I have been wondering why 9MM ammo is built in 115 gr, 124 gr and 147 grain. When I review the specs on the ammo, I find that all the different weights come in at about the same ft/lb energy at the mussle. What is the advantage of the larger bullets?
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Penetration....... That's what she said!
I have long believed that the common 9mm Parabellum bullet weights were chosen not because of their values in grains, but rather grams which was system of weights in use where the cartridge was originally developed.
If I am correct about why the weights were chosen, 124 grains is closest to the nice, round number of 8.0 grams; 115 grains is about 7.5 grams and 147 grains is 9.5 grams. We humans love numbers like that. The 147 weight showed up after the FBI decided that the 115 grain Winchester Silvertip did not penetrate enough and the 10mm and then the 40 S&W cartridges’ ferocious recoil were too much for (some) agents. I’ve never seen any discussion of why that weight was chosen by an American ammunition manufacturer, but I strongly suspect it was by someone who knew the 7.5/8.0 grams history of the round.
Kinetic energy (ft-lb) varies as the square of the velocity, but momentum, which is a better predictor of things like slide velocity and the ability of a projectile to knock over a steel “popper” reactive target, varies directly with bullet mass (weight on Earth) and velocity. A nonexpanding higher momentum bullet will also penetrate better in things like flesh than a bullet with lower momentum. In the gun games that still include “power factor” as part of their qualifications and scoring, they give advantages to momentum (i.e., generally heavier bullets) over kinetic energy (velocity).
Just kind of went through this myself...
I've long reloaded in 124gr , and it's been just fine. My buddy needed some subsonic, so I loaded up a set of 147's for him. The 147 rounds used about a grain less powder per round, so that part is nice.
We went to the range and I shot a bunch out of my various 9mms. And I liked the 147s more than the 124s. It was more like shooting soft loaded 45s, more of a mild shove than a sharp crack. Just as accurate too.
And I just ordered 1500 147gr bullets that ended up only being about 2-3 bucks more than 1500 of the 124s. So reloading costs with less powder ends up being about the same. That's pretty awesome for what feels to me like an nicer to shoot cartridge.
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Higher mass means stronger penetration, as SIG228 and Sigfreund said. So why not just shoot the bigger bullets exclusively? Because the heavier the bullet, the lower the velocity (all else being equal, momentum p = mv). As velocity drops, your trajectory becomes more and more severe; the further out you shoot, the more you must compensate for bullet drop.
115gr for a nice, flat-shooting bullet at longer ranges. 147gr for penetration. I tend to shoot 124gr as a nice compromise (plus it's the standard NATO weight).
However, this isn't the whole story. The different bullet weights have other differences that complicate matters. Heavier bullets will actually impact higher at close range, as being slower they exit the recoil cycle later. Heavier bullets have better wind resistance. You may need a sub-sonic bullet for suppression. The lighter, faster bullet may have significantly better expansion characteristics. Recoil is different (people usually- but not always- say that lighter bullets have less felt recoil). Overall accuracy can be different. You or your handgun might "like" a certain weight over others.This message has been edited. Last edited by: kkina,
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Lawman 9mm ammunition ft/lb.
American Eagle 9mm.
The lighter faster rounds normally expand more and penetrate less and the heavier rounds normally expand less and penetrate more when using the same type ammunition.
In micro-9's I find 147g to be a much softer shooting round.
I much prefer the shooting characteristics of 147gr 9mm projectiles over their lighter options. I find them to be much more accurate under a wider range of loadings, and this is due to the bullet being longer with greater sectional density allowing a more controlled, longer lasting spin. 147gr is especially superior in SMGs when you may be taking longer shots. Felt recoil will be in this order for the shooter:
When I worked in Oklahoma, we often trained with high winds on the range. Between 25-50yrds(and beyond), we noticed wind drift effecting our handgun loads. 25yds wasn't noticeable enough to compensate, but beyond 25yds you'd have to compensate with the lighter bullet weights. So, I decided to do some tests with a Kestrel wind gauge at an approximate cross wind speed of 20-25mph(impossible to get the speed the same with each shot). At 50yrds I setup a bench rest and fired 9mm, .40S&W, and .45acp from Sig P226 and P220 pistols at a DHS Transtar 2 silhouette. With a rest I could usually keep all the rounds in the COM at this range, so I was confident with my ability to keep good control groups. Just to sum it up, here is what I observed after about 10 rounds of each ammo type/caliber.
-9mm Speer 115gr+P+ GD: Drifted between 1.5-2 feet with the direction of the wind.
