These two cartridge boxes look the same.
At a glance, the cartridges look the same.
One end of each box does offer declarations of difference.
Batched way back in early April of 2001
These +P cartridges were marketed as fodder for police duty-revolvers (4''-6'' barrels) and were offered for purchase to the public subsequent to agencies switching over to semi-auto pistols. I scored a case of 1,000 rounds several years ago. For the +P rated steel frame revolvers, I recently decided to use these for range time (and as a decent-enough self-defense load) ahead of everything else that I have in inventory. It seems to be a quality batch of stuff, but I have no sentiment for them; when they're gone they're gone. The P38N just does not have the cachet of the P38M.
Design specs were 950 feet per second / 250 ft. lbs. of muzzle energy. I'm guessing these would launch at maybe ~850 feet per second from a 2'' barrel on a good day with a tight gun. The lead bullets in these loads are a bit harder than that of the P38M (non +p) and to me the hollowpoint looks to have somewhat of a smaller yawn (possibly to keep them from expanding in tissue too soon because of the higher design velocity). My guess is that law enforcement street-effectiveness suffered a bit when this cartridge was used in short barrel revolvers.
As one would expect, these cartridges do have noticeably more recoil that do the non+P P38M cartridges. The recoil is noticeably less than that of the +P 158-grain SWCHP loads.
The S&W 640-1 was the choice for this session.
I decided to forgo the 15-ft and 21-ft distances of my Illinois Qual exercise and just fire 30-rounds at 30-ft. All rounds were slow-fired using a staged-trigger. I dry fired on the empties after firing each full cylinder. The trigger on this revolver MAY be getting a bit smoother from the use it has recently been subjected to ... or my trigger finger may just be getting used to the trigger's native suckiness. My goal was to keep all 30-rounds inside the 9-ring at 30-ft. but I wasn't quite good enough.
Knowing that accuracy would suffer during the fast-shooting drills, I set Target #2 closer at 21-ft.
From a low-ready stance I waited for the target to turn from edge to facing, dumped five-rounds at the target before it timed out (and went back to edge), ejected my empties, speed-reload, back to low-ready and waited for the timer to again face the target at me. Rinse, lather, repeat; when out of ammo, time to skedaddle.
