Please explain +P ammo

[alank2]

Hi,

Great answers everyone.
Lets make sure I understand this correctly... the grains printed on the box is the weight of the bullet, not the amount of powder the bullet is rated for.

Yes, grains on box = bullet weight.
Bullets are not rated for an amount of powder.

Nobody prints how much or what kind of powder they use.

True manufacturers do not, most of the time the powder they use is "custom" for that particular load.

+P means more powder than normal (maybe they pack it in tighter creating more pressure in the casing?)
+P+ is even more powder than that.
So, for reloading purposes, how do you know how much powder to put in the brass? Do you start with half the bullet weight just for plinking (less $$)? Will a bullet that's 115 grain destabilize (meaning to breakup or disintegrate) if one uses too much powder behind it?

A lot to cover here.

Powders range from "fast" to "slow" as well as many types, but for now let's just say they range from fast to slow. The speed controls how quickly they build up pressure. Smokeless powder (what is in most cartridges these days) will build up pressure when confined. Out in the open, lighting it will result is fizzing, but no big bang. A fast powder will build pressure very quickly, but the pressure will also fall very quickly. Slower powders are used for magnum loads because they build up pressure steadily and hold it higher for longer. You do NOT want to use a specific amount of powder such as 50% of the bullet weight. There are many reloading books and manuals with "acceptable loads". These are loads with X bullet in Y cartridge using Z powder and they will say start at 10.5 grains and don't go past a maximum of 14.3 grains for example. THEY (the people who made the manual) have a way of testing the pressure level that X/Y/Z combination will produce. NEVER load without reliable load information and NEVER start at the maximum charge weight.

+P is only a "valid" designation for certain cartridges such as 38 special or 9mm. These cartridges have a normal pressure limit and also a +P pressure limit that must not be exceeded. So, if you have +P ammunition, you should make sure the gun is in good condition and strong enough to handle it. It is +P because the cartridge produced more than normal pressure (which happens to push the bullet faster!)

Bullets do have an ideal speed and pushing light bullets very very fast can cause them to fragment depending on what they hit.

Get a reloading manual and it will be a great read!!!

Good luck,

Alan

 

[Old Fart]

My short answer may be to simple, I was just trying to explain that the +P really only indicated maybe a faster load. Generally speaking produced by increasing charge of powder. That being said more doesn't always equate to better or faster. For instance I can get the same velocity using a smaller charge of Bullseye powder compared to a similar velocity round using more Unique powder. As everyone has stated and I think you understand the grains means the weight of the bullet itself. Also a lot of the manufactures use custom blends of powder to achieve optimum performance.

 

[tul9033]

No, but I have some +p+, a chrono, and a G17 I'll get a reading on next time I'm out chronoing.
Those +p+ rounds feels like a hammer hitting your hand. Not fond of them, but I bought some years ago thinking they were man stoppers. I'm sure they are, but a 147gr HST will work just fine.

anybody ever chrono any 9mm +P+ through a Glock 17 by chance?

 

[Phat Mike]

The way you know how much and what kind of powder to use is to look in a good reloading manual.
If you use too much or the wrong kind, you may win a trip to the emergency room to have the pieces of your gun surgically removed.
If you read the front section of any good reloading manual, you will find an explanation of the principles of reloading, which must be firmly in hand before doing any reloading. It's not rocket science, but trial and error is not a viable way to learn.

Added: Link to reloading data
http://data.hodgdon.com/main_menu.asp

1+ buy a good reloading book! and start out on the low end and work your recipe up !!

 

[CATAHOULA]

Is it me or did a lot of the recipe books from the 60's and 70's contain recipes that were kind of






Seems like some of the recipe books from the 60's and 70's used what are considered +p loads,now as low to midrange loads back then.I think it boils down to liability for the company's that produce ammo.

