REAL ammo will be a surprise.
Before I started shooting USPSA matches, I tested various factory ammunition (Blazer, CCI, Federal, PMC, Remington, S&B, Winchester, etc.) and used whichever was lowest priced.
Shortly after I started shooting USPSA matches, just about every match shooter suggested I start reloading to minor/major power factors as "match grade" reloads with 0.1 gr powder charge variance and 1.0 gr bullet weight variance would produce smaller shot groups than best of factory ammunition. A bullseye match shooting coworker took me under his wing and mentored me to reload and shoot.
When we tested various 9mm/45ACP match loads using Clays/WST/Titegroup/W231/Universal/WSF/HS-6 and later with 40S&W Montana Gold jacketed bullets,
my average groups with match loads shrank by more than 40% over best of factory ammunition. POA vs POI were comparable. When I tested my match loads with different factory premium JHP ammunition like Hydra-Shok/Black Talon/Gold Dot/Golden Saber, POI difference was around 1" at 10-15 yards.
I am approaching around 500,000 pistol rounds shot and have done occasional factory vs reload testing over the decades with similar results.
Anything that hones/improves your shooting skills can help in self defense.
NOT when You are accustomed to mouse fart loads
Time behind the trigger, especially working at speed, against some kind of external time pressure -- is useful.
As others posted, based on my "limited" experience, it is my humble opinion that range practice with lighter recoil target loads is not wasted.
Why?
When I switched my match caliber from 9mm/45ACP to 40S&W (to better meet major power factor), I used 40-9 conversion barrels in my Glock 22/23/27 for range practice with lighter 9mm loads. Using cheaper 9mm loads not only allowed me more trigger time but the lighter recoil allowed me to focus more on my technique and gun handling to better engage my match targets with 40S&W major power factor loads.
To those who claim "gaming" or "match shooting" does not develop useful skills for defensive shooting, our club's match stage designer shot both USPSA and IDPA and often tailored the stages with moving/sliding/bouncing/spinning/bobbing targets and forced us to shoot from unconventional positions, especially from cover. While typical USPSA stages favor faster stage times for scoring, the stage designer wanted to provide us with more realistic shooting situations to better hone our shooting skills. Yes, mandatory one-handed reloads and slide racking along with one-handed weak hand shooting from cover were often thrown in with extremes such as shooting from prone, laying flat on your back, shooting sideways between narrow openings, etc.
My defensive shooting instructor taught PD/SD SWAT and made us remove front sights of our pistols so we had to "point shoot" in darkened range stages. At some point of point shooting practice, type or caliber of pistol became less relevant but the technique used allowed us to produce fast 4"-6" shot groups without use of sights at multiple targets as illustrated in this thread -
https://www.thehighroad.org/index.p...r-good-handgun-shooting.829298/#post-10696936
I transitioned my sister from 9mm to 40S&W using light recoil target loads and now she shoots matches with M&P40 using major power factor loads. If you ask her, she will tell you using "mouse fart" loads helped her overcome the dreaded "flinch". When other male match shooters ask her about the snappy recoil of 40S&W after she out shoots them (she is small framed with small hands), she smiles and says, "What snappy recoil?"
As to match shooting translating to real life defensive shooting, she will tell you if she can see a threat inside her house, she won't miss even using full-power premium factory JHP loads.
