Tight spot in the barrel?

[Petrov]

After cleaning my 686 I tried to use the range rod and it gets stuck as it gets close to the forcing cone. Is that normal? I am using the match range rod if it matters.

I used a camera to look at the grooves and lands it they appear to be clean.

 

[bigggbbruce]

Have you used it before. Match has tighter tolerance.

 

[Petrov]

Yes I used the range rod on my custom PPC revolver. Yeah tighter tolerance is probably the answer. I will get a regular attachment.

 

[madmikeb]

I bought a PC 686 a few years ago and it had a deformation in the barrel right where it meets the frame, it also was a "tight" spot. If you looked closely down the barrel you could see a slight ring in that area. It's my understanding that this sometimes happens when the barrel is tightened, hence it's where the barrel meets the frame. I returned the gun to the factory and the barrel was replaced under warranty.
It actually didn't seem to affect the accuracy but it wasn't right.

 

[CH4]

I’ve seen several Smiths with restrictions just forward of the forcing cone. I’ve always thought it a result of “crush” fitting the barrel to the frame.

 

[Protocall_Design]

When the barrel is screwed on too tightly, it will be slightly smaller where the barrel threads into the frame. I have seen them as much as .003 smaller in that spot. This kills accuracy because the bullet is swaged down to that size, and then is too small the rest of the way. It also can result in bad leading of the barrel in some cases.

The fix is to remove the barrel from the frame. The barrel will spring back to the original size once the pressure is off. Then face off .001 or .002 from the back of the barrel where it butts up to the frame and reinstall. The amount to remove depends on the starting point. Ideally, you want the front sight to be at about 1 o'clock when tightened by hand, looking from back to front, as if shooting.

 

[Petrov]

When the barrel is screwed on too tightly, it will be slightly smaller where the barrel threads into the frame. I have seen them as much as .003 smaller in that spot. This kills accuracy because the bullet is swaged down to that size, and then is too small the rest of the way. It also can result in bad leading of the barrel in some cases.

The fix is to remove the barrel from the frame. The barrel will spring back to the original size once the pressure is off. Then face off .001 or .002 from the back of the barrel where it butts up to the frame and reinstall. The amount to remove depends on the starting point. Ideally, you want the front sight to be at about 1 o'clock when tightened by hand, looking from back to front, as if shooting.

I see.. Off to the gun smith it goes. Probably fix the rest of the screwups by the factory.

 

[1lnbrdg]

Some barrels are "plasticized" and don't return to size. Rugers was bad to do this for a few years anyways. Shooting jacketed and you can get away with it a bit but cast bullets and copper coated, you're asking for accuracy and leading issues.
I have fire lapped a couple of Ruger SBHs to alleviate the leading issue but if I was doing it now I'd just pull the barrel and lap it out.

 

[ralph7]

Colt's claim for their accuracy was just the opposite.
The interior dimensions tightened slightly on the way to the muzzle, don't know
if that's still the case.

 

[Protocall_Design]

The few Colt Python barrels I've measured were an even size for the length of the bore. However they are more accurate with light (slow) target loads due to the 1 - 14 twist rate, as compared to the S&W 1 - 18-3/4 twist rate.

 

[1lnbrdg]

Colt's 1/14 twist is a lot quicker than S&W 1/18. Pioneer Jim Clark Sr was big into putting Colt barrels on S&W frames. There were a couple of barrel makers that produced 1/10 twists, worked even better with the heavier longer bullets.
The shorter lightweight bullets can shoot just fine with the slower twist.
I shot a couple of 2" groups today @ 35yds with a Taurus 1/18 twist, 170gr MP 358-429 cast. I have a couple more loads to try and then I'm stretching it out to 50 and 100 yds.

 

[chief38]

I will say that is not a normal situation. I have tested all my 38 specials with a range rod when purchased or inherited and have never encountered tight spots as you describe.

 

[stansdds]

Barrel constrictions can happen in the area where the barrel is screwed into the revolver's frame. The root cause is a barrel that was over-tightened in order to get the front sight into the 12 o'clock position instead of taking a little metal off the barrel's shoulder in order to get the sight aligned and not over-torque the barrel. This is where skilled hand fitting comes into play and if you have to assemble a large number of revolvers in a day, close enough becomes good enough.

 

[gwpercle]

Slug your barrel ...
Start slug from muzzle ... when you get to suspected tight spot ... you will feel resistance .
Drive the slug through and measure .
If that tight spot is too small ... it slugs bullet down .
I don't like barrels with tight spots at the forcing cone ...
you are shooting undersized bullets and it could affect accuracy ... I shoot cast Lead bullets and undersized is not good .
If the barrel has a tight spot at that location ... I would have it replaced ... should be covered under warranty .
Good Luck,
Gary