 

[Shadowrider]

Is it me or did a lot of the recipe books from the 60's and 70's contain recipes that were kind of






Seems like some of the recipe books from the 60's and 70's used what are considered +p loads,now as low to midrange loads back then.I think it boils down to liability for the company's that produce ammo.

There's really no rhyme or reason. Well there's a reason and I think it's lawyers. LOL!

My Hornady manual for .357 magnum w/158XTP bullet has a max charge of 13.1 grains of VV N110 powder.
Now the VV manual states that a beginning charge of that same powder with that same exact bullet is 15.1 grains.
Both of these are the current version manuals, BTW. But yes the old manuals are generally hotter, but remember that pressure testing has came along way since then.

 

[HiredHand]

Powders have changed, too. They aren't always the same even if the name stays the same.

 

[Sanjuro82]

I was going to type a long response, but I'll just direct you to this Wiki page on the subject instead. It'll explain pretty much everything you'd like to know about higher pressure ammo.

http://en.wikipedia.org/wiki/Overpressure_ammunition

 

[ldp4570]

Originally posted by a friend of mine on +P ammo.

I was a little surprised when I began visiting these Internet forums and saw so many questions regarding +P .38 Special ammo. It seems each new day brings yet another post asking about the safety of using factory +P ammo in one gun or another. I always assumed the short answer was that if you had a Star, or Ruby, or some other gun that might be questionable as far as strength is concerned, then stay away from +Ps. But many shooters seem concerned about using this ammo in quality guns of recent manufacture* and I didn’t expect that. I saw many inquiries about K frame S&Ws using +P and I found it odd that anyone would worry about using factory +P ammo in such a gun. Then I started seeing postings from owners of .357 Magnum revolvers asking if +P .38 Special ammo would harm their guns. One forum member was concerned that +Ps would damage his Model 28 S&W.

Come again? I don’t know what caused such a mystique to surround +P ammo to make people with N frame Magnums think it’s too much for their guns, but it strikes me as overblown all out of proportion. The fact is that +P isn’t “all that” anyway. Winchester, Federal and Remington list the velocity of the 125 grain +P at around 925 FPS. These velocities are actually fairly mild. I have shot many rounds of Remington 125 grain +Ps in a 1942 S&W Military & Police revolver and I can literally shake the fired cases from the gun without using the extractor. In my opinion these loads are actually pretty mild and show no sign of even moderate pressure in any of my guns.

As underpowered as I thought the Remington ammo was the PMC proved worse. I clocked a box of the El Dorado 125 JHP +Ps and from a 4" barrel I got a pathetic 890 FPS. Fired from a 2" M&P (made in 1949, BTW) this ammo ran 795 FPS. How can such puny loads cause so much hysteria among shooters? I also tried some Winchester 110 grain +P+ "Law Enforcement Only" ammo. I was expecting around 1300 FPS but all I got was 1100. Big deal! This load was very mild and easy to shoot through the 2" gun and I fail to see the reason for the fear of +P (or +P+ for that matter) that so many shooters express.

Why is everyone so terrified of +P? I believe that the reason +P exists is twofold. First, it is a marketing ploy used to sell ammo by misrepresenting it as powerful. But any perception that this ammo is powerful is a myth. Second, it gives the ammo companies legal cover should anyone blow up their inexpensive gun because they can say "We warned you not to use +P ammo!" Of course, +P is nothing more than what standard pressure ammo used to be and they created the +P moniker to protect themselves.

The factory ammo made back in the 1970s and earlier was hotter than that made today (see chart #1). I have seen the specifications for standard .38 Special ammunition from a 1940 catalog listing the velocity as 960 FPS with a 158 grain bullet. This load would clearly develop higher chamber pressure than the current +P load and yet it was used for decades in all models from Colt and S&W without incident. The current +P is really about what the .38 Special should be in standard form. But note that today's standard load is no longer what it once was, either. In 1940 it was the 158/960 that was considered standard. During most of my youth I recall the load as advertised at 158/870. I have a copy of the specifications for S&W/Fiocchi ammo that was packaged with new guns that appears to have been printed in 1970. It lists the 158 lead .38 Special load at 910 FPS. It also includes a 158 JHP at 1140 FPS (equaling the mighty 38/44 load), a 125 JHP at 1380 FPS and a 110 at 1390 FPS**. I have seen a ‘70s box of SuperVel .38s with the package labeled as containing a 158@955 load. This was the standard load in the early 1970s (although I didn’t recall SuperVel offering standard velocity ammo). Note that none of these loads were marked as +P, but were considered standard pressure and the ad bears no mention of not using this ammo in older guns or revolvers with alloy frames.

