Here is some chrono data from JFH (Jim H.) he posted on the M&P 340 thread.
I concur with his observations. I find the M&P 340 at 13.3 ounces a good balance and compromise between the 12 and 16 available in the Sc/Ti and X42s.
Chrono test--M&P340, Factory Speer 357-GDSB135gr.
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I found a box of the Speer 357 Short Barrel 135gr cartridges. They went over the chrono this afternoon in the 340:
Velocity: 1031.5
High: 1061.1
Low: 969.9
SD: 35.8
MAD: 24.6
ES: 91.2
FWIW: Here's (one of) the 340 results again for the Speer 38+P Short Barrel 135gr.
Velocity: 895.3
High: 916.0
Low: 849.8
SD: 26.3
MAD: 18.2
ES: 66.2
Buffalo Bore range results:
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Item 20A--"Heavy 38 SPL+P:" 158-gr. LSWHC, factory spec'd at 1000 fps/M.E. 351 ft. lbs.
five shots, from an S&W 640 (2 & 1/8" barrel): Average, 1020.3 fps.
five shots, from an S&W 340 (1 & 7/8" barrel): Average, 1010.0 fps.
Item 20B--"Heavy 38 SPL+P:" 125-gr. L.V. Gold Dot, factory spec'd at 1050 fps/M.E. 306 ft.lb.
five shots from the 640: Average, 1061.1 fps
I've had trouble believe the 20A advertised specs--but they are true. Further, compared to the hand-loaded .38Spl+P loads I've been doing with various powders and a 140-gr. lead bullet, the recoil is NOT harder, and the shot has a noticable "38 Spl" feel to it. Anyone well acclimated to a 340 should have little trouble shooting it.
It is a bit stiffer recoil than the Speer 38+P 135-gr GDSB load, but it's also 'shorter'--and given the historical performance of the 38 Spl 158-gr. LSWC-HC round, it should be a super defensive load in 642s-442s.
As far as the 20B load goes, that's a real light load in comparison. I didn't bother to shoot it in the 340, I feel that confident about its managability
Data supplied by Jim H.
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I agree with the open backstrap. Both my J frames, 642 and M&P 340s currently have Crimson Trace 405s. If you really want to tame those beastie snubs and don't care about grip length, put on a set of Hogue Monogrips. A world of difference in terms of felt recoil and control.