A few Questions About +P and +P+ Ammunition

[DustyGmt]

So I know the simple explanation is that +P ammunition is just a cartridge loaded hotter than a standard pressure load. I have seen referenced time and again that ammo used to be loaded hotter than it is today, and a lil bit of Google tells me that in 1972 there was a shift in standards across the board.

My questions will be a lil scattershot so please bear with me but what I take from that is that anything we see marketed as +P today is just ammo loaded to pre 1972 levels, most likely because of lawyers covering their clients from mishaps involved with poor quality and antique guns,, etc.. so if I wanted a truly hot +P loading I would need to load my own or buy +P+ ?

Also, if I have a gun made before 1972, and the old instruction manual says not for use with +P ammunition, would it be safe to shoot +P ammo in it because it's manufacture predates the new standard?

Also, I have never seen +P rifle ammunition, but I put this in General Gun because I figure it has to exist. I know that 5.56 is for all intents the +P version of .223. Are there rifle loadings that bear the +P designation specifically?

One thing that probably doesn't have anything to do with this but there are two types of Fusion .223, plain Fusion and MSR Fusion, it's interesting that the MSR version is over 100fps faster but doesn't have any kind of labeling designating it hotter, how come they don't call it +P ? Maybe kind of a noob remark, sorry. Just wondering because it seems like a significant jump in pressure....

I know there is lil chance of finding it right now, but in general, was it pretty easy to locate +P and +P+ FMJ ammo for training use to mirror your self defense load or was it primarily only available for JHP?

I would think that +P and +P+ would be very popular and that there would be more squawking about post 72 "watered down" ammunition and that the + would be on more of a pedestal, the impression I get is that the watered down stuff works just fine and people just don't seem too concerned with "hotter", as you'd think they would be. Just an observation.

And I think lastly, is there load data available for +P and +P+ ammo for those that want to load their own or do people usually do their own testing and tweaking for a lil extra velocity? I never really looked into this much, only to the extent that I knew +P would add about 70-80 fps to my 9mm. A lil more for +P+.


Any answers or anything interesting you guys could add about +P and +P+ ? I know the general gist of it, anything more specific or things worth noting about +P/+P+ would be helpful. Again, I apologize for the scattershot battery of noob questions. I guess I'm still a noob.

 

[HowieG]

Wow. Yeah there is +P rifle ammo. What comes immediately to my mind is the 257 Roberts. Perennially underloaded so they boosted it a bit and called it +P. There is +P data for it in Lyman 50th manual. 5.56mm really isn't +P 223. 5.56mm is only supposed to be fired in a 5.56 chamber. It isn't safe to fire in a 223 chamber. Don't use +P in handguns unless they are specifically rated for it. It might not fail the gun, but it will beat it to death eventually. If your gun is pre +P, don't use +P. Basically, always err on the side of safety. If you don't have a pretty good idea about what you are doing, don't do it.

 

[HowieG]

And yes, there is +P data in some manuals. Lyman 50th is a good one for that. The data I see most often is for 38 Special +P, because I load for it.

 

[JohnKSa]

+P ammunition is ammunition loaded to higher than standard pressure but equal to or lower than a specified SAAMI +P pressure established for that cartridge.

There was a SAAMI push to standardize how ammunition velocities were measured, and to standardize the measurement specifications with more realistic barrel lengths. Those changes, especially in revolvers, resulted in a decrease in ADVERTISED velocity, but the testing I have seen using vintage ammo does not support the idea that factory ammo (with some possible exceptions due to concerns about specific firearms or cartridges) has been watered down.

There was also confusion generated by the changeover from CUP pressure measurements to PSI measurements, but again, while there may be a few exceptions, the changeover was primarily a change in the units representing the pressure, the actual pressures did not change--like changing the reported length of an item from 2.54 cm to 1"--that's only a units change, the lengths are exactly identical.

