Up until now I have only reloaded cast bullets for bottle neck cartridges in my rifles and contender pistols. I have utilized the Lyman "M" die for all the different cartridges.

My situation is this. I just purchased a 12" T/C Contender barrel in 357 Mag and had it rechambered to 357 Maximum. I bought a set of Lee Carbide dies to reload with. My dilema is that the bullets I will be shooting are the Hornady 180 grain SSPB and RCBS cast bullets designed for my Marlin 336 35 Remington currently sized .360.

Is the Lee neck expander die sufficient for the job or do I need to purchase a Lyman "M" Die for 357 Max since the bullets I will be shooting are .358 to .360 in diameter?

The set you have should work fine once adjusted correctly.