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Sorry up front, I may not have the nomenclature down on this.. It's really been one of the last areas I don't fully understand about the 1911 and there is a particular question that has been driving me mildly nuts. There was a thread recently about the VIS cut which was really wonderful about explaining the nuances of what goes on with the link, barrel lugs/feet, and the receiving cuts on the receiver. First off, what does VIS stand for? (vertical interface surface?) Secondly, and my main question.. as the barrel moves upward and forward toward lockup/battery, the link pivots until the lug feet mate with the slide stop and the link holes are vertical. Is the link itself the spacer that determines how tight the upper lugs mate with the slide cuts? I have seen Wilson link sets marked 1 - 5 and it seems logical that this is the story. But you know what they say about assuming :rolleyes: What say you experts? As a follow up, I have pressed downward on all of my Colt's barrel hoods with the pistols in battery. My GI pistols and a well used 70 Series from 73 have a slight dip when pressed. (It is slight, I have felt other off brand or parts guns with a more significant dip) All of my other late model Colts have a rock solid barrel lockup when pressed. As I understand it, tight lockup is essential in bringing out the best accuracy. How bad is it at the other end of the spectrum with a sloppy barrel fit? Do you just lose accuracy or can you prematurely wear out or cause other damage? Is it worth while to buy new links for the GI pistols or is the slight dip just ok milspec looseness? Thanks for reading and big thanks for knowledgeable responses! Finally I raise my drink to Army Chief- Thank's for the good reads, I'm extra sorry to see that you were so young.
 

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Sorry up front, I may not have the nomenclature down on this.. It's really been one of the last areas I don't fully understand about the 1911 and there is a particular question that has been driving me mildly nuts. There was a thread recently about the VIS cut which was really wonderful about explaining the nuances of what goes on with the link, barrel lugs/feet, and the receiving cuts on the receiver. First off, what does VIS stand for? (vertical interface surface?) Secondly, and my main question.. as the barrel moves upward and forward toward lockup/battery, the link pivots until the lug feet mate with the slide stop and the link holes are vertical. Is the link itself the spacer that determines how tight the upper lugs mate with the slide cuts? I have seen Wilson link sets marked 1 - 5 and it seems logical that this is the story. But you know what they say about assuming :rolleyes: What say you experts? As a follow up, I have pressed downward on all of my Colt's barrel hoods with the pistols in battery. My GI pistols and a well used 70 Series from 73 have a slight dip when pressed. (It is slight, I have felt other off brand or parts guns with a more significant dip) All of my other late model Colts have a rock solid barrel lockup when pressed. As I understand it, tight lockup is essential in bringing out the best accuracy. How bad is it at the other end of the spectrum with a sloppy barrel fit? Do you just lose accuracy or can you prematurely wear out or cause other damage? Is it worth while to buy new links for the GI pistols or is the slight dip just ok milspec looseness? Thanks for reading and big thanks for knowledgeable responses! Finally I raise my drink to Army Chief- Thank's for the good reads, I'm extra sorry to see that you were so young.
VIS: Vertical Impact Surface. Commonly machined so that a bowtie stands out from the frame. Barrel legs smack that surface at a point closer to where they are attached, so that the bending stress experienced by the steel in that area is minimized.

A slight dip when pressing on the barrel hood is perfectly normal, just not ideal. The 1911, and especially Colts, are built as combat pistols. The looseness just means that they can take a bit more dirt, sand, and grime and keep chugging right along. Ideally, a tighter-fit pistol will run longer than one that is fit very loosely. Most Colts will provide a service life much greater than the large majority of buyers will run them through. A VERY sloppy fit should be corrected, as it can cause relatively premature failure.
 

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The link's primary function should be to tether the barrel to the slide stop pin and force it down during recoil to clear the upper lug engagement before the barrel stops against the VIS. It can also start the barrel up and pass off to the lower lug on the way to battery. Some do not want the link to do anything on the way to battery, only to tether the barrel out of the battery position during recoil. Okay two theories, and ride the link, makes three.

First realize the link goes past center, the slide stop pin and barrel link pin are not vertical when in battery. The slide stop pin hole is slightly oversize which allows the barrel to stay in the battery position for .100" ± of slide movement before the link runs out of allowable length and tethers the barrel down. Ideally the lower lug sits on the slide stop pin when in battery.

