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Old August 13, 2020, 07:29 AM   #1
arcticap
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Diagrams - How to Adjust the Colt Lug Joint



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Old August 13, 2020, 09:54 AM   #2
Deltadart
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How is the lug adjusted when the revolver shoots high?
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Old August 13, 2020, 09:47 PM   #3
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It can shoot high for different reasons.

1. The low front sight can cause it to shoot high.

or

2. The arbor is short and needs to be corrected.

The first thing to do is to determine if the arbor is short and then shim it.
Then if the gun shoots high, at least you know that it''s not the arbor.
So you could adjust the sight.

These diagrams are mostly informational.
If most folks don't shoot past 25 yards, then they may not need to worry about how well their gun shoots beyond that distance.
And with modern manufacturing methods, the lug /frame joint may be well squared at the factory.
I don't know how much trajectory changes by adjusting the arbor and setting the barrel cylinder gap.
That may depend on how the gunsmith shims the arbor.
But some C&B gunsmiths do make these adjustments if they feel that it's needed and are getting paid to do it.
I thought that the diagrams were interesting.

Last edited by arcticap; August 14, 2020 at 09:15 AM.
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Old August 13, 2020, 11:12 PM   #4
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Even with the arbor/lug corrected a .44 Colt style revolver is going to shoot high. The .36 will shoot high but not as much.
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Old August 14, 2020, 07:54 PM   #5
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What part is the lug? Where the barrel meets the frame and has the two locating pins? This term is new to me.
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Old August 14, 2020, 10:23 PM   #6
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So if my 3rd model Uberti Dragoon shoots 1 ft high at 50yds with 40 gr 3f behind a round ball is that too much.
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Old August 15, 2020, 01:27 AM   #7
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I don't think so, their effective range is listed as 80 yards.
I thought that the combat sights were sighted in for 75 yards.
IIRC soldiers were trained to aim for the enemy's belt buckle or the midsection just above it.
By aiming that way the high shot would hit the vitals.

Last edited by arcticap; August 16, 2020 at 12:27 AM.
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Old August 15, 2020, 10:36 PM   #8
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I can attest to the 80 yard effective range. That .454 lead ball seems to pattern, sort of, up to about that range but drops off quick after. Shooting steel at a hundred I noticed impacts squirreling all over the place, where I was able to hit half size plates at 50 yards 10/10 times.
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Old August 16, 2020, 09:42 PM   #9
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Those are really interesting charts arcticap - thanks for posting.

Most of my shooting over the years has been with '51 Navies - a variety of makes but now a Uberti. All of them have shot high and I think the tendency for many of us is to either develop our sight picture to compensate for it or raise the front sight - I did that on a number of them as it was easy to use brass brazing rod to make new ones. The Spiller & Burr is another easy one to do the same way. The first illustration really shows it well how a short arbor can can't the muzzle upwards and just a couple thousandths can make a big difference at longer ranges. I now have a Uberti '51 Navy R & M conversion with 7 1/2" barrel and tomorrow, just out of curiosity,I'm going to put a rigid straight edge form the hammer sight notch to the front sight and see if I can get some measurements from the muzzle to the breech.

As far as shooting left or right - we have all seen the chart that shows how to correct that and IIRC, it is related to your grip (how you grip). On and open top though, a slight can't of just a couple of thousandths could really affect it as the chart shows. You'd like to think that with modern machining, the lug area could be kept square - but . . . .

Each model is of a different configuration - i.e. some have octagon barrels and some round - the '60 Army, "61 Navy,"62 Pocket Police a whole different ball game. So. . . . I'm thinking about it and wondering how yo you could do an easy test to see ir your barrel is canted eft or right by a few thousandths? I'm thinking that you could remove the barrel and cylinder and check the mating surfaces of the barrel and frame with a small machinist square but that would only be accurate if the sides of the frame on each side of the mating surface were machined exactly alike and even if they were, there is no guarantee that they would remain so during the buffing during the assembly / finishing process - the same for the barrels. Anyone have any ideas on a good way to check that?
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Old August 17, 2020, 07:42 PM   #10
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I have made new, taller, front sights to correct elevation, with brass rod and even an old silver dime. Rarely had a bad windage problem and shot steel plates in Cowboy Action. I used an abrasive cutting wheel in the Dremel to widen the rear notch in the hammer on a couple of them, that worked fine.
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Old August 19, 2020, 01:56 PM   #11
arcticap
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Bedbugbilly,

A competition gunsmith posted:
"Normally the frame and lug are fine. It's usually after someone has "tinkered" with it that it needs attention. So, I've only had to "correct" that joint very few times. Correcting the arbor to a .0025" - .003" bbl / cyl clearance rarely makes for an elevated barrel of any significance. The main thing is having the same revolver every time you assemble it ( driving the wedge in). Correcting the sight picture on that setup gets you on target and keeps you there." --->>> https://www.thehighroad.org/index.ph...-joint.873231/

Gauges should be able to determine if surfaces are flat.

I suppose that "if" everything were determined to be squared and properly set up, then it would indicate a problem with the bore alignment relative to the frame...that the bore was not straight.
And that's where the shims can play a role to see how much that the bore is off center.
So maybe it's not the lug per se, but adjusting the lug joint can help to correct bore misalignment.
In addition to using the shims, there's an inexpensive bore sighting laser for handguns that's adjustable from .17 - .78 caliber.
The laser device could possibly help to get a bore to align with a target at various distances with the shims in place.

Then the gun could actually be test fired to see if the sight picture lines up with the POI of the new bore alignment before any permanent adjustments are made to the lug.

635-655nm Windage Elevation Adjustable Red Laser Boresighter Bore Sighter Kit For Hunting .17 To .78 Caliber Hunting Hand Gun

https://www.aliexpress.com/item/3284...E&gclsrc=aw.ds

Last edited by arcticap; August 19, 2020 at 02:06 PM.
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Old September 1, 2020, 08:16 PM   #12
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How do you adjust arbor length?
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Old September 1, 2020, 11:46 PM   #13
45 Dragoon
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Some folks weld material to the end of the arbor, some drill and tap the arbor so they can screw in a set screw (not good), some will stack washers/shims. I like the idea of a single full size spacer that is mounted in the arbor hole. That allows the end of the arbor to fully contact a solid "connector" in the barrel assembly and under tension (from the wedge being properly "driven" in) so the two assemblies will respond as a single unit each time the revolver is fired. It is the length of the arbor that determines the barrel /cylinder clearance of the assembled revolver. I like a .0025"- .003" clearance on cap guns, .002" for cartridge guns.

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