A comparison of 7.62x39 vs 5.56 - let's look at how the rounds stack up ballistically and what each offers over the other for shooters.
Noobie guide to 5.56 AR rifle ammunition. – Matt's Homepage
5.56 NATO vs 7.62x39: Unexpected Results - UBT
Cold War Combatants: 5.45x39 mm vs. 5.56 NATO
7.62x39 Ballistics - Velocity, Energy, Drop & More
A History of AR Cartridges
Are there any rife/carbine that can load both 5.56 and 7.62 rounds? If not, could it be made or is it to complex or heavy? - Quora
7.62x39 Vs 5.56 NATO: Pros, Cons, & What Is Best For You? [2023]
223/5.56 vs 7.62x39: What You Need To Know
5.56 NATO vs 7.62x39: Unexpected Results - UBT
7.62x39 Vs 5.56 NATO: Pros, Cons, & What Is Best For You? [2023]
300 Blackout vs. 5.56: Which is Better?