What's the difference between these two? they're both 7.62x39 right?

The biggest difference is the AKM uses a stamp and riveted receiver while the AK-47 uses a milled receiver.
The Polish made AK is the PMK it is generally the same as a Russian, AK except the selector marking "C" above "P" and the lack of the bayonet lug.
The Polish version of the AKM is the PMK-M, has the same features as AKM except the noted different markings on the selector.

The Polish AKM (PMKM) has the rear sling swivel located on the left side of the stock, and other then the selector markings, there is little difference between this and the Russian one.

Yes, they are both 7.62 x 39mm. The Polish AK-47 (PMK-DGN-60) has a machined receiver, not stamped, and has a Grenade launching extention, and a fucken horrid looking recoil pad which straps on. I am told the recoil is 'unforgetable' when fired from the shoulder when launching grenades.

There is also a valve on the gas cyl (which allows turning off the gas, to fire grenades), and the grenade sights are mounted on the hand guard retaining pin, and there is a special 10rd mag too. This mag has a 'filler block' to prevent standard ball ctgs being used.

Hope this info helps you out.

the polish milled ak-47 grenade launching rifle carries the designation, pmk-dgn-60. it is euipped with the spigot, that recoil boot and a second set of flip up sites, used to aim grenade fire. a special magazine is used that will only accomodate grenade launching rounds.

the polish rifles exhibit top notch machining and assembly quality, and they manufactured kalashnikovs for the the bulgarians prior to the bulgarians establishing their own production facilities.