The Browning Hi Power and 9mm +P Ammunition


A very frequent area of concern for Hi Power fans seems to be whether or not they "can shoot" +P or +P+ ammunition in their Hi Powers.


The answer is a qualified "yes." The use of hotter than standard ammunition will accelerate wear, but it will not make the Hi Power explode or instantly break.


Let's take a look a minute at pressure.  What's being referred to is the amount of pressure being applied to the chamber of the pistol when a round is fired. Standard pressure rounds operate up to 35,000 PSI. The upper limit for +P is 38,500 PSI. There is no SAAMI rating for +P+. If buying ammo, look for either the case head stamp, the box, or both to be marked "+P".  If it is not, you have standard pressure/standard velocity ammunition. Nato-marked ammunition might be thought of as being in the +P range. A cross within a circle on the case head stamp designates it and all that I've seen has been FMJ.


One of the Hi Power's endearing traits is its svelte, petite size compared to other 9mm service automatics.

This also works against it as a vehicle for hotrodding the caliber. Less steel and smaller size simply means less ability to take the punishment more tolerable to larger all-steel pistols in the same caliber. For an example, compare the size of a 9mm 1911 to a Hi Power.


As you probably know, there is a divergence of opinion concerning the older Hi Powers having forged frames vs. the new ones with cast frames. Some say that the gun's been ruined and is made of "cast iron" while others do not. Some don't know the difference and wouldn't care if they did. Pistols having the cast frame will be Mk III's and variants that have "ripples" around the magazine well.  These are horizontal grooves that are clearly visible.  If they do not, the frame is forged. Everything before the Mk III has a forged frame.  The early Mk III pistols did as well.  The advent of the forty-caliber Hi Power brought about the change and that is discussed elsewhere on this site.


This is an early Mk III that has been lightly customized. It has a forged frame. I do use it with +P ammunition, but with a Wolff 18.5-lb. conventional recoil spring and a buffer. The mainspring remains at the factory standard 32 pounds.


I own and regularly shoot both forged and cast frame Hi Powers.  Contrary to what some had said, the slides on none are cast. It is my observation that the Hi Power is best suited for using heavier than normal loads by going from the factory 17-lb. recoil spring to a Wolff conventional 18.5-lb. recoil spring. I also use a buffer.  These recommendations and why are also discussed elsewhere here.  I've fired considerable amounts of ammunition in the 115-gr. @ 1277 ft/sec and 124-gr. @ 1250 ft/sec through both forged and cast frame Hi Powers for decades.  Much has been in the form of handloads, but all of the pistols have held up well.  There has been neither small parts breakage nor catastrophic slide/frame failure. I cannot say that this would be true had I been using the standard spring.


When the Hi Power is fired and the bullet accelerates, momentum or a "push" is transmitted rearward to the slide.  As it moves, the barrel moves rearward and begins dropping.  The locking lugs begin to move out of their recesses in the slide.  After but the briefest instant, they are only partially engaged. Ideally, chamber pressure will be the same as atmospheric when the barrel is completely unlocked, as the bullet should have left the barrel. If the slide were somehow welded in place, there would be no unlocking and no wear on the locking lugs. The faster the unlocking process takes place, the greater the potential for rounding of the locking lugs' edges.  This has been a weak point in the Hi Power in the past. The barrel rides on the barrel cam and its guided movement is around this insert of steel via the cutout area on the bottom of the barrel that engages it.  The cams can break if the recoil spring is too weak or lots of hot ammunition is used with too light a recoil spring.  This does not happen often, but if it does, repair must be done by either Browning or possibly Cylinder & Slide.  Browning does not sell cams to gunsmiths.


The pistol's frame is designed for the ability to withstanding the slide hitting it with a certain level of force.  The same round being fired in a pistol with a 17-lb. recoil spring will cause the slide to hit that gun's frame harder than one with a heavier spring. This is another reason I use the 18.5-lb. springs besides helping reduce the odds of lug rounding. The pistol's mainspring is rated at 32-lbs. Overcoming this also slows the slide's rearward movement as well as slowing the unlocking process.


It becomes obvious that firing a bullet at 1300 ft/sec will impart more wear and tear to the pistol than one at 1100 ft/sec.


Current Mk III pistols have a more "squarish" ejection port, but close examination will show that at the bottom rear, there is more steel than on the Mk II and the classic Hi Powers.  This is to reduce the chance of the slide cracking there after extended use. It seems that the British SAS experienced such problems with old, military issue, Hi Powers after firing extremely large amounts of high-pressure ammunition intended for submachine gun use.  Nonetheless, the Mk III has addressed that problem.


It's been my observation that the cast frame Mk III is the better choice for shooters intending to use a steady diet of +P ammo.  The cast frame is harder and tougher than the forged frame in the Hi Power. This has allowed the slides to be heat-treated to a higher level of toughness as well.  Does this mean that one cannot use +P in his Mk II or classic?  Certainly not, but I believe that wear will be more rapidly accelerated than in the cast frame pistol.  I would definitely go with the heavier recoil spring in the older Hi Powers.  The cast frame for the forty and the 9mm Hi Powers are the very same. The forty imparts much more force to the frame than does the nine, so the cast-frame 9mm Hi Power is quite tough for the caliber. Several years ago, The American Rifleman published a test on the Mk III Hi Power with +P ammunition. Their Mk III digested 5000 rounds of Remington 115-gr. JHP +P with no unusual or exaggerated wear.


