The Poor Man’s SAW: Using A SlideFire Stock For More Than Fun

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The SlideFire stock is an idea that pushes the boundaries of what the ATF considers acceptable for a Title I firearm. Without diving into the world of the National Firearms Act, a Slide-Fire stock is the closest you can get to a fully automatic weapon of your very own. For the most part, these stocks are just a range toy: With no spring to automatically return the gun to the firing position, constant forward pressure is required to continuously activate the trigger. This makes them impractical as a serious weapon, but quite a lot of fun to shoot.

However, Ian and Karl over at InRange thought: What if you could use the SlideFire as part of a system to create a weapon that, at least in certain circumstances, approximated the capabilities of a squad automatic weapon (SAW)? To that end, they developed the “Poor Man’s SAW”:

They found that the combination of a trigger with a short reset (in this case a KE Arms unit), a bipod (to provide the constant forward pull), and a heavy barrel gave them a rifle that fired rapidly when shooting prone or sitting. How practical is such a setup? Well, that probably depends on who you ask, but at least in some situations, the InRange SAW comes impressively close to the real thing.


Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He can be reached via email at nathaniel.f@staff.thefirearmblog.com.


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  • De Facto

    Welp. Now I have to build an AR15.

    • Xanderbach

      I have 2… Now I need to have 3. Dammit. Next build… Go!

  • MPWS

    Karl is certainly master of the subject. I’d guess the last sample firing cycle rate was about 2/3 what natural cycle would be – e.i. cca 600 RPM. Ingenious and simple.

    • Michael B

      You can get it upwards of 700rpm with right components. See my post above.

  • Yomuallty

    ARFCOM has an entire thread dedicated to bump SAW builds and videos of guys using them, I recommend watching this video then going over there to check that thread out, guys there are actually making specific builds that help dissipate heat and etc, really cool stuff!

  • Rod Jos

    Slap in a Valkyrie belt fed system and we’re good to go.

  • KestrelBike

    Now, will Slide-Fire make a stock for FN’s new semi-auto M249??

    • Devil_Doc

      I thought the same thing about an Ares Shrike.

    • Jeebus

      We had M4 stocks on our Para 249s in the Army, so if you can get the adapter that was used you might be able to slap on a slide fire.

      • Joe

        The telescoping stock on the M249 is M4-like, but has a smaller internal diameter. I measured with calipers.

        • iksnilol

          Could you machine a tube for the buffer tube to increase the diameter? A thin tube of aluminum that slips over the buffer on the m249? I don’t know how you’d secure it though? Maybe the extra tube could be fixed to the stock itself?

          • Evan

            Wouldn’t make a difference. On the M249, the pistol grip and trigger are one assembly. As the slidefire stocks require replacing the pistol grip, the whole idea is a non-starter. Which makes the M249S even more pointless. It WOULD work with a belt-fed upper on an AR lower, like the Shrike, but the SAW is a completely different design.

    • Evan

      If the internals are anything like those of the real M249, then no, it won’t be feasible.

  • Vhyrus

    Binary trigger. Just sayin

    • Ian McCollum

      IMO, binary triggers are inherently unsafe. If I want to stop firing, I want to be able to just remove my finger from the trigger.

      • Their timing is also ass. There’s no way to ensure hammer fall after bolt lock with those things.

        • Tassiebush

          this video certainly shows the timing issue of outrunning the bolt with binary trigger. It looks fairly easy to do as it occurs about 2min 20seconds into this video
          https://www.full30.com/video/403c8934a479784b5098a598640f5654

        • I had talked to Fostech about the Echo and they indicated they may have solved the hammer follow issue. Curious to see if true.

          • I would be very interested to know if that problem is soluble without running afoul of the ATF.

          • aka_mythos

            In needing something that would prevent the trigger’s release until the bolt is locked… I imagine you’d need some sort of operation where you pull the trigger to fire but beyond the hammer release the trigger has over travel that can’t be initiated until the bolt reaches a certain point and the second hammer release is after that very short over travel and release of the trigger. Less of a 2 shot pull-release trigger, more like a 2 shot pull-pull-release trigger. Since you can’t lock back the trigger and have it release itself without it being potentially machine gun.

