[usmc07]

This is a common problem with these guns over time the disconnector may pop over the action bar causing the hammer not to cock when there is pressure on the trigger.

If you remove your trigger group from the gun (drift out two pins that hold it in place). Look on the left side of the trigger group where the action bar and disconnector are located see if the disconnector (silver piece coming off the trigger) is sitting on top of the action bar. if it is not this is what is causing your hammer to not stay cocked when your finger is on the trigger. To fix this drift out the pin that holds your trigger in place (bottom back of trigger assembly) from RIGHT to LEFT. Lift up on trigger and gently pry the disconnector up so it sits on top of the end of the action bar. Reinstall the pin through the trigger and pull the trigger, then with pressure still on the trigger the hammer should stay cocked. If this doesn't work or you don't feel comfortable with doing it yourself take it to a gunsmith in your area.