Slow barrel? Slow bullets?

[Jäger]

A 20" barrel length definitely wouldn't be the cause of that much velocity reduction.

Have you contacted Colt Canada yet? I don't consider this normal at all.

Nope, not yet. If I end up with a load with reasonable accuracy at reasonable velocities, I probably won't bother. Haven't done much shooting with other bullets to see if the same situation occurs as well. If it's only this one bullet and results match published data more closely with other bullets, then it's not the chamber/bore. Before I call anyone, I'll have my gunsmith buddy borescope the barrel to see if there's anything unusual to see, and do a Cerrosafe casting of the bore and chamber.

[opngrnd]

Find a way to double check your powder scale. I has this issue once.

[Jäger]

Already checked that out while I was checking out the chronograph as well, thanks.