How Does it Work: Long Recoil

Long recoil operation is one of the most mechanically interesting of the main firearm operating systems. When the gun fires, the recoil energy generated forces the barrel to move rearward, and the bolt remains locked into the barrel until the two reach the full length of travel (the length of the whole cartridge). At that point the bolt is held rearward and the barrel unlocks and moves forward under pressure from a return spring. The empty cartridge case is held in the bolt face, and the barrel pulls forward off the front of it. An ejector kicks the empty case out when the barrel is fully clear, and when the barrel has returned to its firing position a trip releases the bolt, which moves forward under pressure of a second return spring and feeds the next cartridge into the chamber.

Long recoil system are very safe, as they allow the longest time of any system to let pressure vent from the barrel before unlocking. They are also mechanically complex, and tend to exhibit higher than normal felt recoil. The system was employed successfully in a wide variety of firearms including light machine guns (the Chauchat), rifles (the Remington Model 8/81), shotguns (the Browning Auto-5 and Winchester Model 1911), and handguns (the Former Stop). All of these date from the early 1900s, when designers were still exploring ways to safely and reliably build self-loading firearms.

37 Comments

  1. I hunted with my father’s FN built Auto-5. I could never hit a moving target with that gun because of the weird recoil impulse that I never learned to compensate for. I got to be a pretty decent wingshot using his SxS.

  2. I purchased a Browning Sweet 16 in 1967. I have hunted Pheasants, ducks, geese, many rabbits, one turkey and a few squirrels and woodchucks. I especially like the way you can reverse parts to adjust for light and heavy loads. Although I love the gun, I retired it a few years ago and only occasionally shoot it anymore. It never fails to work unless I switch from heavy loads and forget to reverse the rings, then I don’t get ejection and end up with a stovepipe. As soon as I do my part it functions properly again. John Moses Browning knew what he was doing!

  3. “Former Stop”
    What did Rudolf Frommer to being treated with such disdain? Yes he designed long-recoil operated automatic pistol for cartridge where plain blow-back would suffice, but later repaired own error (if we look at that in such categories) and crafted blow-back operated Pisztoly 29 Minta http://hungariae.com/From29.htm for these cartridges.
    In my opinion Frommer Stop might be good starting power for magnum-level cartridge automatic pistol, low bore axis might be useful for lessening felt recoil.
    Long-recoil would reappear in Hungarian arm design, namely Lynx GM-6
    https://modernfirearms.net/en/sniper-rifles/large-caliber-rifles/hungary-large-caliber-rifles/lynx-gm-6-eng/
    self-loading 12,7×99 NATO rifle.

    • In that lastly mentioned Hungarian rifle is AFAIK installed hydraulic absorber. Yet, gun still kicks considerably. I wonder what was their motivation to use this particular operating system and if they have done comparative analysis prior to selecting it.

      • Is it intended to be used in armoured vehicles?

        If it is, then long recoil is one way to allow the propellant fumes to vent out of the muzzle, rather than into the confined space inside the vehicle.

        Ejection of empties from a long recoil, can be made into a relatively gentle and civilised process as well,

        especially compared to ejection in some of the blowback and delayed blowback designs. I’m thinking particularly of CETME and H&K G3 there.

        Though most of the other autoloading action designs still require (or result in) more violent ejection than long recoil designs do

        • So far (and I have see at least a dozen of videos starting with previous Gepard) it was always outside of vehicle and shooting at modest range https://www.youtube.com/watch?v=YSib-rz5eT0

          I am not sure what is actual purpose of this rifle; it can hardly fit to sniper role. Maybe squad support rifle? It may not be however capable of piercing APC’s skin, depending on type of shot and type of vehicle.

        • “advantage of semiauto”
          That you did not have to manually repeat, so you can starts to re-aim faster. So actual rate-of-fire is bigger.

    • My only problem with the Frommer Stop was its size. It was the same size as most 7.65mm or 9mm Short service pistols of the day, most of the rest being straight blowbacks or (rarely) short-recoil.

      The real advantage of the Stop mechanism was that it would allow a very small pistol to accommodate a cartridge more powerful than would be practical in a blowback mechanism. For instance, a Minta-sized Stop could have been built in 7.65mm or 9mm Short, rather than 6.35mm. This would have filled a real need in that time and place, for a defensive pistol that was both reasonably powerful, relatively easily controlled in recoil, and yet also easily concealable.

