I had a few ARs and AKs out of the safe today for maintenance. While they were layed out side by side, I made two observations.

1: My favorite setting on a M4 stock results in a length of pull very nearly equal to that of an AK Warsaw Pact length stock. This setup is for an upright, head-up position. When I go prone I pull the stock out, given the opportunity.

2: My ~16" AKs were visibly longer than my ~16" ARs, so I took some rough measurements. The difference appears to be consistent. After accounting for small barrel length and LOP differences, equivalent AKs are 17.5mm or 0.69" longer (OAL) than AR15s. In other words, an AR15 is around 2/3" shorter than an AK, such as my 5.45 Saiga or Romy 7.62.

I'm sure this info isn't new, but it struck me as interesting. If you are the type to worry yourself over the difference between a 16 +MD and a 14.5 +pin/weld on a CQB oriented, non-NFA rifle, a delta of 0.69" could be somewhat relevant.