fps
 

how much fps do you lose roughly when you go up a bbs weight

it all depends on how much weight you go up... and what fps the gun is shooting already, and how much hop-up is turned up.

Depends on the brands used, but this should give you a rough idea:

http://www.airsoftcanada.com/showthr...hlight=bastard

ok ummm well i have a gear box that shoots 400-500 and i want to drop it into my m4 but i need to figure out what weight i need to make shoot around 350

if you need it to be shooting 350 for indoor play then the bb weight has nothing to do with it.

it will have to be shooting 350 with .2's and you will have to downgrade the gearbox otherwise you will be causing physical damage and be a danger to the other players

What does weight bb does it shoot at 400-500 fps? (that's a huge range btw). Any if the gearbox is out, why not just drop a weaker spring into it to get it to shoot close to or at 350fps?

Field limits are 350FPS for 0.20g BBs only. You need to change your spring, not use heavier BBs.

ok jw and i have never used it but i searched up the specs for the gear box and thats what i said

+1

Bear jew... take notice of this.

Field limits are calculated with .20g bbs. If you present yourself at the chrono's with a hot gun that shoot 350fps (indoors)or 400fps (outdoors) with anything other than .20g bbs; you won't be allowed to play.

PM a gun doc they'll be able to get the gun shooting 350 or less on .2's or maybe be able to tell you what spring to put in it if you want to give it a go, all you need to do is change a spring.
lots o' how 2s on the interweb

ok thanks for the replys

Here's a question: How do you know you NEED the mechbox you plan to get? Why blow a hundred or two to get a drop in when you really only need a spring change and maybe a couple other parts while it's open?

My understanding, and someone can correct me if I'm wrong, is the rough rule of thumb is a drop of ~10fps per 0.02g increase in BB weight. So a gun firing 400fps with .20g will fire roughly 375fps with .25g. Note that the effective kinetic energy doesn't decrease, in fact it will generally increase. So a gun firing too hot will still be firing too hot, no matter what weight of ammo you use. Limits are intended to be with .20g bbs even if no one actually uses that weight except for CQB and maybe not even then. Generally .25g or .28g are used for outdoor games.

Since you stated the mech box will fire 400-500fps that's too hot for practically anywhere. 400fps is the generally accepted maximum for outdoor games, with 350fps being the max for CQB. Note that I said maximum, not desired. My little tm mp5k-pdw is stock at 280fps and does decently against assault rifles firing 100fps more. Somewhere in the middle of 350-400fps (with .20g) is probably where you want to be aiming for unless you plan on using the weapon for CQB, then aim for the middle of 300-350fps

Actually 400-500 FPS??? What is this measured on?

The OP likely isn't pulling an M150 (or an M170) I doubt that he's really firing that hot. Lower 400 FPS I could see (if using .20's) but likely the FPS has been quoted using .12's.

If it was measured using .12's then at 400-500 FPS on .12's you're only looking at around 320ish-390ish on .20's.

That's quite possible. If that's the case then the speed result is pretty much exactly what to aim for, for outdoor games. No alterations necessary.