+P+ ammunition is ammunition that is ostensibly loaded to a higher pressure than any SAAMI standard for that cartridge. There is no specification for what +P+ is, so to know what the actual pressure is, one must contact the maker of that specific loading and ask them.

Also, if I have a gun made before 1972, and the old instruction manual says not for use with +P ammunition, would it be safe to shoot +P ammo in it because it's manufacture predates the new standard?

With only a few exceptions, there was not a new standard, if by that you mean that the actual pressures changed. How velocities were measured and the units in which pressure were measured changed, but for the most part, the actual peak pressures stayed the same.

One thing that probably doesn't have anything to do with this but there are two types of Fusion .223, plain Fusion and MSR Fusion, it's interesting that the MSR version is over 100fps faster but doesn't have any kind of labeling designating it hotter, how come they don't call it +P ?

For one thing, there is no established +P standard for the .223 cartridge. There are only established SAAMI +P standards for a handful of cartridges.

For another, just because the velocities differ doesn't mean that the faster one exceeds the SAAMI pressure standard for that cartridge. There is certainly a lot of factory ammunition out there that is not loaded right up to the absolute maximum pressure possible.

 

[DustyGmt]

+P ammunition is ammunition loaded to higher than standard pressure but equal to or lower than a specified SAAMI +P pressure established for that cartridge.

There was a SAAMI push to standardize how ammunition velocities were measured, and to standardize the measurement specifications with more realistic barrel lengths. Those changes, especially in revolvers, resulted in a decrease in ADVERTISED velocity, but the testing I have seen using vintage ammo does not support the idea that factory ammo (with some possible exceptions due to concerns about specific firearms or cartridges) has been watered down.

There was also confusion generated by the changeover from CUP pressure measurements to PSI measurements, but again, while there may be a few exceptions, the changeover was primarily a change in the units representing the pressure, the actual pressures did not change--like changing the reported length of an item from 2.54 cm to 1"--that's only a units change, the lengths are exactly identical.

+P+ ammunition is ammunition that is ostensibly loaded to a higher pressure than any SAAMI standard for that cartridge. There is no specification for what +P+ is, so to know what the actual pressure is, one must contact the maker of that specific loading and ask them.With only a few exceptions, there was not a new standard, if by that you mean that the actual pressures changed. How velocities were measured and the units in which pressure were measured changed, but for the most part, the actual peak pressures stayed the same.For one thing, there is no established +P standard for the .223 cartridge. There are only established SAAMI +P standards for a handful of cartridges.

For another, just because the velocities differ doesn't mean that the faster one exceeds the SAAMI pressure standard for that cartridge. There is certainly a lot of factory ammunition out there that is not loaded right up to the absolute maximum pressure possible.

Excellent. I guess I had it pretty twisted.... I'll do some reading on some things you mentioned. Not as cut and dry as some posts and sources on the net. Why I asked here.

 

[Alte Schule]

When I was a young man +P and +P+ had a certain appeal to me as well as the largest grain bullet for my big bore pistols and any "cop killer" type ammo that was marketed as such and popular 25-30 years ago. As an LEO way back then we were issued the S&W Model 28 in .357 Magnum. I found I was more accurate with the .38 Spl. +P so I and several others carried those. Years later, when the department morphed to the wonder nines, +P ammo wasn't permitted.

I have several vintage revolvers now but I avoid shooting +P through them. Hornady Critical Defense is my go to ammo now. I know there are several internet gurus out there that would disagree but I know what works for me. I personally see no reason to have +P or +P+ in my carry firearms. If +P ammo works for you that's great and as fun time range ammo I say why not. The stuff is sure ultra $$$ nowadays.

 

[RetiredUSNChief]

It's a good question (or questions, actually) and @JohnKSa summarized it quite well.

