Thursday, July 27, 2006

Corbon 9mm 115-gr. DPX +P

(Fired from Browning Hi Power w/factory barrel, w/Barsto barrel, and from Glock 26)

Today's defensive shooters expect quite a bit from expanding ammunition. In the past, expansion was a "sometimes" thing. While that is still true today, it's my observation that bullets intended to expand actually do…most of the time. No longer is expansion itself enough. Now, we want at least 12" of penetration in calibrated 10% ballistic gelatin, which is considered the "gold standard" in ballistics tests intended to simulate what might be expected in tissue. It is not perfect, but it is the standard and it does pretty well replicate what is seen when expanding bullets are pulled out of flesh and blood. (My primary "test media" used to be living critters called javelina, but I no longer have access to those hunting grounds! It takes me longer to test ammunition on something tough enough to be interesting and perhaps meaningful to defense against human adversaries.)

Corbon advises that the 9mm 115-gr. DPX +P both expands reliably in either bare or denim-covered (4 layers) gelatin and penetrates at least 12". People testing in ballistic gelatin have pretty well confirmed that it meets these expectations and frequently exceeds the now-standard 12" minimum.

I do not have the funds to purchase ballistic gelatin or a means by which to keep it at a constant temperature for repeatable tests. My informal expansion tests use either water or "wet pack." (Super-saturated newsprint that has soaked 24 hours and drained for 30 minutes before shooting. Results are similar to those from gelatin although the wet pack limits penetration more.)

Nevertheless, I do some expansion checking on my own and for this test, I used water.

I thought it might be interesting to do the things often passed over. I don't know if the thought is that such matters are irrelevant, but I tried to provide some information not so frequently reported. I'm speaking of such things as accuracy, felt recoil, reliability, and consistency from shot to shot. In any event, these are things I can do and pass on.

"DPX" is Corbon's acronym for "Deep Penetrating X". The "X" refers back to the Barnes copper alloy X-bullet used in rifle ammunition for several years. In rifle ammo, the bullet expanded in an X shape, hence the name. In a given rifle caliber, the X-bullet would almost always penetrate deeper than an expanding rifle bullet of the same caliber and weight. The pistol ammunition has six "petals." This homogeneous bullet cannot suffer bullet-jacket separation. There is a gap between the petals. It seems reasonable that while this creates a larger wound channel, it also allows for a bit deeper penetration as the bullet is not exhibiting quite the same "parachute effect" as more conventional JHP's. Those petals are tough and not easily bent by hand, either. Edges are somewhat sharp.

Corbon 115-gr. +P DPX uses cases marked with the company name and indicate +P pressure levels. The h ollow point measures 0.175" wide and 0.40" deep. The primer does not appear to be sealed.

The 9mm DPX measures 1.12" LOA and the bullet is seated snugly in the case. Cycling the same loaded round 3 times through a Browning Mk III from a full magazine did not cause set back. The same test was applied using a Glock 26…with the same results.

The 115-gr. DPX was fired into water from a Browning Hi Power from the very slightly slower Barsto match barrel. It's expanded dimensions: 0.61 x 0.59 x 0.50" tall. It lost no weight. As the petals bent outward before folding rearward, the expanded bullet would have measured at least 0.755" across at least for some of its penetration depth. Notice that the bullet still has some "length" to it; this aids penetration. The expanded bullets from the Glock 26 were virtually identical. The average velocities attained by both guns seem with within the DPX bullet's operating velocity envelope.

Though more than a few use service size handguns chambered for 9mm, many use compacts. I chronographed this ammunition from both a Browning Mk III with its 4 21/32" barrel and a Glock 26. The latter has a 3.46" barrel that has polygonal rifling as opposed to the Hi Power's conventional lands and grooves. Both pistols have a twist of 1:10. I also installed a Barsto match barrel in the Mk III. It has bore measuring 0.3565" and a 1:16 twist.

These two pistols were used to evaluate the DPX ammunition. Both have been altered slightly. The Glock uses the two-piece steel Wolff guide rod and standard power springs. The Hi Power was shot using a Wolff conventional 18.5-lb. recoil spring and a Buffer Technology shock buff. (I also fired a few rounds without the buffer to see if function would be affected. It was not.)

Average velocities, standard deviations, etc, are based on ten shots fired approximately 10' from the chronograph screens.

Corbon 9mm 115-gr. DPX +P Chronograph Results:


Low Velocity (ft/sec)

High Velocity (ft/sec)

Average Velocity (ft/sec)

Extreme Spread (ft/sec)

Std. Deviation (ft/sec)

Mk III(factory bbl)






MkIII (Barsto bbl)






Glock 26






In defense situations it is generally acknowledged that slow and precise shots will be the exception rather than the rule. This is probably true in the vast majority of deadly force scenarios, but I personally still place value in a round that is at least capable of being shot accurately should the opportunity present itself. For this reason, I shot the 9mm DPX slow-fire from a rest at 15 yards from the Hi Power with both barrels as well as the Glock 26. I also fired it in more "practical" type shooting drills at 7 yards.

