Gun Design Engineer answers your questions

    Tobias Obermeit, the Chief Design Engineer on the PMR-30 pistol at Kel-tec, generously offered to allow you (the readers) to submit questions for him to answer. Many questions were similar so I merged them into a single question.

    Photo (C) Oleg Volk

    There were a lot of question and I cannot thank Tobias enough for taking the time to answer them. I know that I have learn’t many things that I was not aware before.

    PMR-30 Questions


    How much commonality is there between the new PMR-30 and the Grendel .22 WMR pistol?

    Zero parts commonality. The only commonality design wise is the interior
    of the magazine. The way the magazine stacks the 30 rounds of 22WMR ammo is
    nearly the same. But every other part of the design is new and often very
    different. Trigger mechanism is better, The PMR-30 has a last shot bolt hold
    open, which the grendel did not. The grendel had a fluted chamber, the
    PMR-30 does not need this because of the hybrid locking system.

    Are there any plans for a carbine version of the PMR-30 like the old Grendel R-31?

    Yes, I am working on it right now. there are pictures of the current
    prototype design shown here. Availability and price is unknown at this

    RMR-30: The carbine prototype design.
    The prototype PMR-30 Submachine gun.

    Are there any plans to produce a low-cap (10 round) magazine for those of us who live in capacity restrictive states like NY?

    There are plans to offer a magazine block of some sort that could be
    used to limit magazine capacity (10, 15, or even 20 rounds could be done).
    But there are no plans to mold a special magazine for this, at this time.

    Do you believe that the .22 WMR is an adequate man-stopper?

    I do not believe that a single .22WMR out of a pistol is adequate…but
    I do believe 25 to 30 .22WMR’s are adequate. It’s not ideal, but the total
    amount of bullet weight in a full 30 round mag is 1500 grains (if 50 grain
    bullets are used). This compares to 10 rounds of 147 grain 9mm, or 13 rounds
    of 115gr. Of course bullet weight alone is not enough, but the velocity out
    of the PMR-30 is still quite good. (1230fps for 40 gr)

    Do you have any word on .22 WMR loadings from any manufacturers that are optimized for pistol-length barrels?

    No, but I have asked the question of a few ammo manufacturers. I believe
    it would only happen if there is a large spike in the demand for such
    ammo….which could happen.

    When will you be making a PMR-30 in 5.7×28mm or .22 Long Rifle?

    5.7x28mm most likely never, It’s too long to fit in the grip of the
    PMR-30. 22LR would be a better fit, but will only be done if we can get 30
    rounds in the magazine to feed reliably….which is not easy.

    Why so short a barrel? Will there be a longer barrel/target version?

    The barrel length was chosen to be the shortest possible for a 22WMR
    autoloader, in order to be as compact and lightweight as possible. Compact
    and lightweight is what Kel-Tec is known for. There are plans for a 5 inch
    threaded barrel for use with a flash suppressor, or even perhaps silencers.
    But this will not be released until we know that the extra weight of a
    silencer attached to the barrel will not adversely affect the hybrid locked
    breech system.

    Nobody asked how the hybrid-blowback system worked, so Tobias explained …

    The hybrid locked/blowback system is simple in execution. There is
    technically no mechanical locking system in the gun. The cartridge case is
    the mechanical lock in the system.

    The friction of the case locks the chamber (and therefore the barrel) to
    the case as they both recoil together….as long as the pressure is high
    enough. lower pressure rounds will cause less friction between the case and
    the barrel, and then the barrel stays still, or only moves a little…..It’s
    a balancing act between the bullet friction pulling the barrel forward, and
    the case friction in the chamber pulling the barrel back. Bullet friction
    does not change much based on round pressure, but the case friction will.

    KEL-TEC Questions


    From a multi-caliber point of view, If you had a bullpup in 762 how easy
    would it be to change to 556 – different lower, same upper and bolt carrier?

    In theory the grip/forend assembly could be the same, and a new
    barrel/receiver/bolt/carrier assembly could be attached. Unfortunately since
    the receiver is legally the gun, this would not be a simple caliber
    conversion that could easily be purchased separately. It would legally be a
    new firearm.

    Are Kel-Tec angry with Ruger for using their P3AT design aesthetic for the

    No anger, copying is part of the firearms business, and I am sure you
    will see the P3AT style trigger mechanism in many other pistols (Taurus
    comes to mind). Personally, I was not happy that Ruger claimed to have a
    brand new design, when it was clearly based on our design, though. And when
    an upgrade to the trigger mechanism I designed found it’s way into the ruger
    after coming out in the P3AT, it didn’t make me feel any better. But that
    is the business.