-9mm Speer 124gr+P GD: Drifted between 1-1.5 feet with the direction of the wind.
-9mm Federal 135gr+P TB: Drifted around 1 +or- feet with the direction of the wind.
-9mm Speer 147gr GD: Drifted around .5 +or- feet with the direction of the wind.
.40S&W and .45acp also suffered wind drift with their loads to different degrees(heaviest bullet suffering the least), but not as much as 9mm. The .45acp with 230gr bullet type appeared to suffer no wind drift at all at 50yrds and a cross wind of 20-25mph.This message has been edited. Last edited by: Fuego220,
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For self defense I always go with 147gr in 9mm.
I choose it for penetration. First job of a bullet is to penetrate.
Shoot steel poppers and see how the steel falls.
With 115gr bullets the plate will have to be hit high in order to go over, with 147gr the plate will usually fall with authority when hit almost anywhere.
A factor in the better accuracy of 147 grain 9mm bullets may be the length of the bearing surface.
Long ago someone (FBI, IIRC) wanted to know why hollow point 9mm bullets were more accurate than traditional round nose FMJ projectiles. It was concluded that at least part of the reason was the HP’s longer bearing surface, i.e., the part of the bullet that contacts the barrel rifling. A longer bearing surface helps ensure that the bullet is consistently oriented concentrically with the bore when it’s fired, and that helps with accuracy (or “precision” if we prefer the current term).
At that time it even prompted Hornady to offer a 124 (IIRC) grain FMJ bullet for handloading that had a truncated cone nose rather than the traditional rounded shape*. That bullet has long been discontinued as far as I know, perhaps because traditionalists didn’t like its look, or perhaps there were reliability problems in some guns. I used them for a time and never had any problems.
As an interesting (to me) tidbit about the history of 147 grain bullets in the 9mm Luger cartridge, I believe it was Evan Marshal who pointed out that the earliest versions of loads using that bullet were essentially ballistically identical to the 158 grain unjacketed round nose bullet load in the 38 Special cartridge that was long the preference for American law enforcement agencies, and which had a dismal street reputation. Bullets have improved since those days, but extra mass by itself doesn’t guarantee extra penetration. Bullet velocity and therefore momentum and kinetic energy also play a role in performance.
But more velocity + more mass = more recoil, and that’s part of the reason blamed for the decline in popularity of the 40 S&W and 45 ACP cartridges: “Ye canna change the laws of physics, Captain!”
* The noses of traditional 115 and 124 grain FMJ 9mm bullets have more of a pointed parabolic shape rather than circular round nose as is common for cartridges like the 380 Auto or 45 ACP. That may have resulted in their designs having even shorter bearing surfaces than they might have had otherwise. I have often wondered why that shape, but perhaps it had to do with reliable chambering or maybe enhanced penetration in military applications.
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If you liked the performance of that bullet shape, you should look at the 124gr MatchWinners (MW) from Rocky Mountain Reloading (RMR).
They make all the FMJ (RN and MW) in-house and hold their product to very high standards. I spoke with Jake, the owner, a while back and he said that the RN was still their biggest seller but that it has been his experience that the MW were a bit more accurate...they cut cleaner holes in targets also.
Eley, the .22LR folks, recently selected RMR to supply 124gr 9mm FMJ bullets for their CF line of ammo. They tested all major manufacturers of 9mm bullets before selecting RMR
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Thanks for the information about RMR.
I will probably never handload for 9mm again, but it's good to know what's available.
The above wind drift numbers do not match my experience in windy conditions. I went the JBM Ballistics site and played with what I think are reasonable assumptions for Winchester USA FMJ bullets -- not the most aerodynamic bullets. For all calculations the Density Altitude is 3,000 feet. Muzzle velocities by load:
9mm 115 -- 1240 fps
9mm 124 -- 1190 fps
9mm 147 -- 1050 fps
40 S&W 165 -- 1150 fps
40 S&W 180 -- 1050 fps
45 ACP 230 -- 900 fps
JBM's calculated wind drift for a 20 mph crosswind, in inches, at 25/50/75 yards:
9mm 115 -- .7" / 2.6"/ 5.7"
9mm 124 -- .5" / 2.1" / 4.5"
9mm 147 -- .3" / 1.3" / 2.9"
40 S&W 165 -- .4" / 1.7" / 3.7"
40 S&W 180 -- .4" / 1.6" / 3.6"
45 ACP 230 -- .2" / 1.3" / 2.9"
The above numbers from JBM coincide with my experience of shooting pistols in crosswinds.
It’s too bad we can’t “Like” posts; there’s some really good info posted here.
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