I have a new oly PCR-4 and all my thirty round mags are not dropping free and feel a little hard going in,they all drop free easy from my bushy but for some reason they seat hard and do not drop free,and ideas.
The mags are all USGI and of dif. makes.

This is common in the Oly lower receivers. I have seen it in PCR's and ICR's.

Thanks Imbroglio,but i wonder why the 20's drop free ?

I have the same problem with my 30 rds. in my Bushmaster.

One possible culprit is the front edge of the trigger guard protruding into the mag well. Try inserting mags with the trigger guard in the down position. Take a file to it if that is the problem.

There isn't very much else you can do with the lower, but if you are very careful, the mags can be gently squeezed a little at a time in a table vise. Usually the problem is with the rear spine (overlapping) section not laying completely flat but bowed out slightly, but your mileage may vary, especially if you have the way out of spec Cooper mags.