Trying to Fix an Under-Regulated Revolver Barrel

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MM60

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Hi Everyone! I've been reading the forum for several years and finally decided to join. For my first post, I'm hoping to find an answer to a rather technical question...

I purchased a S&W Model 60 (J-Frame) revolver and the barrel is under-regulated. When acquiring the sight picture, the front sight is slightly but clearly canted to the right. I test-fired the revolver on a full-sized IPSC silhouette target at 25 yards with my own 158gr .357 Magnum loads and all shots grouped in the top left shoulder area of the target (the target's right shoulder) when aiming for center of mass.

The last time I sent a revolver to Smith & Wesson for service work, it was gone for about three months to have a different length barrel installed, and I had to immediately send it back to them when the work was done for being improperly regulated. Two weeks later it was returned to me better than before but still a hair off. That being said, I would prefer to fix my Model 60 myself if possible.

So here is my question... If the barrel is under-regulated approximately 2° (meaning it needs to be tightened 2° into the frame) and I had the proper vice block for the barrel and a frame wrench with the proper J-Frame inserts (I can fabricate these myself) so that I won't bend the frame, can I simply tighten the barrel myself? Or would I still need to remove the barrel and turn the shoulder down using a lathe?

According to this document from Brownells...: https://www.brownells.com/userdocs/learn/076-200-319_Barrel_Set-Back_Fixture.pdf

...S&W J-Frame barrels are threaded 36 TPI and move .028" per full turn of the barrel. I'm calculating that .028"/360°=0.00007"per degree of rotation. So if I need to tighten the barrel by 2°, then that should tighten the barrel's shoulder against the frame by only 0.00014" – 14 ten-thousandths of an inch. That seems infinitesimally small to me, but I'm not sure whether or not such a measurement can be set on a good lathe (I am not a machinist) or would even need to be. Without access to a lathe or the skill to use one, would attempting to simply tighten the barrel myself by 2° – with the proper hand tools – likely crack my frame or over-stress my barrel? Or would this be a safe and reasonable thing to do? Thanks!

Edit: This is not a pinned-barrel model.
 
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Only someone with the revolver in their hands can answer that question.
There are many factors to consider, including condition and how tight the barrel is already.

It could be that the barrel will easily turn and over-shoot the mark. Or, it could be that the 'infinitesimally small 0.00014"' will be just enough to cause problems.
 
One question, before any others, is the direction you need to turn the barrel to get the sight "straight" loosening or tightening it??

Generally when a fixed sight gun isn't on target people look for other ammo to see if its on target with a different load, or they look at filing the sights to get on target with their chosen load.

You're absolutely sure the gun being off isn't your reloads or just you having a bad day??? I'd try other ammo and other shooters before doing any shop work.
 
You should define what you think "under-regulated" means.
You can't even see 28 thou, never mind 14 ten-thousandths of an inch. I'd seriously question ".028" per full turn of the barrel." too.
Has anybody else shot the thing?
How did you determine the barrel isn't right? Your "all shots grouped" really doesn't prove or disprove anything.
 
Mr. O'Heir seems to have missed that you are not seeing the crush itself, but rather the rotation, and 2° is plenty easy to see. Have you confirmed that 2° at the radius of the front sight tip from the bore centerline moves the tip far enough to compensate for the error in POI?

You are talking only 0.154 thousandths of additional crush. That is not enough additional stretch to matter to functionality. Also, if you get a copy of Jerry Kuhnhausen's, The S&W Revolvers, A Shop Manual, on Page 84 he shows the slightly negatively angled shoulder at the root end of the barrel tang and comments that some amount of crush room remained available on all S&W barrels that he's removed. This means you can turn it in further. He also shows the equipment for barrel removal and installation.

You may want to first remove the barrel and apply a very thin layer of anti-seize or automotive assembly lube. Even a little motor oil will make it easier to turn past the original location. Anti-seize makes it easier to get the barrel off again in the future if you need to.

Since these guns have a removable front sight insert, and since these are known to bend if the gun is dropped on its sight, an alternative would be to intentionally bend it. Replacements are available.
 
I did the calculations and presented FLG with a diagram of how much my Italian single action's barrel was going to have to be "tweaked" to correct windage. It is a routine operation on those guns and I don't see why it would not work on a newfangled double action.
 
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