[whofarted]

You want a metal rod with the lowest specific heat you can find. This means it is easily heated up, and heat is easily dissipated. It will draw heat away from the barrel ASAP, and cool down very quickly.

Gold is best, then silver, etc. Copper would be great, aluminum is probably the most practical.

The strut is only the beginning man. Bed it, trigger job, etc. That'll make it a great rifle easily capable of 2 MOA

If you get this guy to make a strut outta gold or silver you will forever be my hero