DPMS vs. MP40
Can an historic automatic subgun rival a modern AR-based SBR?
By Dennis Adler
Recreating the MP40 as a blowback action CO2 model with full auto firing capability gave the Umarex Legends series a second superstar for vintage military arms enthusiasts to enjoy. An original WWII-era MP40 would be cost prohibitive for most firearms enthusiasts, as well requiring a Class III firearms license to own, while the CO2 model, which joined the Umarex Broomhandle Mauser Model 712 as a second vintage select-fire airgun design, provides as much authenticity as possible at a mere fraction of the cost for an original. The Crosman DPMS Panther SBR is a modern counterpart to the MP40 and like original WWII guns, a new centerfire DPMS SBR is also expensive and requires special permissions and expenses to own. But these two have more in common than ownership restrictions for their centerfire counterparts, even as CO2 models they are counterparts in the theory of their design and operation. Like the DPMS compared to the Springfield Armory M1 Carbine, there is that same generation gap that makes the vintage arms so much more appealing. Only here, these guns are on a truly equal footing.
Sizing up past and present
The Umarex MP40 looks very close to the 9x19mm models but there are a few quick visual tells, particularly with the open bolt which does not travel as far back nor allow the bolt to lock up into the rear notch as a manual safety like the originals. The CO2 model’s bolt channel is also shorter, although the notch for the bolt lock is still there. The other quick tell is the added selector and safety switch, on the underside of the foregrip, since the WWII guns were not select fire, only full auto. Beyond that, at a glance the Umarex looks very much like a real 9x19mm WWII era MP40, particularly the WWII version’s weathered finish (currently not available). And since the Bakelite pistol grip and foregrip of the original guns were molded plastic, the polymer pistol grip and foregrip on the Umarex look authentic enough.
In overall length the MP40 measured 32.8 inches with the stock extended, 24.8 inches with the metal stock folded, and weighed in at 8 pounds 13.8 ounces empty. Barrel length measured 9.9 inches. The Umarex is very accurate in these details and no lightweight at 7 pounds, 14 ounces empty. The air rifle’s overall length with the stock extended is 32.75 inches and 24.5 with the stock folded. The smoothbore .177 caliber barrel is 9.0 inches and recessed inside a correct length 9.9 inch outer barrel with a full size muzzle. Overall, more than close enough considering the number of different factories that built MP40s during WWII.
The DPMS is a very modern counterpart to the WWII MP40, especially in size. With an overall length 30.4 inches with the stock extended, and 26.6 inches in length collapsed, the DPMS is a little over 2 inches longer than the MP40 with stock folded and 2 inches shorter with the stock extended. The big difference is in length of pull (distance from the back of the shoulder stock to the trigger) since the trigger and pistol grip is further to the rear on the MP40. With the stocks extended it is 15.125 inches for the DPMS (which is adjustable) while the MP40 is a much shorter 12.375 inches. And last is the weight difference with the polymer and alloy DPMS tipping the scale at 6 pounds, 8 ounces, versus the all metal (alloy) MP40 at 8 pounds, 13 ounces.
Since both CO2 BB magazines use two 12 gr. CO2 cartridges, magazine weight and capacity are also a factor. The MP40 has a massive capacity of 52 rounds due to its overall length of 10 inches, versus 25 rounds in the DPMS mag which is 7-inches long. The magazines weigh 1 pound, 5.5 ounces and 1 pound, 9 ounces, respectively.
The Umarex Legends MP40 is a ground breaking design in several ways, one of which is boosting power for this blowback action open bolt design by using a dual sealed CO2 chamber inside the magazine, which is similar to the inside the shoulder stock CO2 loading system for the Umarex Legends Cowboy Lever Action and new Ruger 10/22 semi-auto. The elongated seating screw in the base of the magazine has its own piercing pin and O-Ring seal, so when the screw is tightened down, the entire polished chamber inside the magazine is pressurized to operate the gun. The twin CO2 chambers on the DPMS are a different design with separate seating screws for each CO2 feeding into a combined air chamber inside the magazine.
Velocity is the next comparison, with the MP40’s dual CO2 driving steel BBs down the 9-inch smoothbore internal barrel at an average 455 fps, versus the DPMS which shoots its steel rounds at 419 fps through a 10.25 inch smoothbore barrel.
Loading and shooting on full auto
The MP40 has a follower that is easy to hold down and a loading port that allows you to easily pour Bs into the channel. The same is true for the DPMS, which also has a speed loader that holds the follower down if you want to run the BBs in even quicker. Once the magazines are inserted in the mag wells, pull the bolt on the MP40 to chamber the first round and the charging handle on the DPMS.
