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Old 01-08-2014, 08:03 PM
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V_Dub V_Dub is offline
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PKM vs. M249 gearbox comparison

Good evening gents,

I decided to take out the gearboxes in both my PKM and my M249 to compare and contrast them in preparation of possibly mounting a m249 polarstar engine in the PKM. I've decided to also do a little internal investigation as well. I'm posting my observations for the general publis as well.

First off, the gearbox shells are almost identical with one key difference: the mounting holes. The m249 is mounted via two screws on the left side of the gearbox versus the PKM, which is on the right. The m249 mounting holes are present on the PKM, but not vice versa. The casting is slight different on the right side of the gearbox shell, allowing for a screw hole near the motor and another near the micro switch. Everything else appears identical.

edit 1: alright first pics:
here is the left side of the gearbox, my apologies for the upside down pic, the PKM is on the bottom and the M249 is on top.

The only major difference on this side is the tab for mounting the quick disconnect plug for the PKM. The mounting holes are the same on this side, so technically I believe you can mount a PKM box in a M249.

Next up is the right side of the shell. the M249 is on top and the PKM is on the bottom.

The main difference here is the two mounting holes for the PKM, the casting is slightly different
Here are the spring guides:

The PKM's is slightly shorter and has a bearing, it's also tapered.
Here are the springs. The M249 is on top, and the PKM's on the bottom.

The PKM's is slightly longer and seems to be of a higher gauge, this gun was shooting 415 when I got it chrono'd, unfortunately I don't have a chrono for the M249 (hop up was f@#$'d).

I'll keep adding pics as I get them.

Also if you have any questions feel free to ask.

Your rank is directly correlated to how many beers I drink to deal with you.

Last edited by V_Dub; 01-08-2014 at 09:40 PM. Reason: adding pics
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a&k, gearbox, m249, pkm, polarstar

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