Using a Sram 22 group with 10 speed crank I have a SRAM Red 22 group set that has a standard crank (53/39), and I also own a SRAM Red 10 speed crank with compact chainrings.  I'll be doing some climbing soon and would like to use the compact that I have already.  I can't swap just the chainrings due to different BCD sizes (130 on the 22 and 110 on the 10 speed).

Can I use the Red 10 speed crank (and compact rings) with the rest of the Red 22 group set, or do I have to bite the bullet and buy compact chainrings?
If they use the same bottom bracket, it's at least worth trying. While 9,10,11 speed chains are different widths on the outside, they are the same width on the inside so
there is a reasonable chance that a 10 speed front crank will work with an 11 speed chain. 

I have successfully used 10 spd cranks and rings with a 9 speed chain. I see two potential problems with the swap you want to make. 


Your front derailler is not designed to work with 50/34 rings and it may not shift well. 
The slightly wider gap of a 10 spd crankset may get the 11 speed chain caught in between the chainrings.


Two is the killer problem, take the crank and 11 speed chain and see if it getting
caught between the rings is a real problem. If not, it's worth a shot. You won't break anything by trying it and you'll have to decide if you can live with the changes in shifting performance.