      For that matter, a PP-sized Stop in 9 x 19mm might have rewritten all our ideas about service sidearms for police and military use. Especially with a double-column magazine holding 12 or 13 rounds.

      The Frommer Stop was one of the great missed opportunities in firearms history. Less due to Frommer than due to the people he worked for. They wanted a 7.65mm service pistol of Browning M1910 size, and that’s what he gave them. If they’d had the sense to ask for it in 9 x 19mm, history might have been just a bit different.

      cheers

      eon

      • “For instance, a Minta-sized Stop could have been built in 7.65mm or 9mm Short, rather than 6.35mm.”
        Note that there existed Frommer Baby:
        http://hungariae.com/FromBaby.htm
        it still was 7,65 mm Browning or 9×17 mm Kurz weapon, yet it have much smaller dimensions. With overall length of 123 mm this weapon it is on par with modern Kel-Tec P-32, although much harder due to all-steel construction.

  4. I guess that we haven’t moved on quite as much as the tech companies might claim we have

    From the days of microsoft’s
    “It looks like you’re trying to… can I completely feck it up for you?” Paperclip.

    And looking at how far out the bots that send me targeted advertising are, from what I’m interested in

    It makes me curious about how much more unreliable the bots are who’s owners have little incentive to actually get it right.

    Like the ones targeting people for no knock dog shooting raids, and droning.

  5. Franchi were still making a long recoil shotgun, derived from the Browning. They might still be.

    I’ve never had the opportunity to take one to bits, to see how far it deviates from the original.

    Unfortunately it’s a truism that deviations from Browning’so original designs are seldom for the benefit of the customer, or for the people and dogs who are around the customer.

    • They’ve got to at least pretend to be “scientific”,

      and they have to pretend even harder, to appear to know what they’re doing.

      Apart from the names of Browning, Garand and Stoner, united state gun selection hasn’t exactly been a world leader

      And even those names were too often handicapped by the poor choices in ammunition that they got the job of designing a gun around.

      • Judging by your tone, I think you would rather try a test like this: blast the pistol with a weak 37mm infantry tank cannon just to see if anything survives.

      • “Browning, Garand and Stoner”
        What is reason of not putting Carbine Williams there? IIRC most negatives opinion about M1 Carbine were along line “being too weak”, but this has more to do with cartridge, which was not choice of Carbine himself. From modern point-of-view requiring tool for stripping might be given as disadvantage, but it was not unique trait of M1 Carbine among fire-arms used during WW2 by USA.

        • ” but this has more to do with cartridge, which was not choice of Carbine himself.”

          No, it had to do with people not bothering to read the original specification. Which clearly states that the objective was a lightweight weapon “To replace pistols, submachine guns, and some shotguns“.

          All of which are relatively short-ranged weapons (effective range 100 yards or less) and except for the shotguns, very low-powered (less than 500 FPE muzzle energy).

          The carbine was intended for personnel not normally issued rifles, unlike the infantry. It delivered greater range and killing power out to 300 yards than any individual weapon except a .30-06 rifle, weighed less than the standard SMG (the Thompson, 12 pounds loaded) or most shotguns, and in the hands of draftees and others who were not pistol marksmen was overwhelmingly more accurate than the M1911A1 .45 automatic.

          Its adoption by paratroops was due to the airborne soldiers realizing that for the weight of a TSMG and ten 20-round magazines, they could carry a carbine and thirty 15-round magazines. Plus it was more compact, didn’t overload the drop harness, and gave them a decent field of fire when confronted by enemy soldiers with 7.9 x 57 Mausers and etc.

          The .30 M1 carbine did exactly what it was supposed to do. People who criticize it for not being an M1 Garand don’t understand what it was supposed to do.

          cheers

          eon

          • “People who criticize it”
            I meant they would also do it, if someone other design would be adopted using same cartridge instead of one made by Carbine Williams.

    • “Beretta tests, monitored by US military observers, have found that random pistols chosen from the M9 production lines for testing fire an average of 22,500 rounds without a stoppage. In one test session, under Army supervision, twelve M9 pistols were pulled randomly from the production line and fired a total of 168,000 rounds without a single malfunction.”

