MP-Pistol Forum banner

21 - 31 of 31 Posts

·
Registered
Joined
·
144 Posts
The Shield definitely leaves more of the cartridge
unsupported. This was the best of the pics I took.
The Shield barrel is on the right.
Interesting.

The next time I go to the range I will take some pictures of expended +P+ brass and post it here.

Well, I will if it doesn't blow up my gun.:blink:
 

·
Registered
Joined
·
74 Posts
Let me introduce the concept of MATH. Pressures are Pounds PER SQUARE INCH. If we assume the interior diameter of the cartridge is close to bore size, the 9mm experiences only 78% of the axial force (in the direction of the bore) that the .40 experiences at the SAME PSI, due the SMALLER AREA. This is the direction that the breech face and locking lip at the front edge of the chamber resist. In the radial direction the force is 89% for the 9mm, and of course the chamber wall is thicker in the 9mm.

So the lockup on a 9mm shield loaded to 44,600PSI is stressed the SAME as a 40S&W loaded to the SAMI 35,000 PSI spec.

I found one reference to +P+ 9mm at 42,000 PSI, which suggests that, if the manufacturer has used suitable cases, it is no more likely to fail than the 40S&W version with standard ammo.

Whether S&W's lawyers are happy with that is a different question.

Let me add that the 44,600 PSI 9mm comes out to 4,400 lbs of peak axial force on the lockup, so what we are saying is that it is like hanging an SUV from the barrel while holding the slide vertical in a support. There is enough hardened steel there to accomplish that using normal engineering calculations.

Don't get in the frame of mind that pressure is pressure -- there is more force on an action from a 458 Winchester than from a 222 Remington, when both are loaded to the SAME PSI.
 

·
Registered
Joined
·
15 Posts
SAAMI

Unless something's changed there's no data in SAAMI for +P+.

I agree that since the Shield is also designed to handle the .40 cartridge it's probably a better candidate than a gun that's design solely around the 9mm like an LC9S. My main concern would be how well supported the round is in the chamber.

SAMMI 9mm is limited to 35,000 psi, +P is 38,000. Not a big difference. But I've seen some +P+ loaded about as hot as you can for 9mm for submachine gun use.
 

·
Registered
Joined
·
140 Posts
Folks, just read the manual and follow the manufacturer's recommendations....just that simple.

You know, I could add a turbo-charger to my car...it would make more power....or NOS system to briefly boost horsepower. Problem is, if the engine and drivetrain components are not upgraded to take on the additional horsepower, problems will arise...perhaps quickly depending how often I put my foot down to feel the extra power.

Just read the manual!
 

·
Registered
Joined
·
709 Posts
Your gun, your choice, your life. If you want to run +P+ through your Shield, at least have others stand clear. If you survive and bystanders are hurt, litigation that follows will bankrupt you.
 

·
Registered
Joined
·
84 Posts
Your gun, your choice, your life. If you want to run +P+ through your Shield, at least have others stand clear. If you survive and bystanders are hurt, litigation that follows will bankrupt you.

Agree!!!! Who cares if the OP wants to use +P+ ammo in their Shield. Let them. But you have been forewarned of the hazards in doing so. Stupid is what stupid does and you cannot fix stupid.
 

·
Registered
Joined
·
3,208 Posts
Kind of pointless to use +P ammo in such a short barrel anyway. Thats just throwing away powder and money at the same time. Conserve powder, we`re gonna need it during the shortage`s again, just buy regular ammo instead. And your gun will last longer too. Besides that, the bigger the bang dosent always meen better.
 

·
Registered
Joined
·
5 Posts
Guys, +p+ ammo is not recommended because there is no standard for it. It could be safe and it might not be. One +P+ round could be substantially different than another unlike +P which is given a standard range of how much pressure it creates.

The M&P shield was approved for off duty use by the NYPD after they tested the gun which included firing over 5000 124 grain +P rounds thru it without significant failure ( I don't know how many FTE or FTF were allowed if any). I wouldn't worry about using +P rounds in it.
 

·
Registered
Joined
·
1 Posts
DON"T!!!!!
Please read the owners manual that came with your firearm.
I contacted S&W customer service and asked if it is safe to use +P ammo with either M&P 2.0 9mm 4” or M&P shield 9mm 2.0 and they responded it is fine to use it with both guns.
 

·
Registered
Joined
·
334 Posts
Watch ShootingTheBull’s videos on testing 9mm ammo in a short-barreled gun.

+P didn’t provide any significant advantage.

Bullet design did.

HST all the way.
 
21 - 31 of 31 Posts
Top