how .any pounds of meat will this hold ? Thanks

The literature say a pound and a half. That seems about right, I do 5 pounds of ground meat at a time and I refill 3 times.

How do you clean the end of the piston rod? Do you take off the acorn nut to clean under the washer and clean the plastic part?

I find it not a 'breeze' to clean or even sorta ok to clean. I notice they don't show any images of the unit disassembled for cleaning. If they did it would mean showing how that once you unscrew the visible end of the piston/pipe (pipe touching the meat is aluminum by the way--NOT stainless) then yes easy to clean the plastic part and the two metal disks. But it's the area up by the handle--where the pipe recedes into when pipe is full of meat. This area becomes NASTY since it's nestled up inside the handle portion and the only way to get to it is to disassemble the entire handle--or face bits of rotten meat the next time you use it. On youtube there's a how-to for cleaning this jerky gun, 'though the name is LEM, and the handle works slightly different, it was surely made by the same company. In youtube search box type in " How to Disassemble LEM Jerky Gun"

Can you use this with steak or does it have to be ground meat products???

This is for ground meat only. You should use http://www.amazon.com/Jerky-Slicing-Board-Carving-Knife/dp/B014KF8KSE for Steak style strip cutting

Does it come with 2 barrels if so why? Do they connect to hold the 2.7 lbs

No they do not connect together. Each barrel can hold approx. 2.7 lbs. I make 10 pounds of ground beef jerky or more at a time, so packing each barrel really saves a lot of time.