Ride the link. This is a production method of barrel prep where the lower lug only stops the barrel's forward movement. And the link holds the barrel up. That's what you have when you can push the barrel down a little in battery. The barrel's position is then positioned solely by the link. As the barrel is pushed forward by the breech face it rides the link, as the link reaches TDC the barrel's chamber end is as high as it can go, however the barrel feet are not yet stopping the forward movement by .050"±. This works as the link pin hole is oversize enough to first push up in compression, and then as it travels the last .050" the barrel is held by the breech face contact under force exerted by the recoil spring, as the link is now in extension.

The gun fires, barrel is pulling forward by the drag of the bullet in the rifling, and the slide is pushed to the rear by the case head bearing against it and the expanding gases between. The slide not allowing the case to budge pulls the barrel back approximately .100"± as the bullet exits, and link down begins. During this phase while the bullet is in the barrel the links position has changed from in extension to compression and back to extension, this in .100" of slide/barrel movement, no foul, as the barrel's position wasn't changed relative to the frame.

The downside to this arrangement is the barrels in battery starting position isn't an exact position as evidenced by your ability to push the barrel down at the chamber end when in battery. So function is acceptable, production is high, but accuracy may suffer.

Better that the lower lug is cut such that it is in contact with the slide stop pin, standing on the pin, not the link.

Hopefully a little light to a very simple design, that gets very complicated. :hrm:

LOG
 
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Good explanation, yet again, Log.
 

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Wow log its good to have people like you around here my head hurts from information overload lol
 

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Barrel links and sizes

I have seen Wilson link sets marked 1 - 5 and it seems logical that this is the story.
Barrel links come in different lengths, but the length is really a measurement of the space between the two holes of the link.....so the wider the distance between the two holes of the link, it is referred to as a "longer link."

The proper link size is important, and is determined by the way the lower barrel feet are cut. Once the lower lugs of the barrel are properly cut, the next step is to find the correct link length:

First measurement: measure the distance from the bottom of the barrel link hole to the to the lower lug surface of the barrel where it will contact the slide stop pin when the barrel is locked into battery.

Second measurement: measure the distance between the two holes of any barrel link. You need to find the proper barrel link length where the second measurement is equal to or slightly longer than the first distance measured.

You then have to make sure the link you use will go through the arc of movement so it does not bind on the barrel lugs when the link is rotating.
I use a black Sharpie pen and mark the barrel lugs on both of the outside side surfaces. I then use a drill rod of longer length than a link pin, and place it through the barrel link hole, then position the link on the "outside" of the barrel feet using the drill rod as the link pin. I can then rotate the link and use a sharp scribe through the slide stop hole to mark both sides of the barrel lugs (do one side at a time) to see if any metal has to be removed. The line scribed on the black marked surface of the side of the lug will show you how much metal to remove if needed as the link moves through the arc during cycling.
 

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You then have to make sure the link you use will go through the arc of movement so it does not bind on the barrel lugs when the link is rotating.
I use a black Sharpie pen and mark the barrel lugs on both of the outside side surfaces. I then use a drill rod of longer length than a link pin, and place it through the barrel link hole, then position the link on the "outside" of the barrel feet using the drill rod as the link pin. I can then rotate the link and use a sharp scribe through the slide stop hole to mark both sides of the barrel lugs (do one side at a time) to see if any metal has to be removed. The line scribed on the black marked surface of the side of the lug will show you how much metal to remove if needed as the link moves through the arc during cycling.
Yup, pretty much how I've done it for years.

And Log - good post.
 

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All are good posts.
 

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Thank you all for the posts above. My question is about the length of the link and its effect on the vertical movement between the slide and the frame. I had assumed that it would be good if the link pushed the barrel into the frame with a certain amount of force so that all vertical play is removed from the slide/frame fit. Now after reading the above, I am thinking that maybe that is not the desired effect. Could someone comment on this? What is the goal in terms of the vertical fit between slide and barrel? I understand that all horizontal play should be eliminated -- but what about vertical play? It seems like it would be a good thing to have the link long enough so that the barrel applies constant upward pressure to the slide (at battery), as it would tighten everything up (at least vertically). Is there a reason why the link at battery is not vertical? Obviously if it has to pass through vertical to get to its final position there has to be some clearance but 1) why not have it stop at vertical, and 2) if it has to pass through vertical for some reason shouldn't there be just enough clearance to allow the link to pass through vertical as the barrel locks into battery?
 

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In an ideal world, all vertical play is taken up by the barrels lower lugs riding up and onto the slide stop cross pin. The link should not play a part in this, although in a lot of 1911's, it does.

