TFB Review: Custom Smith MFG 3D Printed MP5 Upgrades

    Printed MP5 Upgrades

    With the roller delayed blowback renaissance, accessories for the MP5 platform have exploded on the market. With the improved quality of rapid prototyping, now individuals can print out functional parts and sell them. Custom Smith MFG (CSM) makes 3D printed MP5 upgrade parts for the king of pistol caliber carbines. We got their MP5K AFG and binary selector levers.

    Printed MP5 Upgrades: Mp5K AFG

    I got the Mp5K AFG for my Omega K 9mm MP5K clone. As you can see in the photos above, it is designed to somewhat resemble the original H&K MP5K vertical grip, only the grip is angled rearward. One issue I had with the K is the short barrel and thus the short handguard that came with the gun. Due to the short length, the thenar of my palm (the fat part below your thumb) would touch the trunnion of my MP5K clone. This area gets hot rather quickly especially if I shoot the gun a lot and do multiple mag dumps with a binary trigger.

    The CSM printed MP5 K AFG lowers my hand position away from the hot trunion. When you get the MP5K AFG there is some hand fitting required due to the wide variety of clone MP5Ks out there. My Omega was no exception.

    See the short cylinder behind the cone of the barrel? That interfered with the CSM AFG

    I had to hog out the inner diameter of the AFG to clear that part of the barrel. Without modification, the handguard could not move back far enough for the takedown pin to be pushed into place.

    This is as far back as the AFG could fit on the Omega K 9mm.






    You could try and wrap your thumb around the AFG but it is not comfortable and actually rather awkward.

    I found it a lot more comfortable to position my thumb high and while I don’t show it in the photo below, my thumb rides on top of the cocking lever and tube. Almost like a thumb shelf.

    There is a minor issue with the CSM MP5K AFG and that is if you use short magazines. The length of the AFG does not allow you to grab the magazine up high near the mag well.

    I have fired well over 1,000 rounds through my MP5K clone with the CSM AFG and the printed MP5 upgrades held up just fine. The 3D printed part seems to be of a higher quality above simple FDM (fused deposition modeling). It appears to be SLA (stereolithography) which is a better print and less chance of delamination between layers.

    CSM Printed MP5 Upgrades: Binary HK Selectors

    CSM Binary HK selectors

    The Franklin Armory HK binary trigger is one of the best upgrades besides a suppressor you can get for your roller delayed blowback firearm of choice. However, the Franklin Armory factory selector lever leaves much to be desired. They are atrocious and many HK fans very much dislike the selector levers, especially for the higher price that the HK binary costs over a regular AR binary trigger.

    Factory Franklin Armory Binary HK selectors

    The Franklin selectors are milled aluminum but I honestly do not understand why this was their final design.

    The Franklin Armory selectors are an eyesore.

    One issue with the Franklin selectors is how long they are. It is nice that the HK binary trigger has ambidextrous selectors but the ambi side will dig into your trigger finger when you are in binary mode.

    CSM designed and 3D printed HK style selectors to replace the selectors on the Franklin binary trigger pack.

    The CSM Binary HK selectors have an indicator line that lines up with the full auto HK trigger housing. Specifically, the pictogram version as seen below. The line does not quite line up with the SAFE pictogram exactly but it is a small compromise. Franklin’s HK binary trigger has detents for the selector lever so it positions properly on a SEF lower as seen above.

    What about other trigger housings? Here is an H&K SP5 factory trigger housing.

    I have a US-made pictogram “Navy Lower” trigger housing that allows the use of SEF safety selectors. As you can see, the indicator line on the CSM selector does not line up with the pictogram markings.

    The indicator line not lining up with various trigger housings is the only complaint I have. It is not a deal-breaker. CSM charges $35 for a pair of selectors. They sell a painted white line version and an all-black version. I would have preferred it if they offered a version that did not have the molded/printed line at all.

    The 3D printed MP5 upgrades from CSM are of decent quality. There is no avoiding that uncanny valley aesthetic of a 3D printed item but they are functional and allows for immediate release and availability. The CSM AFG functions well and it turns heads but not always in a positive manner. Some do not like the angled look. “It looks like the VFG was bent” is a common comment I have heard.

    What I would like to see is an MP5 wide handguard but designed for the MP5K. The MP5 wide handguard slides over the hot trunnion area.

    This is a photoshop rendering of what I would like to see CSM make. A wide MP5K handguard.

    CSM just came out with a new handguard design for the MP5K. Their Oversized handguards act similar to the concept I envisioned above. There is some extra material that flows over the trunnion and wraps around it to protect the hand. CSM makes a handguard and a VFG version with the rear flare. They sent their oversized handguard to me.


    Just like their other handguards, it required a bit of modification to get it to fit my Omega 9MM K.

    It definitely helps to protect the hand but I wonder why the sides only go up half way and not all the way up?

    The only issue I have with this handguard is that you cannot add any lights or lasers. There is not enough room around the take down pin for a short rail like the HK parts picatinny rail for the front sight tower. If the material behind the screw was pushed back a little bit I could fit the rail segment and at least be able to mount a single accessor to the side.

    The new oversized handguard is available for $79. Their oversized VFG is available for $95 and they make a version that is compatible for B&T telescoping stocks. There is no additional option for the handguard though.

    The MP5K AFG is on sale right now for $75. And for those of you with SP5K aka non-PDW barrels, CSM makes an SP5K style AFG with shroud to help protect our fingers from encroaching near the muzzle.

    CSM makes a whole host of accessories for all the popular pistol caliber carbines on the market. Go to their website to find out more.

    Nicholas C

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

    Any questions please email him at [email protected]