Recoil Test: Vector VS. UMP (Part 3)

This is the third and final part of our series where we have teamed up with KRISS USA. Part 1 can be viewed here and Part 2 here. For this portion we we decided to try and quantify the recoil reduction of the Vector verses its main competitor, the HK UMP (in this case a converted HK USC SBR was used, however it is identical except for the roll marks).

According to this company there has never been a very good way to measure recoil due to the amount of variables involved. Obviously the Vector with its Super V system is marketed as reducing recoil and muzzle climb, as the action recoils down instead of straight back (kind of like a giant upside down Luger pistol) but I wanted to try and see exactly how much relative to the UMP submachine gun. For this I asked my friend CJ what would be the best method. He suggested to me that I look into buying a load cell to place the gun on with a high sample rate and put the two guns against each other. For this I found a company in Virginia who offered a load cell with a high sample rate that expressed data graphically on a PC in the form of a simple line graph and also displayed the peak. I placed the load cell on a Lead Sled and performed the test by firing five shots, three times and taking the middle group from the three samples.


As you can see we had more firearms that we intended to test, but the guy’s flight back to Virginia was in the afternoon and we simply did not have time.



We set the vector in my device and loaded the software on Mike’s PC. Luckily, the Vector and the UMP have the same width stock, so each gun had an equal amount of material resting on the load sensor (give of take a millimeter). To eliminate as many variables as possible I took the following precautions:

  • The equipment was provided by me, an impartial third party employed by no firearm manufacturer
  • I would be the trigger man, as I had no vested interest in any gun performing better
  • An equal amount of material from the stock would be resting on the load cell
  • 15 shots would be taken total, the middle group of which would be used in final data
  • An M4 carbine (Colt 6920) would also be used in order to provide our readers with some familiarity (most people have a good idea of how much a .223 recoils)
  • The same ammunition from the same box would be used

On with the test.


Immediately we got feedback from the Vector and it was neat to see the data in real time.


Next the UMP:



I was anxious to see the data produced and we were all taken aback by how much less pressure the Vector exhibited on the load cell.

Now was the M4. Setting it in the rest properly with the desired amount of stock touching the sensor was difficult:



But of course we managed:



Also, KRISS flew in a member of their media department to film this testing so they can use it in promotional material. I must say that is was neat to have a microphone on talking about my experiment!

Also when you get a bunch of men together with these kind of toys, how can you not expect them to put them to good use?


I did manage to take a video of me on the Vector too:

Lastly as a joke we tried this setup to see if we could max out the load cell, but due to not having a solid mounting point it did not work out so well!


So what kind of results did the test yield? Well I was as surprised as could be.

The Vector:

KRISS Vector



That is a 62.14% reduction in recoil. As we got the figures we all stood there pole-axed in awe of what we had just done. KRISS claims that the Super V system reduces recoil of the .45acp cartridge by 60%, but having performed a test myself first hand and being able to confirm that is amazing.

The M4 carbine exerted roughly the same amount of force as the Vector too at 21-22 pounds (I apologize for the cutoff, but the screen shot was improperly taken):


To conclude, let me say that I knew the Vector recoil was much less due to the shooting test the previous day, but the results of this test were still surprising to me. We even had one sample that showed the Vector recoil was 64% less, but as stated I used the median sample. It is no wonder that the vectors off axis recoil generated less on the load cell as well, and that the UMP’s straight blowback system alongside its heavy bolt exerted much more force on the load cell.

I tried to make this test as fair and as unbiased as possible to provide legitimate information to consumers regarding two firearms. Also note that the data expressed in pounds is not accurate as to felt recoil. It is rather all of the guns recoil forced upon an area the size of a postage stamp, so it is amplified.

Thank you for reading the series on the KRISS Vector SMG, and I hope this is the first of many manufacturer-The Firearm Blog collaborations!

Alex C.

Alex is a Senior Writer for The Firearm Blog and Director of TFBTV.


  • Alex you did one heck of a job on this series! I’m proud to say you write for TFB!!!

    • Steve (TFB Editor)


      • Thank you gentlemen, this was a lot of fun! Also thank you to our readers for making it through the series, hope you guys enjoyed the articles!

