Pistol Phylogeny Part 3 – Delayed

Pistol Phylogeny Part 3 – Delayed

Delayed systems include a good deal more variation than unlocked systems, though they are not as prolific as locked systems.  Nevertheless, while fewer in number, these guns show perhaps the broadest array of unique concepts and novel ideas.  Their strengths over unlocked systems are fairly noticeable, in that they require less mass and spring resistance to safely delay opening; a combination that usually greatly enhances both the ergonomics of handling the gun, and the realities of recoil and back gas pressure in practical shooting.  This, of course, usually comes with much higher R&D and manufacturing complexity and cost.

Their qualities when compared to locked systems, however, are a little less starkly different.  There may be potential for some smoother actions without the mechanical disengagement of otherwise locked pieces occurring… but as so much else can affect this characteristic, there is likely not much difference in reality.  Delayed systems do tend to still open at higher pressures than locked systems, and can sometimes get dirty swiftly in the process.  However, one area they shine in is the purely academic analysis of their mechanics, as they tend to employ more intricate balances between the different forces of firing.  And since that is what is being looking at here, the author shall get on with it.

Delayed system can be broken down at their highest level into two branches that are mirrored in locked systems as well – gas delayed, and mechanically delayed.

Gas Delayed

Gas delayed systems do exactly as the name would suggest, they use gas pressure to delay the opening of the action.  This is actually one of the more (to the author’s mind) clever ideas in handgun design; the goal of auto-loading designs is to wait just long enough to cycle the action so that gas pressure can drop to a safe level, and what better way to determine when that has occurred than using the gas pressure itself to keep the action closed.  While this may be a practical upshot, the downsides are that using gas pressure makes the internals of the gun much dirtier to clean, and much hotter to handle.

There are two extant methods for laying out such an operating system.

Gas Piston

The first, and more common, method of accomplishing this aforementioned task is with the use of a gas piston.  Gas is tapped and vented from the barrel and channeled into small chamber that is sealed on the opposite end by a snuggly fit piston head.  As the pressure of firing the gun fills this chamber, the piston is pressed forward with equal force.  The other end of the piston is attached, or otherwise impacts against, the slide.  Since the force of firing the round is equally exerted in all directions, the pressure pushing forward against the bullet and piston head is roughly equal to the recoil force, and the gun remains closed.  Once the bullet leaves the barrel, the gas pressure drops rapidly in both the barrel and piston chamber, allowing the residual recoil energy to compress the piston in the chamber and cycle the action.

A number of guns have been designed with this operation, including the venerable HK P7, the Walther CCP, and the newly minted Laugo Alien.  The author is accepting donations for the $5000 Alien pistol, if the reader is so inclined…

Gas Chamber

Another design built to take advantage of this system simply flips the gas piston concept around backwards… sort of.  The Steyr GB (and its far lower quality Rogak rip-off) is designed around this idea.  The nose cap of the slide includes a gas chamber that seals around a finely machined portion of the barrel, thus making the slide the chamber and the barrel the piston.  Gas is vented from a port in the barrel directly into this chamber, thus holding the slide forward against the machined surface of the barrel.  Once the pressure drops, the action works much the same way, except with the piston surfaces of the barrel holding fast as the slide-bound chamber reciprocates.

As noted, the author is aware of the Steyr GB being the only handgun to successfully use this system, as the Rogak is, by all available accounts, far to poorly fit and finished to actually achieve its design concept.

Mechanically Delayed

Mechanically delayed systems show a bit more variability than their gas delayed counterparts.  The concept here is the same, to delay opening of the action until gas pressures have reduced to a safe level, but instead of using pneumatics these guns get their delay from what could be creatively described as forcing the recoil energy to solve puzzles.  (pause inserted for confused looks and any wayward chuckles…)

Unlike a locked system, there is no external force required to decouple any of the parts; all the force applied to open the action comes directly from the chamber.  But unlike an unlocked design philosophy of resistance through sheer mass and force, a mechanically delayed system employs pieces that must interact in various ways to bleed energy out of system and thus slow the opening of the action.  The author could continue to attempt to generally describe this, but the concept is better understood via looking directly at some examples.

