How does the extractor and breechface look?
The next thing I'd look at is your magazines. Pull them apart and degrease them inside and out. I like to wax them inside and out with your favorite car wax. This will ensure smooth operation and make it easier to load to boot. Another added benefit is they will be easier to clean down the road when they hit the ground and pick up dirt/moisture.
Cheers,
Toby