AR 15 Brass Catcher
You are reloading your ammo - right? If not, you're throwing money down the drain and you're giving up accuracy by buying off the shelf factory loads. Since you are reloading, you have to pickup your brass (or at least sweeping it up to get it out of the next guy's way). One of the best tools for my rifles is an AR 15 brass catcher. I can't tell you how many times I've been shooting with friends and we get done shooting and someone has a couple of choice words because they had to sweep up their brass. I just look at them and smile as I take my brass catcher off my AR 15 and empty it into my bag of brass.
I think it's funny that after I go to the range with someone twice, the next time we go, they have a brass catcher too.
When I first started checking out AR 15 brass catchers, I noticed they were made with a nylon mesh and I was worried they would melt with the hot brass ejecting into them. I finally decided to purchase one and I have never had a problem with it. The mesh holds up just fine.
I empty the brass catcher about every other magazine (I'm running 30 round mags). You can definately get more in there, but I choose not to (unless I'm just finishing those last four magazines).
Here's the AR 15 brass catcher that I have. I hope you like it as much as I do!