luis032557
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Has anyone shot +p ammo in full size mp 40? The manual says not, that it could mess up the barrel. Has anyone shot this type of ammmo through this pistol??
+p ammo in full size mp 40???
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Fishinfool
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I don't believe there is a "+P" rating that is recognized for the .40 S&W by the SAAMI.
Larry
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luis032557
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Well do you know if it will mess up the barrel or the gun for that matter
The P+ is udes as an advertising gimmick but some of the "p+" ammo can blow the brass out as many barrels don't offer full chamber support. I do not have a 40 m&p pistol but do use underwoods 155gr 1300fps ammo in my tp40 kahr . I would not run it in a glock 27 gen 3 I had .
Heres a photo that shows a few chambers to judge yours by.
http://img.photobucket.com/albums/v238/Gixerman1000/40SWcasesupport.jpg
Note that some handguns are made to handle the higher pressure of the 357sig cartridge and general strength would not be an issue but the back of the chamber can be.
Heres a photo that shows a few chambers to judge yours by.
http://img.photobucket.com/albums/v238/Gixerman1000/40SWcasesupport.jpg
Note that some handguns are made to handle the higher pressure of the 357sig cartridge and general strength would not be an issue but the back of the chamber can be.
shot1971
Member
I had a Glock 27 & it handle +p+ ammo very well. In fact I have fired +p+ ammo in my Shield 9 even though the owner's manual does not approve. But I keep +p ammo in my Shield.
mustangman
Member
I don't know that anyone can answer this question for certain about your gun, but S&W obviously thinks that it might, so I wouldn't take a chance. If you do end up with a problem gun from using it, youre on your own, no S&W warranty. I know Buffalo Bore, and Underwood advertise 40 +P, but I think that the regular 40 stuff that is available from all the major manufacturers is plenty "hot". Just my opinion though, to each his own.
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Venenoindy
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There is not +P .40 S&W, if a manufacturer labels as such I wouldn't buy it or use it. The .40S&W is a high pressure round to begin with and if some irresponsible people are purposely over charging the round is just a disaster waiting to happen.
Mountain Walker
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So little or nothing is gained by hot loading ammo. Rather in selecting ammo or reloading components I look for a good quality bullet and standard pressure. Those loads that exceed standard pressure also lead to premature wear, malfunctions, and sometime firearm failure. If you want more power get a bigger caliber or a long arm.
Wolf1775
Member
It's been pretty well covered already, but...
There is no +P for .40 S&W. You can load the round to max recommended loads and pushing hotter until you see signs of pressure, but that's pretty damned unsafe.
Best case scenario with pushing the limits of safety is that you wear parts out faster. Worst case scenario is that you blow the gun apart. Simply put, don't do it.
The only reason I would load rounds on the hotter side is to make majors in pistol matches. Otherwise, I'd rather find good components that perform well together and are well within safe limits to get the most out of my gun.
There is no +P for .40 S&W. You can load the round to max recommended loads and pushing hotter until you see signs of pressure, but that's pretty damned unsafe.
Best case scenario with pushing the limits of safety is that you wear parts out faster. Worst case scenario is that you blow the gun apart. Simply put, don't do it.
The only reason I would load rounds on the hotter side is to make majors in pistol matches. Otherwise, I'd rather find good components that perform well together and are well within safe limits to get the most out of my gun.
So much factory loaded ammo by the big boy companies has been reduced from it designs standards for there higher production runs so there less chance of screw that they have to deal with. It happens enough as it is. Buy a bow of ammo and pick 10 random rounds out and chronograph them and do it again with a underwood , BB or Georgia arms and a few others and see the spread in fps between round drop in a major way. These boutique companies run ammo at a low level of production and use a stable quality brass like Starline and just make a better product than what you get from remmy, winny fed and the likes.
Its not for ever one or ever handgun. Also many of the problems with 40sw is found with 180gr loads and pressure issues that don't show with 155 or 165 gr bullets.
