10mm Auto Vs. .45 ACP+P (Thor's Hammer Takes on G.I. Joe)

Updated on April 5, 2020
LJ Bonham profile image

LJ Bonham is a semi-subsistence hunter, hunting magazine editor, and firearms enthusiast who lives in the Rocky Mountains.


There’s no middle ground when it comes to the 10mm Auto. Shooters either love it—some to rapture—or they deride it as overrated and unnecessary. For a long time the doubters almost prevailed.

Introduced in 1983, the “Ten” drew little initial interest in the market, what with just one unproven gun available for it: the Bren Ten. A few years later, the world took notice thanks to clever product placement. “Miami Vice” premiered on national television in 1984. Don Johnson, as Detective “Sonny” Crocket, dressed to the nines in the latest 80s high-dollar fashions and wielded a Bren Ten to vanquish dope dealers and other lowlifes in shootout after shootout. Overnight, the 10mm became a star.

Then, just as fast as it rocketed to the top, the bottom fell out from under the Bren Ten and its cartridge. The gun’s maker couldn’t fill all the orders and it had significant quality control problems. Soon, “Miami Vice” producers dropped the Bren and issued Crocket a brand new Smith & Wesson Model 645 in .45 ACP, which is a curious thing. Many 10mm detractors have said from the beginning the round is just a .45 wannabe. This contingent felt vindicated by the show’s weapon switch.

My 10mm Journey

“Miami Vice’s” progression, in a way, mirrored my own experiences with the 10mm. I jumped on the band wagon a few years after the Ten’s savior—the Colt Delta Elite—appeared in 1987. The Delta Elite provided a mainstream platform for the 10mm. In 1990, Colt’s competitor, S&W, rechambered the 645 for 10mm, the Model 1006. Just in time for the FBI to conclude the universe would end if they didn’t dump their 9mm’s for the new kid on the block—albeit with a watered down load.

If the Feds liked the Ten, then so did I. A nice Delta Elite followed me home one day. I loved the 10mm, in both its full-pressure and FBI guises. Then the bottom fell out from under the Ten—again. The Bureau summarily executed the 10mm for the even newer .40 Smith & Wesson: FBI 10mm ballistics in a 9mm-sized pistol. 10mm sales cratered, but I refused to shift with the Bureau this time. I clung bitterly to my Delta as year after year 10mm ammunition choices and supplies dried up.

A decade later, assailed from too many sides, I sent my beloved Delta packing. In its place, I made room on the gun rack for a Glock 21SF in (yep) .45 ACP. The Glock went “bang” every time I commanded, no matter what I fed it. The old Delta tended to choke on most hollow points. A common 1911 problem in my experience. Sorry, 1911 fan boys.

The .45 offered affordable practice ammo, and many self-defense loads. To assuage my lingering guilt, I rationalized I could duplicate my departed 10mm if I loaded my Glock with.45 ACP+P ammunition. The higher pressure .45's ballistics (hence the "+P") with its consequent increased velocity, are not too dissimilar from many 10mm loads—on paper. While I didn’t miss my Delta Elite’s finicky appetite, I did miss the boisterous 10mm cartridge.

I never questioned the factory ballistic charts when it came to .45+P. However, I’ve not put them to the test, either. Now, the 10mm has arisen from the ashes once more and the round enjoys a cult-like following. Gun makers release new pistols chambered in 10mm almost every year, it seems. The Ten is back. So are my misgivings about abandoning my old flame.

In order to re-affirm my choice and quell fevered 10mm dreams, I resolved to settle this issue. Is the .45 ACP+P a valid 10mm substitute?

There are many ways to determine the answer, but I didn’t have much (okay, any) budget for a big ammo blastoff test. So, as any good scientist would, I looked at the research others have done.

Colt 10mm Delta Elite, author's first (and last) 10mm pistol.
Colt 10mm Delta Elite, author's first (and last) 10mm pistol. | Source

YouTube to the Rescue

The 10mm’s resurgence has motivated many people to test the bruiser. Some know a thing or two about ballistic testing and some don’t have a clue. YouTube is awash in videos with people flogging floppy ballistic gelatin blocks with both 10mm and .45 ACP+P rounds.