    Does Kel-Tec plan on exporting their pistols and rifles to Europe?

    Some Kel-Tecs have actually been exported already. But the distributors
    handled that in the past. Now with the newer export regulations, things are
    a little tricky. But I believe there will be expansion in the export market,
    even with the increased complexity of export regulations. I believe Canada
    may see some Kel-tecs soon.

    Will we ever see a Kel-Tec revolver?

    Anything is possible…but I doubt it. It certainly would be innovative if it ever does happen, though.

    Will we ever see a 7.62×39mm SU-16 that takes AK mags?

    Probably not that takes AK mags, but I believe there are AR style
    magazines that accept that caliber. Not saying it will or will not happen

    Does Kel-Tec have any plans for a larger caliber handgun?

    No specific plans….and if we did have any, I couldn’t talk about them

    Gun Design Questions


    What did Kel-Tec learn about bullpups in the development of the RFB?

    Kel-Tec learned how to make a great trigger for a bullpup. Also, Since
    the barrel and chamber is physically closer to the shooter, dealing with
    parts heating up and deflection of vent gasses needs to be handled
    differently as well. Forward ejection took a lot of R&D too.

    What steps can high school and college students take to become a gun design

    Start designing and drawing up your designs. pen and paper is good, and
    I always start there. I still keep a notebook with different design ideas
    that I sketch up as I have them (not all firearm ideas). But when you can
    get access to some 3D design software, perhaps in an art class or a design
    class, start drawing stuff up in 3D. Doesn’t have to be guns, any mechanical
    designs help you get experience in how to draw in 3D and how things work
    together. Pay attention in physics, chemistry, math, and reading/writing
    classes. You might not think reading and writing is that important but you
    have to be able to communicate your ideas and designs with others.

    In general, where is the starting point in designing a gun? Do you start
    from scratch or base it on a previous model? What component is designed

    It depends on what you are trying to do. If you are designing for a
    specific size and capacity you generally design from the magazine out. but
    if you are just designing from scratch then basically you start from the
    bullet back, or from a standard cartridge and barrel length which already
    has an established energy and velocity. Usually you can use a common
    magazine and you have an idea of rifle or pistol. Based on the energy and
    pressure levels of the cartridge you are limited to certain types of cycling
    action (blowback, or locked breech, or gas operated,…) then based on the
    length and shape of the cartridge you can layout where the barrel starts and
    how far the action has to travel and so on. Usually the parts that are not
    primary functions of the gun are designed last, like slide stops, or sights,
    or sling mounts.

    Is it harder to find acceptance with a revised design over a new to market

    No,… but I’m not exactly sure what is being asked here. acceptance is a
    relative term. I would say it is hard for a military to accept a new design
    when comparing it to a tried and true design. But the civilian market is
    often more accepting of new and innovative designs over old designs.

    What CAD software do you use to design your firearms?

    We use Solid Edge ST2 (version 21) currently, but started at version 14
    I believe.

    How much influence do the departments of accounting, finance, and marketing
    have on weapon designs?

    For Kel-Tec…not much. This is mainly due to the fact that the owner
    (George Kellgren) has full control of accounting finance and marketing. What
    he decides goes. But the sellability, market, and price point of the product
    is certainly discussed. That is one of the benefits of a smaller, privately
    owned company like Kel-Tec.

    How does (BATFE and state) regulation fit into pricing?

    Any legal requirement or special modification that needs to be done to
    make a firearm legal in a certain state will add to the price, even if you
    think it might not. Lets say one state won’t allow threads on a barrel. That
    would mean we have to run a special batch of un-threaded barrels and make
    sure they are built correctly and go to the right distributors. these
    batches are usually much smaller than our standard batches and therefore can
    cost more to setup and deal with. Gun locks are required by state and
    federal law for each pistol, so that is added to the cost for all pistols.

    I’m wondering who, in your informed opinion, are the great gun designers of
    all time?

    Personally I like Gatling. His rotary barrel type gun was revolutionary
    and unique. Being a mechanical engineer, I really like the mechanisms with
    gears and cams. Colts revolver mechanism is also quite nice, but Browning’s
    slide locking mechanism has really taken over most modern designs….But I
    think Gatling is my personal favorite.

