Wrong. I reload. I have no idea why you want to go down this tangent with me but I'll take the troll bait and try to salvage this into an intellectual discussion based on my experience.
I've been reloading off and on since 1993. I own two presses; an RCBS Rockchucker with a Piggyback III and a Hornady Lock-N-Load AP. I have more brass than I know what to do with. I go through my dry reloading periods when it's just cheaper for me to buy factory ammo. Prior to COVID-19, I bought my ammo instead of reloading as I factor in my time to reload. If it's not worth my time to reload then I'll just buy factory. When I said previously that I shoot predominately .22 LR, 9x19mm and 12 GA it's because of the simple fact that's the perfect balance of economics factored in with my time. Yes, I still take my 10mms out once in awhile. However, it makes sense for me to shoot what I predominately CCW and use for home and personal defense. I live in an apartment complex so it makes more sense for me to use a shotgun instead of a rifle as I don't want to hit the neighbor's kid should it hit the fan. When I go on road trips where I'm driving through areas where you can hear dueling banjos, I take a rifle with me as I know that I'm on my own.
If anything gets you into reloading, it's 10mm and shooting magnum revolver calibers because of the ammo cost and if you want custom tailored 9x19mm subsonic rounds with heavier than 147 grain bullets. The cost savings becomes worth your time. My preferred 9x19mm rounds are subsonic. I also prefer truncated cone or flat point bullets as they leave nice neat holes in the target making it easier to assess and score your progress during a range session.
Another thing that will get you into reloading is if you want to make your own custom minishells (shorter than 2¾"). Herter's (Cabela's brand) and NSI made 2¼" minishells. For some reason they discontinued them. If you know anything about minishells and shotguns in general, you know that 2¼" are the shortest shells that will reliably feed in a Remington 870 which makes a 7+1 2¾" capacity Rem870 to an 8+1 2¼" capacity Rem870. This is the big selling point of the Keltec KSG. You get 12+12+1 of the Aguila 1¾" minishells in it plus the dual mag tubes.
With the 2¼" shells you lose three 00B pellets with the shorter shells. I prefer having the additional round than the additional 3 00B pellets per round in the mag tube. There's no easy way to modify a Rem870 to handle minishells and if you find a way to modify it chances are it won't cycle 2¾+" shells. We all know that if you have a shotgun with a fixed tubular magazine that minishells become attractive as shotguns are on the ammunition gluttony side plus it a more viable tactical option to have additional rounds in the tube.
Based on this logic of yours I don't see the point of bothering to make a 10mm P320. If it's only ~50fps difference, why bother? If I'm going to the trouble to shoot 10mm, I'm going to want to shoot hot 10mm. MAC also used hot 10mm Underwood ammo in that video, not pud loaded Fedlite loads except when he put .40 S&W through his civilian 1076 just to see if they would reliably cycle in his pistol which they did. Someone who is carrying 10mm is going to want to carry hot 10mm. Alaska DPS troopers have the option of carrying a G-20 in 10mm. Why? As defense against bear. If I was in an area where I had to worry about Yogi eyeballing me instead of a picnic basket, I certainly would want a hot 10mm, .41 or even better a .44 magnum and a shotgun loaded with slugs. I wouldn't want to have a pud loaded .40 S&W.
Same thing goes if I'm going to use .357 or .44 magnum ammunition. I'm going to want to shoot hot magnum ammunition. It's pretty much common knowledge that the .40 S&W is a 10mm special. The advantage of the .40 S&W over the 10mm is that you can drop a .40 S&W barrel and use a .40 S&W magazine in a 9x19mm frame and it will work. This is how the S&W 4006 came about, it's just a 5906 chambered in .40 S&W.
I guess my simple project has attracted your attention to the point you really think I am trolling you when in fact you are the one out to troll.
But I digress now that we have established you know some about reloading and about the same when it comes to firearms.
I too just happen to reload and have reloaded easily over a million rounds between 380, 9mm, 38 special, 357 magnum,
.40 S&W, 10mm, 44 Special, 44 Magnum, 45 ACP, .223 Rem, 6x45, 30-30, 308 Win, 30-06, 300WM, 12ga, 20ga just to name a few.
Mixed between a few different presses from Single stages, 550s, 750s, Super 1050 powered by a Mark 7.
Needless to say I dont shoot factory stuff often and as a matter of fact I could not recall the last time I purchased ammo that was 22lr.
I will take note of your experience in loading 12ga and with the right wad (or gas seals) and data you can load the same weight or count of shot in a shorter shell as the wad or stack often just takes up more space for a longer shell. I love me some good 2-1/4 or 2-1/2 shells for my 870 and Versa Max (shorter shells cycle it perfect).
As for the P320 in 10mm I personally like 10mm and have a few thousand cases for it and it also so happens that the P320 is one of if not my favorite gun. I also happen to like a good challenge.
As for shooting full power all the time even as a reloader that is just not realistic. However I will load and shoot 1250fps 180gr 10mm all day load which is no slouch of a load however is still not "nuclear" (625 ft/lb)
I also load and shoot 1150fps 180gr .40 S&W which is close to a max load but still within safe data (32,000 PSI max 35K) I tell you what that .40 S&W load would (529 ft/lb)
I also load some HOT 357 magnum 158gr to 1600fps (890~ftlb) and 125gr to 1900fps (1000~ ftlb) and I tell you what you don't want to shoot those all day long but its still worth loading some for the woods. This isn't even getting into big bore stuff. Which 10mm is not going to compare to....
The closest load that 10mm has that would compare to 357 magnum would be the 155gr bullet loaded to 1400fps which is still only 675ftlb.
Now based off this logic of mine it would seem that you may have been incorrect again as shooting full power or for better argument close to nuclear boutique reloads from underwood, buffalo bore etc. as you should take a look at their 40 S&W offerings and see that those are much hotter than most off the shelf 10mm loads out there.
While I dont dispute that 40 S&W is loaded lighter than 10mm it by no means is a slouch when you compare it to similar offerings.
"The advantage of the .40 S&W over the 10mm is that you can drop a .40 S&W barrel and use a .40 S&W magazine in a 9x19mm frame and it will work. This is how the S&W 4006 came about, it's just a 5906 chambered in .40 S&W."
Not to insult your intelligence/ with all due respect, but this is not a completely correct statement and dont try this kids it will NOT WORK.
You would need a complete .40 S&W slide not just barrel the 40 breech face and barrel diameter is not the same as 9mm and if you just put the barrel in it will get stuck.
I am sure I missed something but I have no doubt you will let me know.
