TFB Review: MP-57 Chassis By Custom Smith MFG

    Back in March, Custom Smith MFG (CSM) announced a chassis for the Ruger-57 pistol. Well, Michael Bonamico, owner of CSM, was kind enough to send his chassis in for review. It is called the MP-57 and it makes the Ruger-57 a more practical weapon.

    Ruger-57 & CSM @ TFB:

    Upgrade Your Ruger-57 Into an MP-57 PDW

    The Ruger-57 is similar to a SIG P320 in that the serialized component is a removable trigger module which means you can change the frame. Michael Bonamico of CSM capitalizes on this when he designed the MP-57.

    While the Ruger-57 is similar to a P320 in concept, it is not as straightforward as in P320 to remove the trigger module. Michael Bonamico made an install video that helped a lot.

    For those of you who didn’t sit and watch the video, the problem is somewhat reminiscent of a 10/22 trigger pack. There are pins in the Ruger-57 trigger module that can slide out and certain parts are not held in place. Whereas the SIG P320 FCU is self-contained.


    Before installing the trigger module, you need to transplant the mag catch.

    Since the slide will be under the top cover, CSM provides you with a charging handle. You have to let them know if you want a right or left-side charger. Due to the screw holes, it is not possible to have the handle flip over for opposite sides. My Ruger-57 came with the Burris optic mounting plate. It uses similar-sized countersink Torx screws.

    CSM ships with Phillips screws. So if you have the factory Ruger optic mounting plate, you can use those screws instead.

    I used the Torx screws instead of the Phillips screws.

    The bottom of the slide is exposed when the top cover is not installed. The cover slides into position and tabs into the rear. That tab sits under a notch and a pin is driven into the bottom front. This locks the cover in place. It cannot hinge open like the FMG9.

    Here is the MP-57 with some select accessories.

    MP-57 hero shot

    +5 Rds Please

    Just a week after CSM sent me the MP-57 chassis, they came up with a +5rd extension to allow you to fit 25 rounds of 5.7x28mm. Getting closer to the 30rds of an FN Five-seveN and MP7 capacity.

    Just like the MP-57 chassis, the 5rd extension is 3D printed. Do not be fooled with the concept of 3D printing. This is the same high level of printing used for their chassis and is similar to the Panobridge or Nocturn Industries UANVB night vision housing. It is very strong and flexible.

    The Ruger-57 mag body has ridges that run down either side. So the mag extension has matching protrusions.

    The extension has a removable floor plate to facilitate installation or removal.

    20 rounds on the left, 25 rounds on the right.

    My only critique about the MP-57 mag extension is these point corners. I am not sure why they are there other than for aesthetic reasons. I told Michael Bonamico that he should consider rounding those corners because if you hit the mag with your hand, those pointed corners will dig into your palm.

    Shooting The CSM MP-57

    For better stability, I added a Recover Tactical angled mag holder. This one is for Glock 21 sized mags. I hope CSM makes an angled mag holder for a spare Ruger-57 magazine.

    The MP-57 works just as well as the Ruger-57 but has the benefit of adding better optics onto it. I tried using the Leupold D-EVO on the MP-57. While it would be perfect for having 6x magnification in a short package, it does not play with the MP-57. The objective lens of the D-EVO is too far forward and sits directly above the ejection port. I would incur failure to eject malfunctions. I think when the brass is ejected, it bounces off the D-EVO and goes back into the chassis.

    Below, there were two pieces of brass sitting on top of the slide. Once I noticed this, I tilted the MP-57 downward and the brass slid out. Sort of like an FS200 or RFB forward ejection.

    Final Thoughts On The MP-57

    Everyone who shot the MP-57 loved it. The folding SB Tactical FSB1913 brace makes a lot of sense since it is very low profile The only thing the MP-57 needs is a threaded barrel so you can add either a muzzle device/flash can or ideally a suppressor. I would prefer the MP-57 to look more like an HK MP7 since this is the closest we can get to having one for now. I was a little disappointed that I was unable to consistently hit 200 yards but this is not a fault of the MP-57 chassis. It is just the short barrel and lack of energy to push the 5.7x28mm round that far. Out to 100 yards, the round is able to hit targets consistently and accurately. This is just the performance of the Ruger-57. The MP-57 chassis just makes it more stable and easier to use whatever optic you desire. Ideally, you SBR your Ruger-57 so you can use better stocks and VFGs.

    The CSM MP-57 retails for $399.99. If you are uncomfortable swapping in the trigger module, you can send your Ruger-57 to CSM and for an additional $75, they can convert it for you. For more information check out CSM’s website.

    Nicholas C

    Steadicam Gun Operator
    Night Vision & Thermal Aficionado
    Flashlight/Laser Enthusiast
    USPSA competitor

    Any questions please email him at [email protected]