        • Joe

          Correctable design flaw?

          • Ben

            Flawed design concept.

        • Phaideaux

          It seems like making an ar build around ensuring the highest cyclic ROF possible goes a lon way to fixing that problem. Its still not perfect though.

      • Evan

        I agree. That thing is an ND device.

    • aka_mythos

      The article present the interesting notion of building a weapon to suit slide-fire use and I think it’d be just as interest to do the same with a binary trigger.

      The binary trigger gives a semi-auto in a brief moment full-auto rates of fire, and so it has some of the issues associated with full-autos like timing. Build to compensate and allieviate the potential for timing issues.

  • MR

    I was concerned the spring loaded bipod might turn it into something the ATF would consider a machinegun, but the way that’s set up it SHOULDN’T be a problem. Enough backwards pressure would just fold up the bipod.

    • Michael B

      The bipod is independent of the stock. Two separate and distinct items. It makes zero difference how, and of what, the bipod is constructed of, or attached, as long as it isn’t directly attached to the Slidefire or Bumpfire stock.

  • schizuki

    Now everybody be sure and write lots of letters to the ATF to be extra, extra sure this legal thing is really legal.

    • Cymond

      Why do people think that the number of letters is relevant? ATF constantly states that letters only apply to the specified individual and circumstance of the letter. They’re not rulings. No one can rely on someone else’s letter.
      If ATF doesn’t want to get so many letters, they should change how they handle letters.

  • derfelcadarn

    I must admit it was very impressive,far better than I would have imagined

  • Twilight sparkle

    I’m in the process of putting one together… so far I have a lower

    The newer slide fire mod looks and feels a lot better than the older stuff

  • Martin Grønsdal

    I don’t understand ATF’s ruling on the slidefire. Here we have a system that obviously fires “full auto”, yet they call it semiauto.

    But put on a novelty stock on a gun, and they will imprison people for violating rules.

    • Twilight sparkle

      It’s not full auto. It’s bump fire

    • Divemedic

      The definition of full auto is “which shoots …automatically more than one shot, without manual reloading, by a single function of the trigger.”

      Since the Slidefire is causing the trigger to be operated for each shot, this device is NOT a machinegun.

  • Slobberjaw

    Great video!

  • Alien Life Form

    Just who in the hell can afford auto fire in anything bigger than 22lr?

    • Twilight sparkle

      People who reload?

  • Kitsuneki

    How about putting takedown barrel on that and have several bareels?

  • Michael B

    TIP/FYI – Throw a Strike Industries 7 (yes, SEVEN) position buffer tube that has been Nickle Teflon coated internally & externally. Combine that with a PWS Nickle Teflon coated H2 buffer bouncing on a JPE Tuned EP buffer spring for the fastest, most reliable fun you can have. Also, the 7 position buffer Tube takes a lot of the wiggle out of the Slidefire and Bumpfire stocks and allows for precision- ish shots. I do 2″ groups using Hornady 123gr SST at 200yds using an Aimpoint Pro with an AR in 7.62×39. I use a HIPERFIRE EDT3 series trigger, a Black Rifle Arms proprietary NiB coated bolt carrier with a Nickle Teflon coated bolt and an Elftman Push Button Safety. She slings combloc ammo hiccup free down a DEZ Arms spiral fluted HBAR 18″ long w/midlength gas system.
    Range officers gang tackle me every time I air this thing out until they see what it is. Then they line up to shoot it.
    Good vid; never considered the bipod before-may have to try.

  • RickOAA .

    I was mostly impressed by the size of the bipod.

  • Bob

    To my timing the slide fire was near 1200 rpm. When using the 100 round magazine it took 5 seconds to dump the full mag. Very impressive.

  • Trey Odom

    Cool article. I’m wondering how it would run with one of those new binary triggers.