1. The handguards.
2. The way the barrel stays so hot when I “Rock & Roll!”  Semi isn’t so bad, but when I Really start to smile, I have to wait for the barrel to cool off.

As Far as No. 2 is concerned;
There are coolants out in the market place used to electrical systems.  A couple of years ago I went to an electrical supply store.  Way back in the mid-sixties I played with slot-cars.  Every weekend there was a race.  During the race the hand controllers could get hot.  From time to time the owners would spray the controllers with some sort of canned spray.  It would cool things down very nicely.  Now with that in mind I went to the store and did some asking.
The short answer was around $14.00+ per can and I would have to buy a case of eight cans.

There had to be a better way.

Oh, yeah:

3. I don’t have enough “Black Rifles”.