        • Y-man

          Great work here… Shows the passion, nay, the LOVE in every word.

          Good job.
          (So ANY recoil rating readings on the Barrett at all? is the pressure sensor detachable? So one can put it between stock and wall, for example?)

          • Y-man I think Alex is already with the family but from what I understand the readings they got had to be way off.
            Merry Christmas Y-man good to hear from you!

  • Vhyrus

    So, the KRISS had about as much recoil as a M4, which shoots much more powerful ammo and has longer range. So I guess the million dollar question is ‘why pick a KRISS (or any smg) over a bullpup or SBR shooting .223?’

    Out of curiosity, what was the barrel length of the m4?

    • Matrix_3692

      14.5 inch, but the Vector shoots a 185-230gr bullet,while the M4 shoots a 63gr bullet.

      • bbmg

        Kinetic energy is the weight of the bullet multiplied by the square of the velocity, it,s not just about number of grains.

        • The recoil formula looks more like bullet momentum plus powder energy. If you want to minimize recoil per unit energy you go small light fast bullets (5.56) vs big heavy slow (.45). The question then becomes if minimizing recoil is what you want most, vs incapacitating effects, thence to a years screaming back and forth over terminal ballistics…

          • bbmg

            I read the response as “it might have more recoil but it shoots a heavier bullet” implying it is worth the increase in recoil for greater effect on target, I might have misinterpreted that.

            I won’t get into the debate as to whether a light fast bullet is better at close range than a slow heavy slug, as you mentioned that is a whole other can of worms.

      • Suburban

        In the article, it says it’s a Colt 6920, which has a 16″ barrel. Looks like a 16″ barrel to me. Although only a 1.5″ difference, the 14.5″ barrels look noticeably stubbier.

        • Matrix_3692

          sorry, didn’t see that particular line, but i meant the ‘generic’ M4.

    • bbmg

      The only reason I can think of would be effective subsonic bullets in a suppressed weapon, but these days the 300 blackout would seem to be a better idea for that purpose due to its much flatter trajectory.

    • Jesse Mrozowski

      That’s what I keep coming back to with most pistol caliber carbines. I like them in theory but in practice they all seem to have more recoil than a AR15 due to them all being blowback so I do the math in my head and go “More recoil, less power, no thank you.” In this case it’s “Same recoil, less power” so the conclusion is still “No thank you.”

      If it was in 9mm you might be able to argue cost of ammo but in 45 ACP it’s probably a wash.

    • FourString

      The same reason why you would want to go with a submachinegun instead of an assault rifle to begin with: overpenetration in the latter. I.e. room clearing, hostage situations, close quarters/urban environments. That’s why the UMP was initially designed around the .45ACP cartridge. Decent stopping power with less of the complications of overpenetration. A slower, bigger bullet is probably a better choice against unarmored targets, I’d imagine.

      • bbmg

        I don’t buy the overpenetration argument, have a look at this box’o’truth test:

        Granted, 45 ACP “only” penetrated 7 x 3/4″ pine boards while the 223 went through at least twelve – but that still means that if you miss with a pistol round it is still going to make a mess of someone after going through say a wardrobe and interior wall.

        The incapacitation argument is stronger, a bigger hole in a living target it always a good thing, no doubt about that and this is why hollow point bullets are so effective. Make a 0.45″ hole in a bucket and it will drain 4 times faster than it would with a 0.22″ hole.

        • FourString

          ah interesting, i didn’t know that about the pine boards. thanks for the link! i think it’s probably an issue of going through to the next house/apartment unit more so than the next wall, assuming it’s not a studio apartment getting raided? >.<

        • Avery

          The point is not to use ball ammo in a 5.56mm SBR for something like this. M193 used in the Box of Truth test is FMJ ball, the overpenetration tests done above where using hollowpoint ammo. While military users still have to follow international conventions and stick with FMJ, police don’t and have that choice between using FMJ for long range engagements and hollowpoints for close range and dynamic entry situations. Hollowpoints paired with the 5.56mm’s ballistic instability at close range means it expends a great deal of its energy in whatever it hits.

      • fattie03

        Another example showing how, when using proper ammo, .223 can penetrate less that pistol rounds.

