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

[Jim Watson]

Herr Luger and DWM thought 8 grams, rounded to 124 grains, was right.
But they soon went to 7.5 grams, I assume for even a small savings when equipping an army.

 

[481]

For self defense ammunition. Is there really that much difference in standard pressure loadings for the 9mm when you put the 115gr up against the 124gr?
I use 124 HST in Autumn/Winter and 115 Gold Dots for Spring/Summer.
This is out of a Shield and a Hi Power I carry these loads for.

When asking about the difference between 115-grain and 124-grain JHPs, I s'pose that it might be advisable to define the 'difference' that you are concerned with?

If that ''difference' is the terminal performance of JHP ammunition in either weight, the mass of the bullet is just one of three factors that must be considered. Besides bullet mass, impact velocity, and expanded diameter of the bullet must also be considered. At this time, there are no less than five mathematical bullet penetration equations—US Army BRL (Sturdivan, 1973), UTSI (Peters, 1990), WTI (MacPherson, 1995), Q-model (Schwartz, 2012), and the mTHOR algorithm (Schwartz, 2014)—each model is proven against hundreds of correlative ordnance gelatin data. Using these models allows anyone interested to explore the effect of those three parameters upon terminal performance of any bullet—that is, the maximum penetration depth, volume of the permanent cavity, and the mass of damaged tissues within that volume.

In other words, we can play ''what if'' with these models and get a reasonable estimate of the terminal performance of any bullet that we wish to model.

For example, what if a 9mm 124-grain +P Gold Dot JHP struck a human body at 1,220 fps and expanded to 0.60''? To what depth could we expect it to penetrate and how much tissue (in ounces) would be damaged?

9mm 124-grain +P Gold Dot @ 1,220 fps
mTHOR algorithm (Schwartz, 2014): 12.05 inches and 1.67 ounces
Q-model (Schwartz, 2012): 12.09 inches and 1.68 ounces
WTI (MacPherson, 1995): 12.18 inches and 1.41 ounces
UTSI (Peters, 1990): 12.02 inches and 1.67 ounces
US Army BRL (Sturdivan, 1973): 12.41 inches and 1.72 ounces

Or, we could ask: what if a 9mm 115-grain +P Gold Dot JHP struck a human body at 1,210 fps and expanded to 0.59''? To what depth could we expect it to penetrate and how much tissue (in ounces) would be damaged?

9mm 115-grain +P Gold Dot @ 1,210 fps
mTHOR algorithm (Schwartz, 2014): 11.48 inches and 1.54 ounces
Q-model (Schwartz, 2012): 11.58 inches and 1.55 ounces
WTI (MacPherson, 1995): 11.70 inches and 1.30 ounces
UTSI (Peters, 1990): 11.51 inches and 1.54 ounces
US Army BRL (Sturdivan, 1973): 11.89 inches and 1.60 ounces

Of course, shot placement is important, too—but that's a tactics and training issue which cannot be accounted for by mathematical-physical models like these.

 

[Old_Grouch]

OP is asking about pressure.

He never mentioned pressure.
There are internal ballistics, external ballistics, and terminal ballistics. [chamber] pressure is totally irrelevant to terminal ballistics.
x feet per second is x feet per second. It doesn't matter whether a particular bullet striking a target at 1000 fps generated 40,000 chamber psi or 50,000. 1000 fps is 1000 fps.

 

[Rodfac]

If we're talking about viable self defense, I doubt there's a difference between 115's and 124's. None of my 9mm's is any more reliable with one or the other, but the price difference could make a difference in quality modern loadings. But in my guns, all of them...achieve their best accuracy with a 124 over a 115 gr weight bullet. Five Sigs, two Glocks, a trio of Colt 1911's, two Rugers, and most recently, Springfield's SA-35....they all like 124's better than 115's and that's for both cheaper practice ammunition as well as expensive SD rounds...I have no idea why....Best Regards, Rod

 

[wayneinFL]

Why?

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

Does it even evaluate recoil accurately?

A 250 gr 45LC at 660fps recoils the same as a 125gr 357 at 1320fps or a 110 gr 357 at 1500 fps?

 

[wayneinFL]

You are correct, too many variables. Angle of shot, density of tissue, skin, bone, etc.
Even two identical shots made inches apart can take different paths thru the animal and hit different tissue densities along the way. I can tell you that 9mm fmj's typically do not just pencil thru an animal's soft tissue and exit without expansion like many of the You Tube gel tests would seem to demonstrate. I have dug them out of animals where they didn't hit bone and still only had about 4 to 6 inches of penetration. I have also dug them out from under the skin on the opposite side 20" away from the entrance wound.

I think most people envision the typical SD scenario as a full frontal hit to the chest or abdomen of a human. This may or may not be the actual situation. Ballistic gel is never gonna give you an accurate example of any of the possibilities. It can show you how the bullet "might" or is likely to perform, but it can't account for the majority of the variables that are like to be present in any given impact.
What is true is that hollow points will generally transfer more of the kinetic energy into the target, and not as likely to exit without expansion, but this doesn't necessarily equate to being more lethal.