These loads are probably similar to those +P loads offered by the specialty ammo makers like Bear Claw, Cor-Bon and others that exceed the levels achieved by the mainstream ammo company loads. Bear in mind that this was ammo bearing the S&W name and sold through their dealer network for use in their guns. They are now advising against using the rather meek current +P for their revolvers when they used to advertise and sell ammo that was much hotter. Compare these velocities to those offered today and tell me they haven't reduced the loads! Current specifications on the lead 158 are pretty wimpy at 158/750 (some are now showing 730). Again, we see the ammo companies reducing the loads over the years. The current +P (which means +Pressure if you didn’t know) is really only +P when compared to current standard loads. Stacked up against past standard loads the +P looks pretty anemic and the current standard load is truly pathetic.

The fact is that +P is only called +P in comparison to the current standard .38 Special loading, not because it exceeds the pressure limits set for the caliber. I believe the SAAMI pressure limit for the .38 Special is 21,500 PSI (the .357 Magnum is 35,000 for comparison). The standard load for the .38 Special as offered by Winchester, et al, generates 16,500 PSI. This is so far below the maximum allowable as to be ridiculous but the ammo makers fear lawsuits from people using the ammo in cheap guns. The +Ps from these manufacturers run about 18,000 PSI. This is more than the standard loadings (hence the +P designation) but is still far below the maximum allowable pressure. Those "really hot +P loads" from the specialty manufacturers like Cor-Bon, etc., are simply loaded to the caliber's full potential of 21,500 PSI and should be perfectly safe in any quality arm in good condition. Sellier & Bellot sells a 158@975 load that is obviously more powerful (and therefore generates more chamber pressure) than the 125@925 +P yet this ammo isn’t labeled as +P. It’s likely simply loaded near the 21,500 PSI maximum allowed for the caliber and this company eschews the ridiculous +P label on ammo that is within industry standards.

So why are we seeing these less powerful loadings? Because there are some guns out there that are not well made. Because of liability concerns the ammo makers must load their products to pressures that are safe in these lower quality guns. They mark the "high pressure" loads as +P (even though as I noted they really aren't high pressure) to give them legal cover should someone hurt himself shooting this ammo in a cheap Spanish S&W knock-off of dubious quality.

S&W ran advertisements in the 1930s and 1940s specifically stating that the .38/44 load, which pushed a 158 grain bullet at an advertised 1125 FPS making it far more powerful than the current +P load, could be used in the K frame revolver. Colt ran similar ads for using this ammo in the Detective Special. If these 1930s-era medium frame revolvers could handle the 158/1125 Heavy Duty loads, why should anyone worry about the same guns shooting the current 125/925 loads labeled as +P? One former police officer told me that between 1958 and 1960 he fired 2,000 rounds of factory 38/44 ammo through his duty Model 10 without any effect to the gun. If all that shooting with the 158/1125 load didn't harm his K frame I don't see how the 125/925 +P can hope to do damage.

Lee Jurras started Super Vel in the 1960s. This was maybe the first of the specialty ammo companies and he offered truly high performance .38 Special loads. I have some of the 110 grain loads and they clock around 1300 FPS. Based on this I would guess his 125 loads would go around 1200 or so. This would be a true +P load but it’s still lighter than the old .38/44 load. I don’t recall seeing or hearing of guns being damaged by this ammo.

