To +P or not to +P

[wha-tah-hey]

Hi all -

In researching on this forum before I bought my M&P9, one authority (don't remember who) posted in a thread (don't remember/can't find which) that they were "designed for +P".
IIRC, he mentioned barrel lock-up factors specifically.
If true, my question is this: wouldn't it be "better" somehow to use +P ammo?

I know they shoot fine with either; I know it's a personal preference, some use one, others the other; I know the advantages and disadavantages of both types of ammunition.

Not intending to be snitty, but there must be real factors to consider if they're actually designed for the extra pressure so I'm hoping to get "design oriented" responses rather than whether or not an individual's gun has "run N rounds of so-and-so with no problems".

FWIW, I handload, have a few hundred 124gr GDs on the way, and am wondering if I'd be better off to go ahead and develop +P loads.

Thanks.

[KhanRad]

Hi all -

In researching on this forum before I bought my M&P9, one authority (don't remember who) posted in a thread (don't remember/can't find which) that they were "designed for +P".
IIRC, he mentioned barrel lock-up factors specifically.
If true, my question is this: wouldn't it be "better" somehow to use +P ammo?

I know they shoot fine with either; I know it's a personal preference, some use one, others the other; I know the advantages and disadavantages of both types of ammunition.

Not intending to be snitty, but there must be real factors to consider if they're actually designed for the extra pressure so I'm hoping to get "design oriented" responses rather than whether or not an individual's gun has "run N rounds of so-and-so with no problems".

FWIW, I handload, have a few hundred 124gr GDs on the way, and am wondering if I'd be better off to go ahead and develop +P loads.

Thanks.

How about buying a box of several different types of ammo and see which one works best in your M&P?

[F-Trooper05]

Do you hand-load your defensive ammo?

[wha-tah-hey]

"How about buying a box of several different types of ammo and see which one works best in your M&P?"

Right now, KahnRad, it's not about what shoots best, but whether or not S&W designed some elements of the M&P9 specifically for +P loads as someone stated (and iterated, AIR).

F-Trooper05, I handload nearly everything I shoot but .22 RF. :dance3:

[KhanRad]

Right now, KahnRad, it's not about what shoots best, but whether or not S&W designed some elements of the M&P9 specifically for +P loads as someone stated (and iterated, AIR).

I know of a member who has run high speed video of the M&P firing and he said that the barrel unlocks more quickly than other pistols such as the Glock. So, in theory a bullet that leaves the barrel faster would beat out the barrel unlock so to speak. However, I have never heard S&W state that one particular load would be superior to another in the M&P. Why would a company design a pistol which is limited to only higher velocity loads when the primary duty load for many LE agencies(especially Federal agencies) is the 147gr standard pressure load.

Grant at G&R tactical has been doing some gun vice shooting with the M&P and I don't believe that he observed any performance difference between slow and high velocity loads.

[Denali]

Hi all -

In researching on this forum before I bought my M&P9, one authority (don't remember who) posted in a thread (don't remember/can't find which) that they were "designed for +P".
IIRC, he mentioned barrel lock-up factors specifically.
If true, my question is this: wouldn't it be "better" somehow to use +P ammo?

I know they shoot fine with either; I know it's a personal preference, some use one, others the other; I know the advantages and disadavantages of both types of ammunition.

Not intending to be snitty, but there must be real factors to consider if they're actually designed for the extra pressure so I'm hoping to get "design oriented" responses rather than whether or not an individual's gun has "run N rounds of so-and-so with no problems".

FWIW, I handload, have a few hundred 124gr GDs on the way, and am wondering if I'd be better off to go ahead and develop +P loads.

Thanks.

I think you're asking whether the M&P will hold up to a diet of high pressure ammo, my answer is yes it will. The pistol was designed originally as a .40 S&W, in fact it is a .40 S&W, only chambered in 9mm!

The hottest 9mm approaches, or meets certain .40 S&W loadings, so from that perspective you should be fine....

[wha-tah-hey]

...I have never heard S&W state that one particular load would be superior to another in the M&P. Why would a company design a pistol which is limited to only higher velocity loads when the primary duty load for many LE agencies(especially Federal agencies) is the 147gr standard pressure load.

Grant at G&R tactical has been doing some gun vice shooting with the M&P and I don't believe that he observed any performance difference between slow and high velocity loads.

That's sorta why I'm asking - I note that the Owner's manual says (about +P) that it's not for K-frames and no +P+ for any S&W handgun, so M&Ps are obviously not limited to one or the other.
But if the guy knew what he was talking about, it might explain the (perfectly acceptable but) less-than stellar accuracy many report.

*FOUND IT:*
In M&P Problem thread:
http://m4carbine.net/showthread.php?t=52771

Posted by C4IGrant, bottom of p.1:
"Remembe that M&P 9mm barrels are setup for + P ammo and typically shoot the best (accuracy wise) with hotter ammo.
I don't shoot + ammo so I switched out to a Storm Lake barrel which is geared more towards standard loads."

Many would agree that he knows a thing or 10 about M&Ps.

[tpd223]

In defensive ammo for 9mms and .38special I prefer +P ammo.

[Nephrology]

I prefer +P 9mm ammo myself usually 124gr.

[lifebreath]

I prefer non +p with heavy bullets for defense. I've got mine loaded up with Speer Gold Dot 147gr JHP.

[1oldgrunt]

I like Ranger 127gr+p+ that's just me. Almost 357 Sig velocity yet way more controllable.

NOT knocking anyone but a non +P 147 is somewhat akin to a 158 38 special and we know how well that works! 356 diameter 147 grains at approx 925 fprs ...vs.... 357 diameter 158 grains at approx 850 fprs ....hmmmmmm:confused:

BUT carry what you can hit with and are comfortable with just throwing some food for thought out there.

