Locking Block/Barrel

[big50_1]

Have a G17 from 1995 that is in good shape and shoots "OK". If I press on the back of the barrel hood when the barrel is in battery, the hood goes down about 1/16". If I put a heavier recoil spring in, the hood is more resistant to going down (and a little more accurate). My question is should there be any movement at all? Oviously, the barrel does not lock up on the locking block and is kept tightly in-battery by the recoil spring. Also how to fix this if not right, new locking block or barrel? Sincerely, Lee

[DannyR]

The movement is normal.

[Bren]

Originally posted by big50_1
Oviously, the barrel does not lock up on the locking block and is kept tightly in-battery by the recoil spring. Also how to fix this if not right, new locking block or barrel? Sincerely, Lee
The barrel isn't supposed to lock on the locking block - the locking block works like the barrel link on a 1911, to move the barrel up and down - it locks to the slide.

[big50_1]

Just a clarification. I am trying to understand the uniqueness of the Glock design. I understand that usually browning tilt-style barrels lock on the bushing (or hole), barrel hood (in a SIG style) and lower locking lugs or "feet" (triangulation). If the the Glock doesn't lock on the "foot" under the hood/chamber then it appears to lock on the front slide barrel hole (whatever it's called), the hood/slide interface and the back of the recoil spring guide that presses on the barrel "foot" under the hood/chamber. Make sense? My concern is that for accuracy the barrel/slide/frame needs to lock-up the same shot-to-shot. On a 1911 or BHP, the lower lock-up is crystal clear: it is on the barrel lug(s) under the chamber and they lock up solid. But when the Glock is locked up, only recoil spring pressure on the barrel lug, through the back of the spring guide seat, is keeping the hood as high and to-the-rear as possible. That would mean that the greater the recoil spring pressure the better the barrel/slide would lock together. There would be a practical limit whereby you could make the spring so heavy that you couldn't rack the slide and the returning slide would damage the slide stop. Just trying to understand. Thanks for any info.

[Bren]

Originally posted by big50_1
Just a clarification. I am trying to understand the uniqueness of the Glock design. I understand that usually browning tilt-style barrels lock on the bushing (or hole), barrel hood (in a SIG style) and lower locking lugs or "feet" (triangulation). If the the Glock doesn't lock on the "foot" under the hood/chamber then it appears to lock on the front slide barrel hole (whatever it's called), the hood/slide interface and the back of the recoil spring guide that presses on the barrel "foot" under the hood/chamber. Make sense?

"Locking" refers to locking the barrel and slide together while in battery and during the beginning of recoil. The locking parts are the barrel and slide locked together at the barrel hood. The locking block is like a ramp that causes the barrel to slide up and down at the proper time in the slide's travel. The locking block holds the barrel up in a locked position, but it isn't making any locking connection on the barrel to prevent front/back movement. The bushing or hole at the front end of the slide isn't involved in the lock-up.


My concern is that for accuracy the barrel/slide/frame needs to lock-up the same shot-to-shot. On a 1911 or BHP, the lower lock-up is crystal clear: it is on the barrel lug(s) under the chamber and they lock up solid.

The locking lugs on a 1911 are above the chamber. They serve the same purpose as the barrel hood on a Glock - locking slide to barrel. Under the barrel is the barrel link, which rotates to push the barrel up into the locking lugs. There is no such thing as a lower lock-up, unless you are just referring to the link, which doesn't lock the barrel to the slide, but does push the barrel up into its locked position and pull it down to unlock.


But when the Glock is locked up, only recoil spring pressure on the barrel lug, through the back of the spring guide seat, is keeping the hood as high and to-the-rear as possible.

No, the barrel is resting on the locking block, which holds it up


That would mean that the greater the recoil spring pressure the better the barrel/slide would lock together. There would be a practical limit whereby you could make the spring so heavy that you couldn't rack the slide and the returning slide would damage the slide stop. Just trying to understand. Thanks for any info. [/B]
The main problem with a heavier recoil spring it that the gun no longer works. The recoil spring has to have enough force to pull the slide forward and allow the locking block (or barrel link in a 1911) to lock the barrel and slide together, and it does keep the slide from moving enough to unlock the barrel/slide, but it has to be weak enough that the force of a round being fired will move the slide far enough to the rear to extract, eject, cock, feed, etc.

[big50_1]

Appreciate the comments. You learn something new every day!

[One Ragged Hole]

A good 1911 smith always looks for FULL contact between the locking lugs, (side to side pattern also) and the slide release. This prevents the barrel hood from being pressed down, pushes it into the slide, hence a tighter lockup. The less movement in the barrel hood the better for accuracy, but some is normal in the Glock design.
O-R-H

[RandySmith]

When in battery, the barrel lug will rest on top of the locking block as shown in this picture.

http://www.dt-concepts.com/images/cutaway-barrelluglockingblock.jpg

The entire slide might move on the frame a bit but the barrel shouldn't move relative to the slide when pressing down on its hood.

Also, the hole in the end of the slide will 'lock' with the end of the barrel when in battery. With an unloaded pistol and the slide in battery, take your finger and move the end of the barrel around. Does the end of the slide not move with it?

There is a test taught in the armorer's course for checking muzzle to slide lock up - a bit long to type though.

Here is a video (http://www.dt-concepts.com/ca/actionunlock.mpg) showing the action unlocking as the slide moves to the rear. The video was done to show how the locking block forces the end of the barrel down and, as such, the angle of the shot isn't the best to show the barrel lug resting on top of the locking block. The locking block DOES force and hold the barrel into the upward position when the slide is in battery.

