piston fitemnt problem help require

[ashley bramley]

so the problem is recently needed to replace the piston and head in my real steel classic army m15vn. The reason for this is i robbed the piston to fit in my G&P mk46.

I could only get SHS 3 steel tooth poly carb piston and ultimate piston Head polycarbonate so went through the normal fitting procedure. It was clear the new piston head increased the length on the piston assembly causing mis alignment with gears. So made a best guess ad file'd down 3 teeth and rebuilt it all and tried it out. The problem ive got now is the gun is not pulling the piston back and just rapidly cycling the gearbox as you can see the Tappet plate is working efficiently.

Is there a guide or video you could recommend in order for me to understand this more as I've one a lot of searching and either its a dark art or m search words are not accurate.

[Ian_Gere]

I can't say I'm an expert on Angle of Engagement, but I'm pretty sure that filing the piston teeth down is definitely not the way to get them to mesh with the sector gear teeth. I suspect that your problem now is that the sector gear has engaged with too little piston surface area and ground down anything that remained after your filing until there's nothing useful left. You can use washers to Shim the Piston Head to get the sector gear to engage better. You Tube for how to vids.

[RR01]

Did you buy the correct piston for your gearbox? The standard for most V2 / V3 gearboxes is a 15 tooth piston, although I believe 16 tooth ones are also available, as well as the 19 tooth pistons for L85s and SR25s. It sounds more likely that the piston was too long if you had to file off teeth, as the usual problem is the piston is too far in the cylinder and the Sector Gear first tooth doesn't engage with the rear tooth on the piston. Alternatively, did the piston head not sit properly in the small hole in the head of the piston, so making the whole thing too long? I've had that on a couple of new units I've bought, The small nob on the back of the piston head should fit in the hole in the top of the piston, but some don't, so you have to enlarge the hole for it to fit.

 

If the piston is too short to engage then you can buy AOE shims to go between the piston and piston head off Ebay from Lee Precision Engineering. I've got some on one of my M4s that decioded to shred a piston and the replacement was just a little too short to mesh smoothly. 4 shims sorted that and gave perfect alignment.