The 7.62x39 WILL kill elk, if it doesn't hit any bone. The cartridge just doesn't have the balls to plow through an elk's shoulder. The .30-30 ain't a shoulder breaker either on elk. That is where the weakness where those calibers fall short as big time elk killers. They will do the job, but you better be able to place your shots. I'm not even sure how well the 7.62x39 would do against an elk's ribs. The bullets are just not designed to handle that kind of job. Are you using an AK? If you are, I would not be using that thing on elk unless it is a very accurate one. If you are aiming right behind the shoulder going for a double lung shot, and the bullet hits the shoulder, it will blow up, and you will have a wounded elk who will not die from your shot, but whose wound could get infected, and will be in a shit ton of pain because of your caliber choice.