One factor which fueled the 10mm’s return is the fascination more and more people have with handguns fit for defense against bears. Never mind all too many live nowhere near bear country, they still want a bear gun. I, however, do live hip deep in bear country—both black bear and grizzly, if you must know. This is a vital question around here. Since the 10mm is considered suitable for big game hunting in general along with self-defense against humans and bruins, it's worthwhile to review these video tests to see if .45 ACP+P can do the job just as well.

Author switched from Colt 10mm to Glock .45 ACP, like this one, due to spotty 10mm ammo availability and poor 1911 reliability with hollow-points.
Author switched from Colt 10mm to Glock .45 ACP, like this one, due to spotty 10mm ammo availability and poor 1911 reliability with hollow-points. | Source


Not much to say about Thor’s hammer for semi-auto pistols which hasn’t been said before. The “Ten” is the most powerful mainstream auto-pistol round extant. The few bigger ones out there are boutique cartridges with minimal market presence. When loaded to its original Bren Ten era specifications, this beatsie approaches .41 Remington Magnum performance. On average, a full pressure 10mm drives a 200 grain bullet at 1200 fps with almost 650 ft-lbs. muzzle energy, and 180 grain slugs at 1300 fps with 700 ft-lbs. Yeah, it’ll leave a mark. The FBI’s pet load fires a 180 grain bullet at 1030 fps for 440 ft-lbs; closer to Jeff Cooper's original 200 grains at 1000 fps concept for the 10mm. (The Bren Ten's designers insisted on 1200 fps.)

The 10mm is, perhaps, too good. When tossed into ballistic gelatin, full-pressure, hollow-point loads penetrate 18 – 22 inches, and 25 or more with solids. The FBI recommends no less than 12 and no more than 18 inches gel penetration (14 – 16 as ideal) for best results on human assailants. This provides good wounding from any shot angle but reduces risk to by-standers. The FBI load just happens to drive 16 inches deep—surprise, surprise—and reduces muzzle flip.

As a reference point, Winchester’s generic 240 grain jacketed soft-point .44 Magnum load penetrates 30 inches in gel with a large temporary stretch cavity. A deeper and wider wound channel than any, save one, solid 10mm in these tests. So, the Ten is not the death ray some believe compared to the big-bore magnum revolvers.

The 10mm is a bit too much gun for close quarters battle in populated urban areas due to the over penetration. The much maligned FBI load is the most realistic choice for self-defense in such an environment. Where the 10mm shines is hunting deer-sized game, or as a dual purpose, hunting/bear and self-defense gun for open, less populated rural environments. Solid bullets such as FMJ, hard cast lead, or special “penetrators” are best reserved for bear dances.

The 10mm’s other nadir besides excessive penetration is substantial muzzle rise during rapid fire. Modern combat pistol doctrine dictates to fire until a threat is neutralized. This means multiple shots in quick succession. This requires a gun and cartridge combination which keeps the gun as level as practical during rapid fire. Again, the FBI load surpasses all other 10mm loads in this regard.

10mm Auto Gel Test Results (YouTube)

Penetration (inches)
Underwood 220 gr. Hardcast Truncated Cone
Bullet not recovered
Underwood 200 gr. JHP
Moderate Expansion
Underwood 200 gr. XTP JHP
High Expansion
Speer 200 gr. GDHP
Moderate Expansion
Federal 200 gr. HST JHP
High Expansion (Bare Gel)
Federal 200 gr. HST JHP
Moderate to High Exp.
Federal 180 gr. HydraShok FBI Spec.
Moderate Expansion
Underwood 180 gr. XTP JHP
Moderate Expansion
Sig 180 gr. V-Crown JHP
High Expansion
Underwood 180 gr. GDHP
Ultra Expansion
Hornady 180 gr. XTP JHP
High Expansion (Fragments)
Winchester 175 gr. STHP
Moderate to High Exp.
Hornady 155 gr. XTP JHP
Moderate to High Exp.
Barnes 155 gr. VOR-TX
High Expansion
Underwood 150 gr. JHP
High Expansion (Fragments)
Underwood 140 gr. "Extreme Penetrator"
No Expansion (Bare Gel)
Underwood 140 gr. "Extreme Penetrator"
No Expansion (T-Shirt Over Gel)
Underwood 135 gr. Nosler JHP
High Expansion
Average (Solids)
Recommended Bear Loads
Average (Hollow-Points)
Includes FBI Load
All tests with 4 layers denim over gel unless otherwise noted.

