"+P" history

[Jim K]

There is some "apples/oranges" in the manuals shown by Powell & Hyde. The older manual shows only cast bullets, where the newer one indicates jacketed bullets. Since jacketed bullets cause a greater pressure spike at the forcing cone than lead bullets, I suspect the bullet difference is at least as good a reason for cutting back the loads as the "lawyer syndrome."

One thing is sure. We loaded .38 Special a LOT hotter in the olden times (way back in the 1960's) than the +P loads today and I don't recall any cities vanishing in mushroom clouds when we fired a round. But maybe I just wasn't looking.

Jim

 

[Steve C]

We all know that the SAAMI specs were lowered for .38 special in 1972 (?).

1972 there was no +P. Higher pressure loads where called "police loads" or Hi-speed" or some other designation that the manufacturers chose to name it. Pressures where still measured in less precise CUP and ballistics came mostly from fixed breach test barrels, Chronographs cost thousands of dollars, more than many new cars so no one was independently checking the velocity from their own guns.

Below is the Ballistic chart that came from the 1972 Guns and Ammo Annual. Note that for the most part you get similar velocities to current day publications if you adjust for the longer barrels and probably fixed chambers used in the 1972 data. Most of the semi auto velocity data is equivalent to most current published ballistics. Revolver ballistics need to be dropped by at least 100 fps per inch of barrel difference and likely more than that. Someone that shoots the same caliber through a single shot TC and a revolver that has run the same loads from both over a chrono could give us a good estimate of velocity loss.

There's a lot of misconceptions regarding early ammo ballistics, pressures, etc. Those of us who lived though those times know we where mostly operating from faith that the manufacturers and hand loading manuals where giving us accurate information. Now we don't have to rely on guesstimates as to what velocity the ammo being shot from our individual guns are making since a relatively cheap chrono will give you answers.

Chamber Pressure on the other hand is mostly the same as it was in the old days and you are guessing, even with computer programs like Quick Load. You can buy the equipment to measure pressure on your own but its relatively expensive and few people do for the same reason few had chrono's in the 70's.

 

[bigfatdave]

I always assumed it was because of antique guns chambered in whatever caliber is being down-rated, but I could be wrong.

 

[SaxonPig]

ASAIK when S&W introduced the 38 M&P in 1899 it made for 18,000 PSI pressure, same as today's +P. That 18,000 figure was the norm until 1972 when lawyers took over and they decided that after over 70 years with no problems that all of a sudden that chamber pressure was a worry.

I have copies of ads from the 1930s touting medium frame Colts and S&Ws as handling the 38-44 load and that runs 22,000 PSI.'

All this nonsense over +P is the biggest pile of hooey I have ever seen.

 

[atblis]

The fact that +p lets one charge a premium for basically nothing tells me all I need to know.

I suspect the testing methodology figures into the published numbers. There are different ways to come to different values. The fact that a pressure specification has changed over the years might have something to do with the testing methodology.

This looked interesting (haven't read all of it yet).
http://kwk.us/pressures.html

 

[Guillermo]

we all know that +P .38 is the same pressure as pre +P "regular" ammo

I am less familiar with other rounds.

Saxon, well researched, suggests that the only round that +P is hotter than it's "Pre+P" counterpart is .45ACP.

Does anyone else have corroborating or conflicting information on other cartridges?

Also, 9mm luger was apparently a much more mild round in the US compared to European counterparts. Does anyone have an explanation for this?

 

[lemaymiami]

If memory serves the 9mm ammo from Europe was much more designed for submachine guns, so ran at higher pressures. Hope someone will elaborate on this and correct me if I'm wrong. Thanks.

 

[unspellable]

Velocity?

I'm a firm believer that actual velocity is not always the same as advertised velocity, more so back when.

In particular I've run a lot of 7.65 mm Parabellum (30 Luger) over chronos from various pistols of various makes & models with various barrel lengths. Winchester claims 1220 fps from a 4.5 inch barrel. There ain't no way in h**l you're ever going to see that, not even from a six inch barrel. In some cases, SAAMI specs for the test barrel put it att he tight end of the tolerance for the production barrel. But not in the case of the 7.65. The SAAMI test barrel has the exact same nominal dimensions as the production barrel.

Being today a wall flower cartridge, I don't think Winchester bothered to change anything about it in the last 45 years.

Fiocchi's version is even weaker.

 

[AlexanderA]

We all know that the SAAMI specs were lowered for .38 special in 1972 (?). The old "regular" pressure ammo became "+P". "regular" ammo was emasculated.

I'm not sure this is right. I remember that sometime in the early 1970's, when the .38 special "+P" ammo became available, I picked up a box to try in my S&W Victory. I was a member of a civilian shooting club that had access to an indoor range on the Ft. Myer South Post (Arlington, Va.). With the first shot, it was obvious to everyone there that this was not the old standard loading. People commented that I better stop firing proof loads! The blast and recoil were not something that I was expecting, either.

 

[Guillermo]

I'm not sure this is right.

I am as are many with a ton more experience as well as the old reloading manuals, old and current advertisements and other evidence that correctly chronicles the history of .38 Special.

That +P was the same as regular loads prior is not in question.

Other cartridges are the wild card.

 

[45_auto]

The original .38 Special pressures (as well as almost all common pistol cartridges) were established using copper crush cylinders to estimate the pressure (CUP). A longer, low pressure pulse will result in the exact same amount of crush as a short, high pressure pulse. You have no way to know the max value.

With the advent of electrical pressure transducers in the late 60's, engineers could actually make real chamber pressure measurements (that's why almost everything today is in PSI instead of CUP) and see what was going on in the chamber. The SAAMI standards were revised to more accurately reflect the design parameters and assumptions used by the firearms manufacturers in designing their firearms (steel heat treat, chamber thickness, cylinder thickness, etc).