Burn products and aloe vera work well at treating the area after the first hour or so. You first need to help the victim would be to cool the area by whatever means you have, ice, cool clean water etc.
I have treated many minor (less than 4 inch square) burns this way, but when using ice it is...
I doubt you will sway for the 10/22 because of the bang for buck factor, but I love my S&W mp15-22. If you are wanting to add parts the AR platform is limitless.
I have been doing a lot of research on these and have seen that there are issues with the magazine and follower.
hope this helps- http://www.firearmstalk.com/forums/f33/mossberg-100-atr-feeding-issues-8522/index2.html
I didn't realize how bad that red. Sorry! I am a simple kinda guy so weapons like yours always baffle me a to a point, but the machine work looks good.
What are your plans for the rifle?