Wednesday, August 30, 2006

Corbon .45 ACP 185-gr. DPX from SIG-Sauer P220 & 5" 1911

By Stephen Camp

Speaking of their newest ammunition line, Mr. Mike Shovel of Corbon advised, "All calibers in DPX will penetrate 12 to 16" in denim-covered ballistic gelatin." He went on to state that this line of ammunition is designed to meet the FBI protocols for bullet performance and said that DPX also works very well after encountering barriers other than denim. The few test results that I'd seen on this new load fall midway between the penetration depths mentioned by Mr. Shovel when fired into gelatin covered with 4-layers of denim.

I asked what the velocity threshold was to start expansion. He stated that in .45 ACP, it is 800 ft/sec. Mr. Shovel went on to say that the Corbon .45 DPX round works fine in the short barrel forty-five's as well.

The .45 ACP DPX load uses a 185-gr. copper Barnes X-bullet and the cartridge is loaded to 1.23" LOA. The hollow point measures 0.225" wide by 0.37" deep and the wall thickness at the front of the hollow measured 0.02" thick.

The .45 ACP Corbon DPX round is fairly "traditional" in appearance but uses a homogeneous bullet made from a copper alloy. The load is rated +P and is so noted on the case head stamp. The load is nominally rated at 1075 ft/sec. With no jacket and no lead, fragmentation does not occur.

The shortest barrel .45 ACP pistols I own have 4 1/4" barrels. I opted to use a pistol having such a barrel length instead of the very common 5" 1911 pattern pistol for informal expansion testing. The handgun chosen was a SIG-Sauer P220.

Two pistols were used to evaluate the .45 DPX load. On the left is a SIG-Sauer P220 w/4.25" barrel. Next to it is a Kimber Classic Custom with the usual 5" factory barrel. The P220 was fired using factory 7-round magazines. The Kimber used Wilson 7-round magazines, a McCormick 8-shot PowerMag, and a Colt 7-shot magazine using Virgil Tripp's Cobra Mag upgrade kit. The P220 was used for expansion testing.

Fired into water from the SIG-Sauer P220, this 185-gr. DPX expanded to 0.81" x 0.83" x 0.55" tall. The recovered bullet weighed 184.3 grains. Note how "long" the expanded bullet remains; it doesn't flatten out as much as conventional JHP's known to be aggressive expanders. Corbon has long manufactured ammunition to very high velocities for respective calibers. Their 165-gr. PowRball +P is such a round. Weighing 20 grains less than the DPX. It is advertised at a considerably higher 1225 ft/sec.

Here we see the expanded .45 DPX compared to the expanded PowRball after both were fired into water from a SIG-Sauer P220. The side view graphically shows how the DPX retains a longer expanded bullet that is more likely to penetrate than the PowRball "pancake". The PowRball expanded to 0.80" and with the jacket fragments weighed 161 grains. (PowRball averaged 1189 ft/sec from the P220.)

Here is the expanded DPX (middle) compared to some conventional .45 ACP JHP's. Clockwise from the top left we have Federal 230-gr. Hydrashok, Remington 230-gr. Golden Saber, Federal Classic 230-gr. JHP, and Winchester (law enforcement only) Ranger 230-gr. RA45T.

Two expanded Corbon 185-gr. DPX bullets flank Winchester's excellent 230-gr. RA45T, which evolved from the original Black Talon of the same weight. Where the heavier bullet has more weight to aid in obtaining sufficient penetration, the DPX has length and spaces between the rigid copper petals. I suspect that damage from either is both significant and similar in "soft targets".

Shooting was done at 15 and 25 yards with the DPX ammunition. All shooting was slow-fire and single-action only while using a rest. Felt recoil was very similar to Corbon's conventional 185-gr. JHP +P, which uses the Sierra Power Jacket Hollow Point bullet.

These 15-yard groups were fired while sitting and using a two-hand hold. The ammunition proved quite good for its intended purpose. POA was the center of the gray bullseye.

A great number of .45 fans routinely use 230-gr. ball for practice as it almost always has the same POI vs. POA as the 230-gr. JHP ammo most carry. I thought it might be useful to know where the Corbon 185-gr. DPX strikes the target from a gun with its sights regulated for standard velocity 230-gr. ammunition. The Kimber was used for this at 25 yards.

Winchester USA 230-gr. FMJ was fired as the "control" load to compare the DPX load's POI for the same POA in a gun set for standard pressure 230-gr. ammunition. Ten shots were fired with each load. The lines through holes mark the Winchester's impacts. The lighter and faster 185-gr. DPX strikes slightly lower at this distance. Whether or not it matters depends upon the degree of precision the shooter finds necessary. For most of us, there is not enough divergence in points of impact to matter.

As distance increases, so can differences in points of impact. At 25 yards, I fired a group using the SIG-Sauer P220.

POA was the center of the bullseye. Shooting was done slowly, seated, and using a two-hand hold. My wrists were braced. Is there enough difference in the POI with the DPX at 25 yards to matter? It depends on what the ammunition and pistol is being used for. If the intended target is a couple of inches in size, it is two much. For center chest hits on a moving human aggressor, probably not.

The ammunition was chronographed from both pistols. Each set of figures is based on 10 shots fired approximately 10 feet from the chronograph screens. Figures are in ft/sec.

Corbon 185-gr. DPX +P Chronograph Data:


Low Velocity

High Velocity

Ave. Velocity

Extreme Spread

Std. Deviation

SIG-Sauer P220






Kimber Classic






The DPX proved itself consistent and accurate on targets and over the chronograph.

DPX feed smoothly in both guns and there were exactly zero failures to feed, extract, or eject. The slides on both pistols locked back upon firing the last shot. Cycling the same round from a full magazine 3 times in each pistol resulted in no measurable bullet set back; there was absolutely no hesitation in this ammunition chambering.

These Corbon DPX cases were fired in the Kimber (left) and SIG-Sauer (right). Neither shows the classic signs of excessive pressure, but one can see very minor primer flow beginning on the primer fired in the Kimber. Neither case exhibits flattened primers. The telltale firing pin "wipe" is present on the primer fired in the SIG-Sauer. This is typical and to be expected. The SIG-Sauer pistols purposely have a bit slower firing pin retraction to help thwart debris from entering the firing pin channel.

I was pleased with the performance of this ammunition. It proved reliable in expansion and accuracy was more than adequate. Over the chronograph, DPX displayed good uniformity and the ammunition performed to nearly the same extreme spreads in two entirely different 45-caliber handguns. Standard deviations were the same.

You can see that the expansion of these seven 185-gr. DPX +P bullets is pretty consistent. These were fired into water from the SIG-Sauer P220 and impacted at an average velocity of 1062 ft/sec.

Did this ammunition meet my expectations? Yes. I noted that while the 4 1/4" barrel on the P220 averaged velocities barely under the advertised 1075 ft/sec, 5" average velocity from the Kimber slightly exceeded it.

If you prefer "light and fast" in the .45 ACP but have had concerns over penetration, I suggest that you give Corbon 185-gr. DPX a look. I've not yet shot any animals with it, but it appears to provide accuracy, consistency, and more penetration than most other 185-gr. expanding ammunition.