And yes I KNOW I'm overthinking this one. Somehow this whole pressure thing, without math to back it up, got stuck in my craw so to speak.
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Forrest r already gave you the answer to the question concerning pressure for that load (HS-6 @ 10 grains under Missouri bullets rnfp 240 grain cast) with more specificity than you'd get in the majority of reloading manual, of which few tell to you the expected pressure.
The 44 Special tables listed in Handloader #236 (not #246) have been published multiple times in various issues, in one form or another.
Your lighter bullet (240gr -vs- 255gr) will lessen the pressure even more below the 22K max listed.
I have the program QuickLoad (QL) that lets you calculate pressure but you need more specifics than you've given to perform such a calculation & even then the results need to be taken with a grain of salt.
I only use QL when I'm trying to develop loads for an obscure cartridge like the 356TSW or 10mm Magnum, which little data exists anywhere, or for a new wildcat cartridge like my
45WSM which no data exists for, but even then it's only used in conjunction with other data obtained from different calculations to arrive at a safe starting point.
Your load doesn't require this.
I too would suggest that you just use 44MAG cases instead of 44Spcl cases for your reduced loads in the M69 for multiple reasons.
Yes , you're overthinking this one.

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Handloader #236 article, Handloading 44 Special
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I like Power Pistol for my reduced loads in 44MAG cases. Expect velocity lose with the 2-3/4" bbl. compared to data for a longer bbl.
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