I have 2 20P, one is a rebarreled Ruger American and the other is an 18" X-caliber barreled AR I built. Both will shoot the 35gr burgers into 1/2" groups at about 4K fps. At the time I built them 204 brass was not as easy to get as it is today. I have no regrets though. 223 brass is cheap and forming is simple.

They say everything happens for a reason.
For me that reason is usually because I've made some bad decisions that I need to pay for.