By R.K. Campbell
The story of the ‘centimeter round’ or the 10mm begins as early as 1920 when Colt considered producing a mid bore 1911 for foreign sales. Unlike later efforts at different calibers for the .45 ACP 1911, this design was intended to be about three quarters of the size of the .45 caliber 1911 handgun. All others have been of the same exterior dimensions as the original 1911 .45. As far as cartridge development goes, there were a number of experimental cartridges that may lay a claim to the title of primogenitor of the 10mm. The most obvious predecessor of the 10mm is the .40 caliber G and A. This cartridge was intended to combine high velocity with a big bore cartridge. The cross section of the .40 caliber/10mm cartridge was the minimum to provide good stopping power (wound potential) and penetration according to both theorist and those with real world experience. The result was a cartridge close to the modern .40 caliber Smith and Wesson in concept and size. The .40 G and A was a wildcat cut down from .224 Weatherby rifle brass and custom loaded using .38-40 revolver (.401 diameter ) bullets. 180 grains at 1,000 fps was the operating standard. This was a sensational wildcat in its day, chambered in a heavily modified Browning High Power pistol. The pistol was cut to fit the larger cartridge and a custom Bar Sto barrel added. The much more powerful and longer 10mm automatic was developed to give even more power. The larger cartridge demanded a handgun of a larger size than the Browning High Power. The original concept was perhaps the most forward looking.
Another experimental round that enjoyed some current was the .41 Action Express. The .41 AE featured a .410 inch bullet and a rebated case rim. The reduced size rim was the same size as the 9mm Luger case head. As a result the .41 AE was less difficult to chamber in a 9mm Luger cartridge. There was far less breech face work. The .41 AE was a neat and effective conversion of the Browning High Power. There were some hurdles in achieving good reliability with a custom cartridge and handgun but the result was a relatively light and compact pistol with a powerful cartridge. Another development of the .41 AE is little known. This is the 9mm AE. A rather odd cartridge in appearance with its rebated 9mm cartridge case head and bottleneck cartridge case neck, the .41 AE is roughly comparable to the modern .357 SIG cartridge. These cartridges were a remarkable achievement for the time.
This experimentation led to the original Bren Ten pistol. The Bren Ten was a larger version of the Czech CZ 75, a proven service pistol in 9mm Luger caliber. The Bren Ten was not commercially successful for many reasons, most of which seem to center around production capability or perhaps under capitalization. But the new pistol chambered the 10mm automatic cartridge. Longer and more powerful than the .41 AE, as originally loaded the cartridge was probably too hot for continued use in the Bren Ten pistol, with the Norma rounds commercially loaded producing a claimed 1,200 fps with a 200 grain bullet. As a baseline a contemporary heavy duty .45 ACP hand load pushed a 200 grain Hensley and Gibbs #68 SWC to 1,100 fps. Factory .45 ACP 230 grain ball loads break about 820 to 850 fps. The 10mm was a hot cartridge and still is. The new pistol according to Colonel Jeff Colonel would do things at 50 yards the 1911 .45 could not. The 10mm was on the one hand not designed to replace the .45 but to supplant it, while others lauded the new combination as a replacement for professionals carrying a fighting handgun. In any case, Dornaus and Dixon producers of the Bren Ten went bankrupt in 1987, leaving many Bren Ten owners with a pistol and no magazine. The outsourced magazines were not delivered in concert with the pistols. We now had a cartridge in full production with no handgun to chamber it. A smart marketing move by Colt Firearms Manufacturing Company followed. Colt introduced a modified 1911A1 pistol chambered for the 10mm cartridge. The new pistol was introduced in both blue steel and stainless versions. The pistol featured the new Series 80 firing pin block. The Delta Elite was a distinctive pistol with special grips with a stylized red center Delta Emblem. The Delta Elite features a hammer variously referred to as a skeletonized, dowel, or Commander type hammer. A significant change from the 1911 was a special recoil spring and rod, designed to contain the significant recoil of the 10mm cartridge. All 10mm 1911 pistols require some type of shock buffer or cushioning device. The pad or hard urethane device was designed to allow the slide to have a lighter jolt during the recoil cycle to avoid battering. The 10mm is more powerful than the .45 ACP and may exceed the power of many .357 Magnum loads as an example. The 10mm pushes a 200 grain bullet to well over 1,100 fps with modern – and sensibly downloaded – ammunition. The result with the poorly designed first generation recoil buffer – sometimes called a Mickey Mouse affair – led to incipient battering when pressed into heavy use. Competitors and interested shooters found the 10mm quickly showed eccentric wear. There were reports of frame cracking as early as 3,500 rounds. Colt introduced a special frame with a stress receiving slot cut-out to alleviate some of the problem. A full power 22 pound Wilson Combat recoil spring goes a long way toward controlling wear and tear on the pistol when coupled with a full length guide rod. A severe problem leading to excess battering was shooters fitting a lighter hammer spring to improve the trigger without realizing that the lighter hammer spring allowed higher slide velocity and excess battering. A combination of a pistol not set up properly from the factory and shooters treating the 10mm like a .45 when it came to springs and other modifications led to many Delta Elites being prematurely battered and worn.