Check out a reloading manual from the early '70s. The Speer #8 from 1970 has a load listed for the .38 Special pushing a 158 JHP to 1,250 FPS, one for the 125 grain bullet at 1426 FPS and one for the 110 grain bullet at 1536 FPS! A 1971 Sierra manual shows a load for the 125 grain .38 Special at 1250 FPS. Sort of makes that factory +P at 925 seem less intimidating, doesn't it? Now, of course, new manuals don't include listings that are this hot. Now they stop at about the same levels as the factory +P. Why? Lawyers and lawsuits are the reasons why. The reloading manual publishers are just as scared as the gun and ammo makers about being sued. Fear of lawsuits is the same reason the gun makers caution against the use of +P ammo. They also say don’t use reloads. They have to say this on advice of counsel to protect themselves.

I load 125s at 1,100 FPS in my .38 Special carry guns. This load came from the 1970 Speer manual and is not the top load listed. I have shot many rounds of it through both K and J frame guns and they seem to work just fine. Recoil is slightly more pronounced than with standard ammo, but the cases fall from the cylinder with no sticking and I see no signs of excessive pressure. Just for fun I once put 6 rounds of this ammo through an old small-frame Rossi revolver. Nothing bad happened although I wouldn’t advise using this ammo in such a pistol. I once loaded some 110 JHPs to a clocked 1400 FPS from a 4" Model 10. These were hot, let me tell you, and I backed off. But the gun showed no immediate effect from having fired a small amount of this ammo.

 

[ldp4570]

Continued;
Ask yourself this question: Would any ammo maker in today's litigious environment sell any ammunition that would be unsafe or harmful to use in the typical gun that a consumer may own? If factory +P were really hazardous would Winchester, or Federal, or Cor-Bon sell it to the general public?

With all the many, many questions regarding the safety of +P ammo, there must be many reports of blown-up guns, right? How many guns blown-up by factory +P ammo have you seen? How many guns blown-up by factory +P ammo have you heard about? I have been participating in the shooting sports and studying firearms since 1967 and I know of absolutely NONE. I have heard second and third hand accounts of one or two guns that were said to have been damaged by factory ammo but I think it more likely these guns suffered failure due to some manufacturing defect. It happens. I have a S&W .357 Magnum that was returned to the factory for a new frame. Something went wrong with it.

Certainly, using a gun causes wear. A gun is a machine and using any machine will cause it to wear. Using hotter ammo will likely accelerate the process to some degree. But a quality gun from S&W or Colt or Ruger will not blow up with +Ps. Nor will it excessively stretch the frame or split the barrel in my opinion. It will possibly wear a little faster, and I doubt if anyone could predict how much, but I think the added wear on a good gun will not be all that much. The gun would probably still last longer than the man who owns it.

I admit to some paranoia about warm loads in an alloy-framed gun but factory +P is not a warm load. I do not have any alloy revolvers but if I did I would stick to standard ammo (such as +P) and avoid my warm hand loads. In an alloy gun of good quality I have no concerns at all about +P on a regular basis since I consider factory +P to be nothing more than standard pressure (or less), anyway. Also, in 1955 Elmer Keith wrote of shooting the 38/44 load through the alloy J frame guns and he said that it did them no harm but recoil was pretty fierce. Keith favored big guns with heavy recoil so such a comment coming from him is quite meaningful.

This is just my opinion based on personal experience and research. There are differing points of view. Some replies to the +P question are quite adamant about avoiding regular use of this ammo. Others advise occasional use. Some say only carry +P for defense but don’t use it for practice at all. Some say S&W guns with model markings are OK with +P*** (what about the Colts?) while others say only use it in guns specifically approved by the factory. The fact that there are so many answers to this question tells me that there is great confusion on this matter. I’m a simple man and I take a simple course to the truth. I do basic research and try to find the facts. I have presented the facts as I see them. All one must do to find the truth about current factory +P ammo is look at the specifications. I submit that a 125/975 load is hardly high performance, and certainly nothing to cause concern for owners of quality revolvers. All are free to disagree.