        • FourString

          whoaaaaaaa wuuuuuuuuuuuuUUuuUuUUuuut

        • FourString

          But hmm would it have the same effectiveness as a .45acp against an unarmored target? Idk, I just think that’s why SMG’s still persist in usage among SWAT/tactical groups. Like, MP5’s still have a role despite the influx of 5.56 SBR’s, at least that’s what I’m guessing from the subgun’s prevalence in response teams’ armories..

    • 16″— They have different uses in different situations. For a CQB weapon the KRISS is much easier to move with. In a house or other building it’s easier to round corners etc. It’s just faster on target kinda like my Tavor.

      • FourString

        Phil, what experience/views do you have on 5.56 sbr vs pistol caliber subguns for close quarters? Regarding overpenetration in particular and perhaps overall effectiveness

        • Working in the city I have to say I’d prefer a .45 like the KRISS. It’s just not going to go who knows where if you miss.

          I never worked for a Sheriffs office but in a rural setting my preference would be an AR suppressed with a 9 inch barrel in .300 blackout. Not that I need to be stealthy and use a suppressor but you can use it indoors without all the blast.
          I prefer a 300 Blackout over a 5.56 since the 300 is a 30 caliber round and has no more recoil than a 5.56.

          The SMG I was issued in the city environment was an MP5 SD. I really liked that gun and still do.It was a good fit especially in tightly packed housing projects. I think at this point I’d rather use a KRISS in 45 acp and get that little extra power.

          The reason I chose the AR configuration I mentioned above(rural setting) is having the chance to shoot several hundred rounds from one a few weeks ago. All of that was in the Gunsite shoot house which gave me a better idea of how that particular AR would work in house clearing. It was easy to handle in that confined area as well as being easy to change to my left hand going around right hand corners. With the low recoil putting two in the targets chest was pretty easy.

          I hope that answers your question.

    • I shoot pistol caliber guns so I can shoot cheap, cast lead ammo for pennies. My favorite guns to shoot are pistol caliber long guns. I help myself to takeoff wheel weights at work and smelt them down.

    • claymore

      Over penetration is a big factor for weapons used in Police situations.

  • Justin_GA

    It may have less recoil then the UMP, but chambering a round in the gun is ridiculously difficult. If KRISS could make the gun where it doesn’t take 80lbs to pull the charging handle back it would be a winner. If I have to choose between recoil and usability I am always going to pick usability. I am curious if the sample rifle used in the test was hard to charge. I’ve heard from others that the SMG samples are tuned and don’t experience hard charging problems. Apparently retail SBR’s, ect. don’t receive the same treatment.

    • Honestly you thought the KRISS was difficult to charge?

      • Justin_GA

        Yeah it’s really hard. I even sent it to KRISS and when I got it back it was the same. Honest to God it will bruise my fingers if I charge it 10 times. I have to use gloves and point it downward like when I draw a bow. KRISS and forum members said it would get better the more rounds I put through it. Also recommended leaving it with the bolt carrier compressed. Well I’ve put about a thousand rounds through it and always store it with the bolt held open. Have had it about 2 yrs now. I would sell but its a NFA title 2. I even went to my local dealer and played with the normal title 1 Kriss and it was pretty hard to charge as well. I really appreciate your reply Phil. Do you think I should send it back to KRISS? If so do you know someone at the company that will really fix the problem. I really want to love it.

        • Bamboo

          I don’t know if you’ve seen this video, but this might help with your problem.

          • Thanks for posting the video—

          • Justin_GA

            I’ve seen that video too many times to count. I studied it frame by frame to make sure I was charging correctly. I can see how moving you fingers outward would be a problem. But that’s the same with just about any charging handle. I wouldn’t say I’m a “Operator” but I spend a lot of time at the range and instruct DGU technique’s, CQB tactics, 3 gun, first time safety classes (Free for women and children). What I’m getting at is I know my way around firearms. Like I said before I want to love the Vector but I can’t in good conscience recommend it. If you get the chance Phil check out the video I made.


          • No I’d say there is a problem there. Mine was never even close to that hard.

