why +p?

General Firearms Terminal Ballistic Information
1

Please correct me if I am wrong. I understood that +p was developed several decades ago to aid in expansion. Rounds were not expanding reliably enough, and higher velocity was deemed the fix. More pressure = more velocity = more expansion.

However, too much of a good thing was no longer a good thing.

When the 115gr 9mm was driven to +p+ velocity, if frequently expanded too violently and too quickly, offering fragmentation and less penetration.

For the same reason, the .357SIG round does not use a standard 9mm bullet shoved into a .357SIG cartridge. The 9mm bullet isn’t designed to stay together at .357SIG velocities. A different bullet is used for the .357SIG round.

Today, bullet manufacturers have developed bullets that will reliably expand over a much wider range of velocities, including the slower velocities found in short barreled handguns.

If the above is true, why do so many keep recommending +p over standard pressure? Standard pressure offers less recoil, faster follow up shots, less wear on the gun, and is generally a little cheaper to buy. If the standard pressure 9mm round still expands at the lower velocities, what is to be gained by going faster? More expansion? Won’t that result in less penetration?

While some +p and +p+ rounds have achieved outstanding street results, is this not the result of taking an “old” bullet design and driving it faster? The Gold Dot and the Ranger T both excel at higher velocities, but are they not older designs? For comparison, the HST is pretty new, and the 124gr and 147gr have also reported excellent results, both at +p velocity and standard pressure.

While standard pressure 9mm may not offer the most expansion or the greatest penetration when compared to a similar round in +p or +p+ format, as long as the standard pressure round offers reasonable expansion and if penetration meets the FBI minimum 12", why not go with the softer shooting, faster follow up shooting round?

2

A lot of people recommend standard pressure loads. Their reasons are usually that it is easier to handle and it beats up on the pistol less.

The advantages of a +P load are several. Many modern day 9mms are designed to handle NATO pressure loadings. This means that their slides are a little heavier, and their recoil springs a little stiffer. Using a +P loading ensures reliable function when circumstances are less than ideal…such as a dirty weapon, harsh environments, and limp wristing while under stress. Another advantage to using +P is that the higher velocity keeps the expansion reliable, especially through barriers. As good as JHPs are today, they still don’t open up all the time and you are left with a 9mm FMJ…which does not have the best historical record. Lastly, the higher velocity of the +P does give you a marginal increase in momentum. That increase reduces deflection, and allows for the bullet to punch through bone structure better.

So, in my opinion the two arguements that you get a slight improvement in recoil management and a longer life span of your pistol are inconcequential increments. The recoil advantage you gain is very difficult to measure in a competent shooter unless you are doing rapid fire speed drills. Even then, it takes some effort to demonstrate a difference. In regard to pistol service life, I once again believe that to be a moot point. Using +P may decrease your parts life by 10k rounds, but in a pistol that will last 60-100k rounds overall, that’s not very concerning. The money that you spend on 50k rounds of 9mm training ammunition alone would cost you almost $13,000. I’d rather use the more reliable +P ammo , invest in a $400 armorer’s class, replace the necessary springs/parts on regular maintenance intervals, and just buy a new $500-$1000 pistol every 30k rounds and know that I have the ideal package.

I think the hand wringing about incrimental details of modern JHPs is pointless. They rarely work out as predicted and sometimes do better or worse than assumed. Assume that every characteristic will not go as well as predicted, and then plan around that.

3

You pretty much sum things up very well. Nowadays, most bullets work just fine at standard velocities, so indeed: Why +P?

I think it has to do with the macho aspect of higher velocity = more manly. There’s just something inherently more bad-ass in the minds of a lot of people by going to higher velocity/pressures. Look at the explosion of interest in the .44mag when it came out. There was no rational need for a lot of people to own one, yet the image was more than enough to spur record sales. I bet a lot of people won’t admit it, but that’s the reason behind the popularity of 10mm, +P+, .357SIG, etc. Yes, there are times when these offer advantages, but the people who are raving about these loads are typically not talking about those applications.

Like I said - just my opinion…

4

I’ll fall into that category for my 10mm. That being said the current loads from most companies don’t live up to the originals!

Spooky

5

That’s at least 90% of why I do the 10mm thing, no doubt about it. My preference is for +P handloads of 800x in 10mm.

Hell, if you’re going to overkill something, overkill the f–k out of it, that’s my motto.

6

sgalbra76 hit the nail on the head IMHO.

FWIW, I find that in addition to the noted function advantages with the +P 9mm, there are definite performance differences when one uses +P in 9mms and .38 snubs.

7

More velocity equates to more energy and accordingly more damage.

IIRC from terminal ballistics as a Corpsman/Paramedic velocity is the far more significant factor in mechanism of injury.

Mass(Velocity Squared).

