Is there really that much difference 115 or 124gr for the 9mm

Why would you change bullet weights/types dependent on the season?

Yes there is a difference! but not really

If bullet designs is the same but weight is different, I would look at the velocity of the load. and, find the power factor as a numbered base line.

124gn going 1000fps = 124 power factor
115gn going 1080fps = 124 power factor

OP is asking about pressure.

frogfurr said:

OP is asking about pressure.

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ok.. pressure… Ugggh, I don’t know about pressure

nettlle said:

OP is asking about pressure.

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The way I read it OP is wondering about performance of standard pressure loadings of the two mentioned loads.

No, you will be just fine with either. The bad guy won’t notice a difference of 9 grains. Both loads are using great bullets.

All things being equal the 124 is gonna have a smidge more penatration.
Especially from the Shield where you're gonna be down on starting velocity.

357smallbore said:

Is there really that much difference in standard pressure loadings for the 9mm when you put the 115gr up against the 124gr?

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Yes, 7.8% more bullet weight.

In the real world, very likely not. I carry 115 or 124grn SD ammo interchangeably, based on availability. I prefer 124's, because I want as much bullet weight out of my short-barreled Kahrs, but at the end of the day, bullet placement trumps bullet weight.

As a general rule, using the same powder and the same internal volume, the maximum pressure will be reached sooner using the heavier bullet.

The way I figure, 124 gr. is the NATO standard for a reason. Good enough for me.

I think bullet construction would have a greater impact on performance over a slight weight increase if velocities are similar. That being said, I carried Win SXT127 +P+ and 124 gr +P ammo for several decades and felt well armed with them.

I now have 147 gr HST in my SD/HD guns.

IMHO, almost all of the premium self defense oriented ammo available today will perform as well as handgun ammo can do. It really depends on the rounds being placed where it counts.

(And, let us all hope we never need to find out. )

Stay safe.

Well, of course there is a "difference". The "difference" is 9 grains. Its basic math, not too complicated.

Riomouse911 said:

I think bullet construction would have a greater impact on performance over a slight weight increase if velocities are similar. That being said, I carried Win SXT127 +P+ and 124 gr +P ammo for several decades and felt well armed with them.

I now have 147 gr HST in my SD/HD guns.

IMHO, almost all of the premium self defense oriented ammo available today will perform as well as handgun ammo can do. It really depends on the rounds being placed where it counts.

(And, let us all hope we never need to find out. )

Stay safe.

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yes! bullet construction is probably more important

and I hope nobody here ever has to find out either. Sounds very traumatic

Shot placement is what matters in 99.9% circumstances for self-defense.
Magic bullets of the season, not so much.

CONVERSION BARRELS
I have a Glock 22 (.40 cal) that I like to run a 9mm "conversion" barrel.
That gun hates most 115-grain factory ammo. Failure to cycle issues of various stripes.
Swapping recoil springs or extractors doen't change anything.
It runs 124-grain 9mm ammo without a hitch - and with the original recoil spring, and with the original .40 caliber extractor.
And I always use OEM Glock 9mm mags - although it cycles 124-grain 9mm ammo with the .40 cal mags "most of the time."

AVAILABILITY
115-grain ammo is the most-available 9mm ammo you will find.
124-grain is a little bit harder to find - but by no means rare or uncommon.

PRICING GAMES
Sometimes 124-grain ammo is inexplicably priced much higher than 115.
I shop for good prices on 124-grain, and I can usually get it for less than 5% higher price than 115 if I order online.
Sometimes you can avoid sales tax if you order online. So it makes the shipping-cost turn out to be a wash.
I don't know any walk-in sellers that won't charge you sales tax.

I avoid 115-grain ammo because of my conversion-barrel concerns.
Always buy 124-grain, and get it by the case.

POWER-FACTOR AND GUN GAMES
The whole "power factor" is absolutely meaningless in comparison of 115-versus-124 9mm ammo.
Except for one thing - recoil.
And because of recoil, guys shooting COMPETITION can accurately shoot a full magazine of 115 faster usually than 124.
So the rules for some GAMES require that your ammo meet a certain "power factor." Which really is just a RECOIL factor for the purpose of preventing gamers from gaming the game by shooting powder-puff ammo in unique game-purpose-built game guns that would not run "full-power" ammo reliably, or without beating the game gun to death.

RELIABILITY IS ALL THAT MATTERS
The various bullet dot-colors and acronyms for hollow-point 9mm mean very little in the real world.
Just make sure the dot/color/XYZ-TACTICAL cycles in your gun.
Cycling malfunctions in a gunfight should be avoided.
Make sure your preferred hollow-point ammo functions when you are holding the gun in less-than-ideal grip. We can't all have Jerry Miculek mastery of gun-grip when someone is hitting us with chair while we're standing in line to pick up a pizza.
Test your equipment. You might be surprised what happens when you shoot left-handed with a loose grip.
This is why revolvers are still relevant.

SHOT PLACEMENT IS ALL THAT MATTERS
In self-defense situations, any 9mm in the thoracic cavity is probably gonna be fatal.
Reason for that is the thoracic cavity is tightly-packed with organs that will bleed severely and rapidly. Or lungs, which collapse and prevent the brain from getting oxygen.
By contrast, a 9mm of any stripe NOT in the thoracic cavity won't usually be fatal in any rapid manner. I imagine it hurts to be shot in the leg or large intestine with a 9mm. But death will be slow.
A bullet that pierces the liver or heart or lungs - or any major artery/vein in the thoracic cavity will be GAME OVER in a matter of minutes - if not seconds.

357smallbore said:

Just to correct what I was saying. I was talking standard pressure loads of 124 and 115 not +p. Which one really works better was a general question. I've shot them both. I like them both but I was just wondering if it's a tit for tat only being nine grains difference. I know of the 115s faster the 124 penetrates a little deeper, but with all that said, does it really truly matter at the end of the day they both I believe will perform the job admirably. I just wanted to get thoughts on this

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To me, in the end, it's all about accuracy and reliability. Which one works better in a certain pistol and which one shoots better or shoots closer to POA with a certain pistol.

If I were going to switch ammo in the winter due to clothing an attacker might be wearing, I'd just go with a Swc or FMJ vs a hollow pt. I don't think there's enough difference in the two you mentioned to make any difference at typical SD distances.

I'm hearing echoes of Korea in the '50s, and M1 carbine round failing to put down Norks wearing padded winter clothing. Not sure if that really transfers to modern handgun ammo, especially in nines. Perhaps more of a consideration with less powerful rounds, like .380s or .38s from a sub.
Moon

Kleanbore said:

Why?

"Power factor"is used in competition circles, and it has but one purpose: to evaluate recoil.

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maybe they should change the name to recoil factor then

Kleanbore said:

Why?

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Because it directly relates to the momentum of the bullet and momentum is better depicter for the potential for penatration than energy.

If you watch certaun you tube videos, the 9mm fmj penetrates 2 blocks of clear gel vs less than 1 block with a hollow pt. If you watch some where they used FBI gel, there's really not much difference between the two. When you get to 40sw and larger, the difference is larger.
My real world experience with 9mm fmj's on varmints tells me that I'm not really worried about overpenetration. I do use Hp's for my SD loads in 9mm and up. I use Fmj's, Swc, or semi jacket solid nose for .380, 38sp, 32 acp, and .25 acp. These are usaully BUG s.