I've been playing with the 380 ACP quite a bit here lately. Internet lore has often claimed that European loadings are quite a bit hotter when compared to those offered US ammunition manufacturers. I'm not going to delve into that topic. I tend to think a lot of cartridges have been neutered over the years. However, what I have seen in my own research of current and older data indicates that pressures suggested by the various manuals have significantly lowered the bar for this cartridge in particular. If you look to the SAAMI specifcations the .380 ACP it has a max PSI of 21,500. Yet, when you look at the Lyman manual as an example, it seems that most loadings max charge tops out at 16,000 PSI. (btw, yes I am familiar with the differences between PSI and CUP, I'm using data with the same units of measurement). And it would seem this trend actually happened sometime back in the 80s or 90s.
When looking at Data from the 45th Lyman Reloading Handbook, it lists the 358242 92gr variant with charges of Bullseye at 2.4-2.9gr (869-995fps), and Unique at 3.9-4.5gr (952-1155fps). That Unique loading sounds pretty stiff in comparison to today's loadings, and does sound much closer to stories about some of the older 380 ACP loadings. However, if we flip forward to the Lyman 47th Reloading Handbook from 1992 (I do not have a copy of the 46th to reference) we see that the Bullseye load has now been increased a hair, 2.4gr-3.0gr, though with a much lower velocity, 750-915fps. This was probably due to the 3.5" barrel used in the 47th compared to the 5" barrel used in the 45th. But when we look at the loading for Unique, we see a major shift. Now the min/max is 3.1gr-3.7gr for 755-920fps. This new max loading is under the starting load for the 45th manual by a decent margin when considering the capacity of the cartridge.
This seems rather unusual to me. Generally we do expect to see slight variations in data as additional data points are sampled. But a 25% reduction in just the starting load is pretty significant. And it has me wondering why. Surely there was not that large of a difference in the quality of arms being manufactured between 1970 and 1992. At least not in the sense that the newer arms were of lesser quality (except for maybe some of the cheap pistols on the market). And I think 1992 is even before the Alliant takeover of Hercules' powder, which I think happened around 1995. So we're not talking about any supposed change in powder formulation.
Does anyone have a bead on this? Do we have a definitive reason for the reduction, or just speculation that the Unique charge was just way too hot. Curiously, it does seem to be a closer comparison to the Buffalo Bore loadings, particularly the 90gr JHP at 1200fps and the 100gr Cast at 1150fps. My best guess is there may have been concerns about older guns. But, when I plug the numbers into Gordan's Reloading Tool, I only get 17,444 PSI with the max 4.5gr load. Which leads me to believe that this load may possibly still be safe. Lyman just reduced the loading for some unknown reason. Although, admittedly GRT is still not the most accurate tool, and maybe someone who has QL could check these numbers. But I am assuming the data in GRT is fairly close. And if that is the case, it would appear that many loadings we seem in the manuals for the 380s, as well as commercial offerings, are probably under loaded.