This is a later manufacture Mk III and has the cast frame. The Corbon 115-gr. JHP +P is better-handled long term in these pistols in my experience. It is a maximum effort load as the velocity shown demonstrates. I suggest that the Hi Power is better suited to velocities with this weight bullet that are in the 1250 ft/sec range for extended use.  


Some prefer to reduce the mainspring (hammer spring) from 32-lbs. to about 26-lbs. for a better trigger pull and to make the gun easier to cock.  I do not. Very good triggers can be had with the full-strength mainspring.  Reducing the hammer spring strength also allows the slide to unlock faster and strike the frame harder.  If you opt for the reduced mainspring, I would sure go with the heavier recoil spring if I intended to shoot much +P.


The Hi Powers made before circa '75 had mainsprings in the 26-lb., but soon thereafter went with the heavier 32-lb. spring. 


For decades, my two remaining classic, forged frame Hi Powers did not "know" that factory ammo existed and "thought" that all 9mm consisted of a 115-gr. JHP launched at about 1277 ft/sec.  These pistols were initially shot using standard factory recoil springs and the 26-lb. recoil spring common to their manufacture.  Later, I went with the 18.5-lb. spring and have never gone back.  It works well with standard pressure ammo as well. These pistols have been in use since the early '70's and still shoot fine today.  They have NOT worn so badly as to be a bucket of bolts as one writer implies will happen if warm ammo is used in the Hi Power.  Neither have four Mk III pistols that have been shot primarily with the hotter stuff.


I find it interesting that the Mk III pistol handled 5000 rounds of 115-gr. JHP @ 1250 ft/sec fine for the staff at NRA.  The handload I used for decade tossed the same weight bullet but a little faster and the guns have held up just fine.  For these reasons, I do tend toward the idea that the best compromise for serious use in the Hi Power is something like Remington's 115-gr. JHP +P, 124-gr. +P Golden Saber, or Speer 124-gr. +P Gold Dot Hollow Points. The first of these truly averages in the 1250-ft/sec range from the Hi Power while the Golden Saber hits just under 1200 ft/sec.  The Speer goes from about 1180 to 1220 ft/sec in my tests.  These do not seem to stress the gun too much in extended use. I think Winchester's 127-gr. +P+ at about 1260 ft/sec from the Hi Power is well within its tolerance range.


While I like Corbon +P ammunition, but have found it to be a maximum effort, foot-to-the-firewall load in 9mm.  With its 115-gr. JHP, I frequently get right at 1400 ft/sec from the Hi Power.  I think this borders in the "too hot" region for this pistol.  It would be fine in a 9mm 1911.  I suggest that if this is one's choice for defense, shoot enough to be sure the pistol's reliable, but then just shoot modest amounts of it now and then. I will shoot it in my Mk III pistols, but no longer use it in my forged frame Hi Powers.


Most of us cannot afford to purchase the amount of factory +P ammo it would take to truly wear out a Hi Power.  At the same time, none of us want to unduly stress the gun's frame/slide or create grossly accelerated wear. For this reason, my choices in +P ammo for the 9mm Hi Power would be:


         Remington 115-gr. JHP +P: (This load has been altered with a new JHP bullet.  I have not tried it on any animals and cannot report on how well it does or does not work.  I suspect strongly that it is an improvement over the older version.  If your pistol ran fine with the older version, test this new stuff, as the bullet profile is different.)  This load regularly hits around 1250 ft/sec from the Hi Power and seems to be a very accurate number as well.


         Remington 124-gr. Golden Saber +P: Usually averaging a bit under 1200 ft/sec, this ammunition generally feeds fine in the Hi Power and in recent years, has shown greater shot-to-shot consistency.  I think the velocity is held to these levels to reduce the chance of the jacket separating from the lead bullet core as the brass jacket plays a big role in how this bullet wounds.


         Speer 124-gr. Gold Dot Hollow Point +P: I've found it to be accurate, reliable, and consistent.  This seems to be a most popular high performance 9mm load for many shooters.  I believe it is the NYPD duty load.  Its velocity from the Hi Power is normally around the 1200 ft/sec level.


While all of these are "harder" on the Hi Power than standard pressure, I don't think that they grossly increase wear and tear, particularly on those Hi Powers sprung/buffered as suggested previously.


For those wanting to stick strictly with standard pressure loads for serious purposes, I suggest the following:


         Speer 124-gr. Gold Dot Hollow Point: This one seems to expand reliably at its 1100-ft/sec velocity and it's accurate.


         Federal 115-gr. JHP: A reliable feeder and a cartridge that has worked very well for me over the years.  I've seen the velocity range from about 1130 to 1170 ft/sec, depending upon lot number.  Later lots have been at the higher listed velocity.


         Remington 124-gr. Golden Saber: Moving only 60 to 80 ft/sec slower than the +P version, the load has performed well in formal tests I've seen as well as my own informal expansion testing.


The Hi Power, particularly the current Mk III pistols, can handle +P with no problems.  The older guns can, too, but in more modest amounts.  In my opinion, the use of +P is not a problem in any of the pistols if being used only for testing and then for protection or small game hunting. I do strongly suggest using the heavier recoil springs, a buffer, and not reducing the mainspring strength if you plan to shoot quite a bit of +P ammunition.




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