I own an SRC G36K Gen 2 and the internals are very nice. The gears seem plenty durable and the piston is great. Only thing that should be changed is the plastic spring guide. (it doesn't come with a metal spring guide, unlike what ASGI says) The gun should handle an M120 fine and has been running my SP110 for about 10,000 rounds with no wear. My spur gear got a tooth chipped off, but I think that was because I put the motor height too high.
http://www.airsoftgi.com/article_info.php?articles_id=4Granted, ASGI isn't always reliable.....but I wouldn't doubt this test. The AK, G36 series, and XM8s all share the same gearbox.
http://ontargetairsoft.com/store/index.php?main_page=product_info&cPath=1&products_id=94If you are going to get an XM8, get the Gen 3s. The scope can be removed and it reveals a rail underneath.
The Gen 3s have VERY nice internals, creeping up on KWA.
Reinforced shell
8mm bearing bushings
same gearset as Gen 2 (which is fine for an M120)
Nice piston (think it's the same as the one in the Gen 2)
Metal piston head (don't worry, cylinder head has plenty of padding. I think it might be a bearing piston head)
Metal ball bearing spring guide
Reinforced tappet plate
metal air nozzle
metal cylinder head
Overall, the Gen 3s are much better internallya nd they have also made some external improvements. If you like XM8s, go for it.
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