(Emailed to renaissance earlier)
My understanding is as you stated, that it's a combination of dwell time in the barrel, and of course recoil, which effects barrel rise.
The heavier bullet produces heavier recoil, and accelerates slower, thus leaving the barrel later.
I'm going through this exercise with a S&W K frame 9mm revolver (model 547), with fixed sights, which was shooting about 3" low at 30'. It was apparently regulated for 147gr bullets, which were the preferred police load when the gun was produced.
I suspect the slower 147gr bullet may shoot higher, but also drops faster, so any rise due to heavier/slower bullets at 25 feet, may be lost at 50 feet? Testing so far has been inconclusive, as I tried them at different distances, on different shooting ranges.
Hope to get to the range this week to do some more testing.
Bill Adair
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