Ruger’s M16 Alternative: the Select-Fire AC-556

Ruger introduced their semiauto Mini-14 rifle in 1973, and followed it in 1979 with the AC-556, a select-fire version intended for military and police sales. Offered with either an 18.5 inch barrel and solid wood stock or a 13 inch barrel and side folder, the AC-556 incorporated a selector switch on the back of the receiver to change between semiauto, 3-round burst, and fully automatic modes. Like some burst mechanisms, the Ruger model did not reset after each firing, and the round counter increments with every shot in any mode. As a result, when switching to burst, the first burst fired is unpredictable, and may be 1, 2, or 3 rounds.

A fair number of small sales of the AC-556 were made to police and small security agencies, especially those who wanted a gun more “friendly” looking than a black AR-15. A few international military sales were made, the most significant being a licensing deal with the French security services that led to the Mousqueton AMD, a slightly changed copy of the AC-556 for French police. Although Ruger did not sell them directly to civilians, gun made between 1979 and 1986 were transferrable, and many have been sold out of police inventory onto the commercial market. Ruger discontinued sales in 1999, and ceased factory repair service of them in 2009.


  1. I don’t recall if you’ve ever done a video on the Ruger XGI – that’s a real “forgotten weapon”.I understand that a very small number were built before the project was scrapped so it might be very hard to find one.

    I had the opportunity to put 20 rounds through an AC-556 back in the mid 90s. Lots of fun as I recall.

    • Indeed that would be intresting. I remember seeing them advertised in a pouplar mechanics in the 80s.I even rang Ruger a few years later to ask anout them and the woman I spoke to there had literally never heard of them!!! As for the AC 556 ,it also saw limited sales up in Northern Ireland to the Royal Ulster Constabulary (RUC) during the troubles.The majority were semi auto Ruger GBs but a few were 556.The sales were then stopped by Sen Ted Kennedy who was a IRA sympathiser.

  2. The AKS-74U was introduced in 1977. I’ve sometimes wondered if it wasn’t at least partly the inspiration for the AC-556 “shorty”.



    • “(…)AKS-74U(…)”
      Was it publicly known in West back then?
      If AC-556 is Ruger’s M16 Alternative I would say that “(…)shorty(…)” might be equivalent to CAR-15. Though maybe inspiration was HK 53 (if it was already advertised on U.S. market)?

      • No the Royal bermuda Regiment issues the AC-556, but with the fun switch removed. Same as the French Gendarmerie did. The French also fitted their Rugers into M1 Carbine alike stocks. In both cases, because it is really hard to control in fully automatic and both the Gendarmerie and Royal Bermudans have police duties and a soldier (or gendarm) blasting into a crowd accidentally is not desireable.

        The AC-556 is also the weapon of choice of the A-Team!

    • Props for your sarcasm. At least I think that was sarcasm?

      Of course the Mini-14 doesn’t use an M1 Carbine-style gas tappet.

      There is no tiny tappet which smacks the operating rod back. Instead, gas directly blows back into a cavity in the front of the operating rod. In some ways the Mini-14 gas-system is similar to the direct gas-impingement of the French MAS-49 rifle.

      Perhaps that similarity is one reason for the success Ruger had in selling his rifle to the French?

  3. The accuracy of the early mini-14s was not quite as good as later models. I wonder how the Auto version fares.
    As always, most interesting.

    • re: early mini-14s was not quite as good as later models. I wonder how the Auto version fares.
      “Early” being pre-2005, which would presumably include all the ACs. The problems were reportedly due to barrel harmonics and/or thermal drift. So there was both first shot inaccuracy, and warm-up aggravation thereof. For a select-fire firearm, they might have needed to slow the rate to 3 rounds per hour.
      I had a stainless Ruger Ranch back in the 80s, never shot it much due to the inaccuracy, and eventually sold it to a dealer.

  4. I really did not like the limited time I spent with the Mini-14 a buddy of mine owned; he was a big fan of the M1A, and all the other flavors of M1 Garand successors. That was the main selling point he had for the Mini-14: “It’s just like the M14…”.

    Actual point of fact? I’m pretty sure that Bill Ruger would have wound up a lot higher in the pantheon of “bad weapons designers” if the thing had ever seen widespread issue. It was just not suitable to purpose, as a line infantry weapon. Could it have been, with proper development? I dunno… Maybe. But, that “proper development” would have likely seen enough modification so as to make it essentially unrecognizable.

