MP5 A4 upgrading
 

I was looking at these gearboxs,

http://www.redwolfairsoft.com/redwol...l?prodID=18767
http://www.redwolfairsoft.com/redwol...l?prodID=18766

I game at trek more often then not and if FPS is an issue then .25's can be used to help lowwer it a little. Im also curious if they will work with the ICS MP5 A4. Any suggestions would be great as I have never really done any upgrades before.

using a heavier weight BB =/= lower FPS

I understand that. Thats why I said if the FPS is a little to high for trek using .20's then I can use .25's to possibly reduce it a little bit to fit the limitations.

NO. We really measure BB energy, but just use FPS with 0.20's for easier calculations since chronies measure FPS, not joules (well some do but whatever).

Changing the BB weight will still have the same energy. Chronying is done with 0.20's BB's, not any BB you feel like chronying with.

If a gun shoots over say 350 FPS with .2's then using .25's to lower the FPS is NOT okay.

So I take it the http://www.redwolfairsoft.com/redwol...l?prodID=18766 is the one I sould be going with then for the ICS MP A4.

Your link is broken.

http://www.redwolfairsoft.com/redwol...l?prodID=18766
This one is fixed.

Do you really need to spring for a $250+ mechbox?

A $10 spring will also lower your FPS. And a $15 bearing spring guide and $15 metal bushings is all you really need to upgrade unless you're doing something drastic.

Stock ICS guns tend to sit around 330fps anyways. As above, all you need is to change springs and other fps varying parts. You could literally get what you want by paying $50 as opposed to paying $250 and getting the same result.

Other question is: Why do you want to upgrade your gun? I understand the usual reasons, but I've learned to use my 300fps TM MP5 shooting 0.28g BBs outdoors and have no real problems with it. And my other MP5 I downgraded from 400fps to 360fps just because it works better at that velocity with better range.

I agree with the above post. My ics mp5a4 is shooting 330ish and have learned to work with it. My advice is to take time and learn how your gun shoots. Know its limitations and work to make it consistent and reliable.