Quote:
Originally Posted by hyena
I also wanted to try some lighter bullet weights in my 642. My reloads are a coated 158gr RNFP bullet with 4.5 grains of Unique. They consistently shoot very high at only 7 yards. I mean about 4-5 inches high, which frustrates me. (I've never actually measured it to know exactly.) So yesterday I shot 10 of my buddy's reloads, coated 125 grain bullets and 4.5 grains Unique. He also brought some Federal HST 130 grain +Ps for me to try. I hoped lighter bullets would hit lower, and to my surprise both loads hit pretty much to POA at 7 yards. So I have some Speer Gold Dot 135 grain +P's coming, to replace the 158 grain Buffalo Bore rounds I currently carry.
It's funny. My 158 grain reloads shoot POA at 7 yards in my 640 Pro and 686. But way high in my 642. I have a strong grip, but maybe not strong enough.
That's it. Just wanted to share some thoughts and observations.
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It's plain physics. That 12 ounce J-frame is going to have more muzzle flip with the slower heavier bullet. This means the muzzle will climb more during the milliseconds it takes for the bullet to exit the barrel. Both because the greater mass of the bullet creates a greater equal-but-opposite reaction force (pushing the barrel backwards and upwards) AND because the slower bullet takes slightly longer to travel the length of the barrel - giving it more time for muzzle flip to push it even farther off target.
At that distance about the only thing that matters in terms of POI is exactly where the muzzle is actually pointed at the exact moment in time that the bullet exits the barrel. Tiny fractions of an inch of movement make a huge difference in POI.
With the combination of a really light revolver, heavier bullet, and longer time between ignition and the bullet exiting the barrel, the recoil is pushing the muzzle up farther before the bullet clears the barrel than when a lighter faster bullet is shot from the same gun OR when you shoot the slower heavier bullet from different gun with more weight.