Here's an article that clarifies it even more:

https://www.thetruthaboutguns.com/ask-foghorn-what-does-p-and-p-mean/

SAAMI set the standards, and (in case some out there don't understand what this really means) standards are actually very important. When you have a known standard, then firearms manufacturers can consistently design and build firearms in various chamberings that will function safely and reliably with ammunition which is manufactured to these known standards.

They're not "watered down"...they're simply "standards". Many people who use the term "watered down" are really saying "back in the day we could load anything any way we wanted and by golly it was good enough!"

Well by golly, in the engineering world it's actually NOT "good enough".

So firearms are built to a standard which will ensure safe operation with the known ammunition standards and then they're "proofed" with a round that is very deliberately way over pressure to ensure it'll handle it safely. So for ammunition manufactured to SAAMI standards, this will ensure the safe, reliable function of the gun for a very long time before parts even come close to wearing out.

If you shoot +P ammo, then it's STILL within the safe SAAMI standards. It's around 10% over "normal" pressures, but still well below the proof pressure. It just means it works the gun a wee bit harder, but not to any dangerous levels. It amounts to simply more "added wear" on the weapon which may lead to higher wear and an earlier mechanical failure of some kind than would normally be expected.

+P+, however simply means the ammunition is loaded above SAAMI pressures and has no upper limit. This means, in addition to an even higher level of wear and tear, there are no upper limits and ammunition may indeed be approaching imminently unsafe pressures. Theoretically this means it could approach (or even exceed) proof pressures. You won't know how much over pressure unless you can get that information from the manufacturer.

As for the warnings about +P and +P+ in owners manuals, this is simply the firearms manufacturers telling you they have manufactured the gun to safely and reliably operate within the ammunition standards established by SAAMI and operation at any higher pressures means YOU are assuming any risks that come with that, not them.

As an interesting side note, speaking on general engineering principles, handguns are the most underpowered of all firearms. This is inherent with the fact that they are handguns, meant to be smaller, more portable, and easier to carry/conceal. Ammunition loadings produce good results within a fairly narrow range of pressures/velocities given the inherent engineering limitations of any handgun. Above a certain level of pressures/velocities you are really operating at the point of diminishing returns where making a cartridge more energetic simply doesn't give you that much increase in performance characteristics. Attempting to do so means more recoil, less control, and heavier wear. To offset this and maintain the same safety and reliability margin, you have to make the gun more "robust", which makes it larger, more massive, and less wieldy. All for ever smaller performance gains with increasing pressures.

Ammunition and bullet technologies have come a long way in the past few decades. There are a great many choices out there which provide excellent performance in penetration, expansion, and terminal ballistics under standardized SAAMI pressures. Outside specific instances, their performance characteristics are more than adequate for most uses and by far the most significant gains to be had with respect to terminal ballistics is to train enough to actually get those bullets on target (and in the right places) in the first place. There ain't no terminal ballistics to be had if you can't hit what you should be hitting in the first place.

THAT SAID...shooting is fun, and if you want to shoot +P or +P+...by all means. Just be intelligent about assessing the potential risks.

 

[Speedo66]

If you're looking for hot factory rifle ammo that might be the equivalent of +P but not labeled as such, you only have to go Grizzly or Buffalo Bore.

Whether they're using proprietary powders or a mix of commercially available ones, they seem to get the most out of each particular cartridge they load for while still keeping within accepted pressure limits.

 

[Riomouse911]

And to add, most +P+ ammo was the result of a contract between a buyer, usually a larger government agency, that wanted a to reach specific performance goal with a cartridge and bullet combination for their particular firearm(s). This level could only be reached going above SAAMI max pressures with the components the manufacturer was using, so the manufacturer put the +P+ designation on the ammo to set it apart. Since these aren’t usually advertised very often, finding exactly how much more pressure +P+ is developing over standard or +P isn’t broadcast. I guess to really find out would require a shooter to have a pressure barrel and psi measuring set up.