10mm 220 Grain Hardcast Lead Test (Note: Glock prohibits lead bullet use in its pistols)

10mm Gel Penetration for Different Loads

.45 ACP+P

Right about now all the .45 fan boys have smug smiles on their faces. The 10mm has problems, and in their opinion, the .45 ACP solves them. Not so fast.

Nominal specs for standard pressure .45 ACP are a 230 grain bullet at 830 – 850 fps with 350 – 370 ft-lbs. muzzle energy. .45 ACP+P ramps the velocity up to 910 – 1000 fps (420 – 511 ft-lbs.) based on various manufacturers’ claims. The average 185 grain +P load produces 1150 fps and 540 ft-lbs. This is still 100 – 150 ft-lbs. less than full pressure 200 or 180 grain 10mm’s.

While the difference between standard and +P .45s seems substantial, it doesn’t translate into significant differences in actual wounds. Gelatin tests prove this out. Regular .45 ACP hollow-points penetrate between 12 and 14 inches in most tests. Despite their promise, the +P loads deliver just an inch or so more, on average. The exceptions are bullets which display mild to moderate expansion such as Hornady’s XTP or Critical Duty.

In general, the higher the velocity, the greater the expansion for most hollow-points, and larger bullet frontal area impedes penetration. Either you get a wide but shallow wound channel coupled with faster energy transfer (high-expansion bullets), or deeper but narrower wounds with less violent transfer (moderate expansion bullets). Thus, more velocity does not help the .45 ACP because it exacerbates the frontal area problem. There’s not enough increased terminal performance for self-defense use to justify the +P’s violent recoil, muzzle blast, and increased stress on the gun. Although, the extra recoil is less a concern for hunters.

.45 ACP +P Gel Test Results (YouTube)

Penetration (inches)
Underwood 230 gr. JHP
High Expansion
Underwood 230 gr. JHP
Moderate Expansion
Federal 230 gr. HST JHP
High Expansion (Short Barrel)
Hornady 220 gr. FTX Critical Duty
Moderate Expansion (Short Barrel)
Hornady 220 gr. FTX Critical Duty
High Expansion (5 in. Barrel)
Speer 200 gr. GDHP
High Expansion
Underwood 200 gr. XTP JHP
Moderate Expansion
Magtech 185 gr. SJHP
High Expansion
Barnes 185 gr. XPD
High Expansion
Monarch 230 gr. FMJ
No Expansion
Similar to Std. Pres. Loads
All tests with 4 layers denim unless otherwise noted.

Speer's "Flying Ashtray" Meets .45 +P. Same Penetration as Standard Pressure.

.45 ACP+P. Different Load, Same Results: No Advantage Over Standard.

Final Thoughts

Both the 10mm and .45 ACP are great cartridges. The .45 came along before reliable hollow-points and high-performance pistol powders. Handguns then didn’t produce high velocities and required wide, heavy bullets for best performance. Its large diameter limits penetration with modern bullets at higher than standard velocity.

The 10mm is a more modern design than the .45. Its better sectional density and velocity translate into deeper penetration with wound channel widths similar to the .45. However, it penetrates human assailants too much.

Bottom line, the .45 ACP is the better self-defense cartridge, and does its best work at standard velocity. The +P version is not the best choice, in most cases, either for defense or bears. In fact, standard pressure 230 grain FMJ loads are, perhaps, the .45 owner’s best choice for bears since they penetrate deep and make wider wounds than non-expanding 10mm’s.

The 10mm is the better choice here for hunting and bear defense. Full-power loads are not a good self-defense option in most cases given their excessive penetration. Although, they can serve a dual-purpose role in rural areas. Those who insist on a 10mm for defense in urban zones should stick to the FBI load.

© 2019 LJ Bonham


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    • profile image

      James Jensen 

      3 weeks ago

      Excellent article. You addressed my questions/concerns between the two rounds. Very much appreciated!


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