300BLK, 7.62x39, 30WCF. These are among my favorite cartridges. 300 Blackout, my first experience with this was in the form of the 300 Whisper. Some say they are are different. Not really, just different shades of gray. 300 Fireball, 300/221, 300 Whisper, 300 Whisp-R (rimmed version, basically a 360 Dan Wesson run through a sizing die), 300 BLK. They can all be loaded using the same dies. I have Blackout dies, a friend loads his with 300/221 dies. The Whisper was formed from thinner 221 Fireball brass necked up, the Blackout from 223/5.56 brass. 223/5.56 brass has to be neck reamed if formed for the Whisper chamber. That's the biggest difference I see. The Blackout is supposed to be the American equivalent of the 7.62x39. It's not, like 2 peas in a pod, the same but different. The Blackout with a 125 grain bullet has a muzzle velocity between 2100 and 2200 feet per second. The 125gr.308 bullet does have a better ballistic coefficient than the .310/.311 bullet used in the 7.62x39, but it really doesn't amount to much inside of 200 yards where most of these rifles will be used. The Blackout excels over the 7.62x39 and 30/30 in subsonic use with its faster twist barrels, it just throws the 220 grain bullets better. 7.62x39 Russian, one of my biggest regrets is that I didn't buy a Handi Rifle when they were manufactured in this caliber. I think it's one of the best cartridges for the hunter who pursues deer, bear, and hogs inside of 200 yards. Accurate, mild recoil, and readily available. While the 7.62x39 has a reputation for inaccuracy, it not. That stems, I believe, from the AK variants it's fired in. The AK is considered good to go if it produces 4 to 6 minutes of angle. In a Interarms Mini Mauser, Savage M10 Ranch Rifle, or CZ527, it will show what it can do. It's supposed to be the equal of the 30/30, but it's not. The 7.62x39 will propel a 125 grain bullet at 2300 - 2400 feet per second. The 7.62x39 will handle bullets up to about 160 grains, in my experience it does not stabilize heavier bullets well. 30/30 Winchester, still known in some circles as the 30 WCF. The cartridge that would have won the west if it had been developed a little earlier. I load mine with bullets from 110 grains all the way up to 190 grains. The Speer 110 grain half jacket makes a good groundhog load, while I like the Speer 130 grain for deer. The Hornady 170 grain gets the nod when I feel I need deep penetration. Had a supply of 190 grain silver tips pulled from 303 savage rounds, but I have used them up and not been able to find any more. They penetrate very well. One drawback to the 30/30 is case life. Because most 30/30 rifles, namely lever actions, lock at the rear and have "springy" actions, and the cases are thin, they tend to stretch and don't last as long. Sometimes three firings is all you get. One solution to this is to have your chamber reamed to Ackley Improved. Case life is greatly improved. (This is also a solution to another of my favorites, the 22 Hornet, whose thin tapered cases tend to stretch a lot also). The 30/30 will push the 125 grain bullet to 2500 - 2600 feet per second.