        • I’m just really surprised. I had a KRISS to review right after they came out and I really didn’t notice it being hard to chamber a round.
          As far as sending it back again I probably would. If you want I can call and at least ask about the problem and see if they have had that happen on other guns. Depending on the information I get you can decide on sending it back or not.
          I recheck the comments daily so just let me know. I’ll be glad to help if I can.

  • Suburban

    Thirteen seconds! That’s the video you had me on the edge of my seat waiting for?

    Half-joking aside, I do appreciate the trilogy of articles.

    • Ha, I guess I did pull a bit of a George R. R. Martin on that one. I do have a mostly video review of a cool full auto gun coming up though, so stay tuned!

  • IXLR8

    If you only had a Thompson for comparison…
    After 2 boxes of ammo through a Kriss F/A I did get a bruise on my shoulder. I like that you did shoot the Kriss without the suppressor, I found it to be less manageable in that configuration.

    • You got a bruise?? I never experienced that but everyone is different.

      • IXLR8

        Yes, it was a mild bruise but it was hard to see with huge grin on my face…
        They have have a F/A Kriss for rent around the corner from my house. If I need to cheer up, I go and rent the Kriss. It gives me a grin that belt sander couldn’t remove.

        • Belt sander—now that’s a good one. All you have to do is go around the corner! I’m jealous:-)
          I was at Gunsite a couple of weeks ago and after we shot all the FA guns–well I never saw so many permanent grins.
          I think Iain Harrison had the biggest grin:-)

      • RockStarArtist

        lol, everyone is different! My wife always knows when I have been playing around with a rifle in the house. I get red marks against my inner-shoulder from the stock of a rifle(without firing it!), you should see the welts when I do fire a rifle.

        Thank you for this fun and informative article, I am now looking to try out the Vector!

      • claymore

        Hey Phil there is a topic there waiting to be explored “Suppressor use by police” I think there is a lot to be discussed on this topic.

        • That’s true. I need to give that some thought. I’m pretty sure I can write one up. It probably wouldn’t be very long but we could cover most uses and needs.

          • claymore

            I was thinking about their use and if and when they could be used lawfully.

  • clinton notestine

    very interesting write up, rivals the mythbusters

  • Lance

    Still rather go with the M-4 or a UMP over KRISS’s over sized Machine Pistol.

    • DW

      UMP is an oversized machine pistol, even its name says so.

    • FourString

      Mate, the UMP stands for “Universale Maschinenpistole” or “Universal Machine Pistol”

      *facepalm* -.-

  • claymore

    Outstanding to see some science used to make the point. Very nice job.

  • Tony Williams

    Thanks for a very interesting series of tests. There is one problem: the results appear to defy one of the iron rules of physics: Newton’s Third Law of Motion, which is usually summarised as: “for every action there is an equal and opposite reaction”. What this means is that two guns weighing the same and firing the same ammo from similar barrel lengths should produce the same overall recoil force. The only way to reduce the recoil is to fit a muzzle brake, or some other way of diverting or slowing part of the propellant gas instead of sending it out the muzzle. The right gun mechanism can spread the recoil force over a longer period so the peak force is lower, producing more of a steady push than a sharp kick, but it can’t reduce the overall force.

    It would be great if you could present these results to your local university physics department and get them to come up with an explanation!

    • The overall recoil is of course the same in both firearms, however the vector’s recoil mitigation system changes the direction of the recoil downward rather than all rearward like the UMP. Had we placed a load sensor in the right place below the firearm and combined the figures collected from both then I’m sure they would’ve added up to the force exerted by the UMP.

      • Tony Williams

        I suspect that a physicist would point out that “equal and opposite” means exactly that: if the bullet and propellant gas go forwards, the gun goes backwards with equal force whatever the mechanism gets up to.

        I have asked others about these results and the view appears to be that your experiments measured the peak recoil force, which is clearly lower in the Kriss than in the UMP. But that indicates (as I suggested in my previous post) that the Kriss mechanism has a recoil-smoothing effect, delivering more of a long push than the quick kick you get when a bolt hits the buffer. That would account for these results without breaking Newton’s law.

    • David W

      Great article, I have a Kriss Vector, I was upset that I bought the Kriss instead of the IWI Tavor, now I am glad that the Kriss does have role in urban environment. BTW the charging handle on my Kriss is a pain to charge compared to an AK or AR, Thanks for the article

      • Justin_GA

        Thank you I though I was crazy.

