Loading the 10mm Auto at or near "original theory" levels ...
Texas Ammo; CorBon; Georgia Arms; Proload.
Note: the initial 10mm bullets loaded by Norma were a 200gn FMJ and a 170gn HP, and the latter just wasn't that good of a HP, tending to drill thru like a FMJ rather than expand. Today's bullet quality and range of available bullet-weights in 10mm/.40cal is light years ahead of where we were in 1983-84. Some discussion of this is here:
http://glocktalk.com/showthread.php?threadid=82893
Availability of 10mm ammunition and competitive pricing, thanks to the internet and to enterprising outfits like Georgia Arms and ProLoad, is much, much better than it ever was. Without a real and steady demand for 10mm ammo, these smaller companies would have absolutely no economic incentive to spend money on components to make it. Why throw good money after a "dead" cartridge? Answer: it ain't "dead."
10mm vs. .40Swishy-Walker, when both are loaded w/ 155gn Gold Dot HPs?
Don't even get me started.
Georgia Arms 10mm/155gn GDHP @
1375fps/651fpe
vs:
Speer 40S&W/155gn GDHP @
1190fps/484fpe
It doesn't really get any better even when you go "tactical" with a .40 load, as in:
Federal Tactical HP ammo:
.40S&W/155gn HP @
1140fps/445fpe.
When the issue of barrier penetration arises, as in many LE scenarios where wood, auto glass and various thicknesses of metal are encountered, the 10mm has the decisive advantage over all challengers, specifically including the .40, 9mm and .45acp. (Possibly the .357 Sig competes here, but it's early and the jury's still out). In fact, both the 9mm and the .45acp succumbed to the 10mm in the FBI's testing for penetration
and accuracy. See Hall's report here:
http://www.totse.com/en/bad_ideas/guns_and_weapons/10mmpist.html
Still, at the end of the day, I wouldn't "dump" the .45 for the 10mm. Keep both. I have. It's just that my stock .45 SA 1911A1 doesn't see nearly as much activity as any of my 10mms.
Hope this helps.