I have a couple dozen boxes of rotated out Win Ranger 9mm +P+ ammo that I’ve amassed over the past decade-plus that works perfectly in Glock 19, 34 and other 9mm handguns of similar duty-size that I’ve fired it in. I have not fired it in compact-EDC guns because it’s (In my opinion) tough on the shooter and these little guns... and the gain in longer barrels is usually just more flash and bang in these tiny ones. For these guns I preferred 115 gr Critical Defense for a while, but I’ve morphed to carrying Federal HST micro 150 gr now.

Stay safe.

 

[Drail]

I will never understand the desire for +P ammo. Standard loads will do a fine job if properly placed. If they are not then more pressure isn't going to change anything.

 

[DustyGmt]

When I was a young man +P and +P+ had a certain appeal to me as well as the largest grain bullet for my big bore pistols and any "cop killer" type ammo that was marketed as such and popular 25-30 years ago. As an LEO way back then we were issued the S&W Model 28 in .357 Magnum. I found I was more accurate with the .38 Spl. +P so I and several others carried those. Years later, when the department morphed to the wonder nines, +P ammo wasn't permitted.

I have several vintage revolvers now but I avoid shooting +P through them. Hornady Critical Defense is my go to ammo now. I know there are several internet gurus out there that would disagree but I know what works for me. I personally see no reason to have +P or +P+ in my carry firearms. If +P ammo works for you that's great and as fun time range ammo I say why not. The stuff is sure ultra $$$ nowadays.

Most of my carry ammo is standard pressure, I am happy with the performance of standard ammo too. I've watched lots of testing and even done some of my own and never saw anything in the way of evidence that made me think "oh man I'd better run out and get some +P". Interestingly I have some +P 135 gr Hornady CD and Standard pressure 135gr CD. I have shot a couple boxes of each and I mixed up rounds and blind loaded mags, I could not tell the difference between the +P and standard. Maybe a chrono would have told another story, idk.

Only thing I've ever really thought might be necessary to have a lil hotter load for would be for a snub .38 with WC or SWC or a .380. Basically anything with sub 2" bbl.

Thanks for the replies, a few nice summary posts, pretty much exactly what I was hoping for, a general outline that would clear up any of my own misconceptions and not have to go reading a hundred pages of irrelevance. Very good replies guys thanks.

 

[DustyGmt]

I suppose some of the guys that advocate for "hotter" are likely the same that won't be caught carrying anything but the largest grain weight available for a given cartridge. I know a few like this. Bigger, heavier and hotter is always better. Nevermind the science or stats. These are immutable truths.

 

[Terry G]

I have a couple of boxes of Federal 9 MM +P+. Would you say this ammunition would be save to use in limited quantities? The gun's would be CZ's, full size 75b and Compacts. Also in the Ruger 9MM PCC. Thanks for any help.

 

[Jim Watson]

There are different types of +P ammunition.
9mm +P and .45 ACP +P are straightforward, smokeless powder rounds overloaded by about 10% for a 5-8% gain in muzzle velocity.

I have a couple of boxes of Federal 9 MM +P+.

Assuming they are plain hollow points labeled 9BPLE, they have a good reputation with no reports of beating up guns. I figure they are just barely over the +P maximum specification.

.38 Special +P is overloaded by almost 18% for a good 16% gain in muzzle velocity. But that is an original black powder cartridge, converted to smokeless, so there is a lot of room for souping it up in good guns. There is a poster who describes shooting hundreds of +Ps in his revolver with no apparent excess wear. On the other hand, I know an IDPA shooter who wore out two Model 10 S&Ws with no doubt thousands and thousands of +P required to make Minor power factor. IDPA has since reduced the revolver power factor to allow econoball ammo.
But then I know a PPC shooter who has worn out two revolvers with midrange wadcutters, but it took a great lot of shooting.

.38 Super +P is an oddity. It is +P only in relation to the 1902 vintage .38 Auto; there is no "standard pressure" .38 Super. Purely a nomenclature convention to bring it into line with other calibers.

