This is more of a general interest question rather than a gunsmithing question as I do not consider the gun "broke" at this time.

I picked up a used S&W Model 10-5, serial # 5D36***, with a skinny barrel in very good condition. Upon cleaning it after my first range session with it I discovered that there is loose spot in the interior of the barrel where the barrel is screwed into the frame. I have ran several patches through it and measured the spot carefully and it is in the barrel where it screws into the frame. I can not feel a bulge on the exterior of the barrel and there is no sign of cracking or any other damage on the frame.

The cylinder and chambers appear to be fine.

My first range session was a bit of disappointment to me with the gun shooting to 2 1/2" to 3" to the left from 7 - 10 yards. However I attributed much of it due to using the magna service grips which are way to small for my hand, pain in my shoulder from recent surgery and white paint on the front sight causing me to lose the sight picture in the bright sunlight. At three yards firing double action it put 4 rounds plum center inside the X-ring of the target measuring less than 1" outside hole to outside hole

Bear in mind that this is a 30 year old cop gun so who knows what has been shot in it. I was using 158 gr. SWC I reloaded myself so there were not any ammo problems at all. I am unwilling to state the gun has accuracy issues until I can get back out onto the range with grips that fit my hand without the dang white paint and shoot it side by side with another Model 10.

As this is the first revolver I have ever had with loose spot in the barrel I am looking for feedback about what, if any, problems it might cause.

It sounds like another case of Dillion barrel. In a reload that didn’t get any powder the primer usually will propel the bullet into the rear of the barrel. If the squib goes unnoticed the next bullet hits the obstruction and bulges the barrel. Since your bulge is where the barrel is thickest and surrounded by the frame only a slight bulge would be expected. Unfortunately it still may be bulged enough to freeze the barrel into the frame making a barrel replacement problematic. For that reason I hope it still groups well.

Pictures for the gallery;

Deleted fuzzy wuzzy photos.

Is the contour I described on the barrel normal? I'm not really interested in rebarreling it due to the cost and will probably sell it if it doesn't group well.

I’d have a better chance at speculating if the barrel contour in front of the frame is original with a photo shot straight on from the side. Even with a side photo my guess isn’t as good as what you feel with a tight patch for determining where the bulge is and how large it is.

The important thing is whether it shoots accurately. I’d try not to raise my blood pressure worrying about rebarreling or selling it before firing it again.

Nice clear keyboard.

__________________
Memory of Randy Freas-Rimfired

I don't know why the pictures turned out out of focus. They look fine on photobucket.

I am pretty sure the contour on the barrel is normal. The barrel starts out straight from the frame a very short distance on all sides except the bottom then tapers down to being skinny.

On Friday I am going to shot it side by side against a Model 10-6 heavy barrel I have. In fact I am going to use the same box of ammo and same grips to rule out as many variables as possible. Based on where the bulge is I really don't expect it to have any effect on accuracy.