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Thread: Small Caliber PDW's: FN 5.7 mm/HK 4.6 mm

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    Site Supporter DocGKR's Avatar
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    Feb 2011
    Palo Alto, CA

    Small Caliber PDW's: FN 5.7 mm/HK 4.6 mm


    Small caliber PDW's like the MP7 and P90 are niche weapons that have very narrow and specific roles to play.

    Below are comments specifically on the MP7 by a combat experienced senior SOF NCO currently serving in the U.S. military:

    ”When employing the MP7 up close, you literally use it like a fire hose and sprinkle 4.6 all over the torso of the guy you want to reduce (usually on Auto, which is a CQB no-go anyway), and you have to keep hosing him down with bullets until his brain figures out that you are filling him in. Usually this takes longer than shooting a NSR with a rifle, so by the time that your brain figures out that the guy has quit and is crumpling, you are almost out of bullets and any other threats in the room have most likely started to engage you. IF your team is on their **** and everyone grasps the true importance of primary/secondary sectors of fire, then perhaps you can get in there and all of your guys can sprinkle 4.6 liberally on all of the bad guys in an efficient manner, but if you fail to do that, then bad things will happen quickly.”
    Pat Rogers, a former NYPD officer and combat veteran Marine, is a highly respected firearms trainer who has also commented on the use of small caliber PDW’s like 4.6 and 5.7 mm:

    ”Multiple rounds are required to incapacitate. This means significantly more training, which translates into significantly more ammunition expended, at a higher cost per round and with limited sources available. To ensure immediate incapacitation, brain shots will need to be emphasized. Which requires more training, and also more insertion of luck into the equation- especially dealing with multiple opponents. Limited capability within the system means engagement at anything outside of CQB distances may be problematic. This means movement to objective, egress etc will present a whole new range of difficulties. The gun is easy to shoot and fun as well. This does not always translate well to real world applications. If there is a single reason why these platforms are in any way superior to the M4 FOW, it is not apparent to me.””
    A decorated, experienced SWAT officer at a U.S. LE agency that has had multiple OIS incidents with 5.7 mm FN P90's has written the following--note that his comments equally apply to the 4.6 mm MP7:

    ”The 5.7 pistol as a carry gun is a mistake. There are far more effective weapons and ammunition combinations out there. The only factor that comes close to equalizing the P90 (not the 5.7 pistol) is it's full auto capability: 900 rpm of very controllable fire. Even this advantage is limited to close-in, CQB type engagements. I can put more rounds on target faster with the P90 than with my M4 in close contact engagements. Unfortunately you may HAVE to put more rounds in the threat due to the lack of damage the projectile causes. The 5.56 is far more effective at getting the attention of men than 5.7 mm. This is not speculation. We have been using 30 P90's for five years now. There have been multiple BG's shot with them. We will not be buying more 5.7 mm or other small caliber PDW systems”

    - 30 P90's for five years
    - 100,000 rounds per year through those weapons
    - very reliable weapon
    - very user friendly
    - very easy to shoot
    - everyone happy
    - three OIS's later and some unbelievably poor terminal balistic performace we dropped them...quickly.
    - 22+ OIS shootings using AR-15's with .223...everyone happy (except the 21 dead bad guys)."
    As a result of poor terminal performance, a large Federal agency is also no longer running P90’s like they used to. Likewise, some military units that tried small caliber PDW's in combat are procuring other options, like 9" .300 Blackout uppers to run on M4 lowers.

    When a civilian LE agency chooses a full-auto system, significantly more time is needed for training. This increases costs, both in the amount of ammunition necessary to purchase, as well as the need to pay officers for increased time in training, rather than being in the field. Instead of a 1-5 shot NSR with an AR15 based system, with an MP7 each officer is now going to be routinely shooting 15-20+ rounds into each target both in training and in actual OIS incidents, thus the amount of ammo expended is going to be 4 times what would be used with an AR15 based system shooting any common CQB caliber like 5.56 mm, .300 Blackout, 6.8mm, or even 7.62x51mm. How is an LE agency going to afford four times more training ammo for a weapon system like the MP7 that needs to be always shot full auto and whose ammo is more expensive than other common calibers?

    In the civilian realm, how is an LE agency going to explain to their Admin and media why they are now needing to shoot every suspect 15-20+ times? In addition, when you are having to shoot 15-20 rounds full-auto at every target, there is a higher likelihood that some of those rounds may miss the target; how is an LE agency going to handle the liability from the potential increased number of missed shots that can occur with a system that needs to be used full-auto like a "fire hose" in order to offer adequate incapacitation of threats?

    With the data now available, a U.S. LE agency would have to be woefully ignorant or colossally stupid to purchase the MP7 (or P90) for SWAT use given the numerous weapon systems available for LE SWAT/CQB use that are both better and more cost effective than small caliber PDW's. If SBR's are desired, consider a 10-12" 5.56 mm using properly selected good quality barrier blind ammunition (see:, 8-12" .300 Blackout uppers when appropriate LE ammo is finally released (6-12 months away); even better get 8-12" 6.8 mm's uppers, or if you want to have the best terminal performance go with the new group of 16" .308 rifles like the KAC SR25 EMC, LaRue Predatar (or OBR for precision use), or the FN Mk17/SCAR-H using appropriate ammunition (see:
    Last edited by DocGKR; 06-02-2012 at 01:04 PM.

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