"It's a 1911A1. The 10mm is pretty much the same as the .45 ACP. It doesn't do anything the ACP won't."
As the owner of both a Glock 20L (6" slide and 6" 10mm barrel)
and 21L (6" slide and 6" 45acp/45 Super barrel) I have no grudge for or against one platform as I have, handload for, and shoot all three.
I shoot all three calibers in my custom 6" Glock longslide I developed way back 15 yrs ago in 2004. With thousands of rds of both full power 10mm and thousands of rds of 45acp / 45acp+P and in the last 5 or 6 years, full power 45 Super, I'm comfortable with evaluating the performance of all 3 calibers.
So, I am confident that I can give an accurate assessment of all 3 calibers and that assessment is that O'Heir's statement above is patently false as both factual and anecdotal evidence abounds disputing his claim.
Pistol Platform: Glock G20/21L 6" German steel slide, Convertible pistol I developed in 2004. The 45 cal barrel is a 6" Jarvis while the 6" 10mm barrel is KKM's 1st ever 45-10MM conversion barrel I commissioned Kevin to build for me in mid 2004. Neither barrel has a muzzle brake.
Chrono Test Circumstances: Oehler 35 Chrono set up at my range - 6,100ft asl on an 84° day. 10 shot strings averaged.
Results:
G21L 45acp: 200grn Speer Gold Dot bullets over full published load of Unique Powder in Winchester 45acp brass w/CCI 300 (LP) primer: 1,014fps producing 457ft/lbs ME
G20L 10mm: 200grn Hornady XTPHP bullets over full published load of Power Pistol Powder in Starline 10 Brass w/CCI 350 (LPM) primer: 1,350fps producing 809ft/lbs ME
As anyone can see, the 200grn 10mm produces 33% more Velocity and 77% more Muzzle Energy in the same platform, on the same range, on the same day, with the same chrono.
The performance of the rds is even more dramatic when one considers that the smaller diameter 10mm with it's higher BC, has a flatter trajectory giving it a hunting advantage.
Now, lets look at the 45 Super vs the 10mm to see if a more powerful .45 cal than the .45acp/.45acp+P can outperform it.
Pistol Platform: Same as above.
Chrono Test Circumstances: Same as above.
G21L 45 Super: 200grn Speer Gold Dot over full published load of Power Pistol Powder in Starline 45 Super Brass w/CCI 350 (LPM) primer: 1,307fps producing 758ft/lbs ME
G20L 10mm: 165grn Speer Gold Dot bullets over full published load of Power Pistol Powder in Starline 10 Brass w/CCI 350 (LPM) primer: 1,589fps producing 925ft/lbs ME
G20L 10mm: 180grn Hornady XTPHP bullets over full published load of Power Pistol Powder in Starline 10 Brass w/CCI 350 (LPM) primer: 1,479fps producing 874ft/lbs ME
G20L 10mm: 200grn Hornady XTPHP bullets over full published load of Power Pistol Powder in Starline 10 Brass w/CCI 350 (LPM) primer: 1,350fps producing 809ft/lbs ME
The 10mm can produce significantly better performance when shooting a 165grn 10mm loads as they produce 29% more Velocity and 22+% more Muzzle Energy than the 200grn 45 Super.
Further, the 10mm can produce significantly better performance when shooting a 180grn 10mm loads as they produce 13% more Velocity and 15+% more Muzzle Energy than the 200grn 45 Super.
And finally, as identified above, even the 200grn 10mm load beats the 45 Super's in both velocity and muzzle energy. And, as I said before, the performance of the 10mm rds is even more advanced when one considers that the smaller diameter 10mm with it's higher BC, has a flatter trajectory giving it a hunting advantage.
Conclusion: If you want something to punch holes in paper at close handgun ranges with a semi-auto handgun, a 45acp will do as well as the 10mm. However, so will a 40s&w, a 9mm, or even a .380. That's not the point of the 10mm. It's a high performance caliber suited very well to take hunting either as a primary, or as I do when I go 'woods walking' in the Rockies, as a sidearm for protection against both 2
and 4 legged threats.