Parallel developments at Smith and Wesson resulted in the Smith and Wesson 1076, built on the Smith and Wesson 4506 .45 frame. This pistol was adopted by the FBI and was not without its own set of problems. An important development was the availability of two power levels of 10mm ammunition for Bureau use. When the FBI issued .357 Magnum revolvers, they used two power levels. The .38 Special +P was the standard while the .357 Magnum load was approved for certain uses. The full power 10mm was much the same as the .357 Magnum. The FBI ‘lite’ load used a 180 grain JHP at 980 fps. The Federal Hydra Shock loading proved to be brilliantly accurate, which is true of very few 10mm loads. This level of power generated the same energy as a 185 grain .45 ACP. That it had the same stopping power is debatable since the bullet diameter is smaller. The 10mm reduced power load led to the development of the .40 Smith and Wesson. Ammunition and gun makers realized they could chamber a short case .40 caliber of the same power as the 10mm ‘light’ loaded cartridge in a 9mm package. While the .40 is a high pressure number with pressure spikes and problems all of its own it has proven to be an immensely popular cartridge and gun combination. The .40 caliber pistols are shorter and lighter than the original 10mm and the .45 ACP pistols, which is desirable in a service pistol to be carried at all times. Placing convenience ahead of tactical ability is the norm in police service pistols.
The 10mm got into a lot of shootouts in the hands of police officers. Officers in special teams and those at risk were the first to jump to the new product. Some of the early results were poor. Felons were absorbing several rounds of 10mm without the desired immediate effect. My research indicates the culprit was poorly produced foreign made ammunition. Unfortunately, as detailed in several professional reports during this period, police departments did not actually test the ammunition they purchased. They would determine that the service cartridge would be as an example a 9mm Luger 115 gain JHP. They may not specify Winchester Silvertip or Federal 9B. They asked for a certain type of load and in several cases the low bid was a poorly performing substitute. This often happened until agencies wised up. The same thing occurred with the 10mm. Underdeveloped hollow point bullets did not expand. Many of us realize that stopping power does not exist while wound potential is important if the bullet is delivered to the right place to achieve the most good for the shooter. Today there are far better choices in 10mm ammunition including the Winchester Silvertip and the Hornady XTP. In any case, the .40 caliber was introduced in 9mm size handguns and the 10mm suffered a rapid fall of popularity.
A number of police departments issue the 10mm, but the Colt is seldom seen. Glock’s Model 20 is the most likely home of the 10mm. However, the Delta Elite retains a following and with the reintroduction of the Colt Delta Elite after several years out of production the situation may change and we may see more pistols in use in America. The Delta Elite illustrated is an early version in good condition. For the purposes of this review and to qualify 10mm ammunition performance we tested several types of ammunition. Performance was impressive as far as exterior ballistics are concerned. These loads are not loaded to the original levels, which were really too hot for use in a 1911 platform. Accuracy was acceptable if not outstanding. Poor 10mm accuracy is often traced to improper spring selection, leading to inconsistent lockup and poor accuracy. This pistol is properly sprung but accuracy is not on the level with comparable handguns in .45 ACP and .38 ACP Super previously tested. The 10mm is accurate enough for personal defense and some forms of competition. The 10mm is simply not a gilt edged accurate number in the majority of 10mm caliber 1911 pistols. Reliability cannot be faulted. During the firing tests there were no failures to feed, chamber, fire or eject. We used high quality magazines including the original Colt and the modern Metalform magazine, with flawless performance from the well designed Metalform.
|Load||Velocity||25 yard group|
|CCI Blazer 180 grain FMJ:||1,090 fps||4.0 inches|
|Cor Bon 135 grain JHP:||1,530 fps||3.9 inches|
|Cor Bon 165 grain JHP:||3.0 inches|
|HSM 10mm FMJ:||---------||3.5 inches|
|Federal 180 grain Hydra Shock:||983 fps||3.5 inches|
|Winchester 175 grain Silvertip:||1,229 fps||3.75 inches|
|Hornady 155 grain XTP:||1,355 fps||3.25 inches|
The 10mm is a viable option for service use. The 10mm offers excellent penetration against light cover and intermediate barriers. The extra recoil of the 10mm and the extra training time needed to master the 10mm makes it an impractical firearm for general issue. Just the same, the 10mm remains a popular choice for a small group of armed professionals.
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