10mm 135 gr Mihec 10:1 lead/tin alloy over 12.5 gr SR 4756 fired from 4.25" barrel S&W 1076 through four layers of denim into calibrated gelatin.

BB: 594.1 fps, 3.4"

Gelatin results:

Impact velocity: 1,548 fps
Penetration: 7.1"
Retained weight: 73.0 gr
Min Expansion: 0.651"
Max expansion: 0.708"

We fired a few rounds over a chronograph with the same powder and alloy but different charge weights and these are the velocities we got:

11.0 gr  1,512 fps
11,5 gr  1,484 fps
12.0 gr  1,568 fps
12.5 gr  1,610 fps

It is a hollow point projectile.

The only 10mm I own is a Witness. I've enjoyed shooting the 1076 and Delta Elite and I hope my wife buys me an OD G20sf.

I would strongly recommend a full size steel frame Witness without the wonder finish. It seems that there were some reports of frames cracking on 10mm Witnesses with the Wonder finish.  I like my polymer frame pistol just fine but there are fewer holster options and it did the hand a little differently. I can't complain, though because it was a Christmas gift from my wife. The standard model has a really mediocre trigger, too. The Elite, Match, and Hunter models are all dramatically better guns and I think they're probably worth the extra money. Of course, if you aren't set on high cap mags, S&W 10xx series pistols can still be found for very attractive prices, too, and Smith really does triggers right (except for Sigmas and M&P).