Short filter cycle

[ritcheyd]

I recently replaced the sand in my filter. I had information that said I needed 250 lbs. and information that said I needed 300 lbs. I put 300 lbs. in . When I started up the pump (new prime) it wouldn't pull any water in the filter position. When I switched to backwash it did eventually start.
Now I'm having very short (about 1 hour) filer cycles before I have to backwash.

If I put in too much sand, would that be the cause of the above?