Beretta 92 locking block operation?

[Rmiked]

I think the 92 design is very cool. I am wanting to more fully understand it. I previously thought the forward movement of the slide was stopped (in part) by the slide bearing against the back of the locking block lugs. Today , I inspected my pistol in battery and the rear of the lugs are not touching the slide. The fitting is such that the barrel hood hits the breech face (in battery) with a slight gap between the front of lugs and slide. I see the wear marks on the front of lugs and corresponding slide marks, which makes me think the main force imparted to the lugs is upon firing. The recoil on the breech face moves the slide back and the rearward barrel movement pushes in the plunger pin, which using the sloped interface pushes the locking block down. Not wanting to sound dumb here, but what is the main function of the locking block lugs? The recoil spring keeps the “battery forward” position of the slide . With slide bearing against barrel from recoil spring force, the sloped surface under the block keeps the barrel forward against the disassembly pin. The slots in the frame near the disassembly lever align the barrel laterally. I mean if you cut the lugs off, it seems the main function you lose is the direct method of lower the lugs to permit rearward slide movement. What do those lugs do to help form the battery position before firing? Thanks

[Stony Lane]

This might help... it does show function.

https://www.youtube.com/watch?v=nvt_BKA7goM

[Rmiked]

I appreciate the link. I have watched them all. I don’t see enough detail to know what the lugs are doing to help form battery. I’m thinking some lateral support? But since I was wrong about stopping the forward movement, I’m now confused. Thanks

[jetfire]

The lugs are what allow the barrel to consistently return to the same position and prevent rotation. If you designed a 92 without the lugs, the barrel wouldn't always return to the same position, and the force of firing the round would also cause the barrel to rotate minutely each time, eventually knocking the recoil spring off the lug in the gun.

[Rmiked]

I can see what you are saying. If you cut the lugs off, the pistol would still fire. The slide forward movement would still be stopped by the barrel breech face it is bearing against. But the repeatability of lock-up would vary, hurting accuracy. It appears then the biggest load imparted to the lugs is the collision occurring when the slide moves rearward which is why you see the polish wear marks between the front of lugs and their corresponding wear marks in the slots cut into the slide.

[MattyD380]

It appears then the biggest load imparted to the lugs is the collision occurring when the slide moves rearward which is why you see the polish wear marks between the front of lugs and their corresponding wear marks in the slots cut into the slide.

That seems to make sense, since you see the wings fracture from the front (where the corners are radiused)—suggesting it’s the rearward force bearing on the front of the wings that causes the crack.

This shows the P38’s cycle: https://www.billstclair.com/weaponsman.com/index.html%3Fp=19389

It’s got upward-pointing “hooky nubs” (as opposed to the Beretta’s more horizontal “wings”) which seems to suggest they’re designed to resist rearward force from the slide? Which supports your theory? Maybe?

It’s an interesting design. And I still can’t figure out how a 92 can be so accurate even when the barrels aren’t perfectly centered in the muzzle hoop (at least my 92s definitely weren’t).

[Redhat]

With your pistol disassembled, place the barrel in the slide with the locking block in it's up (locked) position. Hold it in that position and try to move the barrel forward within the slide. Then with the locking block in it's down (unlocked) position, do the same thing.

Maybe Langdon Tactical will stop by and explain in better detail.

[Rmiked]

Looks to me like the locking block is performing the same function as the tilting barrel of say a SIG 226. In those applications the barrel tilts down to allow slide rearward movement. The forward movement of the SIG slide is stopped with the breech face of slide bearing against the barrel chamber; with barrel tilting back up on forward movement. In the Beretta 92 it’s the same interface. Except the barrel doesn’t tilt. The locking block moves down to allow rearward slide movement and the block moves back up on forward movement wedging the block under the barrel. There is a nice fitting saddle cut out on top of locking block. What confused me is that the front of the lugs fit so close against the forward slide slots it almost looks like that is a bearing point on forward movement. It is not. If the lugs stopped the forward movement the bearing would have to be the rear edges of the lugs (not front) and it would be pushed by the rear of the slide slots. As stated earlier, there is no contact in that direction. I never understood that wedging design feature on bottom of barrel. The 92 is an amazing design. I guess I read somewhere the design was actually borrowed from a Walther P38; perhaps refined a bit.

