If you don't know, don't shoot it until you do. I had a crash course on a Barret M107 which lasted 4 minutes, and was able to put it together and zero with no formal range time on it. I just laugh at all the civilians rushing to get an AR15, and are dumb founded when they go to break their rifle down. If you can't clear a mis-feed, or a jam, and remove the bolt/firing pin, you shouldn't be allowed to own an AR15. Not to mention, I love watching virgins fire and AR15. You can't get a good sight picture holding that bitch a foot away from your face. Most come with adjustable stocks for LOP (Length Of Pull) so you can keep your nose on the charging handle. If you can't zero within 20 rounds on a standard zero target, you fail.