Heckler & Koch

Heckler & Koch page last updated: 02/19/07



Heckler & Koch

Model Description Status Rating
MP5-10 8.5" barrel, select-fire submachinegun. Uses 30-round polymer magazines. Available with either fixed or collapsable stock. Discontinued
USP 40 Conversion Modified version of the full-sized USP 40 rechambered to fire 10mm Auto. Available
Additional Notes: The HK MP5-10 was built at the request of the F.B.I. as a shoulder fired counterpart to their S&W 1076. Even though the 1076 was replaced years ago, the MP5-10 is still in use by the F.B.I.


The only firearm HK manufactured in 10mm was the MP5/10 made specifically for the FBI and the American law enforcement community. The gun is basically a standard MP5 as far as design and function, but is beefed up for the larger round. Because of the existance of both full-power and reduced-power loads there are two bolt carriers for the gun. For loads under 1,100fps the low-impulse carrier would be used. Loads rated with higher velocities would use the high-impulse carrier to reduce battering. Another interesting feature is that the MP5/10 (and the MP5/40) has a bolt hold-open catch which holds the bolt back after the last round in the magazine has been fired. Standard 9mm MP5's do not have this feature.




As noted, there are six different Smith & Wesson autoloaders chambered for the 10mm Auto. Probably a more accurate description would be that there are three different configurations, each in two different barrel lengths. Decoding the S&W 4-digit numbering code can be rather interesting. The first two digits refer to the caliber. The third digit refers to the what I guess you would call the model configuration (barrel length and trigger/safety operation). The final digit indicates the material the gun is constructed of. Smith & Wesson's 10mm offerings include the following models:

MP5-10 - The HK MP5 is probably the best known and most easily recognized modern submachinegun in the world. Though the M4 carbine has eaten away at the MP5's dominance in the past few years, there was a time when just about every S.W.A.T. and anti-terror team deployed the MP5.

While the MP5 is an excellent subgun, the American user often lists two deficiencies with the MP5 design. The first deals with caliber. Though the 9mm Parabellum is often considered as being towards the top of handgun power in other parts of the world, it is often viewed as "marginal" here in the U.S. We Americans like lots of power and relatively speaking the 9mm just doesn't qualify. Secondly, U.S. shooters of military-style longarms are used to a "last shot bolt hold-open" capability which the MP5 doesn't have. When the F.B.I. decided to upgrade their firearms they told Heckler & Koch they wanted a major caliber (10mm Auto) and they wanted the bolt to lock back after the last round had been fired. It took a bit of re-engineering, but HK did it.

The result was the HK MP5-10 and MP5-40. The MP5-40, chambered in .40 S&W, was targeted more at various state and city LEAs, but the 10mm MP5-10 was built specifically for the F.B.I. When the F.B.I. adopted the 10mm cartridge its performance was downloaded to improve it's shootability. The 10mm Auto was still being manufactured in its original full-power loading, however, and this range of power was a bit to wide for the MP5 to handle. If you designed the gun to operate with "F.B.I. Lite" low-power ammo the full-power ammo would eventually destroy the gun. If the gun was built to work with the full-power loading the lower power ammunition would not reliably cycle the gun. To deal with this problem the MP5-10 is designed to use two different bolt systems (termed "Low Impulse" and "High Impulse"), depending on the ammunition used.

The HK MP5-10 is still used by the F.B.I., even though the S&W 1076 has been replaced by Sigs and Glocks, but I have heard reports of other LEAs who also purchased the 10mm HK having dumped the gun because they wouldn't stand up to the abuse of the 10mm cartridge. I have no doubt that HK could have made the 10mm version of the MP5 work, but unfortunately both the MP5-10 and MP5-40 were dropped from production in favor of the UMP which is available in 9mm, .40 S&W and .45 ACP.





USP 40 Conversion - While there are a number of different 10mm pistol styles out there, one gun that isn't available in this caliber is the Heckler & Koch USP. The USP is an excellent design, is quite strong and has good capacity. The only problem is that the 10mm Auto caliber is missing from HK's lineup. If you're willing to spend a little money and don't mind altering a perfectly good gun in the process there is an option available to the 10mm fan.