        • David W

          Let us know if Kriss ever fix the charging handle issue for you, good luck.

        • KJQ6945

          I also have a Kriss SBR, and it is very hard to pull the charging handle back. I just attributed it to the unusual design of the Kriss. I’ve found that as long as I have the weapon shouldered it is manageable.

          Loved the article. The one thing I would have suggested, is to show the bolt, buffer and spring from the Kriss alongside the massive bolt from the UMP. It would explain a lot to the physics crowd.

  • Joey S

    Nicely done. Very informative, and a great read. Can’t wait to see what you have up next.

  • gunslinger

    a guy at my last job was getting one of these. but the paperwork for the SBR was taking forever. i ended up switching jobs before he ever got it. i bet he has fun though.

  • Doops

    What should we do if we use a .45 pistol caliber AR vs a Kriss?

  • Greg

    I understand that for the vast majority of the audience on this blog this experiment was pretty complete, however as a member of the firearms testing community this test is pretty sloppy at best. The Army (as well as other organizations) have been doing recoil analysis for decades, so saying there is no good way to do it is a misinformed comment. The procedures are in many reports some of which are openly available to the public. If you are merely comparing recoil of the systems onto the shooter then you can possibly pull that from the test, however of you want to attribute the recoil differences to the design of the specific firearms you can’t do that without measuring the weight and recoil velocities of every moving piece including the mount…not extremely difficult. Even measuring force in two locations between the gun and the mount and the mount and some “fixed” reference will give you a better idea. You need to look at the impulse not just the peak values, the effective perseption of recoil changes based on how it is delivered. I know I’ll get some heat saying that this is fine since everything was fired side by side however without controlling the variables you get minimal real data out and making a comparison like this from that data is pretty bold. Comparing your data to published M4 data may be a start, the recoil limit for safety is currently 60ft lbs which is archaicly based on some research measuring the force required to seperate the shoulder of a cadaver. Your values seem higher than actual values. I would just recommend that before you publish data arguing for or against a certain weapon system that you do your homework and at least check your test setup with other sources.

    • We haven’t the equipment a test facility dedicated to testing would have. We do the best we can with what we have and the knowledge we have as well as those of those in the firearm industry.
      In fact if I understood it correctly a company (unnamed) was interested in this and contacted Alex about it.

      • Greg

        I understand that you do the best with what you have as far as equipment, I just recommended that you compare your results against other sources of data that are available before you go promoting the performance of a certain system. As far as a company contacting you guys, if they are attempting to use this setup to measure recoil and not just as a quick check to see if something they did changed the impulse, they likely shouldn’t be in the firearms testing business.

        • The company had no experience in testing recoil, and have no plans to produce such a device. I simply asked them to help me reverse engineer a load cell to measure recoil. I contacted them with what I needed, and they helped. I just figured a simple load cell would be an easy way to show readers how the Vector’s Super-V system mitigates recoil.

      • The outfit I got in contact with sells all sorts of tech equipment. When I told them about the recoil test, they really helped me get what I needed and compiled the program for me. My budget for all of this was about $1,000 but I am sure if I had the budget of the US Army I could produce much better data.

        As stated, the figures are exaggerated because all the gun’s recoil was focused on an area the size of a postage stamp, so the numbers are high. I had one purpose in mind when performing this experiment: which firearm exerted more force on the load cell. I think we did a good job in that respect. However, if a company with big bucks wants to fund another test with better equipment, I am sure the gentlemen from KRISS would come on out 🙂

        The whole time I was ordering equipment and planning this experiment, the one thing I had in mind was “what are people on the internet going to tell me I did wrong,” haha.

  • Gresso

    You mean the gun with a bunch of weights in the bottom has less recoil than one without? Imagine that.

  • Charles Applegate

    The police aren’t buying integrally suppressed .22 pistols, are they?

  • MrTorben

    I put a few hundred rounds through a KRISS with the fun switch. I agree that it shines on a mag dump. I also shot a semi SBR version that same day, and decided that it was not worth the $ unless you can buy the real thing. You just don’t get the full benefit out of it. I’d buy it as a toy and for the cool innovation factor, if money was no object.