Rear sight off center

[steelslaver]

As some of you know I took and crusty 2" model 15 frame and used a nickle model 19 recessed cylinder and nickle python barrel to make a pinto Smolt.

I took it to the range and it shoots fine. But, the rear sight has to have left almost flush with sight body to center it. I take it home thinking, I must have gotten the barrel not quite perfectly aligned when I changed the threads to .540 36

I turned a 12 in piece of 3/8 round stock to .346 which was the smallest pin gauge I could get in barrel. I drill a 1/16" hole in the end still using lathe. I make a 1 3/4" of 1/16" piece of tig to slip a 1" into tip and have 3/4" sticking out for a pointer. Slide it down the barrel and it hits firing pin hole dead center?? Barrel is not out of line of bent. Plus, the rod slips down barrel and into each chamber with no hang ups.

Front sight is vertical and barrel is a 12 o'clock. I added a ball detent to the yoke that holds the yoke in place pretty firmly with no cylinder. Gun closed up tight and carries up well.

Why does rear sight need to be off center???

 

[WR Moore]

Assuming both frame and barrel faces are square to the bore, and they seem to be...................Hummmmm. By any chance did you shoot it in original condition to confirm POA/POI?

Only things that come immediately to mind are if the sights are actually located on centerline of the barrel/frame. Possible that the hammer is hanging up somewhere on the way down causing the pistol to move. Finally, operator error (apologies, but need to include it).

Only time I've encountered anything like this is a 1911 barrel that somehow got finish machined with the bore off center at the breech end. And, it was wildly off POA.

 

[Pig Hunter]

Do you have a Ransom rest available to use to see if human error is involved ? You might also try different grips ? I know I can move the point of impact around on fix sighted guns with different grips and trigger pressures ie during trigger pull putting a bit more pressure on the right or left side of the trigger. Good luck with your trouble shooting, at least it shoots straight within the adjustment of the sight.

 

[Pisgah]

Only one explanation possible -- you're cockeyed... ;-)

 

[steelslaver]

I do have a home build ransom rest. I did have regular magnas on it which I almost never use. I am used to a few clicks one way or the other being enough. You would think if a groove dia. rod slides down the bore and hit the firing pin hole dead on you would think the barrel is square to the frame. Maybe I should give a hard eye ball to the muzzle or polish it

I never fired it in its original condition. lol

Original condition pic.

 

[D Brown]

Is it possible that the rear sight trough was machined slightly off-center in the frame? Just speculating.

 

[Protocall_Design]

Just because the bore is on center doesn't mean the front sight is. The front and rear sight have to be parallel to the bore. If the front sight is off to one side a little, the rear sight has to be off that much on the same side to match it. You can probably fix it by turning the barrel a little in the frame, even if that's not the particular problem.

 

[weatherby]

On such a short barrel perhaps the crown of the barrel is throwing them off some.

 

[2152hq]

Could the front of the frame be slightly bent?
The front edge of the frame can be square and fit the bbl which is square.
But if the entire front section of the frame is twisted even a couple .000 the end of the bbl is going to point way off target and require a rear sight adj like you have.

Placing a range rod down the bore with such a small tweek to the frame may not show any issue. Certainly not with the chambers as the throats are around .357 and the range rod is .346. That'll slide through easily if there is ay slight misalignment.
As far as the tip hittig the firing pin hole,, that's not really a very precise point of measurement to look at it and say it hit's it. Plus the firing pin hole is not always in the perfect center of the bore line.

Could you mount the revolver in the mill.
Use a point/scribe to indicate the deadcenter of the front sight.
Then crank the mill so the point travels along the sighting plane towrds the rear sight.
See if something is out of alignment, frame, rear sight.

Other than that,,maybe the Colt bbl doesn't like the S&W home.

 

[steelslaver]

I can put it in a mill no problem. But I have held a 2' straight edge across top of recoil shield and a square off rib of barrel. Measurement right at frame and almost 2 ft out match. That is about as square as you can measure such small surfaces.

I realize the mismatch between cylinder throats and range rod. In theory the firing pin is supposed to be centered in frame. That method checks bore alignment better than using something on out side the barrel. Bores are not always centered in barrel or 100% in line with something like the rib.

It is possible sight channel is off a bit or sight body itself is off a bit. I will check in morning. I will also insert rod and then try to measure from it to side of frame at barrel shank and again at recoil shield and do it from both sides of frame.

I think will also explore cylinder alignment to frame. Possible the yoke tube is a bit off. I have not checked that yet DUH.

It no longer has the 2" barrel it has the 6" Python barrel.

I have had other guns with the sight off to one side some. This one makes me extra curious because I put it together.

 

[chief38]

Without actually seeing, holding and shooting your project gun I will reserve comments as I would only be speculating. I'm sure there is a valid reason your sight must remain off center but I have also seen Factory production guns (Smith's, Colts and others) that have similar issues. You sound like a persistent guy who will eventually get to the bottom of this - please let us know.