    For all its flaws, the M16 was always a better weapon.

    • Backin the seventies and 80ies teh Mini-14 was cheaper than an M16 or an AR-15 on teh civilian market. I guess the governement pricing was similarly low to undercut Colt or the Europeans.

    • I’ve found the Mini-14 fine as a civilian rifle but I think pushing it past police use is stretching it into things it was never supposed to do.

  5. It is interesting that the notoriously nationalistic French chose the AC556, but I imagine this was because they wanted a 5.56mm selective fire rifle for the Gendarmerie Nationale, and the FAMAS was still a project. CRS agents armed with AC556s killed the infamous gangster Jacques Mesrine in an ambush with AC556s, and this is accurately depicted in the movie made about his life.

    In Northern Ireland the Royal Ulster Constabulary used Mini 14s, not as far as I am aware AC556s. They also used Ruger .357 magnums. I think this must have been in the late 1970s, and caused a big stir at the time, because American politicians in thrall to the IRA lobby tried to get the sale blocked. I also remember rubbish in the British press that the .357 could blow a hole in an engine block. In fact the sale of the magnums seemed to cause more controversy than the Mini 14s, probably as something to do with Dirty Harry more than anything else.

    Of course, if the RUC wanted a 5.56mm rifle, there was no need to go to America, as Sterling were at the time building AR18s in England. However, no doubt due to the long standing antipathy between Royal Ordnance and Sterling this did not happen. They would rather the order went abroad than go to Sterling.

    I am nor sure if the Police Service of Northern Ireland, which took over from the RUC, still has the Mini 14s. They would be getting a bit long in the tooth by now. They certainly don’t use the SA80.

    • A retired RUC constable told me that the reasons they chose the Mini-14 were a combination of they had been using the M1 Carbine, which were getting worn out, and wanted something similar to replace it, plus they wanted something that didn’t look “military”.

      He said it was an excellent rifle for their purposes and he was quite happy with it. He said that a further advantage of it was it was quite sturdy and the butt of the stock was quite effective on doors and on the skulls of miscreants. He didn’t think those factors were part of the official decision making, but the police constables still found them quite useful in that respect.

    • Regarding the French nationalism, they can proudly claim any Ruger under the French umbrella because they get to pronounce it like: “uuusshhRooogggeeeehhhhhhhjhjrrrrrrr.”

    • There were a few 556s up in RUC armouries alright,but more experimental than std issue as far as I know.PSNI use like most police globally HK products.MP5 is std issue.
      Ironically I saw on a German website a few weeks ago a semi auto ex RUC mini14 for sale.

      • You are right, the PSNI guys I see on TV seem to be armed with MP5s. I think the Mini 14s must have been removed from inventory.

        I am intrigued that an RUC Mini 14 might have turned up in Germany. Most British government agencies prefer to trash surplus weapons rather than sell them to dirty civilians. I wonder what the story behind this one is?

  6. My Mini-14 always worked well. When I bought around 1980, I also bought 7 Ruger 30-round magazines and a Ruger flash hider. Ruger stopped selling those as accessories shortly thereafter. On of the magazines was missing the hole in its front wall for the catch at the end of the action spring guide, so I marked it and drilled my own hole. When I was learning reloading, and not smart enough to know better, I could finish the resizing process on cartridges by chambering them as far as they would go, then beating on the operating handle until the bolt locked. Dumb, but it worked, and the rifle still works fine.

  7. Back in the 80s I was planning on getting a mini 14, but the ban looked all too likely before I got the money saved.

    I tried to read up on the burst fire control system from the patent, about 15 years ago. Today’s vid would have saved me a lot of time and head scratching.

    Thinking about the commercial side, I guess that the ac556 could be produced in the numbers required at minimal additional cost, on the back of the mini 14 line.

    I wonder whether Ruger even tooled up with a full set of dies for moulding the wax for casting the ac556?

    Or whether they glued additional bits of wax to mini 14 receiver wax and a few bits of ceramic to the cores?

    Ruger, and most other investment cast actions, tend to be designed so they can be “finished” with minimal skill, on belt sanders.

    Ruger metalwork was (and probably still is) designed so that the stocks can be inlet by vertical routers using the wood working equivalent of endmills or slot drills.

    Again, there’s the possibility that mini 14 stocks could be given the additional cuts on a small batch basis, perhaps using a pantograph type duplicator, without needing to interrupt mini 14 production, or set up a new production line.