This USP 10mm conversion belongs to MBSL (from HKPro.com). Starting out with a standard full-size HK USP in .40 S&W he had the barrel reamed out to 10mm length. (It must be noted that a standard 10mm chamber reamer doesn't exactly match the HK .40 S&W chamber and so some finish work on a lathe will be required.) The stock ejection port was large enough to eject empty 10mm cases, but not loaded cartridges. Because of this the ejection port has been opened to allow for proper clearance. In most instances the main problem with converting .40 S&W pistols to 10mm is mag well and magazine issues. Basically the OAL of the 10mm cartridge is just too long to fit. Strangely enough though the mag well of the .40 USP is large enough to accept widebody 1911 mags which happen to be big enough for the 10mm. In this case STI .40 mags were used (Paraordnance P16 mags also work). To work though a new mag release notch need to be cut and the follower modified to properly engage the slide stop. The only other thing needed is a stronger recoil spring, which in this case is a Wolff 16lb unit. The final product is a HK USP 10mm Auto!



Heckler & Koch is well known for their excellent military and police weapons. One of their most famous firearms is the MP5 family of 9mm submachineguns. The MP5 has been the "weapon of choice" by elite military and SWAT teams for some three decades now. When the F.B.I. decided they needed a carbine/subgun chambered in 10mm to compliment their newly adopted S&W 1076 pistols it was HK that got the contract.

I have not had the opportunity to fire the HK MP5-10, but from all accounts it is an excellent firearm. It is reported to handle very well, is quite reliable with appropriate ammunition, and packs quite a punch. Though the MP5-10 (and it's .40 S&W counterpart) is no longer produced, the MP5-10 continues in the service of a number of law enforcement agencies, including the F.B.I.

The HK USP line of semiautomatic pistols are excellent guns. I have both a full-size USP 40 and a .45 Compact and both guns have proved to be strongly built, ultra-reliable, and quite accurate. About the only thing wrong with the USP is that it isn't available in a 10mm Auto chambering.

Shooting Characteristics

I have not shot either the authentic HK MP5-10 or the USP 40 10mm conversion so I cannot speak to the specific shooting characteristics of either of these guns. I do have experience with both the HK94 (9mm semi-auto version of the MP5) and the Coharie Arms CA-5-10 clone of the MP5-10 though.

Every Heckler & Koch firearm I've handled has been extremely well built. They are designed to be simple to operate and reliable in the extreme. The HK94 is a compact carbine and functions flawlessly. I have also heard this of the MP5-10, but that it is much more ammo sensitive than either the 9mm or .40 S&W version. When shooting the Coharie Arms CA-5-10 the recoil is more noticeable than the 9mm HK94, but it is still very controllable. In fact, the Coharie clone is one of the easiest guns to get on target quickly and make multiple accurate hits with that I have ever shot.

I purchased a full-sized HK USP 40 back when they first came out. I have shot it extensively and have been so impressed with it's handling, reliability and durability that I bought a tactical light for it and made it my "house gun." If you're not familiar with HK's USP pistols they are available in a number of different trigger/safety configurations. Mine is a "Variant 1" with a safety/decocker on the left side of the frame. The gun can be carried with the safety off for a standard double-action first shot, or carried with the safety up and the hammer back like a cocked-n-locked 1911. By depressing the safety down past the "fire" position it decocks the hammer. Unlike many .40 S&W guns the USP 40 is not a modified 9mm design, but was built from the ground up as a .40 S&W. There are two things that make this conversion possible. First off, the USP's magwell is large enough to take .40 caliber doublestack 1911 mags (such as the Paraordnance P16 mags). This is key that makes it possible to get the longer 10mm cartridge to feed and fire in a .40 S&W-sized gun. Secondly, the USP 40 is overbuilt for the .40 S&W cartridge. By making the USP 40 stronger than it needs to be HK has made it possible to safely fire the more potent 10mm cartridge with no ill effects to the gun. I have heard that the recoil of the USP 10mm conversion is pretty snappy, but nothing that could be considered uncontrollable, or even uncomfortable. I believe there are only two or three of these conversions out there at this time, but I have not heard of any reliablity problems. I have no plans to convert my own USP 40 as I like it the way it is, but if I ever have the opportunity to pick up another one "on the cheap" so to speak I would definately go for it!


March 1999 S.W.A.T.

I have not seen a lot of articles on the HK MP5 in 10mm. As sales are restricted to military and law enforcement I guess the gun magazine community felt there wouldn't be a lot of interest in a review of this particular firearm. S.W.A.T. magazine did do a short article on the MP5-10 though, and so I have included it here.


Heckler & Koch Military/Law Enforcement Catalog

Looking through HK's Military/LE catalog is always fun (all those cool toys!). I've included the two-page picture of the MP5-10 which includes velocity and energey data on the various calibers in the MP5 line.

Click on the picture to see the full-size image.