  6. I’ve had a Winchester 1911 for most of my life. It sits in the back of the safe, and is never shot. It’s remarkably unpleasant to fire, and every single one of them has a cracked forearm – as does the video example.

  7. Since I spent some time in conceptualising, it is clear to me that for long recoil gun there is added requirement when riding over magazine with barrel. This necessitates barrel to be made thin in rear portion (which weakens it) or arrange for magazine to drop down (added complexity). For this reason alone I do not see long recoil operation as particularly attractive. I remember though that Chauchat got around it in some clever way which I cannot recollect right now.

    • The Chauchat gets around this problem by having its feed ramp separate from the barrel. When the bolt shoves a cartridge up the feed ramp, the bolt’s extension arm hits the ramp and causes it to pivot down on its hinge. The recoiling barrel does not hit the magazine because it is mounted well below the area of travel. There’s a pretty good animation of the Chauchat’s workings on YouTube…

    • “thin in rear portion (which weakens it) or arrange for magazine to drop down (added complexity”
      Wait, what about Gabbet-Fairfax Mars automatic pistol?
      http://historypistols.ru/wp-content/uploads/2013/11/Mars35.jpg
      (from http://historypistols.ru/blog/pistolety-pod-unitarnyj-patron-avtomaticheskie/pistolet-mars-gabbet-fairfax-mars-automatic-pistol/ )
      Is that case of magazine to drop down you described? Certainly it is complexity but magazine seems to remain stationary.

      • Remember, the Mars had a separate cartridge lifter which extracted the to round from the magazine backwards, then moved upward to position it in front of the bolt head to be rammed into the chamber.

        It was very like the “loading tray” of a naval gun on a much smaller scale, with the pistol’s bolt taking the place of the powered chain rammer system.

        It mostly proved that long recoil in handguns is rarely worth the added complication.

        cheers

        eon

    • “I do not see long recoil operation as particularly attractive”
      Also, due to long travel of barrel (which is most often heavy part) there is big shift of point of center-of-gravity, which might increase vertical spread when firing hand-held machine weapon utilizing this principle.

  8. I have an old Remington Model 11(copy of Auto 5) in 20g that is an absolute joy to shoot. Every time I shoot it I am reminded of the way the barrels in old Navy AA guns recoil. The recoil in 20g is very controllable and while not soft on the shoulder, it is not bad. Just enough to remind you it’s a shotgun, but not enough to bruise.

  9. Anyone whose shoulder getsoverly bashed by an A5 or clone thereof did not properly install the “brake rings” on the magazine tube. You can still buy them from Browning and you can install, I think, up to three. Browning was very proud of coming up with this particular idea, and back in 1899 the part cost a nickel apiece, material and fabrication costs together.

    • I just reviewed my source and it cost “less than a dime.” Of course in those days a dime got you a sandwich and two sides at most diners.

      For anyone who doesn’t know, one of Browning’s great accomplishments in designing the A5 was that it looked somewhat like a normal long arm. The recoil spring for the bolt extended back into the buttstock; the barrel recoil spring encircled the magazine tube, butted up against the receiver at the rear and at the front engaged a ring of steel, welded beneath the barrel, that also encircled the magazine tube. All of this was hidden and kept clean by the fore-end.

      The “brake ring’ or shock absorber consists of a tapered split ring held behind a solid ring; the barrel recoil ring pushed on the solid ring, which squeezed the split ring around the magazine tube to slow the barrel down — the harder the push, the tighter the squeeze, the more the braking effect. Self-adjusting! Multiple rings could be installed.

      The Winchester 1911 was a desperate attempt to catch up with Browning once FN and Remington sold scads of A5s — Johnson, Winchester’s chief engineer, tied himself into knots getting around Browning’s patents, resulting in such absurdities as cocking the arm by pulling the barrel back — a checkered section in the steel was thoughtfully provided for the purpose. The 1911 was such a failure that Winchester in the end offered to take them all back in exchange for pump guns.

  10. At age of starting autoloading systems, fear of controlling the discharge in a most supported media, directed the inventors finding ensured methods like long recoil operations keeping the fired shell from starting to the end in the barrel and since the very big amount of remaining gas wasted off, the empty case should be ejected through gained momentum by extractor and
    ejector. Paper shells of that era used in the shotguns were also a factor preferring that method of autoloading. lMHO.

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