    What do you think will be the next great leap forward in gun design?
    I’m not talking about layout changes (bullpup) or caliber/bullet shape.

    If battery technology keeps progressing, perhaps some electronic
    rail-guns will be possible, but that is at least a few decades away.
    firearms are simple, effective, and proven. Perhaps some simpler and cheaper
    electronic ignition systems. I don’t see anything specific that is on the
    horizon right now. there are many new coatings that are becoming cheaper and
    useful, I know I would love to use some carbon fiber in some designs, but
    the cost is still rather high on that.

    How do you measure the ‘timing’ of a breech-locking mechanism? I.e.
    how do you make sure that the bullet has left the barrel and the pressure
    dropped acceptably before the cartridge case starts to be pulled free of the
    chamber [Ed: This comment refers to the Kel-tec RFB rifle. ]

    This is done at the computer first, during the initial design process.
    simple Newtonian physics combined with interior ballistics software can
    predict pretty accurately how long a certain weight slide will take to
    unlock and how much pressure is still in the barrel when this happens. Then
    a prototype can be made and high-speed video can be used to verify this if

    Do they use advanced brainstorming techniques and market research? Or is it
    more of an “Eureka!” thing. Actually, do all the people involved in the
    design have an extensive firearms background? Or is it sometimes those with
    little prior firearms experience that bring in ideas from “outside the box”?

    Kel-Tec has a small design team. about 3 to 6 people are involved in the
    design to some extent, Generally one or two people will work primarily on a
    design, and consult with others if issues or questions pop up. we do consult
    with others who have some or even little firearm experience. Often these
    other people mention issues that you would not think of. I did not come from
    a firearms background when I first got this job, but I am certainly an
    enthusiast now. The CEO (George Kellgren) has been professionally designing
    guns since 1968, and we have machinists and technicians with military or
    even competition shooting experience as well as those who have little
    experience with firearms at all.

    Professional market research is not used. But a few of us do regularly
    check the blogs (like this one) and forums and read magazines to get a good
    idea of what is going on in the firearm communities as a whole.

    The vast majority of polymer framed pistols use nylon-6 or some variant, but
    until recently Ruger used a polyurethane “Isoplast”
    polymer for its pistols (P95, P97 using it, SR9 apparently using nylon). Why
    has nylon-6 been the overwhelming choice over other polymers?

    Cost, Availability, and performance would be the reason to switch. There
    are many reasons to choose one product over the other, perhaps it gets used
    in multiple products, and buying in bulk will save money. the Nylon seems to
    have the edge in handling heat over the isoplast. We have stuck with Nylon
    from the beginning and have not had any need to switch, though we have
    changed glass content in the nylon as needed to increase or decrease

    Plastics/polymers are a relatively new material, with materials like nylon 6
    seeing widespread use only in the last 60 years or so. How much do we know
    about their long term durability? Should a buyer expect a Kel-Tec, Glock, or
    other nylon-6 framed pistol to be completely reliable and as good as new in
    30, 50, or 100 years?

    30 years absolutely yes, 50 to 100 yes, if it is cared for correctly. As
    long as the nylon is protected and cleaned with the correct products, it
    should last as long as the steel, and certainly longer than wood. All the
    modern polymers have add-ins that protect it from UV rays from the sun.
    Early plastics did not have this and would eventually get brittle.

    The RFB appears to be one of the more successful forward ejection bullpup
    designs of late. Did you choose tilt-locking specifically because of the
    extractor arrangement, or because perhaps you were working from a bullpupped

    The locking system is specific to the forward ejection system. The way
    the extractors rotate up, does not allow the bolt to do anything but tilt.
    FAL mags were chosen because the feed lips are setup to deal with a bolt
    that tilts down into the magazine a little. (compared to an AR-10 mag which
    does not need to deal with this)

    When shopping for a new gun, what are the signs of a good design? A bad one?

    Materials are the first thing I would look at. good quality material is
    a must in any design. whether it is steel, aluminum, or plastic, or even a
    casting. I personally stay away from zinc cast guns, but they can be
    designed well these days. But the design should match the materials well. If
    there are lots of sharp edges or corners in a cast or molded part, these
    could be high stress areas that are likely to break in the future.

    Steve Johnson

    I founded TFB in 2007 and over 10 years worked tirelessly, with the help of my team, to build it up into the largest gun blog online. I retired as Editor in Chief in 2017. During my decade at TFB I was fortunate to work with the most amazing talented writers and genuinely good people!