    With regard to accuracy, the way that the mini14 family of guns all hinge out of their stocks on disassembly, precludes getting decent bedding of the vertical surfaces on the receiver. You’d actually need surfaces that were within the arc of that stock rotation, almost like the “draws” on a British Lee, or the “draw” on a two lump shotgun barrel.

  8. Till about 3 years ago ex french police rugers were the cheapest neutralized gun on the french market They were selling for as little as 300 euroes
    One thing however I have been in France since 1972 and I have never seen a policeman or a picture of one with an M1 carabine only Mat49’s I don’t dispute the fact that they had them heck they apparently used P38’s till the 1960’s But none of my french gun friends have seen them either perhaps somebody could direct me to a photo

  9. I remember in 1989 while a Federal Agent there were more rumors that the Mini-14 was going to be upsized to an M-14 type rifle. The 7.62X39 came around, but never the .308 version.

  10. It was intended as Ruger.
    A fairly high-quality product for little money. Although in need, sometimes, in some finishing, but the price justified it.
    But modern production management techniques have contributed.
    And the device turned out to be of quite mediocre quality, at the price of M16.
    And the same amount (if not more) will have to be given to the gunsmith… 😉
    I also heard about problems (or rather misunderstandings). But, apart from the constant trifles with accuracy and reliability, it seems that no serious problems have been noticed. 😉

    The tales of “military use” are nothing more than fairy tales. It is possible (even likely) that the Ruger team dreamed of military orders in their wet dreams, but they initially did not have a chance.

  11. Does anyone else think that the three round burst fire device is an unnecessary complication, especially as it might deliver 1, 2 or 3 rounds? The best burst fire device is surely the trigger finger.

    • “(…)might deliver 1, 2 or 3 rounds(…)”
      This is also true for M16 (when applicable). So if AC-556 is Ruger’s M16 Alternative then usage of sloppy burst device is… cargo cult?

    • This is proof that nothing is so bad you can’t make it even worse 😀

      Here I thought the M16 burst mode was bad, but counting and causing short bursts in *all* firing modes and not being able to go from burst to full-auto depending on the burst device position (if I understood this video and the range video right)…who thought this was a good idea?
      I’d have rather left out the burst mode in the M16 already, and even more so this abomination.

    • Practice has shown that the shot counter, for a rifle, is not only useless, but also harmful.
      This is an unnecessary opportunity to reduce reliability and increase cost.
      The two-shot cutoff mechanism makes much more sense.
      And three cartridges (if the person is not disabled) at a rate of fire of 500-600 rpm can be made with your finger.
      They played with this on the M16A2 and very quickly threw it into the trash.

      The device (possibly) will behave better if you replace the stock with a pistol grip and play with the selection of the muzzle compensator.

      • The only occasion I had firing full auto made me doubt there being any benefits to a burst fire system, being that I was able to fire 2-3 round bursts in both rifles within a minute of picking them up. Presumably a soldier properly trained in either of their usages could do much better.

      • Actually, the M16A2’s ratcheting 3 round burst persisted into the M16A4 & the M4, and was only done away w/ in the M16A3 & the M4A1 – so around 35 years.

        According to the Marine officer that led the M16A2 development project, the 3 round burst mechanism preserved the ability to someday switch back to full-auto fire across the force – which we finally did w/ the adoption of the M4A1.


    And a cherry on top comparative tests of the reliability of the M16A1 and M16A2 by firing 26,000 rounds.

    “M16A1-Failures to fire – none
    M16A2-Failures to fire – 52 (27-bad ammunition, 25-mechnanical malfunctions)”(C)

    It says “bad ammunition”.
    IMHO – bullshit.
    There cannot be as many defective primers.
    This is most likely a trigger problem, when something hits and slows down the hammer.

    And, for those who are not enough, about the problems remaining after the cancellation of this “improvement”.

  13. And a cherry on top comparative tests of the reliability of the M16A1 and M16A2 by firing 26,000 rounds.

    “M16A1-Failures to fire – none
    M16A2-Failures to fire – 52 (27-bad ammunition, 25-mechnanical malfunctions)”(C)

    It says “bad ammunition”.
    IMHO – bullshit.
    There cannot be as many defective primers. This is most likely a trigger problem, when something hits and slows down the hammer.

    And, for those who are not enough, about the problems remaining after the cancellation of this “improvement”.

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