Regarding your "link going past vertical" comment, remember that the link doesn't actually do anything while the pistol is in battery, it's primary purpose is to pull the barrel down and out of the slides way during cycling. The fact that the link is past vertical is due to the lower lug/slide stop contact. Having them in that position relative to each other lengthens their time together as they start moving back together after the pistol has fired.
 

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My question was more about the idea or goal to fit the parts in such a way that there is force being applied upward to the barrel and slide. I understand that it is better that this upward force be caused by the barrel feet riding on the stop pin -- but it could be caused by the link being long enough also. I'm not asking which is better -- just asking if it is a good goal. Is this upward pressure desirable -- does it lock things up tighter and more consistently -- does it make for a more accurate firearm? It makes sense to me that it would. But if this upward pressure is desirable then why is it important (or is it) to eliminate the vertical movement of the slide to frame fit?
 

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My question was more about the idea or goal to fit the parts in such a way that there is force being applied upward to the barrel and slide. I understand that it is better that this upward force be caused by the barrel feet riding on the stop pin -- but it could be caused by the link being long enough also. I'm not asking which is better -- just asking if it is a good goal. Is this upward pressure desirable -- does it lock things up tighter and more consistently -- does it make for a more accurate firearm? It makes sense to me that it would. But if this upward pressure is desirable then why is it important (or is it) to eliminate the vertical movement of the slide to frame fit?
One, let's assume the barrel is cut to true match specs., that is the first upper lug recess is cut .040"-.045" deep, instead of .055"+. Realize there is considerable difference in the lower lug riding up on the slide stop and causing the upper lug recess to bottom out in the slide, and the barrel riding the link. When riding the link the barrel will be as high as the link can force the barrel at top dead center, and lets assume the exact same place when the lower lug is on the pin, but the barrel goes past top dead center, the link is no longer in compression. So when riding the link the barrel's position is held at the high point simply by the friction between the hood, or barrel face and breech. So not the same thing at all.

LOG
 

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The animations are great, but have yet to see a correct one that shows the slide pulling the barrel back the .100"± it does while the bullet is still in the barrel. The last .150"± is all that is left for complete link down before the lower lug strikes the VIS.

LOG
When I envision the round going off I see the slide being forced backward and the barrel being forced forward by the pressure of the expanding gasses that are between the bullet in the barrel and the case head against the breech face. I see the forces being equal and opposite -- but I must be wrong. Why does the slide pull the barrel back while the bullet is still in the barrel?

Thanks, I'm new at this and still trying to visualize what is going on inside the 1911 throughout the entire firing and reloading cycle.
 

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When I envision the round going off I see the slide being forced backward and the barrel being forced forward by the pressure of the expanding gasses that are between the bullet in the barrel and the case head against the breech face. I see the forces being equal and opposite -- but I must be wrong. Why does the slide pull the barrel back while the bullet is still in the barrel?

Thanks, I'm new at this and still trying to visualize what is going on inside the 1911 throughout the entire firing and reloading cycle.
Because the bullet is slipping down the tube and the breech is holding the case head. The pressure is equal in all directions, but the bullet moves, so the slide pulls back.

Another example is a tug of war by two equal opponents, except one has sweaty hands, he lets the rope slip, and the other falls back.

LOG
 

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One, let's assume the barrel is cut to true match specs., that is the first upper lug recess is cut .040"-.045" deep, instead of .055"+. Realize there is considerable difference in the lower lug riding up on the slide stop and causing the upper lug recess to bottom out in the slide, and the barrel riding the link. When riding the link the barrel will be as high as the link can force the barrel at top dead center, and lets assume the exact same place when the lower lug is on the pin, but the barrel goes past top dead center, the link is no longer in compression. So when riding the link the barrel's position is held at the high point simply by the friction between the hood, or barrel face and breech. So not the same thing at all.

LOG
I understand that it is not exactly the same thing -- but I think it is the same principle. The principle being that upward force IS being applied rather than no pressure being applied at all. If it's riding the link and the link in long enough then the link compresses under the load (and maybe other parts spring a little under the load--the pin itself, the rails, imperfections in fit) at vertical but then these parts do not fully decompress when the link gets just past vertical. Like I said I agree that the pressure should be applied by the lug and the pin -- but that is really not what I am asking about -- I'm asking: is it desirable to have upward pressure? If so how much?
 
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