[rjacobs]

The M&P is designed to physically stand up to the "abuse" that a +p round has, same as just about every new, modern, auto loader. The reason they say no +p+ is because there is no SAAMI standard for +P+, it could be hot, it could be weak, there is no standard, thus no manufacturer is going to tell you its ok to run it.

Now whether the gun runs better with +p ammo is a different topic all together and not the subject of this thread(although most responses would indicate otherwise).

[KhanRad]

I like Ranger 127gr+p+ that's just me. Almost 357 Sig velocity yet way more controllable.

NOT knocking anyone but a non +P 147 is somewhat akin to a 158 38 special and we know how well that works! 356 diameter 147 grains at approx 925 fprs ...vs.... 357 diameter 158 grains at approx 850 fprs ....hmmmmmm:confused:

Modern 147gr work just fine. It is a primary staple for many LE agencies across the country, especially Federal. The old .38spl 158gr load that you are referring to was designed in the water tank era. This was an outdated bullet design that was flawed from the start. Since there was no performance standard in the past, ammo manufacturers tested their loads in water tanks. This was a cheap method, which resulted in inaccurate expansion and penetration characteristics. The problem with water testing, is that the human body is NOT 100% water. So what reliably expanded in water did not always expand in flesh. In fact, most lower velocity loads from this era didn't expand at all in actual shootings. Once the FBI ballistic gel test protocol became the standard for testing, ammo manufacturers followed the example and redesigned their loads to meet the FBI performance standards in calibrated ballistic gel. Ballistic gel duplicates the water percentage of human tissue. Since then, every load that does well in the testing standard, has also done well in the field.

About the best source you can get now-days for ammo/caliber advice:
https://www.m4carbine.net/showthread.php?t=19887

[ST911]

When choosing ammunition, I would first worry about whether or not it was high quality, domestically produced, SAAMI spec ammo. Then, if for defensive use, if it was on Doc's list of acceptable defensive loads. Somewhere thereafter, and not even necessarily third, would I think about whether or not it was plus-anything.

[wha-tah-hey]

Now whether the gun runs better with +p ammo is a different topic all together and not the subject of this thread(although most responses would indicate otherwise).

Actually, that is the practical issue involved.

My original question was intended to elicit discussion of the design elements implied by Grant's statement quoted in my last post, so we might understand why +P would the "proper" choice.

If the M&P is in fact designed for +P, it's sorta like running .22 Short/Long in a .22 LR semi-auto - spring rate, slide mass, whatever, aren't properly balanced.

Can any of you Tech-Gurus shed some light?

[okie john]

NOT knocking anyone but a non +P 147 is somewhat akin to a 158 38 special and we know how well that works! 356 diameter 147 grains at approx 925 fprs ...vs.... 357 diameter 158 grains at approx 850 fprs ....hmmmmmm:confused:

The non +P 147 is closer to 1,000 fps, so with a good JHP, it's closer to the 38 Special "FBI" load, which is a pretty solid performer. The classic 38 Special 158/850 earned its reputation with a RN bullet, which truly did suck.


Okie John

[KhanRad]

If the M&P is in fact designed for +P, it's sorta like running .22 Short/Long in a .22 LR semi-auto - spring rate, slide mass, whatever, aren't properly balanced.

I can tell you one thing. If S&W designed the M&P to only shoot +P ammunition, they would not have won so many LE contracts, and with so many years of testing it would have become apparent that there was a problem with using 147gr loads. No such problem has been observed with function, or accuracy.

[wha-tah-hey]

I can tell you one thing. If S&W designed the M&P to only shoot +P ammunition, they would not have won so many LE contracts, and with so many years of testing it would have become apparent that there was a problem with using 147gr loads. No such problem has been observed with function, or accuracy.

Understand I'm not knocking M&Ps at all - and FWIW, no one has said they were for +P only - I'm just very curious about Grant's statement and it's implications.
.
As I mentioned, while accuracy is perfectly acceptable, it's often noted by owners as being less than "target" accuracy, and pressure could be a key.

As context, I've often found, in customizing a load for my rifles, that a grain or two more powder (so more pressure) can make the difference between 1 3/4 moa groups and sub-moa groups.

Could be the same thing in play.

[rjacobs]

Actually, that is the practical issue involved.

My original question was intended to elicit discussion of the design elements implied by Grant's statement quoted in my last post, so we might understand why +P would the "proper" choice.

If the M&P is in fact designed for +P, it's sorta like running .22 Short/Long in a .22 LR semi-auto - spring rate, slide mass, whatever, aren't properly balanced.

Can any of you Tech-Gurus shed some light?

You asked "is the gun designed to withstand the higher pressures". Yes they are.

As far as if they shoot better with hotter ammo, that is also in the affirmative. It has been stated(maybe from Grant, maybe from Randy) that the M&P was designed for 9mm NATO round which is a slightly hotter round(36.5k PSI) vs standard(35k PSI) vs. +p(38.5k PSI). The NATO round, if I am not mistaken, is also a 124g round. Thus people say the gun shoots best with a hot 124g round. Barrel twist, springs rates, etc... are all designed around the 124g NATO round. And that is if what I have read is correct regarding how S&W designed the gun. So if the gun is designed to shoot 124g hot loads the best, every other load will be a sacrifice of something.

However, with that said, Randy has brought up a lot of things, and is in the process of attempting to fix those issues, that will make the M&P a better shooter that S&W screwed with to try to either make the gun cheaper or easier to build or a combination of the two.

[wha-tah-hey]

I never asked if they were designed to stand the higher pressures, as I know +P are fully compatible, but those design factors you mentioned were what I was wanting confirmation about.

Thanks. ;)