[LangdonTactical]

The lugs are what allow the barrel to consistently return to the same position and prevent rotation. If you designed a 92 without the lugs, the barrel wouldn't always return to the same position, and the force of firing the round would also cause the barrel to rotate minutely each time, eventually knocking the recoil spring off the lug in the gun.

Well, kind of, but not really, maybe a little bit.:)

The locking block is the mechanism that holds the slide forward and locked up. When the gun fires, the barrel wants to move forward, with the direction of the bullet. The brass case expands to fill the chamber and keep "most" if not all of the gases moving behind the bullet toward the muzzle. The locking block ''ears" hold the barrel into the slide keeping it from moving forward. It is being pulled forward by the barrel and pushed up by the frame and the disassembly lever.

As soon as the bullet exits the barrel, the pressure pulling the barrel forward drops, but the remaining pressure in the barrel is pushing the barrel rearward suddenly. The barrel and the slide move rearward together for a short distance as the locking block is pushed down by the locking block plunger, which is hitting the frame right below the chamber, and as it comes off of the disassembly lever and frame, allowing it to move downward away from the barrel. The "ears" of the locking block disengage from the slide allowing the barrel to fully un-lock from the slide.

There are more details, but that is the basics of how the locking-block work.

[Rmiked]

I don’t think I ever considered the barrel wanting to move forward until the bullet exits the muzzle. That is the explanation I was looking for. Thanks

[SSGN_Doc]

The locking block also keeps the slide and barrel and slide locked together for the moment of highest pressure inside the barrel, so the high pressures to not break through the thinner walls of the cartridge case. Part of the differences in a locked breach vs. blowback operating system.

Remove the lugs and the barrel can move forward as the slide moves rearward too soon, and hot gas is going to find the weakest point to escape. That would be the cartridge case walls forward of the cartridge case head. Nobody wants that.

[Maca]

Quick question, is this wear on the right side only (not bilateral), normal during break in? You can feel it with your fingernail.

For context, this gun has had 175 rounds through it.

67383

[Rmiked]

My initial reaction is that is a machining mark and not a wear mark. My guess is that mark was there when you bought the pistol. And you are just now noticing it. I would be interested in thoughts of those with more 92 experience than me however.

[Joe in PNG]

I suspect it to be a proof mark of some sort.

If you look at the photo on the Brownells page (https://www.brownells.com/handgun-parts/barrel-parts/barrels/barrel-92-inox-assembly-prod75725.aspx?avs%7cMake_3=Beretta), you can see the exact same mark.

[Maca]

I suspect it to be a proof mark of some sort.

If you look at the photo on the Brownells page (https://www.brownells.com/handgun-parts/barrel-parts/barrels/barrel-92-inox-assembly-prod75725.aspx?avs%7cMake_3=Beretta), you can see the exact same mark.

Thanks a great find! Thank you.

[TiroFijo]

Well, kind of, but not really, maybe a little bit.:)

The locking block is the mechanism that holds the slide forward and locked up. When the gun fires, the barrel wants to move forward, with the direction of the bullet. The brass case expands to fill the chamber and keep "most" if not all of the gases moving behind the bullet toward the muzzle. The locking block ''ears" hold the barrel into the slide keeping it from moving forward. It is being pulled forward by the barrel and pushed up by the frame and the disassembly lever.

As soon as the bullet exits the barrel, the pressure pulling the barrel forward drops, but the remaining pressure in the barrel is pushing the barrel rearward suddenly. The barrel and the slide move rearward together for a short distance as the locking block is pushed down by the locking block plunger, which is hitting the frame right below the chamber, and as it comes off of the disassembly lever and frame, allowing it to move downward away from the barrel. The "ears" of the locking block disengage from the slide allowing the barrel to fully un-lock from the slide.

There are more details, but that is the basics of how the locking-block work.

As with any other pistol that is recoil operated with a locked breech, the barrel+slide start moving rearwards as soon as the bullet starts moving forward. The barrel+slide recoil a small distance (normally in the order of 0.1") at the moment of bullet exit, and the jet effect of the expanding gases leaving the bore behind the bullet give it a little boost.

