In a short recoil system, the barrel and bolt are locked together for just long enough for the pressure to dissipate, and the barrel only travels a short distance before unlocking the bolt, bolt carrier, or slide.
In the long recoil system, the bolt and barrel recoil the full length of the cartridge. Then the bolt (and cartridge case, held by the extractor) are held back, while a return spring returns the barrel to battery position. When the cartridge case clears the chamber, the ejector punches it out away from the bolt face. When the barrel reaches battery (in some cases, just before it does, but when it’s about to), the bolt is released and comes forward, picking up a new loaded cartridge from the feed system and brings it into battery. When the firearm is fully in battery, a safety interlock of some type (which is there to prevent out-of-battery ignition) clears and the weapon may be fired again.
If you see it, it’s very clear how it differs from familiar short-recoil operation, as generally used in handguns and pre-1945 and large machine guns. Here is a GM6 .50 bullpup rifle to illustrate long recoil for you.
Sure, everybody else uses the Browning Auto-5 as their long-recoil illustration.(The ancient shotgun works the same way as this new autoloader). But we try not to be “everybody else.”
Since long recoil is mechanically more complicated than short, somewhat load-sensitive, and tends to take a lot longer to cycle, why does it still exist? Well, for the sort of hunting the Auto-5 (and it’s Remington Model 11 cousin, and various clones) are used for, it’s fast enough; and it was here first. John M. Browning got the original long-recoil shotgun design just about perfect — as long as you’re willing to adjust the gun to the load you’re using.
We don’t know why the designers of that rifle in the video (which was made by Sero in Hungary, a company whose website, at least, is defunct) chose long recoil, but we’d guess it was to manage the recoil of powerful heavy MG cartridges by spreading the recoil impulse out over a longer period of time. The GM6 was meant for short-range use, according to various blurbs on it (Defense Review; The Firearm Blog; World.Guns.ru) and for carrying on patrols, unlike most .50 rifles, and is much lighter than a Barrett (~25 vs. ~35 lbs.). It is (was?) available in 12.7 x 99 (.50 BMG) and 12.7 x 108 (.50 DShK) calibers. One interesting design feature, mentioned only by Guns.ru:
One unusual feature of the GM-6 rifle is that it can be transported (carried) with the barrel / bolt group locked in the rearmost position to make weapon even more compact. Barrel is released into “ready to fire” position by a button release at the front of the barrel jacket. Providing that the loaded magazine is inserted into the rifle, release of the barrel from “transport” to “combat ready” position will also load the rifle and make it ready for instant action.
In addition to that, the GM6 was designed from the outset to be user-convertible between the two global 12.7 rounds by changing barrel, bolt, and magazine, something that may initially sound like a solution in quest of a problem, but actually would benefit those nations that have over the last century received both Eastern and Western aid, and thus have weapons and ammunition in both chamberings already.
Kevin was a former Special Forces weapons man (MOS 18B, before the 18 series, 11B with Skill Qualification Indicator of S). His focus was on weapons: their history, effects and employment. He started WeaponsMan.com in 2011 and operated it until he passed away in 2017. His work is being preserved here at the request of his family.
19 thoughts on “The Difference Between Short Recoil and Long Recoil”
On this side of the pond, Sero’s website is still working: http://www.sero.hu/
Unusual beast to say the least.
Hognose Post author
Live here now, too.
I always wondered what the difference was between these two! I understood short- vs long-stroke piston but not recoil. Thanks, Weaponsman!
Does long recoil affect accuracy as well as felt recoil? I see you mentioned it wasn’t meant for long range.
Other things being equal, the more the barrel moves, the less repeatable its return to battery is = lower mechanical accuracy. (Also, the more the barrel moves off-axis, which is not a factor here).
Other things being equal, the more weight moves the more distance with each shot, the harder it is to hold the firearm on target = lower practical accuracy. This can also lower the rate of accurate fire.
Makes sense. Make this an all the more unusual beast.
One of the reasons why the Auto-5 is the prevailing example of long recoil is that on a shotgun, being super-precise in how the gun locks up again isn’t a huge deal. So the long recoil idea really isn’t showing much of a deficiency there. Also, all that energy used to hurl the mass of the barrel and bolt rearward is soaking up recoil you don’t need to absorb with your shoulder. The Auto-5 was one of the single best designs for allowing you to use a wide range of shells before the modern Benelli and Beretta designs in semi-autos.
However, if one studies John Moses Browning (insert Mormon Tabernacle Choir here, singing a rousing chorus from Handel’s “Messiah,”) and his works, you see that there were rifles that used the long recoil idea. One that is a direct use of the A-5’s long recoil method was JMB’s design for the Remington Model 8, the only one of which I’ve seen through my hands was chambered in .30 Remington, the parent case for the 6.8 SPC cartridge.
A buddy owns a Remington 81, in .300 Savage, which he claims is a “whitetail-slaying sumbitch” in Kentucky. He, a fellow gunsmith, tells me it is a direct descendant of the Model 8.
So there’s two US sporting rifles that were somewhat common in the US that used the long recoil system, designed by John Moses himself (cue the Choir here again).
Yep, the Model 81 is essentially a very slightly updated Model 8. Kalashnikov’s safety/selector was inspired by the Model 8’s.
I’ll bet the sound of going from “transport” to “combat ready” puts the sound of an AK being taken off-safe to shame. Quite the announcement that things are about to get really, really loud.
Hognose, you could have used a Chauchat to show long recoil. 😀 https://youtu.be/bCwP3Dm52Ls
But the GM6, awesome DMR?
The brave choice in showing off long-recoil would have been the Chauchaut.
Why brave?
French chauchats in 8mm lebel work as advertised. And the americanized ones work if the chamber has been reamed again to get them into spec.
My choice for long recoil exemplar is the Prophet Browning’s Remington Model 8, in the penultimate caliber of .35 Remington.
Thus endth the reading.
It’s always surprised me that Sero doesn’t get a U. S. manufacturer for those rifles.
Smiled when reading this, thinking about the oiled-piston cycle feel of an 81. There’s certainly a rhythm to it.
Had one in .35Rem like Major Mike but the current representative is a .300Sav, a beautiful match of semi-anachronistic cartridge and action.
DaveP
Jeez, now there’s two of us.
Hey, you’re both welcome here. We can never have too many DaveP.’s. As long as it’s not like “I am Spartacus!” — didn’t end well for that lot.
I’m not very good-looking, so they should be able to tell us apart….
DaveP
Huh. Seems like long-recoil would have application to a heavy recoiling handgun too. Heh, and CCW with barrel in recessed mode!