Mark, I mean to post this before I left this morning, but late is better than nothing at all.
First off, the bores in ak/sks are .311 and not .308. The reason that I bring this up is if you plan to reload for all three rifles, you want the bore on the AR to be .311 as well. This will save you from having to buy .308 and .311 bullets.
Now on to reloading,
First off, all of the steel case Russian ammo is berdan primed. This means if you are saving the steel cases to reload, throw them away. Standard primers will not work in berdan primer pocket cases, even after you have went to the effect of picking/ hydro punching them out (read a stander resizing die with deprimer tool will not work to for these cases.
That brings us up to the next points, which are brass cases. Only USA produced ammo in brass cases use boxer primers. This means when you do buy ammo/cases to reload, it's going to be on the very spendy side. When you do go to reload the new/once fired brass cases (read buy all the components), you are going to see that the price of the gunpowder, the primers, and the bullets often cost as much as the price of the Russian ammo already loaded. So in regards to reloading, the only satisfaction that you will achieve will be that you should be able to load more accurate ammo than what the Russian ammo has to offer. But again, depending on the condition of the AK and SKS, the only payoff may just be in the AR platform alone.
Now myself, If say I had shit load of 7.62X39 spent brass cases, and was looking to use the cases in the 24" AR rifle, it sure in the hell wouldn't be the ballistic challenged round stated above. Instead, a given amount of the cases would be resized in either 22PPC or 6PPC (read the PPC is based on the 7.62x39 case). So to recap, the PPC rifle (built on a AR-47 receiver to use AK mags) would use the same bolt and mag as the 7.62X39, and only the barrel/chamber would need to be PPC. As for wither to go 22 or 6, it just depends on what is being shot. And, if you have to ask why the PPC, you just need to do some research on the PPC, and figure this one out for yourself.