Sig 320s are rated for +P ammo and can handle it. But +P means "higher pressure" and a steady diet of it will cause faster wear and tear on your gun. +P tends to have more violent recoil and muzzle blast. It should be loaded for carry after practice with FMJ range ammo and not for regular range practice. So shoot a few to see where they hit and how they feel then just save them for carry.
Most excellent; thanks for the quick reply and good scoop... Had read somewhere that +P and +P+ ammo caused greater chamber pressure, warning that it should only be used if the weapon could handle the same. What I didn't know was that the Sig P320 series were +P ready... Think I'll pick up a box just to see how it (& me) reacts, as you sagely suggest. Many thanks, once again...
Probably wouldnt hurt to change the recoil spring at a faster rate or use a stiffer spring to begin with like the 40/357 RSA. I know the surplus M17s came with 2 springs one for regular +p nato and one for commercial junk
More pressure = more wear. There is nothing in your pistol that can't be replaced economically except the frame and slide itself which are not the primary wear parts beyond break in. Once broken in, the barrel and recoil spring are the main wear parts. I would love to have to replace a barrel because it's worn out. That means I had fun shooting the gun an incredible number of times.
Page 18 discusses over pressure issues. They don't make reference to +P ammo, but do indicate the gun is designed to use SAAMI specified ammunition.
SAAMI publishes specifications for standard velocity and +P ammuniton, but NOT +P+. Therefore I would not use +P+ in your SIG.
The higher pressure ammunition is marginally higher than standard velocity. Perhaps a few hundred FPS muzzle velocity. That delivers higher terminal energy in self defense ammunition. It also stresses the gun's action more than standard velocity ammunition. Therefore, practice mainly with Standard Velocity ammunition, and occasionally with +P to learn to manage the recoil.
These are the SAAMI specifications that SIG made reference to:
The pressures are discussed on page 17, and you can see that the difference in pressure isn't that much - just at about 10% higher than standard velocity ammunition.
Understand that manufacturers may be focusing on shipping +P ammunition right now because they can almost double the price for self-defense ammunition, with only a fraction of a cent increase in cost (for a few grains of smokeless gunpowder).
So... buy and shoot a little +P ammunition, and generally carry it for self defense. Buy and shoot mostly standard velocity ammunition and preserve the action of a high quality handgun.
All NATO military approved firearms are rated for +P+ just not all are recommended to shoot +P+ all the time, day in and day out.
As already stated, any higher pressure load will increase wear and tear and that's why springs sometimes need to be swapped-out and sometimes, as was the case with the 92FS (M9) a buffer was added because of a well documented catastrophic failure issue we had back in the day when using German made Hert 9mm during a Reforger exercise.
Surplus Hert, pre-1988, was loaded +P+ because the Germans made their firearms to handle it specifically .... particularly both the P225s and P226s and their venerable MP40s and MP5s. Hert has since dialed it back to +P and the catastrophic failure issues have disappeared. Hert didn't dial it back because of the M9 failures, they laughed at those, but they did dial it back when it started causing issues in their German made H&K sidearms.
SIG wouldn't offer +P ammo if it even remotely caused an issue in their sidearms. It's purpose built for very specific needs not the least of which is self defense. Modern pill design combined with increased velocities has made the 9mm a potent offering even against heavily outfitted enemy troops and terrorist bad guys.
The Hert +P+ ammo was loaded specifically for the MP5 and that's where they ran into problems in some of the M9s.
There was this catchy little rhythmic saying about the M9s, it was damning actually, I wish I could remember it ... used to hear it all the time. Something about the M9 slide hitting you in the face ... it just escapes me at the moment in my older age. I'll remember it when I'm not thinking about it.
I honestly do not understand the need for a +P 124 grain commercial load given modern pill design. The HST is a man stopper with optimal velocities and maximum expansion through 4 layers of clothing without it being difficult for novice shooters to control recoil-wise. For that matter the good old Federal HydraShok, in all of its variants, works really well at slightly hotter velocities that are just below +P Sammi standards.
I don't have a M18, but have used Winchester, IMI and SIG NATO and +P ammo in a variety of 9MM pistols, to include SIGs, and Ruger and S&W revolvers. Over the years, I've used thousands of rounds Winchester and IMI 9MM NATO, and would have no concern at all about shooting NATO or +P in any good quality, properly maintained, 9MM pistol, revolver or carbine. I've never been able to detect any accelerated wear, and nothing has bent, cracked, broken, etc.
Reference the SIG 9MM NATO +P in particular, I've tested it in a few different guns. I found that it consistently displays a bit less velocity than the Winchester and IMI NATO. Strangely I think, the SIG 9MM "NATO" is not marked with the NATO cross in a circle, and does not have sealed case mouth or primers. The SIG NATO seems to be quality ball ammo, loaded slightly warmer than most US commercial 9MM ammunition, but otherwise unremarkable IMHO.
The "M17" labeled ammo is about 40 fps more than Sig's standard 124 FMJ Elite Ball rounds.
Every 320 is randomly checked with proof rounds much higher in pressure than these rounds.
Constant use??? Maybe things will loosen up a bit and changing the recoil spring assembly or use a higher lb spring would be advisable.
In one screwup, the tester in QC was newer and instead of using one proof round, he loaded the three full magazine's with them. Gun was in no way damaged after it.
These days no one is shooting great amounts of ammo.
Excellent discussion and supplemental reference material, folks. I, too, thought that "SIG wouldn't offer +P ammo if it even remotely caused an issue in their sidearms.", but remained hesitant nonetheless, given to any assumption that it "should" be ok to cycle some number of +P in my new M18.
It's my understanding that NATO 124 grn ammo wasn't really designed for pistols anyway .... it was designed to make sub-machine guns run better in freezing cold temperatures. As for me I can't afford to burn +P ammo for range days.... the FMJ range ammo prices are so high I've gone to shooting mostly .22s.
Last year I picked up 25 boxes of Winchester 124gr NATO on sale for about $9 locally. At first this thread had me wondering about using it all, but now I’m glad now I bought all they had. I’ll shoot it freely eventually but will keep some for the Zombie Apocalypse.
Yeah, I agree. I keep my house gun (a 320C) loaded with Sig V-Crown 115 grn. I just like the way it shoots ... very manageable recoil for fast double taps, very accurate, clean and it seems pretty powerful from my side of the sights. And I bought a lot of it when prices were reasonable. I have probably 20-25 boxes. If I ever feel it's not enough I'll carry a .45 or .357 magnum.
The V-Crown in 230 grn ,45acp is pretty stout too ... and really runs great in my Sig TACOPS and 320FS .45s.
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