This group would be smaller if the human error was removed. It is obvious that this load has more than enough accuracy at this distance for self-protection and that misses will not be the fault of the ammunition or pistol.

Here's a group fired with the same gun using the factory barrel. The POI is slightly lower and closer to the POA. Accuracy is for all purposes equivalent to that with the Barsto…with this ammunition. I have seen some jacketed rounds that grouped quite a bit better through the Barsto, but the greatest improvements I've seen have been when using cast bullets.

My Glock 26 is fitted with Aro-Tek fixed sights and the 115-gr. DPX is dead bang "on" at 15 yards. The all copper bullet appears to work well from either polygonal or conventional rifling.

Moving up to 10 yards and using a Weaver stance from a low-ready position, I fired 4 sets (8-shots) of controlled pairs on humanoid type target with a dotted circle in the chest as the target. This was not timed, as I didn't have access to a timer today. (When I do, I usually have hell getting the thing to work right!) I would estimate each controlled pair to have taken about a second from start to finish.

This ammunition does not have the felt recoil of the Corbon 115-gr. JHP +P. It is distinctly easy to shoot and control from the Hi Power. This one's wearing Craig Spegel checkered, black delrin grips and uses the factory fixed sights.

The same drill was performed using the Glock 26. The holes with the marks were from the Browning Hi Power. As with the Hi Power, the Glock was extremely easy to handle with this load.

At this point, I moved up to 7 yards with the Mk III. >From a low-ready, I raised the gun and fired one shot as quickly as I accurately could as in the "rescue shot" scenario. This was repeated 8 times.

There is no question that Corbon 9mm DPX could be used in situations requiring "finesse" in insuring the elusive "one-shot stop."

So far I am quite favorably impressed with this ammunition. It works fine in two distinctly different pistols. Groups leave nothing to be desired for the ammunition's intended purposes. Expansion seems uniform and penetration should be satisfactory to most. Felt recoil is noticeably less than with the Corbon 115-gr. +P and POI was very close to POA.

Let's compare some similar 115-gr 9mm loads to the 115-gr. DPX +P from the Hi Power and the Glock 26.

From the Browning Mk III w/factory barrel:

Corbon 115-gr. DPX +P:

Average Velocity: 1244 ft/sec

Corbon 115-gr. JHP +P:

Average Velocity: 1411 ft/sec

Remington 115-gr. JHP +P:

Average Velocity: 1264 ft/sec

Federal 115-gr. JHP:

Average Velocity: 1177 ft/sec

The Corbon 115-gr. JHP +P generates about 12% more felt recoil while the Remington is near equivalent at but 2% greater. The standard pressure/velocity Federal has about 5% less "kick" when fired from the same gun as the others.

From the Glock 26:

Corbon 115-gr. DPX +P:

Average Velocity: 1181 ft/sec

Corbon 115-gr. JHP +P:

Average Velocity: 1305 ft/sec

Remington 115-gr. JHP +P:

Average Velocity: 1239 ft/sec

Federal 115-gr. JHP:

Average Velocity: 1111 ft/sec

From the little gun, the 115-gr. Corbon JHP +P has about 10% greater felt recoil than the DPX. Remington 115-gr. JHP +P, + 5% and Federal 115-gr. JHP offers 6% less.

These two Corbon DPX rounds show the primers after firing from the Hi Power (left) and the Glock. In neither case are the primers flattened. Though rated +P and clearly marked as such, these do not appear to be loaded to as high in the +P range as the company's 115-gr. JHP.

With Corbon's history of loading pretty energetic, fast +P rounds, I began wondering why this one's not, too! I pulled a DPX bullet and compared it to a bullet pulled from the JHP load. The DPX is approximately 0.685" long and is seated approximately 3/10" deep. The JHP is measures 0.51" in length and is seated about 1/10th inch less. 9x19mm has a relatively small case capacity and the reduced volume limits the amount of powder that can be used.

I also think there may be another reason: Pushing the DPX faster probably only increases penetration. It expands only to the depth of the hollow point and it obviously has the velocity needed to do this. Corbon is seeking an effective defense load that would provide the penetration levels so many find essential, but not excessive penetration. This is admittedly just a guess, but it seems reasonable.

Only 60 rounds total were fired through the two test pistols. That is not enough to prove reliability in one's personal firearm, but it appears that there will be few problems in guns designed to feed other than FMJ ammunition. Magazines could be fully loaded without binding and feeding was "slick" in both guns; there was zero hesitation in chambering. There was no "bump" and then feed. In short, DPX feed as slick as glass in these guns.

The 9mm DPX load fed without hesitation in both the Glock and Hi Power pistols.

For some that have used X-bullets in rifles, fouling could be extreme. I am happy to report that such is not the case at these more sedate handgun velocities. Cleaning the barrels was no more difficult than with standard bullets using standard gilding metal.

I am extremely pleased with my initial experiences using this ammunition in these two pistols. I think this is going to prove both popular and effective. I seldom say this without considerably more shooting/testing, but assuming reliability, I would not be afraid to use this ammunition for serious purposes. In 9mm, this is impressive stuff.