G&P Gearbox (assembly)

[davidz58]

Hi all,

Wondering if someone got any pointers on this.
I opened my G&P gearbox following numerous YouTube videos (including Mechbox tutorials).

I am having great difficulty (after swapping the spring) to close the gear box. It seems almost impossible to align and close the case.

Just hoping someone can point in me in the right direction. Really want to learn the basics of assembly and disassembly of the gear box.

Thanks in advance.

[dodgetheram]

Each time i try and close my mechbox, it seems its either the piston or the tappetplate that isnt sitting nice for the groove on the upper plate of the mech box, so make sure you are holding the piston upright so that it meets up nice... and never force it, she'll pop together nice eventualy, check the trigger, antireversal latch blah blah blah... one last thing i have opend my g&p box 6 times and it gets easyer to close each time! good luck

[MaciekA]

This gets easier with practice. You need to make sure that your spring guide is seated within the grooves that keep it from moving around. I like to start from there when bringing down the one side of the shell and then kind of pulling the tab on the spring guide towards the front of the shell so that I can shut the top part around the cylinder head.

At that point, you should be close to aligning the shafts of your gears to the holes in your bushings. Press down hard, then grab a 2-3mm flathead screw driver, and press on the shafts to guide them through the bushing holes. Same thing with the ARL. Everything will just snap into place.

Another tip is to weigh down the trigger with the end of a heavy hammer or other tool so that it doesn't pop out or fly around.

Once your mechbox is closed, take your long 2mm hex driver and stick it in the air seal nozzle to push your piston. Make sure the piston can move up and down. Check the springs on your trigger, selector plate, and press the nozzle in and out as well. Those checks will alert you to any problems that have crept up.

[jordan7831]

Good tips there ^. Its best to close it working from the back where the spring guide is and then closing up towards the front. Think of it as a clam shell phone. Use the spring guide as a pivot point and close downwards.

[ThunderCactus]

Originally Posted by MaciekA

At that point, you should be close to aligning the shafts of your gears to the holes in your bushings. Press down hard, then grab a 2-3mm flathead screw driver, and press on the shafts to guide them through the bushing holes. Same thing with the ARL. Everything will just snap into place.

This.
Also want to elaborate more on the previous statement, when putting the shell on, start at the spring guide end THEN close it over the cylinder head, THEN over the gears.
If the spring guide tabs aren't seating, put a 2mm allen wrench into it's screw hole and wiggle it around till it pops in.

Be glad you're starting on an easy G&P shell, on some lesser quality V3 mechboxes you need 4 hands to close up lol

[jordan7831]

Nope you got it all wrong. On the cheap ass mechboxes you need 4 hands a strategically placed foot, wife/girlfriend, and spring clamps.

The misses is for making you food while you are slaving away.
The spring clamps are to keep the misses from yelling at you for letting dinner get cold.

[venture]

Originally Posted by jordan7831

Nope you got it all wrong. On the cheap ass mechboxes you need 4 hands a strategically placed foot, wife/girlfriend, and spring clamps.

The misses is for making you food while you are slaving away.
The spring clamps are to keep the misses from yelling at you for letting dinner get cold.

Ditto that. When I have to work on certain brands, I warn customers that the bill may be a couple dollars more due to the extra time it takes to work on crappy gbs. I love working on Marui gbs. They just snap together in seconds.

For the OP:

1) Make sure everything is sitting properly on the left side of the shell. Sometimes the trigger mech can move slightly and stop everything from fitting together.

2) Just as thing look like they are going together the safety bar can be in the way. You may need to push it up into the gb with a screwdriver.

3) Make sure your piston is properly seated in its groove, or the gb may not fit together correctly. It certainly will not work correctly.

4) Ensure the cylinder and head are correctly aligned to fit the right side shell.

5) The right side shell should have nothing but bushing / bearings in it. All shims should be sitting on their appropriate shafts on the left side.

[davidz58]

Guys, thanks for the advice! I finally got it to closed... and it shoots - so it feels pretty good!

I think the part that kept catching me was the spring guide.

[jordan7831]

On an unrealated note; lets say you had a mechbox with a quick change spring, are those super easy to put back together? I would think they are because your not fighting that big powerful spring in there. Anyone want to chime in?

[venture]

They are easier, yes. As you said, you just put the spring in after you close it.

The Systema Revolution Gearbox is also much easier. The spring guide locks in and there is no AR latch.

Boxes with ASCU or Raptor FET's are also often easier to close, but I have run into a problem on cheaper boxes where the old trigger mech would hold the tappet down and when I installed the FET the tappet would want to lift out of its slot, making the box difficult to close.

[MaciekA]

Another thing that makes mechboxes easier to close is short springs, like on DBoys mechboxes (for example).

With respect to very strong and bendy springs, I use a very narrow Torx screw driver and insert it into the spring guide. Then, if the spring is so bendy that it makes the piston and cylinder pop out, I'll bend it downwards to straighten out the spring while grabbing the other half of the gearbox shell. Stick your index finger through cylinder window so that you can use that finger to press down on the piston and seat it in its groove. Then simply lower the shell down and use the left end to grab the spring guide tab. Focus on the spring guide tab seating into its groove properly and "wrapping" the shell around the cylinder head on the other end. The gear shafts are always a piece of cake after this (using the method mentioned way above, with a tiny flathead adjusting where the shafts are while pressing down hard).

[davidz58]

Hi guys, so I had a chance to chrono it yesterday at Paintball City. With the M100 spring, it is still shooting at 360fps to 390fps. Mostly around 385, and than it drops to 360s every couple of shot. This is a G&P M4 Colt gun. On the same gearbox and spring shoots at 330s at Paintball City's chrono (but using a VFC gun).

[cetane]

Air seal issue at the hopup perhaps on the vfc?

[davidz58]

Originally Posted by cetane

Air seal issue at the hopup perhaps on the vfc?

I was told that the Paintball City chronos about 20fps lower than elsewhere.

My VFC shoots at about 355fps at other chronos.