That's an excellent post. I've only seen a handful of handgun shots on hogs, but even "good" handgun calibers didn't impress me as super reliable. If a 357 doesn't always stop a hog, I can't imagine there's enough difference in 115 vs 124 gr 9mm to spend a lot of time parsing it out.

 

[Simple Shooter]

The answer to the 115 vs 124 grain argument is to me no different than the Winchester White Box vs. $2.00/round super duper great gazoo self defense round argument. And my answer is that it just doesn’t matter as much as the ammunition manufacturers want us to believe it does. If I double tap you center mass with one round of WWB 115 grain JHP and one round of 124 grain Federal HST are you going to be able to tell me which was which? Is it really going to matter?

 

[481]

Does it even evaluate recoil accurately?

A 250 gr 45LC at 660fps recoils the same as a 125gr 357 at 1320fps or a 110 gr 357 at 1500 fps?

Power Factor does not consider the mass of the firearm, so no, the equation for Power Factor does not correctly compute recoil.

 

[wayneinFL]

Power Factor does not consider the mass of the firearm, so no, the equation for Power Factor does not correctly compute recoil.

It also doesn't consider action, barrel length, etc.

Please assume ceteris paribus. Both handguns, both same action, same barrel length, bore axis, both same mass, etc.

 

[481]

It also doesn't consider action, barrel length, etc.

Please assume ceteris paribus. Both handguns, both same action, same barrel length, bore axis, both same mass, etc.

The problem with assuming ceteris paribus (all things being equal) is that they almost never are.

Action, barrel length, bore axis are not components of the Power Factor equation which only computes the momentum (bullet mass multiplied by bullet velocity) of the bullet itself.

 

[jmorris]

Yep, 9 grains by my math. Probably slightly different shapes too.

As far as what you see in or on a target, how its made is much more important.

For example, a plated version of either, won't be as accurate as a good JHP version of either weight.

 

[Rexster]

I would start with reliability. Then, I would choose the one that shot closest to point of aim, while also being reasonably accurate. I do not understand why “pressure” would have anything to do with it. (Obviously, some pistols should not be fed +P.) Shot placement trumps kinetic energy, in the real world.

 

[Hartkopf]

Here is an old partial list of what the FIB approved in 9mm. Only one 115gr load on the list and it’s solid copper. Most law enforcement uses 124 or 147gr. Will it really matter in any given situation? Probably not but I’d pick something off the list and not worry about it.

 

[golden]

.357

For me, it is a matter of what I believe works and can confirm that belief, not bullet weight. My usual home SD and carry load for my 9m.m. pistols is FEDERAL HST 124 grain. If they had 115 grain, I would consider that. I do not believe in using the 147 grain load, although my agency is now issuing various, low bid 147 grain ammo since we went to the 9m.m. We used to use the FEDERAL 180 grain jhp HST load when we still used .40 S&W caliber. Never heard a complaint about it.
We used hotter .40 caliber loads with good results, but they wore out the guns quickly and had many qualification failures.

I have shot and carried 115 grain jhp, +P 115 grain and 124 grain +P and was issued and carried 115 grain and 124 grain +P+ ammo. I use the 124 grain HST, because it has proven very reliable in the field with many agencies. Since the 115 grains usually are faster, I like the lighter bullets as it makes expansion more likely in conventional bullets. The premium bullets now offered are more reliable in expanding, due to their more modern design.

I do not see much difference in the GOLD DOT and HST performance, so I would go with whichever is the more accurate rounds in your guns.


They will both expand and the difference in penetration is minimal and not worth considering in a self defense situation.

Jim.

 

[cougar1717]

For 9mm 115gr vs 124gr, quality defensive ammo, these would be my considerations:

1. Where does the ammo group in my specific firearm? Various ammos group differently in different guns. Windage is a simple with a sight pusher. Too high or too low in elevation is not an easy adjustment with the same sights unless training a workaround of "equal height" on the draw. That's not the best solution. Various height front sights are usually available, but not always available in a front night sight. Adjustment is much simpler if running a RDS.

2. Can the firearm generate enough velocity to reliably expand the defensive ammo? If the S&W shield has the 3.1" barrel, it's the heavy clothing gel tests where some ammos can fail to expand. 124gr HST's are good, but 124gr Gold Dots seem to need more than 1,100fps - which may or may not be achievable in a 3" barreled handgun. 115gr Gold Dot may give the extra velocity required to reliably expand through heavy clothing. It performs great through a 4" barrel: https://le.vistaoutdoor.com/ammunition/speer/handgun/details.aspx?id=53614

3. How is the recoil? We talk about defensive ammos as if they all recoil equally. The laws of physics can't be broken, so faster ammos in small guns typically turn into either slow or off target follow up shots without significant training. This is where non-ammo considerations are important with grip sleeves, pinky extenders on mags, etc.

4. Once the goldilocks ammo is found, why change? I understand carry ammo rotations for application, but not solely for preference. Maybe there is a good reason for using 115GD in the summer, but I don't get why the 124HST wouldn't be a just as good in the summer. There should be no surprises in a CCW carrier's kit.

 

[JDeere]

124s year round and at the range for me. A few bucks more a case I don't worry about. I don't get into all the numbers and stuff. What I learned in my Physics classes tells me what I need to know. 9 grains can make a difference. I may however visit 147s in the near future and see how they perform...