9mm Grain Weight

The 9mm Luger, being the most popular handgun cartridge in the country, comes in a vast variety. This includes bullets of numerous weights, from loads packing 43 grains of birdshot to rounds loaded with a 165-grain bullet.

The majority, however, are either 115 or 124 grains. From full metal jackets to advanced self-defense expanding loads, roughly two-thirds of 9mm ammo is one of these two sizes.

This is why so many people, especially newcomers to the cartridge, wonder about the differences between these two sizes. Can 9 grains really make a difference in ballistic performance?

To find out, we need to examine the stats for these two grain weights. But first, it helps to briefly review the basics of bullet weights and measurements so we better understand the 115- vs 124-grain debate.

Beginner’s Lesson: What is “Grain Weight”

When looking at a box of cartridges, you’ll see “grains” or the abbreviation “gr.” A grain, which equals 1/7000th of a pound, is the standard unit of measurement used for weighing a bullet.

The weight of a bullet impacts how the bullet travels through the air, how fast it’s going, and how it performs on impact. It’s one of the most important considerations when you are purchasing ammo or selecting a cartridge for hunting, target shooting, and personal defense.

The difference between these two sizes is nine, which means the difference is 9/7,000ths of a pound. Less than 1/700th of a pound, and yet it will have a noticeable difference in the precise physics of ammunition ballistics.

115-grain vs 124-grain: Ballistics

Velocity

9mm Luger Product	Muzzle (fps)	25 yards	50 yards
115 grain Speer Gold Dot	1,210	1,133	1,071
124 grain Speer Gold Dot	1,150	1,092	1,044
115 grain Remington Range FMJ	1,145	1,092	1,048
124 grain Remington Range FMJ	1,110	1,068	1,031
115 grain Federal Premium FMJ	1,180	1,106	1,048
124 grain Federal Premium FMJ	1,150	1,095	1,049
115 grain Hornady Black XTP	1,155	N/A	1,038
124 grain Hornady Black XTP	1,110	N/A	1,027

If all other factors are the same, a lighter bullet will have a faster muzzle speed. This is a predictable advantage for a 115-grain projectile, as this size almost always has a higher muzzle velocity. The advantage, however, is minimal. Most of the 115-grain rounds have a speed advantage of roughly 30 to 50 fps; hardly a difference maker.

Despite starting slower, a heavier bullet maintains kinetic force for a longer distance. Therefore, at 25 or 50 yards we often see 124-grain rounds catching up with their 115-grain counterparts.

Speed goes to the 115-grain round, but it’s not a massive difference; certainly not one that would drive your ammo decisions. But what about energy? Does nine grains of weight create a noticeable difference in power?

Energy

	Muzzle (ft-lbs)	25 yards	50 yards
115 grain Speer Gold Dot	374	328	293
124 grain Speer Gold Dot	364	328	300
115 grain Remington Range FMJ	335	305	280
124 grain Remington Range FMJ	339	314	293
115 grain Federal Premium FMJ	356	312	280
124 grain Federal Premium FMJ	364	330	303
115 grain Hornady Black XTP	341	N/A	234
124 grain Hornady Black XTP	339	N/A	257

One could, with good reason, assume that the 124-grain rounds would seriously overpower the 115-grain options. This is not the case. In fact the muzzle velocities are split: two of our comparisons go to 115, two to 124.

Downrange we do see an advantage for the 124, as the heavier bullet maintains its speed, helping to deliver more force into the target. But once again it’s not a massive advantage; we can’t honestly say that the 124 grain out-powers the 115.

Penetration and Terminal Expansion

124 Grains	Penetration (inches)	Diameter (inches)	Muzzle Velocity (fps)
Federal JHP	18.3	0.5	1,121
Hornady Critical Defense	13.62	0.52	1,064
Hornady American Gunner	17.72	0.49	1,032
Federal Train & Protect	33.28	0.35	1,074
Speer LE Gold Dot	33.38	0.35	1,079
Federal LE Hi-Shok JHP	25.44	0.36	1,086
MAGTECH Guardian Gold +P	14.36	0.58	1,166
Barnes TAC-XP +P	11.78	0.7	955
Carbon DPX +P	12.3	0.68	1,046
Black Hills XP +P	13.76	0.69	1,084
Black Hills JHP +P	18.38	0.48	1,112
Average	19.02	0.59	1,074
124 Grains	Penetration (inches)	Diameter (inches)	Muzzle Velocity (fps)
Hornady Custom XTP HP	21.96	0.44	1,005
Federal LE Tactical Hydra-Shok	29.12	0.36	1,008
Federal LE Tactical HST +P	18.72	0.68	1,106
MAGTECH Guardian Gold	19.44	0.38	1,032
MAGTECH First Defense	31.54	0.35	1,076
Winchester Defender +P	23.38	0.47	1,044
Black Hills JHP	20.96	0.45	1,055
Speer Gold Dot Personal Protection +P	18.58	0.44	1,090
Sig Sauer Elite Performance JHP	19.26	0.47	1,116
Remington Golden Saber +P	16.02	0.57	1100
Speer Gold Dot LE +P	19.62	0.51	1110
Federal LE Tactical HST	18.46	0.62	1054
Average	21.42	0.48	1,066

Energy and velocity matter, but if you’re using a 9mm handgun for personal protection and concealed carry, you need to consider penetration and bullet expansion. The FBI, after all, looks at bullet penetration in ballistic gel to measure the effectiveness of a round. They don’t, as far as we know, look at velocity and energy.

Testing of 115 and 124 grain 9mm loads gave us a ton of data to sort through. We fired the ammo into synthetic ballistic gelatin and a 4-layer cloth barrier.

The results show that the 115 loads penetrated an average of 19.02 inches with bullets mushrooming to an average of 0.59 inches, while the 124 rounds penetrated to 21.42 with a diameter of 0.48.

So, for whatever reason, it appears the 115-grain rounds actually expand to a larger diameter while still maintaining excellent penetration. Expansion, it seems, could be the defining factor for 115- vs 124-grain rounds.

(The FBI testing system is based on points. For example, rounds get 10 points if they reach 14 to 15.9 inches of penetration. But to limit over-penetration, if they go beyond 19 inches they only get five points.)

Recoil Between 115 and 124 Grain Ammo

Felt recoil is a matter of personal use and preference. While the 124-grain round is larger and has more energy, many feel that recoil is actually more manageable. Some report that the gun pushes instead of snaps, so follow-up shots are easier with the heavier round.

Ultimately, the best bullet weight depends on your weapon and your personal preferences. In nearly all cases, it helps to try both sizes and see which performs best. Which grain weight gives you the tightest accuracy? Which feels better? Testing different sizes is the only way to decide between a 115- and a 124-grain round.