You be the judge
As with any decision on which ammo to use, one must always weigh the benefit vs. the risk.
The benefit of +P+ 9MM is supposedly increased velocity. This velocity might translate to increased terminal performance, such as greater depth of penetration of an expanded bullet through a body, or the ability to break through barriers like a windshield or car door. Police officers and military can use such penetration to their advantage, thus some commercial manufacturers market +P+ 9MM ammo as Law Enforcement (Only?). Does use of such ammo beat up a gun faster? There are tales of agencies signing gun manufacturers' warranty waivers, but I'm not personally familiar with that.
Since SAAMI does not have a pressure specification for +P+, a manufacturer can load such a round to any pressure they want. Interestingly, examination of different +P+ rounds rarely shows much if any increase in
pressure. The designation has become more a marketing term for
supposedly increased performance rather than
increased pressure. Very few commercial manufacturers are willing to step outside of SAAMI specs because of the increased liability. +P+ loads may be at the upper end of SAAMI pressure allowances but they are touted for increased
velocity. There ways to increase velocity marginally (different powders) without exceeding specified pressures. Hornady's
Superformance line of rifle ammunition delivers up to 200 more fps without pressure increases--because of special powder blends.
Standard SAAMI 9MM pressure is 35,000 psi
SAAMI +P is 38,500 psi
Only .357 Sig (40K), 454 Casull (65K--you know that hurts!), and 480 Ruger (48K) are higher in common handgun loads.
Max Chamber Pressure - SAAMI Specs
So, how much increase in performance is there with +P+ ammo? Any increase in performance is not consistently noticeable because so many factors effect real world terminal performance. The standardized FBI protocol testing has not definitively proven +P+ to be better than high quality self defense loads at standard or +P SAAMI spec pressures.
As is always the case for terminal performance, shot placement, volume of hits and proper expansion and penetration of the bullets are the most important factors--not velocity or pressure. Heavy, slower bullets can be as effective as faster lighter bullets. Velocity is produced by pressure, granted, but with the multitude of variations of powders and loadings, the goal is not just increased pressure; it is
consistent terminal performance.
Bullets designed to expand and penetrate 14" at 1,000 fps in ballistic gelatin may break apart if shot at 1,300 fps, or their petals may fold back, giving less frontal area with less wound channel damage and much greater (wasted) penetration. Trade-offs.
9MM Nato is a higher pressure round in part because the Europeans (and Israelis) used submachineguns with blowback actions (UZI, MP5) extensively for their military and police, typically with FMJ bullets for barrier penetration. They needed the extra pressure for reliable full auto cycling. Their method of measuring pressure is different than what we use in the US, so the resulting pressure differences are not apples-apples comparisons. I have fired both Israeli and European loaded rounds, and they are higher pressure with noticeably higher recoil than US ammunition. Many European manufacturers do load to US SAAMI specs for export, different than their NATO loadings.
It is true that Europeans require proof testing of their barrels and guns with ammunition loaded to pressures that are generally 15%-20% over maximum allowed loads. However, US manufacturers design and manufacture to similar standards for liability reasons, even though they are not required to proof every gun. European guns are not "stronger" than US manufactured guns. A European gun will blow up just as soon as a US manufactured gun when
improperly loaded over pressure ammo is fired in it.
The risk of blowing up your gun, especially with a fully supported chamber as in the M&P 9MM, is very low with any (properly loaded) commercial US ammo. You may experience a little more wear on the gun, sooner, with higher pressure/velocity, harder recoiling ammo, but on a limited diet of such fodder the gun will hold up.
If the ammo you have is really above SAAMI pressure specs, do you want to deal with the increased muzzle blast, muzzle rise and recoil impulse in a self defense situation where firing very accurately and very fast means saving your life? I don't.
Check out the table at the bottom of this Wikipedia article. Interesting ammo comparisons. Note the terminal effects of the different loadings/bullets.
9×19mm Parabellum - Wikipedia, the free encyclopedia
The ATK/Speer LE Handgun ammunition website does not list pressures, just velocity and foot lbs of energy.
115 grn +P+ 1300 fps. with 432 ft lbs energy.
Standard velocity LE 115 grn is 1210 fps w/374 ft lbs.
+P
124 grn bullet at 1220 fps delivers 410 ft lbs.
Many states require minimum handgun bullet energy for big game hunting to be 500 ft lbs (more in some states) at 100 yards. Average self defense rounds come nowhere near this threshold, even at bad breath distances. That is why shot placement, expansion, penetration and volume of fire are key factors in a self defense shooting. A minor increase in velocity and energy is not a game changer.
If I can practice with economical 115 grain FMJ ammo that shoots very similarly to my 115 grn self defense load, I am probably going to be a better, more accurate, faster shooter, with less expense, and less wear and tear on my gun. I don't mind paying a premium price for good self defense ammo, but I don't want it to shoot substantially differently than how I train.
To me, searching for and buying and using +P+ ammo is a waste. You got some? Sell it and buy what you really need.
+P+ is not magic. It's marketing.
