LCP guide rod while firing - what happens?

[Carmady]

I've never given much thought to the guide rod and spring system as used on the LCP. It's very simple to assemble, and I never wondered what was going on while the gun was in operation, until recently. I'd just assumed that the nail head end of the guide rod remained seated in its spot on the barrel.

Now I'm thinking that can't be so, because when the slide is held back with the hold open the barrel has a lot of wiggle room. It's free to flop around, up and down, forward and back, left and right. Lots of wiggle room on BOTH ends of the barrel.

At the same time, slide locked open, the guide rod isn't moving, at all, anywhere. It appears to be held secure by spring tension.

Since the barrel is free to wiggle, I figure the nail head end of the guide rod must be held elsewhere than the little cutout in the bottom of the barrel used during reassembly.

But I still have a very hard time believing that the nail head end of the guide rod is becoming unseated and reseated from the barrel every time the slide goes back. That's mighty fast.

What's going on with the guide rod while firing?

Please make your answer shorter than my question.

 

[Doyle]

Well, I can't speak for the LCP but on the LC9 Ruger had to do a redesign on the guide rod. It originally looked like a nail head (like the LCP) but the new one looks like the top of a golf tee. As I understand it, the change was needed because the original design wasn't seating correctly when you racked the slide.

 

[Carmady]

They've (guide rod and barrel) got to be separating when the slide goes back because the front of the guide rod stays about where it was, and the barrel moves back about 1/4". That would have to unseat the rod from the barrel. I guess the bottom of the big end of the guide rod catches on something in the frame.

 

[Walt Sherrill]

But I still have a very hard time believing that the nail head end of the guide rod is becoming unseated and reseated from the barrel every time the slide goes back. That's mighty fast.

What's going on with the guide rod while firing?

You're looking at two different aspects of how that gun operates -- and misunderstanding how the barrel moves when the gun is fired. It's an easy thing to misunderstand -- I've been there and done that, too.

When the slide goes to the rear, the barrel separates from the recoil spring and guide rod -- but the base of the guide rod is still (depending on the the gun's design) seated against or connected to a part of the frame. Without a solid (fixed) base or connection to the frame against which the spring can press, the spring can't store any of the recoil force it needs to power the slide for the next shot. In other words, it can't just dangle!

Here's a video from YouTube that demonstrates the process: https://www.youtube.com/watch?v=uT_B1HoaR_E Most locked-breech guns function in a similar manner. Even an LC9, while smaller, works in the same way.

Note: These animations don't always get the details right. The slide will begin to move as soon as the bullet is fired (equal and opposite reactions). With a 1911, the bullet will leave the barrel before the slide has moved about 1/10th of an inch -- I'm not sure when it happens with a Glock (different caliber, etc.) That part of the animation may be incorrect, but how the barrel moves and the recoil spring functions is correct for all Browning Short-recoil Locked Breech designs.

As the slide and barrel move to the rear several things happen: a physical link between the barrel and the frame causes the barrel to try to separate, and as the pressure in the barrel drops when the bullet exits, the pressure holding barrel and slide together is reduced. While both continue to move to the rear (momentum), they take different paths.

With many guns, when the barrel and slide are at the rear, there's not much of a physical connection between the slide and barrel, and the barrels is free to move around a bit -- just how much movement is possible will depend on the design of the gun's lockup system. But, as the slide begins to return, grabs the next round, and things are jammed back together, and the breech is closed, lockup is re-established.

If the barrel and slide (and, in effect, the SIGHTS) return to exactly the same place with each shot, you'll have an accurate weapon. The consistency of that lockup -- the ability to do it over and over again -- is what defines PRECISION, a term frequently used to describe a GUN'S (not the shooter's) accuracy.

 

[Carmady]

"Here's a video from YouTube that demonstrates the process: https://www.youtube.com/watch?v=uT_B1HoaR_E "

Thanks for the video, but that gun's operation has some major differences from the LCP's.

It looks like the rear end of the guide rod remains motionless throughout the cycle, and is never in direct contact with the barrel. Its center line stays the same in relation to the frame since both ends are stationary.

The LCP's guide rod lifts a bit in the front, and might also go down in the rear, remaining close to parallel with the barrel. In the video, the barrel's center line changes, but the guide rod stays fixed in one position.

There's none of that seat/unseat/seat/unseat/etc action going on with the guide rod, which I suspect happens in the LCP.

 

[Walt Sherrill]

It looks like the rear end of the guide rod remains motionless throughout the cycle, and is never in direct contact with the barrel. Its center line stays the same in relation to the frame since both ends are stationary.

The LCP's guide rod lifts a bit in the front, and might also go down in the rear, remaining close to parallel with the barrel. In the video, the barrel's center line changes, but the guide rod stays fixed in one position.

There's none of that seat/unseat/seat/unseat/etc action going on with the guide rod, which I suspect happens in the LCP.

The differences aren't as great as they seem. The biggest issue is that the LCP is relatively small and the parts that move don't move all that far.

The guide rod base isn't motionless. It does SEAT and UNSEAT, but it does it in a slightly less dramatic way than in the Glock demo. It doesn't move as far as in the video, so it's hard to see.

-----------------
As the slide moves to the rear and begins to separate from the slide, the rear of the barrel drops down a bit (following the path dictated by the barrel lug's kidney shape) as it moves along the slide stop pin. The reason the barrel seems to be raising at he front is because it's tilting: the rear of the barrel is dropping a bit, being guided down by the slide stop riding on the barrel lug.

