I recently bought one of the affordable Chinese hand pumps for my new Mrod and it died. It pumped up the rifle tank on the first two sessions but it was difficult to use and made an odd slurpy noise.On the third use it lost pressure and failed to pump up. I could hear an air leak when I pumped. Since my pump came with some (not all) o-rings I decided to take it down and see what the issue was. Note: No condensation or water anywhere in the pump.One of the small o-rings failed. I'm not sure why this took place so I just cleaned all the pump internals and sealed it back up. I had some Crosman Silicon chamber lube for the o-rings. After the clean and seal job the pump worked much better. The strokes were very smooth from top to bottom and it seemed to pressurize much faster until it got upwards of 2k psi. I think I counted about 80 strokes to achieve 3k psi after starting at about 1900 psi.I just hope it keeps working. It's now very easy to use and I'm an old guy.