8

[i]"More velocity equates to more energy and accordingly more damage.

and

IIRC from terminal ballistics as a Corpsman/Paramedic velocity is the far more significant factor in mechanism of injury."[/i]

Not necessarily. As clearly illustrated in the relevant scientific literature over the past 20 years, kinetic energy or momentum transfer from a projectile to tissue is not a wounding mechanism. For that matter, neither is velocity. The amount of energy “deposited” in the body by a bullet is approximately equal to the amount transferred to the body when a person is hit by a fast pitch baseball. The amount of kinetic energy “deposited” or momentum transferred to a body by a projectile is not directly proportional to the amount of tissue damaged and is not a measure of wounding power. Wounds of vastly differing severity can be inflicted by bullets of identical velocity, kinetic energy, and momentum. What the bullet does in the body–whether it yaws, deforms, or fragments, how deeply it penetrates, and what tissue it passes through is what determines wound severity, not velocity, kinetic energy, or momentum.

9

I’m not one for the whole energy dump debate since I’d agree that it’s not something that substitutes for shot placement (a baseball is significantly heavier than a bullet resulting in similar kinetic energy) but all other things being equal (projectile weight and range), and in broad strokes…You’d agree that the greater the velocity, the greater the crush/tear damage caused by the projectile?

10

Maybe a different way to look at it is the added velocity transfers to the projectile ensuring it expands in the medium, and the added expansion therefore achieves greater permanent crush cavity.

11

Indeed. There is really no “measurable” disadvantage to using the +P loading other than theoretical arguements. Reliability in pistol function and ammo function are top priorities which are improved with the use of +P ammo.

12

The other advantage of +P ammunition is that it can influence the psychological portion of the stopping equation. +P rounds tend to be louder, have more concussion and seem to do a better job of convincing folks that they should stop.

I am familar with a case where a suspect fainted from a full-house .357 from a 3" barrel gun. Interestingly, the round never struck the subject, it just convinced him that he should stop.

13

I believe your right on with this Post!!

14

+1!

This is part of why I bought my last P226 in 357SIG. Much more reliable than 9mm in my experience. Have not had a single failure to-date (only 247rounds), but my case is already proven by this, in my case.

15

Why +P?

For use for compacts and subcompacts. The reduction in barrel length reduces velocity, so compensation is ideal with +P ammo.

There was a FAQ link on TOS about the comparison of standard velocity and +P, and the author(s) specifically recommended +P for anything smaller than full-size. Can’t find the link, and current search is now distracted by the Night Vision section :wink:

16

“…but all other things being equal (projectile weight and range), and in broad strokes…You’d agree that the greater the velocity, the greater the crush/tear damage caused by the projectile?”

Not necessarily. Imagine a JHP being driven too fast, so that the expanded “petals” fold back against the shank, thereby reducing the amount of tissue crush–in this case the greater velocity actually reduces the crush/tear damage caused by the projectile.

“For use for compacts and subcompacts. The reduction in barrel length reduces velocity, so compensation is ideal with +P ammo.”

Not necessarily. You may get a lot of flash and blast, but little increase in velocity, depending on caliber, barrel length, load, etc…

17

I think the increased blast and recoil are most definitely measurable disadvantages.

As far as reliability with +P is concerned - that’s why you make sure the particular load you’ve chosen is reliable in your gun in the first place.

18

BARREL LENGTH plays a role in this as well. While +P loadings may not be required in most cases, they can compensate for short barrels and the resulting loss in muzzle velocity. For example: In 9mm, the 124gr Gold Dot is a good choice in barrel lengths of 4" or more. In compact guns of 3.5" or less, a higher-velocity loading would be advised. This is Dr. Roberts take on the issue:

[i]Actually, all our testing has traditionally been done in 4" barrels for 9 mm, .40 S&W, and 4.25" for .45 ACP, although recently most of the organizations we test for have been asking for 5" barrel data for .45 ACP. There is really no difference in performance between a 3.5" and 4" barrel in 9 mm and .40 S&W. In .45 ACP, we see a reasonably significant change in performance going from a 5" to 3.5" or less barrels. Since almost all viable pistols in 9 mm and .40 S&W use 3.5-4.5" barrels, there are no "short barrel" worries for serious end-users. Likewise, almost all .45 ACP platforms worthy of hard use use barrels greater than 4", so again, the short barrel question is moot...[/i]

Please be aware that if you venture into guns with a barrel length of less than 3.5", you’re in uncharted territory.
Link

My P228 9x19mm is a 3.9" length, but actual barrel lenght is about 2.5". Given that is is a compact pistol, I believe there is not much excuse to go with +P.

19

Understood but statistically speaking does “not neccesarily” mean probably? Or probably not?

20

This also reminds me of the caliber war arguments. What we’ve been hearing over and over again is the that there is no major difference between the major service calibers when it comes to terminal effects. Basically a 9mm that expands to a RD of .60" is just as good as a .40 that has a RD of .65", and a .45 that has a RD of .70". The primary requirement is that the hollow point expand in order to have the flat frontal area which dramatically aids in permanent crush cavity creation versus a rounded nose.

If this is the case, why would it be a problem for the higher velocity 9mm to have the petals fold back against the shank resulting in a RD of around .57"? A .03" reduction in the expanded frontal area makes the round now unacceptable? Who draws the line in the sand for these hole size minimum requirements?

I think that it is more important for the petals to open up, period. If they fold back a little too far, iIve still got a projectile(9mm) that is over a .50 caliber, and it has a waddcutter profile. I’m far more worried that the JHP will not open up, and them I’m stuck with essentially a 9mm FMJ.