Mansfield sillcock - repair help needed

Hi,
I am a homeowner and this is my first post. I have a 300-series Mansfield sillcock that was leaking. I removed the handle, unscrewed the plastic bonnet, and pulled out the entire assembly. I saw the rubber packing had completely disintegrated. I bought a replacement kit 630-7755, and replaced everything. No problems, except when finished, the handle was just about impossible to turn! I tried loosening the bonnet, which makes the handle easier to turn, but then it just leaks.
Any ideas on what I may have done wrong?
Thanks,
Nelson

Put a little Plumbers grease pn the brass stem where the packing rides. When you put it back together attach a hose with the nozzle in the off position, turn on the hose bibb, and adjust the packing just tight enough that the leaking stops.

Too tight and it will be hard to turn the handle and wear out the packing prematurely, too loose and it leaks.

Thank you!

It took a while to find plumber's grease. The closest I could find was a silicone grease. Anyway, I think the key was to re-install the sillcock with the handle in the off position, and then tighten the bonnet, as you said. It is working perfectly now. Thanks Redwood!
Nelson

Glad you got it fixed! Thanks for posting back with your results!