M249 gearbox.

[jfox61]

The piston on my CA M249 keeps stripping teeth. This has only just started to happen. So a couple of questions.

Setup is a 7.4 25C Li Po but was previously an 8.6 3000 mah Nimh. No issues with either of these two batteries until the following happend.

My brother stuck an 11.1v Li Po in and it immediately stripped the piston. I bought a replacement piston (Ultimate) and new head (CA). Refitted my 7.4 Li Po and it stripped the piston after about 2 minutes of firing.

Any ideas why it would suddenly start to strip pistons with a battery setup it was previously fine with?

Secondly I have been looking on a couple of sites for a different piston and have decided on a full steel toothed piston for strength. Considering the gears are CA, I envisage no problems with this.

But, I was thinking of putting a silent head on it rather than the standard CA piston head, and this is where my other problem comes in.

I should know this but I can't remember. The head I was looking at asks for gearbox version and the option are 2 or 3. Which version head would be best suited for the M249's gearbox?

[richardy]

Re: M249 gearbox.

forget the silent head...

try a prometheus POM head.

from what i understand the CA gearbox rails are slightly thicker than normal gearbox rails, changing to a different piston other than the original classic army will slow down the return speed of the piston compared to the original, thus youll need to remove the secotr gear and installthe piston and cylinder set and close the casing up tight and check for completely free movment back and forth of the piston.. depending on access you might need to ditch the cylinder to check this.

Also the classic army piston head was aprently ever so slightly thiner than a normal marui compatible piston head, thus a different piston / clasic army piston will sit a little to far forward... like so



meaning your aoe is slightly of, a spacer between the piston head and piston will push this out slightly and prolong the life of your piston...

try 1 first then the other...

Other things like worn cylinder head can have the same affect, once again a spacer will solve that. but check the free movment first.

also a picture of the piston wear would be cool too. non fuzzy please :D

[jfox61]

Re: M249 gearbox.

Will get some pics up tomorrow of the pston damage and the piston head and cylinder head wear.

[richardy]

Re: M249 gearbox.

regardless of wear, this should be a case of practical testing to track down any binding or aoe problem.

Seriously brand new TM sopmod m4 upgraded gears and piston and i was sanding the piston back for 30 min the other day... so times its not as simple as just dropping in a new part and sometimes it is, but theres always more you can do if you look closely enough how how part A interacts with part B.

[jfox61]

Re: M249 gearbox.

No binding or untoward noises at all. I will get an original CA piston as per the one that broke first time using the new head I bought and basically try it with the original set up rather than a retailers "recommended" upgrade part, as I did this time around.