I’ve seen the ballisticsbytheinch.com site in the past, and personally, while I admire their effort, professionally, a couple guys with too much time on their hands isn’t necessarily what I would call a highly sophisticated and reliable experiment. They admittedly only tested a few shots and report the average velocity for each load, which may be SIGNIFICANTLY altered by atmospheric conditions. This does nothing to combat the known issue with lot-to-lot and shot-to-shot statistical variability for factory ammo. Additionally, these tests were conducted outdoors and on different dates. Several papers have been published regarding barometric pressure and temperature effects on powder burn rates, which would suggest that these tests do not have a high statistical validity.
For the sake of argument, let’s pretend that this data came from a scientifically sound laboratory and not from a couple guys shooting at an old log cabin (which it DID)…
I spent a bit this afternoon looking over their data to specifically find the points you referred to.
I spent a little time digging on their site and did not find data for a standard pressure 124grn 9x19mm from a 16” barreled rifle for the Corbon load. None of their testing showed a Corbon standard pressure 124 or 125grn 9x19 load. The charts DO list a Corbon 125grn .38spcl, that tracks
I DID, on the other hand, line up the bullets and barrel lengths for the Federal Hydroshoks. For Federal Hydroshok JHP 124grn 9mm vs Federal Hydroshok JHP .38spcl, the 9mm showed MORE ENERGY for every test barrel in 1” increments from 3” to 18”, except for the 16” and 18” length. The 9mm was more powerful in 15 out of 17 test barrels. In REAL WORLD FIREARMS, the 9mm Federal Hydroshok proved more powerful IN EVERY SINGLE LENGTH! The 9mm was more powerful in all 5 barrel lengths. Overall, the 9mm proved more powerful than the .38spcl with Federal Hydroshoks in 20 out of 22 experiments.

But that’s just one load. Unfortunately, they don’t have any other EXACT loading matches, so I evaluated the rest of the data based on average energy per barrel length.
Statistically, the Average Energy of all loads tested for a given barrel length was HIGHER for the 9mm than the .38spcl for EVERY BARREL LENGTH, AND EVERY WEAPON, test barrels and real weapons included. The strongest load tested for each cartridge (highest energy for a given cartridge in a given barrel length) was ALSO higher in the 9mm FOR ALL BARREL LENGTHS. The MINIMUM energy load for each cartridge for a given barrel length was ALSO higher in the 9mm FOR ALL BARREL LENGTHS EXCEPT TWO. Essentially, the 9mm was more powerful in every case except for two of the weakest loads out of the bunch, which were weaker than the two weakest .38spcl loads.
So the whether you compared the data based on the STRONGEST, the WEAKEST, or the AVERAGE, the 9mm had more energy than the .38spcl in 97.5% of cases.
An interesting piece of evidence regarding the effect of the BC gap on energy level, from your own source. This actually surprised me, because I would have thought the BC gap wasted more energy than this data suggests. Check out the real weapon data for the .38spcl, specifically the last two weapons (shortest barrels). A 3” closed breech Bond Derringer compared to a 2.125” Colt Detective Special Revolver. The variance between the two is no more than 5% for any of the 4 loads tested, and two of the loads are FASTER in the revolver, complete with both a shorter barrel, AND a BC gap. The 2.125” Colt Detective Special revolver exhibited similar energy to the 3” test barrel as well, and SIGNIFICANTLY better energy than the 2” closed breech test barrel. The S&W 642 with the 1.865” barrel exhibited more energy with ALL LOADS than the 2” closed breech test barrel as well. The reported velocities for the Colt Python with a 6” barrel were also largely within 8% of the closed breech 6” test barrel numbers as well. Based on this, it is apparent that even though the BC gap DOES vent some amount of gases, NO, it is NOT a substantial portion of the total volume, and does NOT have a substantial effect on the overall power factor of the weapon (within a 10% margin). Like I said, these results actually surprise me, as I would have expected the losses to be much more significant. It makes sense to me that the SHORTER barrels exhibited LESS loss than the longer barrel, since the shorter barrels will hold less back pressure (lower chamber pressure) and the gases have less impulse (time) exposure in a shorter barrel, therefore proportionately less gas will be driven through the BC gap on a short barrel revolver than on a longer barrel model.
Also interestingly, the 9mm exhibited nearly TWICE the statistical deviation as the .38spcl for almost all barrel lengths. In my evaluation, this confirms that the 9mm is MUCH more sensitive to bullet weight than the .38spcl. As expected, the .38spcl’s oversized case allows it to maintain a consistent powder charge, and consistent energy level across a broad range of projectile weights. The 9mm’s smaller case starts dropping off in energy as bullet weights increase and the bullet base displaces powder capacity.
But with that aside, sometimes if it walks like a duck and quacks like a duck, it really does turn out to be a duck…. The numbers from the front of their standard platform, a .38spcl revolver and a 9mm semiauto pistol show the same results that the data from ballisticsbytheinch.com…
The 9mm Luger simply IS more powerful than a .38spcl. How much? Not much, but like I said in my original post, at worst, they’re even, in fairness, the 9mm gets an edge. Muzzle velocities for the same barrel length will be within 10% on average, meaning 20% energy. For a human target, the energy TRANSFER RATE (i.e. bullet DESIGN, as I mentioned in my other posts) will be much more important than the difference in energy.
No I’m not suggesting that the .38spcl is markedly inferior to the 9mm, but I think it’s time to dispel the common misconception that the 9mm is inferior to the .38spcl.