Heres a bit of reading for the 40sw loader.
Speers 155gr factory load is 1200fps , mine from underwood 155gr same speer bullet is 1300fps, using a better controls during loading and better brass. I can shoot these loads and turn around and the brass drops clean back into and out of the barrels chamber with no flatting of the primer shown do to high pressure. Try that with the slower lower pressure 40sw ammo you use now and see how that works out.
These pistols were designed to handle the higher pressure 357sig cartridge and use the same recoil spring as a 9mm?? That could be part of the early unlocking issues m&p's are known for. Could also be part of any problem you have with group size. I going to look at heavier springs from wolff to try with our 9mm and some underwoods hotter laods for velocity and group size.
You can also note that corbon uses starline brass and there 165gr hp load runs at 1150fps from a 4" glock where underwood advertises 1200fps and meets that velocity in a 4" barrel just like corbon load does. That's only 50fps faster . Some companies spread in velocity is more than that 50fps.
Its not for ever one or ever handgun. Also many of the problems with 40sw is found with 180gr loads and pressure issues that don't show with 155 or 165 gr bullets.
Heres a bit of reading for the 40sw loader.
Speers 155gr factory load is 1200fps , mine from underwood 155gr same speer bullet is 1300fps, using a better controls during loading and better brass. I can shoot these loads and turn around and the brass drops clean back into and out of the barrels chamber with no flatting of the primer shown do to high pressure. Try that with the slower lower pressure 40sw ammo you use now and see how that works out.
These pistols were designed to handle the higher pressure 357sig cartridge and use the same recoil spring as a 9mm?? That could be part of the early unlocking issues m&p's are known for. Could also be part of any problem you have with group size. I going to look at heavier springs from wolff to try with our 9mm and some underwoods hotter laods for velocity and group size.
You can also note that corbon uses starline brass and there 165gr hp load runs at 1150fps from a 4" glock where underwood advertises 1200fps and meets that velocity in a 4" barrel just like corbon load does. That's only 50fps faster . Some companies spread in velocity is more than that 50fps.
Ofc.JL
Member
What ever body else said. .40 S&W is already at +p pressure. It's how the round was developed. That's why S&W's first .40 cal pistol(the 4006) didn't hold together well. S&W used the 59(9mm) series of guns basically bored out to.40, and over prolonged shooting, the 4006 was just not holding up. The pistol was getting literally beat to death from the pounding. The .40 S&W round being "hot", so to speak is the reason Glock went to the 3rd pin in it's pistol frame. They were having the same problem with the .40 round beating the cam block out of the plastic frame. I believe that is also the reason the M&P series of pistols have their stainless steel subframe. Stops the flex and stretch in the polymer frame when shooting the .40. .40 S&W is a hot round to begin with.
Anyone advertising "+p" .40 is loading past SAAMI specs. S&W says don't, then don't. You are flirting with disaster.
Anyone advertising "+p" .40 is loading past SAAMI specs. S&W says don't, then don't. You are flirting with disaster.
Johnmuratore
Member
I've got a 40c and the manual that came with it.
I've read it from end to end and there's nothing in there about a +P round messing up the barrel.
Where does it say that?
I've read it from end to end and there's nothing in there about a +P round messing up the barrel.
Where does it say that?
Wolf1775
Member
+P rounds won't be mentioned because there is no standard for what constitutes a +P round. There are minimum and maximum suggested loads, but that's it. When people discuss +P rounds with .40 S&W they tend to mean that they're loading rounds either on the upper edge of what's considered a safe maximum load or they're loading past that to squeeze out more velocity.
The former can be done safely depending on the condition of your brass, the primers used, bullet weight and material, barrel rifling, consistency from round to round, and experience. The latter moves into dangerous territory since you're now going beyond what's been found to be safe tolerances for the round.
