Personally, I was interested in chrono'ing a factory load to see what it would do, and tangentially to see why it caused (-es) such a variety of perceptions as to its effectiveness or lack thereof.
First off, the factory .38SPL round I chrono'ed at 605fps (2" bbl) is indeed lighter than I personally would want to depend on. ME-wise, it's about 162 fpe.
By contrast, the .38SPL 200g "Highway Patrol" load, which was advertised at about 770fps (6" bbl, I believe), is the basis for my reload velocity goals of 750/4" bbl, and these offer a different level of power than the milder factory load I tested. My reload thru a snubbie gives 229fpe at 718fps; thru a 4" bbl. it is 250fpe at 750fps. (Modern-day standard vel .38SPL 158g at 755fps is 200fpe in 4"-V bbl. for comparison.)
To the extent that ME is any guideline, then, a "Highway Patrol"-equivalent load offers:
1. 41% increase in ME vs. the "standard" W-W 200g load in snubbies (229fpe vs. 162fpe)
2. 24% increase over (today's) factory loaded 158g in snubbies, assuming 158g MV = 725fps. (229fpe vs. 184fpe)
3. 15% increase in a snubbie vs. modern factory 158g in a 4" bbl. (229fpe vs. 200fpe)
4. 25% increase in a 4" bbl. over today's 158g/4-V bbl. (250fpe vs. 200fpe)
Key conclusions, as I see them:
1. The appropriate comparison btwn. the .38 S&W "Super Police" round (aka the British service .380/200 round) and the .38SPL is at the velocity offered by the W-W "mild" factory load I chrono'ed in the original post, i.e. about 600fps in a snubbie and 680 (albeit only a single chrono'ed shot) from a 4" bbl. This is very similar to the British vels of about 630fps in their service revolver.
2. Comparing .38SPL 158g to .38SPL 200g, which was the greater focus of comparison for US police agencies some decades ago, the "mild" 200g W-W load at 680fps (again, I chrono'ed only a single round of this in a 4" bbl.) gives 205fpe, almost exactly the same as today's 158g grain load (200fpe). Thus, no real difference in ME.
3. Comparing the standard 158g load to the 200g "Highway Patrol" load, however, the latter offers a significant upgrade in ME. ***Indeed, in a snubbie, it is more powerful than a 158g load from a 4" barrel--I suspect that was the key point for police agencies exploring how to get the most out of the .38SPL.***
4. I also need to shoot a standard 158g into milk jugs and check penetration--one poster on another forum said his 158LRN penetrated only four jugs, vs. my 5 for the 200g LRN and 6+ for the 200g LSWC-K. His result may offer more insight about US police attempts to use 200g loads: they got better penetration. Granted, I'm shooting milk jugs--not scientific, not car windshields, etc., and that could decisively alter things.
5. When you change bullet profiles from the blunt 200g LRN to the LSWC-K, the ME figures remain the same for a given velocity, but the bullet track remains absolutely straight, without the deviation I've experienced with the LRN. This seems to get at the quality the British admired in their 1920s testing--the 200g carries straight through. (I don't know how my water test compares to their media--perhaps my 18" before deviating thru water equates to a "straight-through" in whatever they used.)
6. In sum, even the 200g "mild" W-W gives increased penetration over 158g. Once you boost power to 200g "Highway Patrol" levels, you have increased penetration and increased energy vs. 158g loads. When you add in LSWC-K configuration to "Highway Patrol" vels, you have depth of penetration, straight wound channel, improved permanent cavity wound characteristics vs. LRN, and increased energy.
7. Although the performance described in #6 above is probably bested by the more recent 158g +P "FBI load" and its addition of expanding bullet/better wound channel and (probably) less danger of overpenetration. . .many have commented that the FBI load often fails to expand from a snubbie. Therefore, my "bottom line" is that a "Highway Patrol" level 200g load with LSWC-K profile still seems to offer an outstanding standard pressure snubbie SD option for those who hesitate to place their bets on expanding bullets from a short barrel. Too bad it's available only to those who reload. . . .
Thanks for listening as I tried to reason my way through the history of these 200g loadings! Of course, the Brits simply may have screwed up in the 1920s, but the line of thinking I've outlined above seems consistent with much of their rationale, and barely scratches the surface on low pressure/controllability advantages, plus the apparent fact that they weren't comparing the 200g lead bullet to modern JHPs or even LHPs, I guess. Thus, their criteria seem to have been penetration and wounding characteristics of an essentially non-expanding bullet. (And I think Fackler might argue they were onto something!)
So not a lot of umph to the loads I was working with. I was not happy with any of the loads, so I'll refrain from listing what they were. Having fun messing with the old warhorse.