If you're using 240g XTP's you might consider seating them atop a stiff charge of W296, using CCI350 primers, and finishing with the superb accuracy-enhancing Redding Profile Crimp die.
W296 is the correct powder for heavy 44 loads. You will have unburned powder exiting the barrel, but ignore it.
Barrel length is not the critical issue; powder burn rate (W296) and dwell time (Redding crimp) is.
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