Even when one of my friends is loading to see how far he can push that powder/bullet combo, he starts at .3 grains under the max and steps things up by .1 grains to see where pressure signs start. Then he dials it back by .2 grains just to be on the safe side since that'll allow some breathing room.
1hatchet
Member
What the manual does say is the below:
"You are responsible for selecting ammunition that meets industry standards and is appropriate in type and caliber
for this firearm.
Never use a cartridge not specifically designated for use in your
firearm. The wrong type of ammunition may exceed the capability of your firearm and may damage or even rupture your firearm."
SAAMI | Sporting Arms and Ammunition Manufacturers' Institute
Here's a fired .40 +P case 
Luckily, it was fired in a steel frame gun.
"Ya pays yo mony, ya takes yo chances."
Or not. Plenty of good quality .40 ammo to had.
ETA- This wasn't factory ammo, it was a reload that was trying to be a "+P"
Luckily, it was fired in a steel frame gun.
"Ya pays yo mony, ya takes yo chances."
Or not. Plenty of good quality .40 ammo to had.
ETA- This wasn't factory ammo, it was a reload that was trying to be a "+P"
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While not all boutique ammo companies push the envelope, some do. Before you tout the qualities of their ammo, check with SAAMI and see if they're members. I know of several boutique ammo companies who are no longer in business due to lawsuits.
And yes, there is no .40+P standard. There is a least one company that uses the rating for advertising purposes.
Actually, the 357 Sig operates at the same pressures as .40 S&W. The recoil spring may be the same for several calibers, slide weights aren't.
Well what do you know one other guy has figured it out. Advertising trickery buy some. Just have a supported barrel and recoil springs for the job.
Acually the 357 sig saami is designed to 40,000psi ,not the same as the same 35,000 of the 40sw. But you could be right that the larger ammo companies don't load to a 40,000 saami scale but to a lower "safer" level. 40sw may be the same and loaded lower too by the same companies.
2hawk Show the base of that brass. Looks like something other than starline maybe a glock pop, no fully supported chamber or not fully in battery when fired. RP maybe??
https://www.starlinebrass.com/brass-cases/40-Super-Brass/
Acually the 357 sig saami is designed to 40,000psi ,not the same as the same 35,000 of the 40sw. But you could be right that the larger ammo companies don't load to a 40,000 saami scale but to a lower "safer" level. 40sw may be the same and loaded lower too by the same companies.
2hawk Show the base of that brass. Looks like something other than starline maybe a glock pop, no fully supported chamber or not fully in battery when fired. RP maybe??
https://www.starlinebrass.com/brass-cases/40-Super-Brass/
hardluk1 - you know what you're looking at 
That blown brass is RP.
That was a reload at the top of the loading chart, maybe even a bit over. And yes, I think there's a good chance that case had been "glocked".
I just wanted to show what can happen when you go seeking something that is over spec. In this case it wasn't catastrophic, just blew the floorplate off the magazine and unloaded everything, including spring and follower, at the shooter's feet. But, in a plastic gun, the results may well have been quite a bit worse for gun and shooter.
Almost every type of ammo made has a bigger faster version, ie, .40<10mm, .45acp<.45 Super or .460 Rowland, .38<.357, etc. IMHO, if you want more than what SAAMI spec is on a round, then you really want a different round.
That blown brass is RP.That was a reload at the top of the loading chart, maybe even a bit over. And yes, I think there's a good chance that case had been "glocked".
I just wanted to show what can happen when you go seeking something that is over spec. In this case it wasn't catastrophic, just blew the floorplate off the magazine and unloaded everything, including spring and follower, at the shooter's feet. But, in a plastic gun, the results may well have been quite a bit worse for gun and shooter.
Almost every type of ammo made has a bigger faster version, ie, .40<10mm, .45acp<.45 Super or .460 Rowland, .38<.357, etc. IMHO, if you want more than what SAAMI spec is on a round, then you really want a different round.
