Lantac Shows their RPS (Ratchet Plate System) QD MSR End Plate

Just when I thought the single Primary Weapons System system was the be all and end all of the awesome uber castle nut debate, Lantac just had to go out and release a similar system. Dubbed the RPS or “Ratchet Plate System” the RPS adds another viable solution for the home-builder to avoid staking their castle nuts.

Unlike the PWS offering, the Lantac RPS opts for an internally oriented design. As the name implies, teeth (facing the end plate, hence “internal”) are locked into place with a corresponding ratchet hook on the end plate. Once installed, Lantac states, “the nut cannot vibrate loose through firing but can be removed through the use of an armorers wrench if necessary.” By having the grooves on the internal face of the castle nut, the system cannot be damaged during normal usage.

For function, the RPS features a standard Q/D socket machined into the end plate. For aesthetics, both the external shape of the end plate and castle nut are milled (though Lantac does not that they do not guarantee alignment once at the proper torque specification). Construction and finish are not stated, but it’s likely steel and a nitride based on Lantac’s other product offerings.

Final release date is not yet set, but Lantac has stated across forums and through reps that the patented RPS is in production for launch as soon as possible.





Nathan S.

One of TFB’s resident Jarheads, Nathan now works within the firearms industry. A consecutive Marine rifle and pistol expert, he enjoys local 3-gun, NFA, gunsmithing, MSR’s, & high-speed gear. Nathan has traveled to over 30 countries working with US DoD & foreign MoDs.

Nathan can be reached at Nathan.S@TheFirearmBlog.com

The above post is my opinion and does not reflect the views of any company or organization.


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  • I like the idea, but I wish they could make one with the same appearance as a normal receiver end plate and castle nut.

    • FOC Ewe

      That wouldn’t fetch nearly as hansome a price. Todays builders need everything to be pretty.

      • None

        I can build a functional rifle with my eyes closed. But there are times I like to make a pretty gun.

    • Slim934

      Yeah this just looks stupid. They’d have been better off just making it look flat and sleek.

    • Havok

      You mean like PWS did?

      • Pretty much except with the ratcheting part on the inside, so from the exterior it looks normal.

  • Twilight sparkle

    Why not just buy a punch and stake a regular castle nut??

    • Machinegunnertim

      Because there are far better options instead of smashing metal together, which seems so medieval and primitive. But i can appreciate the simplicity.

    • mk18

      While I agree, there is also the fact that you may want to change something and with this setup (anf the PWS), you can do it w/o ruining a part (the end plate for example).

      • Steve

        I bet you can buy 5-10 standard castle nuts and end plates before hitting the MSRP of stuff like this…

        • Jack

          Cheaper is always better!!

        • Twilight sparkle

          That was exactly my point. Glad someone got it lol

        • Havok

          $30 for the PWS set, and from Brownells you’ll pay $8.00 for a set.

  • PK

    “(though Lantac does not that they do not guarantee alignment once at the proper torque specification)”

    What does this even mean?

    • Basically it means that those useless scallops on the two pieces may not line up. Thus driving the ADHD in your crazy.

      Not only that, but I don’t think that they are even meant to line up as the scallops appear to be completely difference sizes, or at least different spacing.

      • Irfan Zain

        You’re referring to OCD instead of ADHD right?

        • Yeah probably, my mind slipped… oh look a butterfly!

        • Independent George

          I always hated OCD. It should be renamed CDO so that it’s in alphabetical order.

    • Christian Hedegaard-Schou

      Pretty sure it’s a typo: “though Lantac does not(E) that they do not guarantee alignment once at the proper torque specification”

      Note. Not “not” 🙂

  • jerry young

    Unless you fire thousands of rounds frequently through your AR or fire in full auto there is no real need to stake the castle nut, most home builders won’t be building a full auto version (against the law) anyway and as long as you perform regular maintenance like checking to insure there are no loose parts staking is not needed and if you build your own or just buy the proper tools you don’t need this gimmick, but it looks cool and if you’re into spending money for looks rather than performance this is for you!

  • billjohnso20

    I have only ever built one AR. I see no need for this or any other shortcut device. Why? Quite simply, the more complicated a machine is, the easier it is for it to fail. Simple designs stand the test of time whether it is my 105 year old Colt 1911 or my 2016 personally built AR-15. I believe the K.I.S.S. principle applies here.