Friction Delay

The simplest method for delaying the movement of various parts is by gripping them more tightly.  This is essentially what friction delaying mechanisms do, though it is highly debatable how effectual such designs are.  The most notable of these would be the Blish Lock employed in earlier versions of the Thompson submachine gun, wherein it was posited that the friction between brass and steel would be substantial enough to slow action… spoiler alert, it didn’t so much, and that gun handled the .45acp recoil by having a 2lb bolt.

In handguns, the best example of this as a specific design component that the author is aware of is in the Mannlicher 1901.  This gun increases friction and force within itself with the hammer weight and geometry, spring weight, and by pressing components up snuggly against the bolt itself.  (For a far more competent explanation of this, the reader is directed to the host’s video on the subject.)  Ultimately, it is questionable how much different from an unlocked design this really is, and it could arguably be considered a straight blow back gun, as the Thompson is remembered.  Nevertheless, the author has included it here for its apparent design intent as opposed to its realistic application.

Barrel Rotation Delay

In a similar vein of “how much does this actually delay the action”, we have the rotating barrel delay of the Savage 1907/1917 pistol family.  When at rest, this gun’s barrel has a small camming surface on the top that engages into a cam track in the slide.  When fired the slide must rotate the barrel slightly in order to clear this cam and open.  (It is key to note that this surface is angled so it can be pressed out of the way by chamber pressure, as opposed to being locked into place and requiring an outside force to decouple as in rotating barrel locked systems.)  This alone would provide next to no delay on the system, but the direction of camming delay is cleverly opposed to the rotational force of the barrel.  At first glance, the rifling angles in the same direction as the barrel rotates – clockwise when viewed from the breech.  But since the bullet is resistant to being spun, the force it exerts on the barrel is actually counterclockwise as it tries to instead spin the barrel around itself.  This counterclockwise force on the barrel opposes the necessary clockwise rotation needed to open the action.  Of course, the counter rotational force isn’t nearly as strong as the recoil force, and it quickly dissipates as the bullet begins to take on spin, so the exact amount of delay this provides is dubious.  In his shooting of this gun, the author has noted a not insignificant amount of smoke and general grime issuing from the breech end of the barrel, suggesting that the opening of the gun is likely not delayed by much… once again, donations for the high speed 4k video equipment necessary for split second analysis would be considered.

Chamber Ring Delay

If you want to delay ejection of a spent casing, why not just make the casing harder to eject?  One method for carrying out this simple idea, is to cut an annular ring into the chamber itself.  Upon firing, the gas pressure pushing the bullet down the barrel also presses outward as chamber pressure, thus swelling the brass case into the shallowly recessed ring.  The resultant minor bulge in the case itself makes it harder to yank free, thus slowing the system to a safe speed.  Once again, the question of how much of the delay is conceptual vs. real is debatable, especially since the only examples the author is aware of are chambered in calibers otherwise conducive to direct blow back operation anyway.

This comparatively crude concept has actually been deployed in a few handguns.  The Fritz Mann pistol was a 1920s example of this system in a diminutive vest pocket pistol size.  For a more modern take on the same idea, the reader is referred to the currently produced Seecamp line of tiny mouse guns.

Roller Delay

Without a doubt, the most famous and successful of delayed designs is the roller delay.  Tracing its design history back to at least the 1940s, an entire lineage of well regarded arms have employed this system.  That said, of this litany, only one was actually developed in a traditional handgun format – the HK P9.  (Whilst the author is very proud of his MP5 clone braced pistol, it does not quite have the same ergonomics).

So how does it work?  Well, the slide design in the P9 is fairly similar and analogous to the bolt/carrier group in an MP5 or other more common roller delayed firearm.  The slide has an attached “locking piece”, which is confusingly named since the gun isn’t locked, but oh well.  Over the locking piece fits a floating bolt head containing the two rollers.  When at rest, the slide is pressed forward by the recoil spring, which in turn presses forward the affixed locking piece with its two angled surfaces.  These press the bolt head into battery and at the same time, wedge the two rollers into corresponding grooves in extensions of the barrel (analogous to a trunnion).

