I noticed that that are different barrel link (b-l) sizes. When does someone fit a b-l of < .278" and that of > .278" to a barrel?
I also noticed that my slow fire shots (handheld using string of eight shots) hit 2" above the point of aim (POA) at 25 meters (m) when wth an Ed Brown b-l .278" in an Ed Brown barrel. But my shots hit 7" above POA at 25m when I put in a Wilson b-l .278" in that same barrel. Why is that so?
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I noticed that that are different barrel link (b-l) sizes.
There are indeed. Here's all the different sizes I was able to find a few years ago:
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When does someone fit a b-l of < .278" and that of > .278" to a barrel?
It all depends on how the barrel is fitted to the slide and frame and the various dimensions of those three parts. An individual gun may have more than one proper sized link, and its length (their lengths) are selected to meet the following criteria:
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I also noticed that my slow fire shots (handheld using string of eight
shots) hit 2" above the point of aim (POA) at 25 meters (m) when wth an Ed
Brown b-l .278" in an Ed Brown barrel. But my shots hit 7" above POA at 25m
when I put in a Wilson b-l .278" in that same barrel. Why is that so?
That does seem weird, because your POI's seem to indicate the Ed Brown link is about 0.022" shorter than the Wilson link! Must be something else going on inside your gun. And I don't know how sizes are marked on Ed Brown links.
Thank you very much. It's indeed very informative.
I just placed back the Ed Brown link in its barrel. I can live with the 2" just above the POA at 25m . Honestly, I'm still figuring it out. The pistol is a Norinco fitted with a drop in Ed Brown barrel. I shoot it 200gr LRN loaded 6.4gr V-V N340.
If the links are both standard "278" links and not worn too much, the web between the holes should measure 0.097"/2.46mm, as shown here:
But if they are different, that difference should be visible with magnification if the links are placed one atop the other.
Another possible reason for the 5" difference in POI's would be if the link pin was badly worn in the center on one side.
What kind of gun it this?
If you know one of the links is an Ed Brown link, it probably is a 278 link because that's the only size listed on the website:
http://www.edbrown.com/barrels.htm
If so, the Wilson link would, I think, be longer than a 278 link.
Few things I noticed 1) that Wilson nr.3 is thicker (0.137") that Ed Brown (0.135"). 2) The distance between the bottom end of slide stop (ss) hole to the surface bottom center of the Ed Brown b-l link is .87"; Wilson b-l's is .77". 3) The Ed brown has a chamfered ss hole,whilst Wilson is not.
Both b-l look the same viewing through the naked eye until one looks into their details. Would the anatomic variances of the b-l's give a difference in hits despite with the same center to center b-l distance?
BTW, the hand held slow fire shots were were done about three times on different occasions. I used the magazine as a distance guide. I just stopped doing it lest I ruin my barrel and the link pin through replacings.
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Few things I noticed 1) that Wilson nr.3 is thicker (0.137") that Ed Brown
(0.135").
The maximum thickness is 0.136", but as long as the Wilson is free to swing on the barrel and fits in the relief slot in the frame it shouldn't make any difference. However...
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2) The distance between the bottom end of slide stop (ss) hole to the
surface bottom center of the Ed Brown b-l link is .87"; Wilson b-l's is
.77".
...indicates the Wilson link is too wide in this area. It should be between 0.07625" and 0.08175", so it's about 0.005" too wide.
If all the parts involved are within specs, the bottom of the link should come no closer than 0.014" to the bottom of its clearance slot. Is there any evidence the bottom of the Wilson link is contacting the bottom of its clearance slot in the frame?
True, it Wilson nr. 3 was a bit fit and stiff (no freeplay) when I placed it.
No sir. I placed the slidestop and the link and it was not touching the bottom. I viewed it with a help of a bright light.
I have no idea how two different links that are the same length could cause a 5" shift in POI at 25m. Even the fact that the Wilson link is a bit thicker than it should be and is not truly free-swinging when pinned to the barrel doesn't seem too important to me.
But it should be free-swinging, so maybe stoning or filing it down might help.
Maybe somebody else has an idea. I'm out of them.
I placed the Wilson Nr. 3 link in an Ed Brown barrel out of curiosity and tested it. That's how I found that kind of discrepancy. I replaced it back when I couldn't figure out either. That's the time I started typing an SOS in this forum
As an inveterate tinkerer, I might do it again in another barrel some other time until I figure out.
The dictum still stands, "Don't fix a thing that is not broken."
I'm starting to grasp at straws on this one, but do this the next time you have both links off the barrel. Refer to the drawing in Post #4 and measure the distance shown as "0.4590 +/- .0015" on each one. The pointy ID nibs on most slide calipers do a much better job measuring this than the rather stubby OD jaw tips do on the 0.097" web between the holes - because they go farther into the holes.
Any significant difference between these measurements may have something to do with the POI difference - the link with the longest ".459" might give the lowest POI. Maybe.
P.S.: Any other Forum member with an idea is more than welcome to chime in - I'm dyin' here!
If the barrel is being held out of the lugs by a couple thousandth of an inch this would made a change of a few inches in POI over the 25 meters.