 

[steelslaver]

I made a rod that just fit in yoke tube with one end that slipped into rod hole and pointed on big end when yoke is closed and rod is presses forward it hits center of bolt tip so yoke is fine,.

I machined a pied of steel that fit between barrel shank and recoil shield with a groove in the center of its length. Installed range rod and placed piece on range rod. The top edge run straight with top edge of frame

Every way I check bore of barrel is square to frame.

Yoke is fine.

But, running a parallel from my mill along the top rib of barrel shoe me to be just the slightest over clocked, On one side their is maybe .002-03 between parallel and sight tang and other side is perfect. The Python rib id a bit wider than sight tang. Also measurement shows the rear of sight body is just slightly off center. Which made me think about the fact I had to replace the badly damaged rear sight blade. When I got it and never even really looked at where it was positioned, just saw it as something that needed to be fixed. Then, more messing around shows the front sight is not quite dead center over bore. Took some figuring with the bottom of barrel on level square, frame level, to prove this to me. More of a problem than the slight over clock for sure. Interesting on the fabled Colt barrel. Maybe why it was not on a gun??

So, it is just a case of a little bit here, a little bit there, tiny bit more in another spot to stack up to a bit more than 1/2 the rear sight opening.

I could turn the barrel back a tiny bit. I could clamp the barrel and use a brass rod and hammer to tap the front sight a bit straighter. But, I will just leave it. I know the whys and except for bring just bit over clocked it wasn't anything I did.

 

[M29since14]

Take your rear sight blade out, trim a few thousandths off the left side, so it doesn't appear to be so off-center, put it back in place… and TRY to forget about it.

 

[steelslaver]

I thought about that. You could trim a bit of one side, but so much and you would see more material on one side of notch than other. I also thought about just making a rear sight blade. Anyone know off hand what thread they are. Take a piece of steel drill and tap it for wind age screw, then machine blade. Last operation would be cut bottom of threaded tube free. Be a pain though. Blade in sight now has not been staked as I wanted to check it would work for elevation before staking

I could turn the barrel back a tiny bit. But, moving the sight body over would be a real pain. First even it you opened up one side of channel then peened other side to force metal over and resurfaced the top it would be hard to move the slot for elevation nut. Then how would you move rib and front sight over on top of barrel especially a nickle barrel. LOL. I could cheat some by under clocking barrel just a bit and gain a little bit. I could also make a front sight and have the blade offset from the piece that fits in barrel slot. The other thing I could do is tweak the frame just a bit just like adjusting a fixed frame POI.

What I am going to do is just leave it, bide my time and wait for a nicer model 14, 15 or 19 frame to come along. Use the Python barrel and nickle 19 cylinder on it and then stick the 2" barrel and a 38 cylinder back on this frame.

 

[chief38]

Sometimes when someone gets a heart transplant the body just rejects it. Maybe your Smith side is just rejecting the Colt side - LOL. That's a joke of course.......

 

[Protocall_Design]

The thread size for the windage and elevation screws is #3-80. You can get taps and dies for that and many other sizes from Victor Machinery - Metalworking tools and supplies.

 

[WR Moore]

steelslayer
Then, more messing around shows the front sight is not quite dead center over bore. Took some figuring with the bottom of barrel on level square, frame level, to prove this to me. More of a problem than the slight over clock for sure. Interesting on the fabled Colt barrel. Maybe why it was not on a gun??

WR Moore
Only time I've encountered anything like this is a 1911 barrel that somehow got finish machined with the bore off center at the breech end. And, it was wildly off POA.

Ya think maybe this says something about Colt quality? May be time dependent, back in the 1980's, half of an order of 1911 slides I got had to be sent back.

 

[steelslaver]

3-80 huh.. I know I have a 1-72n 2-56, 3-56 an 4-40 an 4-48 etc. 3-80 is kind of an odd ball #3 fine lol. Thanks for the link

 

[steelslaver]

Sometimes when someone gets a heart transplant the body just rejects it. Maybe your Smith side is just rejecting the Colt side - LOL. That's a joke of course.......

LOL. But, I put a 4" blue Python barrel on a 10-7 frame that I milled for adjustable sights and it came out pretty much dead on. In fact last week I used it during our defensive pistol get together. It has about 100 rounds though it with narry a hitch and at this point I wouldn't expect any.

I think I will go out and run the pinto using my machine rest if the expected rain showers give me a opening. I just got done doing the muzzle, chamber and extractor cut and assembled a little Stevens Crackshot I relined using a turned down Marlin 22lr barrel. The chamber and first few inches of rifling were horrible on it. They are such neat little guns.

 

[minconrevo]

Wonder if the bore is not concentric to the body of the barrel? Some careful measuring should determine this.