444,
A 180 gr. bullet is close to the edge of the M1's "safe zone" for the gas system.
I'm not saying you should not use that bullet, but it's probably going to be hard on your op-rod over time.
BTW, the two rules of thumb for M1 gas system (as issued) is:
1) NEVER load bullets HEAVIER than 180 grains.
2) NEVER load powder SLOWER than IMR-4320.
It would make things easier on the gas system to install an adjustable gas bleed lock screw (made by both Schuster and McCann) in your M1, but then it would not be "as issued". I use the McCann in my Match Grade M1 and it works as advertised.
Because of it's gas cutoff design, the M14 gas system is a bit more forgiving of higher port pressure than is the M1.
Best regards,
Swampy
Garands forever