What ammo are you using?
Alex,
What brand ammo are you using? Some may "stick" a bit to the stripper clips.
I've found that several of my stripper clips had some grease on them which made it a Mighty Pain to operate.
I piled them all in my sink, poured hot water (not boiling, but as hot as I could get the tap -- boiling might work better) on them while agitating them with a stick. I drained all the water, then sprayed all of them with a moderate amount of concentrated Simple Green, filled the sink with more hot water, and agitated more. Drain the water, rinse them off again.
I took the stripper clips to my desk, put down a towel and a bunch of paper towels (about half an inch worth) then sprayed top and bottom of the clips with Remington Action Cleaner (brake cleaner might work too, but I'm not using that inside). Vigorous scrubbing with a bronze brush on all the bearing surfaces and inside the grooves for the cartridge rims got all the goop out. I wiped them all try, then lightly sprayed them with RemOil (it's the only aerosol gun oil I have), let it soak for a minute or so, then wiped them dry.
All in all, it took about 10 minutes for 30 clips. Now they're smooth as silk with Wolf polymer-coated ammo.