A Challenge

[Embalmo]

Guys,

My challenge is for someone to explain to me in very few words how delayed recoil operation works. I've read articles and I've seen animations, but I can't wrap my head around why/how the slide locks briefly, and why/how the barrel tilts down to release the slide to cycle the next round. It just bothers me that I can't understand entirely how my guns work. My wife's BT .380 is easy-BOOM the slide blows back, the spent cartridge is jettisoned, and the next round is chambered.

Thanks in advance,

Embalmo

[bizarrenormality]

The barrel and slide move together for a brief moment, still locked up, under recoil.

After some distance, and time, the barrel tilts or rotates and unlocks from the slide.

Based on conservation of momentum, the light and fast bullet should leave the barrel before the heavier barrel and slide unlock.

[jimlongley]

Guys,

My challenge is for someone to explain to me in very few words how delayed recoil operation works. I've read articles and I've seen animations, but I can't wrap my head around why/how the slide locks briefly, and why/how the barrel tilts down to release the slide to cycle the next round. It just bothers me that I can't understand entirely how my guns work. My wife's BT .380 is easy-BOOM the slide blows back, the spent cartridge is jettisoned, and the next round is chambered.

Thanks in advance,

Embalmo

The best graphics can be fond here: http://www.m1911.org/full_1911desc.htm" onclick="window.open(this.href);return false;

[Embalmo]

Thanks for the article, but it's similar to what I read before. It tells me what, but not why. It tells me that the slide stays locked until the gasses diminish, and then the barrel tilts and unlocks the slide, and then it works like a blowback system.

What I don't get is what (part of the gun) locks it initially, and why does a diminishment of gas pressure make the barrel tilt to release the slide. If theoretically I was Superman, and I could rack the slide as forcefully as a fired cartridge, would it lock until I exerted slightly less pressure? Kinda' like a seat belt being forcefully tugged on?

In my next post I'm gonna' tell you guys what I think and you tell me if I'm right.

Embalmo

[boomerang]

It's not the pressure. It's the distance traveled by the barrel (in relation to the frame.)

[jimlongley]

A closer look at the action, in action, if you will excuse the pun, would suffice.

Unlike the long recoil .50 BMG machine gun and some submachine guns, the 1911 does not rely on a magical metal contact to keep things locked up until it is safe to unlock, just simple physics and Newton's laws.

While the barrel and slide are locked together they are relatively massive, so much so that they react very slowly to begin with, but they do start moving almost before the projectile departs. At this point in time think of the barrel, slide and cartridge case as being a single unit with high pressure gases blowing out of the only opening.

There are some really neat videos on youtube that show that part of the process externally.

As the barrel and slide begin to recoil the link also starts to pull the barrel down and out of engagement with the slide. This action also begins the separation of barrel and slide horizontally, and the first increment of extraction of the spent casing. I wish John's demo moved a lot slower because the interrelationships are all there to see, it just moves too fast.

There is always a lot of pressure left over at this point, also quite evident either on your hands after firing, or on other videos on youtube, but the total volume of the pressure vessel formed by the barrel and cartridge is finite and relatively small, so it isn't long before pure inertia is doing all of the work.

The rest is pure mechanics, and all the genius of John Moses Browning.

It isn't the drop in pressure that allows the unlock, it's the simple little rotating link, which is why, even doing it ever so gently, you can still cycle the slide by hand.

On the other hand pure blowback guns have to have very strong operating springs, making them tough to cycle by hand, and somewhat impractical in combination with powerful cartridges.

[jimlongley]

I should have dug a little deeper, there is an excellent slow motion on SV1CEC's photo bucket page here:

http://smg.photobucket.com/albums/v323/ ... deview.flv" onclick="window.open(this.href);return false;

Before the hammer falls, place your cursor just where the barrel and slide meet at the locking grooves and the motions will be more evident. Then watch the link.

[davidtx]

Jim - Thanks for the excellent answer and the link to the animation. Now I know how that part of my gun works!

[Excaliber]

I should have dug a little deeper, there is an excellent slow motion on SV1CEC's photo bucket page here:

http://smg.photobucket.com/albums/v323/ ... deview.flv" onclick="window.open(this.href);return false;

Before the hammer falls, place your cursor just where the barrel and slide meet at the locking grooves and the motions will be more evident. Then watch the link.

To expand a bit on what's been well said elsewhere here, in the 1911 and similar guns the locking lugs on the top of the barrel just ahead of the chamber mate up with the matching grooves on the slide. This is what keeps the barrel and slide locked together until pressure has dropped to a safe level, and is clearly shown on the video Jim was kind enough to post if you look carefully where he suggested. On blowback guns like most .22 through .380 pistols, these lugs are not used the and slide and barrel are held together only by recoil spring pressure and the inertia that comes from the weight of the slide. Why not use the same system on higher pressure calibers? Because the recoil spring would have to be much stronger and the slide much heavier in order to maintain the closed breech relationship between the barrel and slide long enough for the pressure to drop to a safe level. Most folks would find such a gun big, heavy, and clumsy. Consequently, there's little market for them and few are in production.

You might then ask what keeps the barrel and slide locked up on Glocks, Springfield XD's, etc. which have no visible locking lugs on the barrel in front of the chamber. On these guns the lockup function is achieved by the large rectangular part of the barrel that mates up with the ejection port opening. It works basically the same way as on the 1911 pattern guns, but this approach simplifies machining, reduces fitting adjustments, and keeps down manufacturing costs.