.257 Roberts +P is another oddity. Standard pressure is less than its parent 7mm Mauser and +P only brings it up to the level of .30-06. (In CUP, as originally manufactured, in pizeo psi it is a bit over 7x57 and +P is a bit less than .30-06.) The only reasonably satisfactory answer I have heard is that light loads gave the best accuracy in a day when IMR 3031 was the latest and greatest in powders. No, a .257 Remington Roberts will not even chamber in a wildcat .25 Roberts, no danger of overloading a customized Spanish Mauser.

 

[JohnKSa]

I have a couple of boxes of Federal 9 MM +P+. Would you say this ammunition would be save to use in limited quantities?

Any ammunition that is not defective, and that comes from a major U.S. manufacturer, will be safe to shoot in the sense that it is really unlikely to blow up a good quality firearm in good condition that is chambered for the caliber. But the standard rules apply for recoil operated firearms--the hotter the ammo, the more stress/wear on the components. In other words, your guns won't blow up, but shooting that ammo will stress/wear the firearm more than standard pressure ammo would.

I remember seeing a post on a forum by a person in a foreign country who was shooting ammunition that had generated several official warnings in the U.S. about non-suitability for use in handguns due to being loaded very hot. It was all he could find where he was. He was shooting it in pistols known to be robust and durable but noted that the use of the heavier ammunition seemed to decrease the service life of the pistols considerably. The guns were wearing out 2-6 times faster than would be expected with normal ammunition.

I wouldn't worry about use of 9BPLE in full-sized, good quality guns in good condition. Personally, I think I would be disinclined to use it in compact/subcompact pistols, but not because I would be worried about the gun blowing up. It's just that smaller guns are already doing the same work with less material and my engineering mindset balks at giving them more to do.

As always, the best course of action is to contact the manufacturer of the firearms and ask them what they recommend.

 

[Speedo66]

As always, the best course of action is to contact the manufacturer of the firearms and ask them what they recommend.

Unfortunately, you're probably as likely to get an answer from their attorney as an engineer.

 

[JohnKSa]

Which is not necessarily all bad. Attorneys care about things that might generate lawsuits and liability. Think about what that would mean in the context of this discussion.

 

[Speedo66]

Which is not necessarily all bad. Attorneys care about things that might generate lawsuits and liability. Think about what that would mean in the context of this discussion.

On the other hand, you also get answers like billboards of safety messages destroying gun aesthetics (I'm talking to you Ruger) or "May contain peanuts" on a bag of peanuts.

They can go way overboard in pursuit of client safety, sometimes to the detriment of the purchaser. I understand we live in a litigious society, but safety wise I'd rather hear it from an engineer.

 

[JohnKSa]

I understand we live in a litigious society, but safety wise I'd rather hear it from an engineer.

Well, as an engineer, I appreciate the sentiment--it can be really frustrating at times when warnings get hung up on liability at the expense of common sense.

At the same time, I think that if there were no potential for a negative outcome, the lawyers wouldn't care. They may get exercised for different reasons than the engineers, but the bottom line is if that if there's no chance of someone getting hurt or suffering a loss of some kind then there won't be any warnings. Coming at it from the other side, if there are warnings, it's because there's a chance (based on risk calculations which combine both magnitude of the potential loss and probability of the incident) of someone getting hurt/killed or someone losing property.

The engineer is more concerned about the proper use of the product and design parameters. The lawyer is admittedly far more concerned about liability and that can mean that less likely events make the cut for a warning if the magnitude of the potential loss is very high, but it's unlikely that either of them is making stuff up.

It irritates me that my company does things that are purely about limiting their liability and then pretends that it's done out of concern for the employees or customers. But in the final analysis, if I can overlook the motive and just look at the actions, there's almost always some benefit to the employees/customers even if the actual motive is purely selfish.

 

[RetiredUSNChief]

I understand we live in a litigious society, but safety wise I'd rather hear it from an engineer.