When fired, the force of the recoil presses back on the bolt face, but the rollers hold the barrel and bolt head together.  If the gun were locked, this would be unsuccessful at opening the breech until some other force entered the party, but instead the rearward force on the bolt begins to roll the rollers inward.  This is allowed since the locking piece has angled surfaces that can be “pinched” rearward as the rollers act against it; however, since the locking piece is held forward by the mass of the slide and recoil spring, the rollers must first overcome all of that force to move the locking piece out of the way so the breech can open.  Essentially the system is cleverly designed in a way that forces the recoil energy from within the chamber to move the slide rearward at an initially faster rate than the bolt head itself, thus delaying the cycling of the gun.

Got it?  If you answered no, the author would refer you to some recent videos from one Mr. McCollum on his YouTube channel entitled “Forgotten Weapons”.

Flapper Delay

Flapper locking is the predecessor to roller-based systems, and works similarly, just with wing-like flappers in place of rollers.  But flapper locking in handguns appears to have never gotten out of the prototype phase for handgun designs, and this section isn’t for locking systems anyway.  That said there is at least one gun that does use a flapper to provide an at least minor delay to the bolt.  The Roth Steyr/Krnka 1907.

This Roth pistol is in fact a rotating bolt, locked breech system, but it has an additional delaying mechanism that the author shall briefly discuss here as it fits nowhere else.  On the side of the bolt, there is mounted a small lever, which when in battery, extends out of the bolt and out of the way of the firing pin, and into a recess in the frame.  When pressed inwards by the frame under recoil, it accomplishes its primary function of blocking the firing pin and providing an out of battery safety.  Nevertheless, this action does bleed energy out of the recoil force in order to squeeze the flapper inwards as the bolt travels rearward.  How much energy, the author cannot say until the dreamt-of-someday that he can shoot one in a controlled setting.  Regardless, this does make the Roth Krnka/Steyr 1907 an additionally unique gun in its mix of systems.

Camming Lever Delay

As of 2020 there are two guns on the market utilizing this mechanism; the FN Five-seveN, and the Ruger 57.  Both fire the 5.7x28mm cartridge, and employ a similar system which uses a camming lever under the barrel.  The author owns the Ruger 57, which will be used as an example here.

When at rest the slide presses forward on the barrel, which (unlike other delayed systems) moves forward and into battery as well.  As the barrel moves forward, it presses against a surface on the camming lever whose fulcrum point is affixed to the frame.  The lever then cams up and forward, extending two wings into corresponding cutouts in the slide.  When fired the recoil energy presses rearward on the bolt face, but to open the slide must first swing the wings of the camming lever down and out of the way.  To do this, the lever must also rotate backwards with the barrel a short distance, adding more inertial mass to the recoil stroke.  Additional forward drag from the bullet travelling down the barrel, and forward gas pressure against the shoulder of the necked casing, work in opposition to the rearward pull of the lever, providing a delaying tug-of-war between opposing forces until the bullet leaves the barrel and the pressure drops.

Just as some of the earlier systems described are arguably very near to simply being unlocked, the camming lever delay system here discussed could arguably be considered locked.  It could be argued that the lever locks the barrel and slide together, and the normal force of the frame at the fulcrum of the lever is what pivots the lever and unlocks the two pieces, thus making the gun a short recoil, locked breech system.  On the other hand, the lever does not fully lock the barrel and slide – the slide engages the lever further out from its pivot point than the barrel, and thereby can actually move rearward faster than the barrel (if only by a minuscule amount).  Furthermore, there is absolutely a delaying action brought to bear on the lever by the forward drag of the bullet; this occurs in locked systems too, but the use of a lever to harness this force increases its leverage and usage within the system.

Ultimately, these guns can and have been argued both ways, as they have features that can be categorized as either locked or delayed depending on the reader’s point of view.  The author has made the potentially contentious decision of identifying these as delayed systems, ultimately because that is how their respective manufacturers have chosen to define them… and whether that is due to physics or marketing, the system is pretty cool regardless.


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