[Embalmo]

You might then ask what keeps the barrel and slide locked up on Glocks, Springfield XD's, etc. which have no visible locking lugs on the barrel in front of the chamber. On these guns the lockup function is achieved by the large rectangular part of the barrel that mates up with the ejection port opening. It works basically the same way as on the 1911 pattern guns, but this approach simplifies machining, reduces fitting adjustments, and keeps down manufacturing costs.

I really think I've filled in all the mental gaps, except one itty bitty detail. My LCP and Bersa UC9 are like the above description, which is, of course, a simpler version of the 1911 design. My only "mental gap" is, "What makes the spent cartridge, barrel, and slide behave differently immediately after the trigger is pulled?" that is, "why can I rack the slide with it not locking together (briefly), when it does lock together (briefly) when the trigger is pulled?"

Working theory: The speed and force causes the back, top portion of the barrel to "catch" against the ejection port opening just briefly until the force is reduced enough to allow the gun's design to perform its natural function of tilting the back of the barrel down and through the ejection port to safely open the port and eject the spent cartridge.

Am I right?

Embalmo

[Embalmo]

The barrel and slide move together for a brief moment, still locked up, under recoil.

After some distance, and time, the barrel tilts or rotates and unlocks from the slide.

Based on conservation of momentum, the light and fast bullet should leave the barrel before the heavier barrel and slide unlock.

So the "locking cam" system is a method of monkeying with Newton's 3rd law of motion that indicates, "...without an external force," because the locking cam, or excessively heavy spring of a simple blowback system acts as an external force? I'm not sure myself, but the simplest application of "Conservation of Momentum" is a cannon shooting a cannon ball where the momenta of the cannon/cannonball "system" cancel to zero; the cannon recoils back, but nowhere near as far as the cannonball travels do to is larger mass. In this application, However, there is nothing behind the cannon holding it back temporarily like the aforementioned heavy spring, or locking cam system.

Short answer, I donno', but I think Newton's ideas stop at the slide blowing back, and Browning's ideas pick up with its delay.

Embalmo

[jimlongley]

So the "locking cam" system is a method of monkeying with Newton's 3rd law of motion that indicates, "...without an external force," because the locking cam, or excessively heavy spring of a simple blowback system acts as an external force? I'm not sure myself, but the simplest application of "Conservation of Momentum" is a cannon shooting a cannon ball where the momenta of the cannon/cannonball "system" cancel to zero; the cannon recoils back, but nowhere near as far as the cannonball travels do to is larger mass. In this application, However, there is nothing behind the cannon holding it back temporarily like the aforementioned heavy spring, or locking cam system.

Short answer, I donno', but I think Newton's ideas stop at the slide blowing back, and Browning's ideas pick up with its delay.

Embalmo

I some older cannon, yes, recoil was merely an annoying byproduct, but naval cannon that protruded through the side used the recoil to move the gun back to where the crew could serve it. Some old cannon that were emplaced on land did similarly, and one kind of neat innovation had the gun fire over a parapet and the recoil compressed springs that moved the gun back into position.

The 5 inch guns I worked on in the Navy used air pressure to move the guns back into battery and the start of recoil was immediate. One difference between the 5 inchers and most modern small arms is that extraction and ejection took place as the gun returned to battery.

[UpTheIrons]

My only "mental gap" is, "What makes the spent cartridge, barrel, and slide behave differently immediately after the trigger is pulled?" that is, "why can I rack the slide with it not locking together (briefly), when it does lock together (briefly) when the trigger is pulled?"
Embalmo

I think they work virtually the same in both cases. Under recoil, the system is forced backwards by recoil, which causes the barrel link to pull the barrel down and 'unlock' the action. When you rack the slide, the same movement is happening, except the force is applied to the outside of the slide initially (where you grab it), instead of the inside (when it is forced back by the barrel under recoil).

That seems to agree with your working theory. Except under recoil, the fired cartridge pushes on the "bolt face" and sends the slide back, and when you rack the slide, the slide pulls the barrel back with it's lugs.

Or something like that.

[Excaliber]

My only "mental gap" is, "What makes the spent cartridge, barrel, and slide behave differently immediately after the trigger is pulled?" that is, "why can I rack the slide with it not locking together (briefly), when it does lock together (briefly) when the trigger is pulled?"
Embalmo

I think they work virtually the same in both cases. Under recoil, the system is forced backwards by recoil, which causes the barrel link to pull the barrel down and 'unlock' the action. When you rack the slide, the same movement is happening, except the force is applied to the outside of the slide initially (where you grab it), instead of the inside (when it is forced back by the barrel under recoil).

That seems to agree with your working theory. Except under recoil, the fired cartridge pushes on the "bolt face" and sends the slide back, and when you rack the slide, the slide pulls the barrel back with it's lugs.

Or something like that.

I think the confusion here is over when the barrel and slide are locked together and when they are not. They are in fact locked together by the lugs on the barrel and grooves in the slide whenever the pistol is in battery (slide fully closed) and during the actual firing of the cartridge, not just after the cartridge is fired.

When the pistol is discharged, the lugs remain locked together for a brief time until the high pressure in the barrel subsides and the energy from the cartridge overcomes both the inertia of the slide and the resistant force applied by the recoil spring. The slide then moves rearward enough to cause the barrel to pivot downwards on the link and pin and become unlocked as the slide continues its rearward travel to its stop and begins its return forward under pressure from the now compressed recoil spring.

When you cycle the slide by hand, once again it starts out locked, and when the slide moves rearward the same process occurs.

As UpTheIrons pointed out the only difference is that the energy to move the slide rearward is provided by the cartridge when the gun is fired, and by you when you cycle it by hand.