You can do a lot with $1500. I highly recommend that you get a $500 AK, 2k rounds, and some training. Take a look at Armory USA AKs. You could also get a WASR, a pile of magazines, a wider rear sight, and a Red Star trigger along with the other stuff. Don't forget a rifle bug out bag (onesourcetactical.com has them).
The AK will do everything you need for self-defense to within 300 meters. Just remember, as the AR15 is not a 1911, the AK is not an AR15. Therefore, 1911 and pistol techniques will NOT work well for the AK (pistol techniques have been applied to "black rifle" training). Correct training is essential. Suarez International offers AK specific classes and I have taken the first class: Kalashnikov Rifle Gunfighting. It was excellent and included more than shooting; the AK is a great club and arm
breaker.
Get on
www.warriortalk.com and check out the Kalashnikov subforum. There is a sticky on maximizing the AK, which includes links to parts sites. There is a thread on alternative rifle bags, some of which are very functional for under $30.
If you decide to go with an AR15, then you'll need to learn different techniques. Again, I recommend that you emphasize training over gear. See if you can get a USED basic AR15. There are many trainers who are good; ask around.
If you go with a battlerifle, a CMP Garand is the best deal going. You can buy a Garand, get some 'smithing done to it, and buy a pile of clips and ammo off the CMP. One advantage of the Garand is that milsurp 30-06 ammo is available.
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Accuracy:
If 1 MOA means the rifle will shoot a 1 inch group at 100 yards, then the same rifle will shoot a 5 inch group at 500 yards.
4 MOA is NATO standard for the AR platform. 6 MOA was the commie standard. Will a goblin notice the difference at 100 yards? Probably not.
Will a paper target notice...yeah. Define your game. If it's shooting games, then get a game gun. Otherwise, "minute of man" accuracy is all you need.
Any rack grade rifle that is 4 MOA is minute of man at 500 yards. Granted, 5.56x45mm and 7.62x39mm are not 500 yard cartridges. So, if you go for either of those, figure out what is acceptable at 300 yards.
4 MOA @ 300 = 12"
6 MOA @ 300 = 18"
Since the average man is 18-20 inches wide, both are "minute of man". My CMP Garand is around 2-2.5 MOA out of the crate. My AKs run between 3.5 and 6 MOA. My Bushmasters were around 3 MOA out of the box. All worked just fine for my purposes.