What kind of electric saw can cut through food grade barrels?

You could use any type of circular saw I'd Imagine.

There are lots of saw options avialible at Home Depot:

http://www.homedepot.com/Tools-Hardware-Power-Tool...

there are a lot of them under 100$ too. Hope this helps!

The type of blade required depends upon the metal the barrel is made of Hardened steels or high temperature steel alloys are best cut with a diamond saw blade on an angle grinder. If the metal is poor quality steel then a bog standard hack saw will do the job. Shortening the barrel of a firearm is a criminal offence and caries a heavy penalty, besides which if you get it wrong the gun blows up!

I have cut those food grade barrels with a fine toothed blade on a hand held power jigsaw. You can buy a decent jigsaw for around $30 or $40. You may have to start the cut with a hand saw but once you have a small cut you can plunge the electric sawblade in and continue the cut. It is easiest to do it outdoors with the barrel lying on its side -- just roll it as you cut to keep the line straight.

http://www.homedepot.com/webapp/catalog/servlet/Co...

http://www.homedepot.com/buy/tools-hardware-power-...

that one would work fine.

The correct saw would be either a jig saw or saws all using a metal blade