5" over 25 meters would roughly equate to 1/4deg or about .004" change in the lockup.
The Wilson link is either shorter or the excess thickness is causing it to hold the barrel down.
Keep in mind that the link is first and foremost a method to unlock the barrel. Some people think they can use the link to improve accuracy by forcing the barrel higher and tighter into the upper lugs. That method can work to some extent, but the barrel ideally should not stand on the link in the first place. Second, as you force the barrel higher, you are changing the unlock timing and may eventually cause the upper lugs to crash. Third, you are altering the position of the firing pin relative to the primer.
It sounds to me like the source of your inaccuracy is because of overall barrel slop and not simply a link problem. For accuracy, the barrel has to return to the same place every time and a number of things besides the link are involved. Ideally, the link would have no effect at all on the accuracy of the gun, because the barrel feet would be standing on the slide stop pin. I would recommend starting anew with a Kart EZ fit barrel and a better bushing. Link fitting is the last step in barrel fitting, not the first.
Well Lazarus, in my busy day I've been trying to ask the question about the link-binding method of accuarcy improvment. I wasn't taught to fit barrels and links that way. I too agree that the barrel's feet should sit on the slide stop pin. I have "fixed" one pistol that was link-bound by welding the feet and re-cutting them? May save the price of a new barrel. But a new Kart EZ fit barrel would be cool for Vito.
I'll keep this in mind. After I replaced the Wilson Nr 3 link to the original Ed Brown Nr. 3 link, the pistol just shoots 2" up the POA which suits me fine. I might try this in my spare barrel (Taurus) in my quest to built a pistol. I am still waiting for my receiver to arrive in order to finish this business. This spare barrel is fine in its original stamped barrel link but would shoot 2" low from the POI if I place in the Wilson Nr. 3 link and shot it in my Norinco pistol.
Honestly, I find it a bit boggling (and exciting) that thousandths of an inch in would really give different results.
If your 4" change in POI at 25 meters is due to nothing but a change in link length, the change in link length would theoretically be 0.018".
Vito... don't get an ulcer over this-lol...
...My take on it is no two barrels are machined exactly the same. The line of the bore in each of the barrels could be machined off center. Also,the placement of the barrel link "hole"in the lower lugs might be off slightly between the two barrels. Just because the armory drawings call for a certain spec doesn't mean that is what you have since you are dealing with two different manufacturers.
Best way to troubleshoot this problem is to start by measuring your barrel lockup into the upper slide lugs and adjust up or down from there and then refit the lower lugs, and finally select a link to properly time the barrels link down. Then adjust your sights. Unfortunately, I don't have the time or energy to outline a complete hard fit barrel installation with theory and specifications tonight.
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"But my shots hit 7" above POA at 25m when I put in a Wilson b-l .278" in
that same barrel."
I must have not read Vito's posts correctly. I was under the impression he was talking about the same gun & barrel - with the only difference being a link swap. Time for a little remedial reading?
Edit: This is where (in Post #1) I got that impression:
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I wasn't taught to fit barrels and links that way.
What way was that?
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I have "fixed" one pistol that was link-bound by welding the feet and re-
cutting them?
Yes, this was done early on along with adding metal to the upper lugs and hood. This was before NM barrels were available. Labor intensive!
If you think about it, given enough metal on the critical surfaces, the most important thing to think about is to maximize upper lug fit into the slide recesses. Unfortunately, you can't do it by trial and error because the barrel hood is in the way and it should be cut after the upper lugs, not before. That trick assumes you have an adequate way to measure both the barrel upper lugs and the slide recesses. Most people settle for lug #1 in bearing only, acceptable for most work, but definitely not the ideal.
After getting the best upper lug fit possible and assuring your firing pin is lined up, then the focus shifts to the barrel feet relative to the s.s. and finally to the link length.
All those things are done with a loose (sloppy fit) bushing. Fitting the working bushing is actually the last step before range testing - or some might say 'lug equalization' at the range. These days, lug EQ happens slowly or not at all because the steels are harder. If only one lug is bearing and the other 2 aren't even close, the only result is that your hood to breech face gap (and headspace) open up a little.
Yup, it's just link swap between the original Ed Brown nr.3 and Wilson nr. 3 barrel links. I am using it in my Norinco. The barrel is a 5" drop in Ed Brown.
I have a gut feeling that it's not in the link but somewhere between the link and receiver. I may be just looking in a wrong place. I'll resume that quest when I my new receiver arrives. Same barrel and those two link swapped together but with different slide and receiver which are STI's. The slide and receiver are for a new build. I'll just piggyback this little unfinished business until I figure out what's really happening.
Why don't you just adjust your POI with a sight-change or filing if the barrel works well with that link?
I'll do it with a new build. I'll put an adjustable rear sight just in case. I don't want to muck up something until I really find cause to this kind of silly puzzle.
I don't try to do that with my Nork since I have it with a good fixed sight. I know where to place my aim to get a good shot. I have a feeling that the root cause could be in the Nork receiver and not the link itself.
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I have "fixed" one pistol that was link-bound by welding the feet and re-
cutting them?
When you welded and recut the barrel pads, did you send the barrel to have it rehardened?