the AK74 actually has more range then the AK47 because the round is smaller lighter and travels faster. When it impacts a human torso it startes to tumble causing more damage. Really it's the russians answer to our 5.56 and on full auto it's more controllable then the aK47. When it comes to penetration the AK47 will go straight through a cinder block wall where the AK74 might or might not depending on the situation.
Personally I prefer the 7.62x39 ammo is cheap easy to find and knocks the living hell out of what ever it hits.
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"You can be as mad as a mad dog at the way things went. You could swear, curse the fates, but when it comes to the end, you have to let go" Benjamin Button