Early M16s and ARs had a 1 in 12" twist which was great for bullets up to 55 grains (the old M193 was 55 grains). With the A2 variation, the 1 in 7" was used. It was found that 1 in 9" would stabilise the 62 grain SS109/M855 62 grain round fine, but not the corresponding tracers. Thus, they went to 1 in 7" so both would be stabilized. Currently, commercial AR-15s can be had with twist rates from 1 in 5" to 1 in 12", with 1 in 9" being the most common.
As for what is the twist rate on a particular AK variant, it is my understanding that most will be 1 in 12" while very recent guns may be 1 in 7". I advise having your gunsmith determine this for you using a borescope.
One other way to see if you have a 1 in 12" twist is to fire a 62-grain bullet at 100 yards. If the bullets keyhole and hit all over the place, you probably have a 1 in 12" twist rate.
Hope this helps!