I have a 1x in my contender. I did not do enough load testing prior to determine if it made a significant improvement, but the overall lockup and lack of slop is much improved. The gun shoots sub MOA with my two barrels (10" 7TCU and 21" .309JDJ), so somethings working. What size you need depends on how much slop your current gun has, I believe starting with a 1x cant hurt since they are cheap.