Honestly, I'm not too put out by all the legal disclaimers we see with firearms these days.

Like @JohnKSa said, some people just need those warnings to think "maybe I ought not do this".

The ammunition, and therefore the firearms, are manufactured to be safe and reliable based on known engineering standards. The legal disclaimers, when you think about it, is the company telling people this in legalese. "Operate this firearm as it was built to be operated or we will not be liable for any damage incurred".

 

[guyfromohio]

The only +P I own and use are .38spl +p when I carry my 642 instead of my 640. I’ve never bothered with it in the other guns.

 

[Virginia Jim]

If you get called before a judge for a righteous shooting, is someone going to bring up your decision to use +P ammo?
I’m kinda stirring the pot here, as I am NOT in the “don’t use handloads for self defense “ camp.

 

[jmorris]

I know that 5.56 is for all intents the +P version of .223. Are there rifle loadings that bear the +P designation specifically?

They are two different things, intents aside. 257 Roberts, as mentioned is one.

it's interesting that the MSR version is over 100fps faster but doesn't have any kind of labeling designating it hotter, how come they don't call it +P ?

You are confusing pressure with velocity, they are not the same. It is possible to have a higher peak pressure in a barrel and lower velocity using powder “A” and a lower peak pressure and higher velocity using powder “B”, all else being identical.

so if I wanted a truly hot +P loading I would need to load my own or buy +P+ ?

SAAMI has operating pressures, and they also have set standards for some over pressure designations (+P). +P just means “over pressure” unless you pick a chambering. +P for one round likely won’t be the same as others. +P is not like a blanket +10% in pressures, they vary from one round to another, as do operating pressures. Many normal operating pressures for some rounds are well above what would constitute +P+ in others.

So +P means over pressure by some arbitrary amount, all +P+ means, is that pressure is above max +P pressure for the round. That can be by a single PSI over or so much higher the firearm blows to pieces. That means you can’t load a “truly hot” +P, you can load to maximum +p pressure or over and a chronograph can’t tell you what pressure you are operating at.

I understand the pursuit, when I was a kid I loaded 357 magnum up to 41 magnum power levels; however, with years of experience passing by, I take a 44 magnum and download them to 41 mag levels.

Point being, you don’t have to ride the edge of the envelope to achieve a certain power level. I built a 50 BMG years ago to quench that fire, after that is just picking the right round for what you want.

 

[AK Hunter]

If you get called before a judge for a righteous shooting, is someone going to bring up your decision to use +P ammo?
I’m kinda stirring the pot here, as I am NOT in the “don’t use handloads for self defense “ camp.

Right now handloads is about all you are going to find for carry ammo. My hand loads are never at max powder loads, so let the lawyers & judges chew on that.

 

[RetiredUSNChief]

If you get called before a judge for a righteous shooting, is someone going to bring up your decision to use +P ammo?
I’m kinda stirring the pot here, as I am NOT in the “don’t use handloads for self defense “ camp.

Right now handloads is about all you are going to find for carry ammo. My hand loads are never at max powder loads, so let the lawyers & judges chew on that.

First of all, if you should end up "before a judge" for any shooting at all, the prosecution WILL question EVERYTHING about the shooting you were involved in. And it won't matter if you're shooting +P or +P+ ammo, target ammo, hollow point ammo, or reloads. Your actions, your firearm, your caliber, your ammunition...the very fact that you were present in the first place. Anything an everything will be subject to questioning.

The single, most important aspect of any violent encounter you may appear in court for isn't the weapon or ammunition...it's whether or not you were in compliance with the jurisdictional laws on deadly force.

As for hand loads and "let the lawyers & judges chew on that"...rest assured, they most assuredly will "chew on that". That's what they do.

As with anything involving legal opinion, I'm not an attorney and not pretending to be one. Best you can do with my opinion is add a dollar to it and buy yourself a cuppa coffee at McDonalds.