With my we scar some times my bolt will not lock back when its cold. But i have found that its to do with the mag bolt mechanism in the mag and not the gun bolt catch. The pins that hold the the bolt catch mechanism in the mag are tight and need lube and are located right where the gas comes out of the mag. So fast fire or cool weather makes it stuff and slow moving with in turn will not lock bolt back.

I fixed it! :D

http://www.airsoftcanada.com/showthr...76#post1735876 <--- Link to my tutorial on how to fix this issue.