While the DPMS uses an AR-style safety and selector on the left side of the lower receiver, the MP40 CO2 model is fitted with a discretely hidden manual safety and selector on the underside of the receiver. (The WWII guns had a bolt locking safety and were full auto only, so no selector switch was required). The added safety/selector on the CO2 model is large enough to easily operate without have to search for it or turn the gun over, but still completely out of sight. The large checkered magazine release button on the left side of the receiver is pushed in firmly to release the drop free CO2 BB magazine for a reload (extra magazines are a must). Same for the DPMS which has a right side mag release only (centerfire guns are ambidextrous).
The MP40’s reciprocating bolt action imparts a slight sense of recoil, but has zero effect on shooting accuracy, much like the DPMS which actually runs a little quieter than the MP40.
The sights on the MP40 are large, easy to pick up and get on target at 25 feet, which with the 9-inch barrel will keep rounds pretty tightly grouped on target. Trigger pull on the test gun averaged a modest 7 pounds, 5.2 ounces with 0.25 inches of travel, light stacking toward the end and a clean break. It takes a full let off to reset on semi-auto. On full auto, pull the trigger and keep the gun on target. With its overall weight, very light recoil, and barrel length, you can maintain a remarkably tight pattern with burst firing. The folding iron sights on the DPMS are also easy to get on target, but as noted in the DPMS review, the gun has a very heavy trigger pull at 10 pounds, 6 ounces. It is, however, a very consistent, single stage trigger and as you pull through, about one third of the way, there is a definite felt and audible click, then heavy pull until it breaks. It isn’t progressive (stacking) it is just a long, hard, single stage pull that has almost no change from shot to shot. On full auto there are two distinctive clicks as you pull through, then the same resistance and pull through to auto fire that allows you to easily shoot short bursts, release, and fire again with absolute consistency. It is heavy, but nonetheless a very good trigger for this type of blowback action, select-fire air rifle. The MP40 is just a little less demanding of your trigger finger.
For the shoot off, selectors were set to full auto and tests done with stocks extended and firing from the shoulder in short bursts 21 feet out from the target. The weight of the MP40 combined with the short length of pull, keeps the gun close to the body yet the sight radius is long enough (16 inches, compared to 13.5 inches on the DPMS with a longer length of pull) to give you a sharp sight picture downrange. With the lighter trigger pull and smooth reciprocating bolt action, the MP40 is pretty easy to hold on target with short bursts of five (6 to 10 rounds).
At 21 feet, I loaded the MP40 with only 25 rounds to keep it even with the DPMS. My series of short bursts put all 25 shots into a spread of 2.437 inches aiming at a red dot I placed below the A in the A-Zone of an IPCS silhouette target. My first shot group (about five or six rounds) hit at the bottom of the red dot measuring 0.45 inches and burst fire spread out from there as I held my POA. There is another 5-shot group that hit below POA at 0.5 inches, so groups of individual bursts were all pretty tight. I think this is about as good as this gun can get from the shoulder on auto fire.
I repeated the test with the DPMS unloading 25 rounds into another IPSC target from 21 feet, and it gave me a spread of 2.375 inches with one solid burst of at least 10 rounds that punched into a concentrated circle measuring 0.625 inches.
Round for round, the tightness of the groups between the MP40 and DPMS are pretty close, with a slight edge toward the modern DPMS AR design, which snugs up as firmly as the old WWII subgun, but doesn’t have as crisp a sight picture, nor does it shoot to POA as well, actually hitting a little low, requiring a 2-inch hold over above the red dot to keep shots close to the A in the A-Zone.
For me, I like the feel of the old war horse over the modern AR design, and the accuracy is not much of a trade off, though it is hard to beat a shot group on full auto that punches out a section of the target. I give the overall win to the DPMS, but I’m still keeping the MP40.
A word about safety
Blowback action airguns provide the look, feel and operation of their cartridge-firing counterparts and this is one reason why they have become so popular. Airguns in general all look like guns, blowback action models more so, and it is important to remember that the vast majority of people can’t tell an airgun from a cartridge gun. Never brandish an airgun in public. Always, and I can never stress this enough, always treat an airgun as you would a cartridge gun. The same manual of operation and safety should always apply.
DUE TO SEVERE WEATHER, SATURDAY’S AIRGUN EXPERIENCE WILL BE PUBLISHED ON SUNDAY