Mechbox.com used to be a great source for How-To videos. They did a "replace your spring" guide for a TM M4. While the disassembly of the rifle is different from yours the mechbox is the same. Don't know if they're still around.
There's lots of other Youtube videos as well...I think Airsoft GI did some decent ones and there's probably hundreds of homemade video ones as well.
Watch a bunch of those...then dive in. Some general tips...
- have a little tray or a bunch of cups to put screws and parts into (i.e. the grip and the grip screws and the grip plate...etc...)
- have a little bag to put your motor into (keeps debris from getting into it)
- use allen keys and screw drivers that fit properly...stripping a little screw is a PITA to get out
- work on a towel...it'll help with preventing little springs and screws from rolling off onto the floor
- if you feel like you need to...put a towel over the mechbox when you're opening it...that way if it gets away from you all the bits won't be flicked across the room
- if you get it apart without any problems (i.e. the gears pop out and you're looking at a bunch of shims laying randomly about)...then just take a look at how each piece works, how things work, reassemble it and test it. Then take it apart to clean it up and make changes
- there's probably shims (thin metal discs) on both the top and the bottom of the gears on the axel. Sometimes they're stuck to the gears...sometimes they're stuck to the bearings/bushings. Just pick them off and keep them together.
- it's easier/clearest to re-shim the gears if there's nothing but the bushings/bearings in it
- you don't have to put the whole thing back together to test...you can just put the mechbox on the grip, put in the motor and manipulate the side selector plate for safe/semi/full.
You're going to want to consider having the following on hand:
- allen key set
- rubber safe grease
- paper towel or rags
- regular sized and micro + screw drivers
- needle nose pliers
- shim set (a package that has lots of various shims thicknesses)
For upgrades...I wouldn't advise a first timer doing any on the first go when they're doing it themselves (unless something's broken). Just take it apart...clean the parts...reshim/regrease...reassemble/test. That way you're pretty sure you've got everything in order. You'll want to take a good look at the fins of the switch assembly. They'll probably look burnt/corroded. You can touch them up with a bit of fine emery cloth....if there seems to be enough metal left then you can leave it at that, if not, replace the switch. Then...unless parts are overly worn just change the spring. If after 10K your piston is in good order and the teeth of your gears are ok, then count yourself luck and leave the rest of the mechbox alone. A M110 will get you under 400fps...run a bunch of test mags through the gun before you chrony.
You'll want to consider changing the hopup rubber while you've got it apart...and really clean the inner barrel if you do that. A cloth patch with silicone oil does the trick...or windex. Don't use any polish/abrasive/cleaners.
If you've got a bit of extra money...buy a second mechbox. Keep one working at all times while you monkey around with the other. That way you won't find yourself in a jam with a game coming up soon and your mechbox a mess on your bench.
Best of luck
***Venture makes an excellent point***
- if it's been solid all year...then just leaving it is an option for sure. TM guns (which used to run at 280-300fps vs. 400+) would go for ages with almost no wear. The metal contacts on the switch or the motor would wear out well before the internals would (generalization).
- but it's still not a bad idea to take your hopup apart, inspect your houp rubber (for wear/tears) and clean your barrel.
Last edited by m102404; December 3rd, 2012 at 10:12..