The top half of the guide rod base starts out pressed against the barrel lug -- where you placed it when reassembling the gun. But when firing, the barrel and slide mov more to the rear. Then, the guide rod and barrel lug (and a drop of pressure as the bullet leaves the barrel) force/allow the barrel to separate from the slide.

The barrel and slide are still moving to the rear (momentum). The barrel separates from the slide and drops down slightly. The top portion of the guide rod base is still resting against the barrel lug, but as the barrel continues to move to the rear, *the bottom half of the guide rod presses against the receiver STOP. The barrel continues to move and pulls away from the top half of the guide rod base.

*modified to clarify a very poor explanation. It originally said "and STOPS, " not "STOP."

If the guide rod base didn't stop by hitting the receiver stop on the frame, there'd be no way for the spring to compress --and no way for the the force of the recoil to be stored to later load and chamber the next round. (In theory, the spring might still compress, but it would not move as far or compress as much, unless it stopped while the slide and barrel continued to move...)

After the guide rod base has come to a stop against the frame, the barrel moves a bit farther and the slide moves even more. Because it's such a small gun, the whole slide/barrel assembly is moving less far than in the Glock demo, so it's harder to see -- but the principle is the same.

If you want to see this process more clearly, you can take your slide off, remove the barrel, and reinstall the slide stop. You can then let the barrel set on the frame and slide stop as it would in the gun, and manually move the barrel to the rear (as the slide would move it.) You'll see that the barrel's motion and distance is controlled by the the shape and orientation of the the kidney-shaped opening in the barrel lug. The farther back the barrel moves, the more the rear of it drops.

If you slip the guide rod in UNDER the barrel and repeat the process (trying to keep pressure on the front of the guide rod as would be the case if the slide were on the frame and the slide was compressing the spring), you'll find that while the barrel moves away from the top of the guide rod base, the bottom of the guide rod base will press against the frame.

The guide rod hasn't moved a great distance to the rear, but the rear of it has dropped a bit vertically. But he base is now pressed against the frame and the spring can now compress to absorb the force of recoil for later use.

After the round is fired (or when the slide is manually released), the compressed spring moves the whole assembly forward, and the mechanism's design causes the parts to return to their original positions/locations.

 

[Carmady]

"The top portion of the guide rod base is still resting against the barrel lug, but as the barrel continues to move to the rear , the bottom half of the guide rod base hits the receiver and STOPS. The barrel continues to move and pulls away from the top half of the guide rod base."

I appreciate the detailed explanation, and while it may apply to Glocks (and/or other guns), but I think the LCP is a little different regarding the bottom half of the guide rod base.

When the slide/barrel start to move back, the front tip of the guide rod stays right where it was. It doesn't go back at all. Since we know that the guide rod becomes unseated from the barrel during this, the bottom of the guide rod base must still be in contact with what it was before firing. That's how it looks to me, and I'm guessing the top half of the guide rod base very close to being unseated from the barrel, can't tell enough to guess which way.

It also seems like the guide rod base might pivot a little on its stop, because the front tip of the guide rod does rise up a little. The slide goes back, the guide rod hole in the end of the slide gets closer to the guide rod stop in the frame, that changes the angle of the guide rod and raises the front tip up and causes the base to pivot on its stop.

I also poked around with a little steel ruler, and it looks like I was wrong about the center lined of the guide rod and barrel being parallel. It looks like they're a little closer together at the front, slightly further apart at the rear.

I got curious about this because the slide locked back recently, the guide rod was wedged in the hole in the slide, and that prevented the slide from returning. I'm trying figure out what might have happened. LCP's aren't supposed to lock back.

 

[Walt Sherrill]

When the slide/barrel start to move back, the front tip of the guide rod stays right where it was. It doesn't go back at all. Since we know that the guide rod becomes unseated from the barrel during this, the bottom of the guide rod base must still be in contact with what it was before firing.

If it doesn't move it's because it's already resting against the receiver stop. With most guns that's what happens, and I must have garbled that explanation, but that's what meant by "but as the barrel continues to move to the rear, the bottom half of the guide rod base hits the receiver and STOPS." That wasn't written clearly. My error.

Said properly, its "the bottom half of the guide rod base hits (presses against) the receiver stop." (Too many revisions and edits as I was writing that).

(With my much-loved CZs, the guide rod presses against the barrel lug AND the receiver stop when the gun is in battery, but when the slide and barrel move back and the barrel lug moves away, the guide rod base presses ONLY against the receiver stop. With the small CZs, you can see the guide rod tilt a bit as the slide goes back.)

With other guns the method of fixing the position of the guide rod (so that the spring can compress) will be different.

 

[James K]

Specific to the LCP:

Remove the slide, along with the barrel, guide rod and recoil springs.

Look down into the top of the receiver, just above the front of the trigger.

See that half round hole that looks like a trough? That is where the rear of the recoil spring guide rests when the gun is fully assembled. The notch in the barrel is only a place for the spring guide to sit temporarily while the gun is being assembled.

Jim

 

[Carmady]

"The notch in the barrel is only a place for the spring guide to sit temporarily while the gun is being assembled."

That's what I was thinking, and I'd noticed the trough for the springs/rod while assembled. Thanks.