Easy to see in any slow motion video detailing the moment of bullet exit.

[Evil_Ed]

As with any other pistol that is recoil operated with a locked breech, the barrel+slide start moving rearwards as soon as the bullet starts moving forward. The barrel+slide recoil a small distance (normally in the order of 0.1") at the moment of bullet exit, and the jet effect of the expanding gases leaving the bore behind the bullet give it a little boost.

Easy to see in any slow motion video detailing the moment of bullet exit.

There was a great slow-motion video compilation on Youtube from...I think it was Kurzzeit? One of their compilations; they took an IPSC 1911 (probably 2011 tbh)-pattern gun with a full length dust cover, and then put graph markings lined up on both the slide and frame. When they fired it, you could clearly see the markings start to move/mis-align before the bullet left the bore. I would expect that if a similar thing were done with a Beretta, you'd see the same thing...the barrel/slide start to move back before the bullet left the bore.

[TiroFijo]

There was a great slow-motion video compilation on Youtube from...I think it was Kurzzeit? One of their compilations; they took an IPSC 1911 (probably 2011 tbh)-pattern gun with a full length dust cover, and then put graph markings lined up on both the slide and frame. When they fired it, you could clearly see the markings start to move/mis-align before the bullet left the bore. I would expect that if a similar thing were done with a Beretta, you'd see the same thing...the barrel/slide start to move back before the bullet left the bore.

Twenty years ago slow motion videos detailing everything were hard to get, they were expensive and manufaturers treated them like inside information.

I wrote to Werner Mehl ten years ago asking for that close up, and predicting the amount of slide movement, and he kindly obliged... :)

https://www.1911forum.com/threads/1911-dynamics-2.3141/

Sadly it is no longer on his site or YouTube

There is also footage of a cutaway 1911 made by Virgil Tripp showing the same thing, he made it after some email exchanges with me, even engraved the front of the frame to measure the movement.

[Evil_Ed]

Twenty years ago slow motion videos detailing everything were hard to get, they were expensive and manufaturers treated them like inside information.

I wrote to Werner Mehl ten years ago asking for that close up, and predicting the amount of slide movement, and he kindly obliged... :)

https://www.1911forum.com/threads/1911-dynamics-2.3141/

Sadly it is no longer on his site or YouTube

There is also footage of a cutaway 1911 made by Virgil Tripp showing the same thing, he made it after some email exchanges with me, even engraved the front of the frame to measure the movement.

So we have you to thank for those videos! Awesome! I remember when they hit youtube way back when, and they were super illustrative of how things actually work in a Browning-type locked handgun. It really opened my eyes up as to the physics and timing behind things.

[TiroFijo]

So we have you to thank for those videos! Awesome! I remember when they hit youtube way back when, and they were super illustrative of how things actually work in a Browning-type locked handgun. It really opened my eyes up as to the physics and timing behind things.

How it all originated...

https://www.1911forum.com/threads/1911-dynamics.2977/

It is amazing what an exchange of ideas between people who live on the other side of the world and do not know each other but share a common interest/hobby can lead to, the magic of internet forums and email.

[zaitcev]

Most guns made today do not have barrels start tilting before the bullet exits the bore. They do it by having a little straight area in the cam cut. But most are designed so that it starts unlocking immediately. I saw some videos that were done at such speed that bullet's outline is captured, and the barrel starts to tilt when bullet is literally inches away from the muzzle.

[TiroFijo]

Most guns made today do not have barrels start tilting before the bullet exits the bore. They do it by having a little straight area in the cam cut. But most are designed so that it starts unlocking immediately. I saw some videos that were done at such speed that bullet's outline is captured, and the barrel starts to tilt when bullet is literally inches away from the muzzle.

All recoil operated, locked breech pistols start recoiling the barrel + slide before the muzzle exits the bore.

But no pistol is designed so that the barrel tilts or rotates before bullet exit. Not in the 1911 with its barrel link, not in more modern "improved browning system" where the caming surface is in the bottom of the barrel, in a Walther/Beretta whith a locking block, or a PX4 with a rotating barrel.

In a tilting barrel design when there is early tilt (the barrel starts unlocking before bullet exit) is st for some reason you see drag marks on the primer and vertical stringing.