Randy

[big50_1]

Thanks for the reply. No button for a video came through, so if you could send the URL or shortcut for a video that shows the Glock lockup, I'd appreciate it. To clarify, the hood on a Glock should NOT move down when pressed. If it does, should it be sent to the factory or should I get a locking block to replace the existing one?

[SlammedDime]

Originally posted by big50_1
Thanks for the reply. No button for a video came through, so if you could send the URL or shortcut for a video that shows the Glock lockup, I'd appreciate it. To clarify, the hood on a Glock should NOT move down when pressed. If it does, should it be sent to the factory or should I get a locking block to replace the existing one? Click the word 'video' in Randy's post. :)

[Steve in Az]

I see what he is saying. You'll notice than when you do push down on the barrel hood, the reason its moving down slightly (mine moves about 1/32") is because you're forcing the barrel/slide to cam back slighty.

Push down on the hood and watch the rear of the slide...

Because there is just a small engagement between the barrel lug and locking block, what you are doing is actually forcing the entire assembly back, "camming" the barrel down the back of the locking block, hence the slide moves the same amount of distance rearward.

[Bren]

Originally posted by RandySmith
[B]The entire slide might move on the frame a bit but the barrel shouldn't move relative to the slide when pressing down on its hood.
I think he is talking about that tiny 1/32-1/64 or so movement when you push down and the barrel dips and slide moves a hair and stops. I just tested that on 3 glocks of different ages and generations - they all move about 1/32 (maybe less) down in relation to the slide when you push down on the barrel hood.

Also, the hole in the end of the slide will 'lock' with the end of the barrel when in battery.

I think you (and maybe Glock armorers) are using the term "lock" in a nonstandard way there. Locking is a step in the cycle of function where the breach is locked closed to contain the force of the round being fired. The end of the barrel and slide may fit tightly together and may move together by virtue of the fact that the slide and barrel are solidly locked together at the barrel hood, but there are no locking surfaces between the muzzle end of barrel and slide - i.e., cut out the section of slide in front of the barrel hood and the slide can move freely back and forth (except for spring pressure) without the barrel needing to move down, back or anything else.

[RandySmith]

I think he is talking about that tiny 1/32-1/64...


That could be. I didn't measure it, but it doesn't seem like anywhere near a 1/16".


I think you (and maybe Glock armorers) are using the term "lock" in a nonstandard way there.

That could be too. It is hard to say and mean 'lock' without using the term 'lock'. It is more like a bind, in that the barrel is binding in the limits of movement allowed by the hole in the end of the slide. Once 'bound', it is very tight.

Randy

[big50_1]

Interesting comments. For Glock Armorers: does Glock say anything about barrel/slide/locking block lockup (when you have to replace the locking block or barrel)? -- By 'lock' at the front of the barrel, I mean up-and-down motion is minimized or prevented, not back-and-forth. -- Will a recoil buffer extend the life of the frame? Does it matter? Chuck Taylor has well over a hundred thousand rounds through his G17 and that is a lot of life-times of shooting for a lot of people and the gun is still going. I use a buffer and have been firing the G17 since 1995 and the place where the front of the slide hits the frame looks brand new (no plastic deformation). Does Glock have a design life-number-of-rounds for their pistols?

[RandySmith]

For Glock Armorers: does Glock say anything about barrel/slide/locking block lockup (when you have to replace the locking block or barrel)?

No. These parts aren't replaced unless broken.


By 'lock' at the front of the barrel, I mean up-and-down motion is minimized or prevented, not back-and-forth.

You won't have relative movement between the slide and barrel in any direction (left/right, up/down, or fore/aft) with proper lock up.


Will a recoil buffer extend the life of the frame? Does it matter?

No. These are gimmicks. I don't have a gun in front of me right now to look at, but I cannot think of a single place where the slide contacts the frame in normal operation (save from the rails - although, that isn't the steel on polymer contact you were eluding to).

I have never seen a design lifetime specification for a minimum number of rounds.

There are (supposedly) guns with over 1M rounds through them.

Randy

[big50_1]

By polymer-to-steel contact I mean the front part (lug, flange, ??) of the slide that goes around the guide rod recoils back and hits the plastic frame. That projection of the slide prevents the slide from coming backward off the gun. Apparently the Glock plastic is hard or resiliant enough to take repeated impact without significant permanent deformation.

[big50_1]

Just after I posted the above, I realized the slide would be prevented from coming backward off the frame also by the interaction of the slide, barrel and locking block if the projection that goes around the guide rod broke off.

[Steve in Az]

Originally posted by Bren
I think he is talking about that tiny 1/32-1/64 or so movement when you push down and the barrel dips and slide moves a hair and stops. I just tested that on 3 glocks of different ages and generations - they all move about 1/32 (maybe less) down in relation to the slide when you push down on the barrel hood.



Exactly, thats what I'm seeing as well. This is perfectly normal.

[RandySmith]

The nose ring (part of the slide that circles the guide rod) does not impact the frame during recoil.

The slide is held on (the frame) by the barrel, which is held on the frame by the slide lock.

Randy

[RandySmith]

Originally posted by big50_1
By polymer-to-steel contact I mean the front part (lug, flange, ??) of the slide that goes around the guide rod recoils back and hits the plastic frame. That projection of the slide prevents the slide from coming backward off the gun. Apparently the Glock plastic is hard or resiliant enough to take repeated impact without significant permanent deformation.

Ok - I finally got some time to sit down and look at this with a pistol.

The contact points between the slide and frame when the slide is moving to the rear are: 1) right above the nose ring on the side and 2) the steel-reinforced polymer section of the frame just forward of the front slide rails.

Can you see the steel in that area? It is exposed on both of the guns I looked at here.

Randy