Some forum members have accused me of being irresponsible in recommending the loads I mentioned. Of course, I am not recommending anything, only stating what I do. Also, all of the loads I use came from reputable reloading manuals. If the loads were safe in 1970 I don’t see why they aren’t safe now, but I don’t recommend anything to anyone. Each of us has to make our own choice. If you think any of the loads I mentioned are too hot then avoid them. If you are in any way uncomfortable with +Ps then stick with standard loads.

Notes:

* The manufacture and tempering of steel was imprecise before around 1930 or so. Any of my guns made before this date get reduced loads just to be on the safe side. Note that early S&Ws, those made before around 1918, had cylinders that were not tempered at all. A similar situation likely is true with Colt revolvers but I have no specific knowledge of when Colt began tempering their cylinders.

** This same document advertises a 125 JHP .357 Magnum load at 1775 FPS. Current factory ammo in this caliber with this bullet usually clock around 1250-1300 FPS. Apparently the Magnums have also been "downsized."

*** I never understood using the "model marking" on S&W revolvers as the cut-off for +P. As far as I can tell the last S&W made without the model number stamped on it was exactly the same as the first revolver to have the model number stamped on it. They didn't improve the steel or strengthen the guns in any way. All they did was start stamping the model numbers. Also, how could S&W have intended for the model marking to be a benchmark for +P when the ammo wasn’t invented until 25 years later?

PS:

This same situation that has affected the .38 Special occurs with the .38 Super. The original loading for the Super was a 130 FMJ at nearly 1,300 FPS. But the Super cartridge is the same physical size as the old .38 ACP, just loaded to higher pressures so the ammo makers started fretting over some yahoo stuffing Supers into his 1905 Colt in .38 ACP and spreading parts all over the range. That’s why Super cases were nickel and the .38 ACP were brass until a few years ago, so shooters could instantly recognize which ammo they had. I was curious a few years ago when I noticed that they stopped doing this and I saw Super ammo in regular brass cases. I guess there’s no need any longer since factory Super ammo now clocks about the same as .38 ACP. The last box I checked ran 1,120 FPS, only 40 more than the ACP. They have down-loaded the Super to nearly the same level as the ACP. No lawsuits. Of course, the Super isn’t so… super… any longer, is it?

Some people claim that the standard .38 Special load today is the same as 30-50 years ago and the only difference is the claimed velocities in the past were greatly exaggerated by the test barrels they used. Everyone back then knew real-world velocity would be a little lower but not as much as some would have us think. Below are some actual measured velocities of various vintage ammunition.

Chart #1:

Some .38 Special velocities actually measured (not claimed by the manufacturer) from a 4" Colt Official Police:

Remington 158 grain lead made in the late 1960s-early 70s...840 fps
Peters 158 grain lead made in the 1950s...800 fps
Western Super-X 158 grain lead made in the mid-late1960s...810 fps
Western 150 grain metal-piercing made in the mid-late 1960s...1000 fps
Remington 158 grain lead "Hi-Speed" made in the 1950s...920 fps

The 158 loads from the 1950s-1970s are clearly more potent than the current offerings that achieve a claimed 730-755 FPS velocity. The observed 800-840 FPS is consistent with the manufacturer claims at the time of 870-910 FPS since they used a 6" "pressure barrel" to achieve the claimed velocities and actual velocities from 4" revolvers ran somewhat lower. But clearly not the huge difference some people claim in their assertions that factory .38 Special ammo has not been reduced in power. Also, bear in mind that the ammo being tested was all 30-50 years old and may have exhibited some deterioration in the powder which may have caused lower velocities than the ammo developed when new.

The bottom line:

Each man must do what he thinks is best. After a great deal of research and testing I do not consider factory +P ammo to be very warm at all and it concerns me not one bit in a quality revolver.