new spring in for you.

[Figjam]

Re: Advice on decreasing FPS

did a quick google, the only UK retailer I could find was quoting 360, and the first EU retailer was quoting 375. Retailer FPS estimates are usually pretty inaccurate, am I assuming that your 400 figure is coming from user reviews?

If its 360-375, that is very likely to be drop-able simply through the process of bedding in the spring over a couple of thousand BBs and if desperate leaving the spring compressed for a couple of weeks.

But it is a gamble as these things won't always work. If you have other guns that are playable, I'd just try it out and see, but if this is a gun that you are relying on being skirmishable straight out of the box, you may need to downgrade it or get it downgraded (depending on your technical ability) just to be safe, in which case make sure you give yourself plenty of time to do so before you need skirmish it.

Nothing worse that either night-before gearbox rebuilding or desperate refreshing of tracking status.

[RitchieTheBrit]

Re: Advice on decreasing FPS

Other option if it beds in at around 360-370 fps, you could clip a few coils off the spring? I've only ever gone as far as two coils, but three is usually possible. I think it usually equates to around 10-15 fps per coil on an M110, but this varies.

You then grind or file the sharp left over bit to smooth it out. I read ages ago that the clipped end should always go into the piston to allow the spring maximum rotation at the guide end.

[callum89]

Re: Advice on decreasing FPS

Alright, cheers for the advice guys. I'll go with testing it when I get it then replacing the spring if needed, if that doesn't work i'll try the clipping the spring trick. Much appreciated