Looking at Faxon barrels for pistol build. What is better 4150 QPQ, 416-r stainless, or 4150 5R chrome lined?

Any of those barrels will be good.  Faxon makes awesome stuff.  Which one is better would depend on your intended use, but I think you would be hard pressed to notice any practical difference between them.

My preference lately is 4150 with QPQ.  It has the advantages of chrome lining, plus very good corrosion resistance, and the heat resistance and toughness of 4150 chromoly steel.  The 5r Chrome Lined is also interesting.  I've never been a stainless steel guy.  But again, it is largely going to be personal preference.

Thanks for reply. The QPQ is $149 while the chromed lined is $199 offered exclusively through rainier arms. (10.5" inch)

The QPQ is also 1:8 twist while chrome lined is 1:7

Thank you! I ordered the QPQ barrel after reading a little more about it.