PJ Hardtack,
I use 4.5 grains behind a 240 grain SWC in 44 magnum all the time.
With standard primers the ignition will be a little erratic.
With magnum primers it works extremely well.
I don't know what the effect of your lighter bullet would be on the equation, but I do know that the change to the magnum primer made a big difference for me when I dropped below 5.0 grains.
For what it's worth, I seat the bullet so that I can crimp over the WC edge.