I've long been a High Power aficionado; over the years I've owned 3 of them (including my current one), all in .40. Trivia for the day: While all High Powers are manufactured by Fabrique Nationale (FN), FN rollmarked ones are considered "High Powers," while Browning rollmarked ones are marketed as "Hi-Powers." 'Murrican marketing and all that, I suppose. My current one is one of the FN rollmarked ones, a "MX" coded piece signifying 2003 production, purchased brand new in box in 2007 for a ridiculously low price of $459; prior to that both FN USA and Browning had been concurrently marketing High Powers, and FN eventually decided to divest themselves of their accumulated ones, leaving (at least in North America) High Power marketing solely to Browning. In 2007, this resulted very briefly in numbers of drastically discounted 9mm and .40 FN rollmarked High Powers being available, most (if not all) that I recall being in the base Mk III black epoxy finished variants, including SFS action models.
This was a huge savings for a high quality pistol, as concurrently sold Browning Hi-Powers were selling in the high $800s discounted, around $1,000 list for the same pistol (historically, Browning marketed pistols have been available in a greater variety of finish and model variants; the FN models were presumably marketed primarily to the LEO/military communities, and concentrated on the basic fixed-sight, epoxy finished MK III models).
The ergonomics of the High Power are pretty decent; for an all-steel double-stack semi-auto they're remarkably slim. The .40 models have slightly wider, taller and heavier slides, but ergonomically that's of no consequence. Virtually all post-1993 High Powers have cast frames-a necessity for the .40, and expeditiously carried over as a commonality of manufacturing practice for the 9mm versions. The cast frames and smaller components since 1994 have been more thoroughly heat treated, and the casting process (versus forging) has left edges a bit more softly broken, especially regarding receiver tangs, which is welcome.
Th .40 guns also have an improved magazine in two aspects; first, the tubes are finished in silver-gray nickle-teflon, providing a slick and protective finish, and factory magazines include a special booster (AKA mousetrap) spring at the base, expediting magazine ejection even with the magazine safety in place (which imparts drag on the front magazine face, serving a a sort of an inherent magazine brake). The slick finish also improves the triggerpull if the magazine safety is left in place-many remove them to smooth and lighten the triggerpull action, but I've always left mine in place, and two of my three (including my current one) have had excellent triggerpulls with it regardless. Later-production Hi Powers reportedly have had the magazine safety's pad that impacts on the magazine face changed in composition from steel to polymer; I've heard of zero issues resulting from this material change, but personally prefer the steel piece. An additional later production change was that FN slightly broadened the trigger flange in 2006; I may eventually change out my OEM narrower one for this, as I think it's an improvement, but it's not a compelling need.
Grips on the High Power have always been a bit of an issue for me; I have a medium-size hand, and while on my first Hi Power Standard I'd had Craig Spegel make a beautiful set of Kingwood presentation grips with great fit, color and grain for me, they were just a tad too thin, with my triggerfinger protruding just a bit too far past the trigger. Subsequently for years I used one of Hogue's rubber finger groove models, which ergonomically worked well, but were aesthetically a bit challenged....A year or so ago, I discovered Hogue's "Seconds" (which seem to actually be more discontinued "Firsts" than blemished "Seconds") on their website, and picked up a magnificent set of Olive-Gray G10 grips in their older discontinued pattern (which I frankly preferred anyhow). These are still available the last time I checked, in various styles and finishes for around $45. The nice thing about G10 is that it has a very nice inherently chalky finish, with or without checkering, which very nicely anchors your grip hand(s)-especially desirable in a bare frontstrap model like the High Power or 1911.
The Hogue G10 grips seem to be of adequate thickness for me, as the gun seems to index very nicely with them, as does my firing grip. I prefer to use a small rubber "O" ring with the grip screw to help anchor the grip screw, making it less susceptible to unscrewing under use.
My High Power is equally amenable to both 165 gr and 180 gr .40 cartridges, although I usually gravitate to Sellier & Bellot's 180 gr flat-point ball for practice and matches, and carry Federal 180 gr HST or Remington Golden Saber JHPs for carry. The High Power is one of the most reliable firearms I've encountered, I literally cannot think of any malfunctions encountered with any of mine with any cartridges (I only use factory loadings).
The trigger on my current Mk III is excellent, and has been since out of the box; it's crisp and predictable, albeit with the characteristically long High Power reset-which is the trigger going to the fully forward position. Even with the heavier .40 slide, the muzzle is a bit whippy compared to my HK P30L and VP40 and Glock Gen4 G22 .40s, but certainly not uncontrollably so.
The pivoting trigger has a bit of a learning curve to excel with, but it's eminently do-able with a bit of experience. Similarly, the OEM sights are excellent, with white square paint inserts (my front I kept white, my rears I changed to neon orange-the combination works well for me with this pistol).
For lubrication, I prefer to use Lucas Red "N" Tacky #2 grease for all reciprocating/metal-on-metal components, and Weapon Shield as a general lubricant/anti-corrosive. I've had excellent results with this combination for years of use.
The square and unbeveled receiver magwell makes fast reloading much less natural than on many other pistols. Best results are in bringing the butt up to your visual workspace when speed reloading-I've also added a white index mark on the inside of the left receiver well to aid invisual acquisition and positioning when reloading.
The .40 High Power was discontinued in 1911, and 9mm Hi-Powers en toto discontinued in 2018, although I believe that NIB custom finished examples may still be available from the FN/Browning Custom Shop.
All in all, the High Power (or Hi-Power!) is a superb classic pistol-and one I consider very usable and viable today, albeit with some factoring in for and awareness of needed for some of it's quirks.
Best, Jon