On Tue, 18 Feb 2014 08:20:56 -0500, "Mr. Luddite"
wrote:

I had a Ruger .177 pellet rifle but recently gave it to my son-in-law.
It shoots lead pellets at a muzzle velocity of 1200 fps and the "high
velocity" type pellets at 1400 fps. When fired, it is louder than my
.22LR rifle (also a Ruger).

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That's because the pellet is breaking the sound barrier and creating a
shock wave. If you could tune the velocity down to a bit under 1000
fps it would be a lot quieter.