Narrow Bore S&W 629

[guywitha3006]

I got a new to me S&W 629 classic a couple months ago. I noticed one chamber was tighter than the other 5 so I brought it to my local gunsmith to have him slug the barrel and open up/even up the throats. To my surprise he called me and told me my barrel actually slugs at .428". Currently he is opening up/evening out my throats to 0.4295" so I can size .001 over bore. But it is odd to me as most jackets bullets are .429". I plan to mainly feed it cast but is this anything to be worried about if I do shoot jacketed at some point?

Thanks!

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[gnostic]

Sounds good to me. It's been my understanding, that the barrel should be .001 smaller than the bullet. The only barrel I've measured was a Python and it measured .356...

[Moleman-]

Is there a .001" constriction near the barrel threads?

[guywitha3006]

Is there a .001" constriction near the barrel threads?

He didn't say, we only talked briefly I know he used a cerrosafe casting instead of actually slugging it would that have anything to do with it?

[Moleman-]

Cerrosafe *depending on the type* initially shrinks to easily be driven out, then grows back to size. If he didn't wait for it to grow back to size then yes that could be it but being a gunsmith he should know that. Measured a well used 29-3 and a .432" minus pin gauge fit in all 6 and a .433" minus in in a few, almost started in a couple and absolutely refused to even think about it on one throat. On a lightly used 629-2 a .432" minus fit all 6 and a .433" minus refused to start. Brand new 29 cylinder I got to someday replace the one on my 29, .429"minus gauge fit, .430" minus didn't. Weird, looks like I'll be opening it up for cast bullets when I fit it. Haven't bothered to slug the barrels on them as they shoot better than I do. Will be replacing or setting back the barrel on the 29 as the forcing cone is pretty eroded.

If the barrel was over tightened it can cause a slight constriction from the V threads which isn't unheard of.

[guywitha3006]

Hey Moleman, I have enough faith in this Smith that he accounted for shrinkage. It is 629-5 classic. I am curious to see if he thing it is a thread constrictiom or tight bore. If it is .428 that would mean factory jacket bullets would be .001 over but weirder thing happen...this particular Smith started life as a tool and die maker so hopefully accurate measurements shouldn't be an issue.

[dubber123]

.428" isn't all that tight, and I'd bet there is a thread constriction :)

[guywitha3006]

.428" isn't all that tight, and I'd bet there is a thread constriction :)

Well if that the case, any idea how hard that is to fix? I haven't had that issue before. I may try to stop in and chat a bit more with him today if life allows.

[dubber123]

Well if that the case, any idea how hard that is to fix? I haven't had that issue before. I may try to stop in and chat a bit more with him today if life allows.

Slugging with a pure lead slug from the muzzle will tell you right away. As you push it down the bore, you will feel any tight spots. If it has a thread constriction, it will likely stop and need a few taps to push through. Any revolvers I have found with this condition, (a lot), have gotten firelapped. It is safe, easy, and has worked in every single instance I have tried it.

[guywitha3006]

Slugging with a pure lead slug from the muzzle will tell you right away. As you push it down the bore, you will feel any tight spots. If it has a thread constriction, it will likely stop and need a few taps to push through. Any revolvers I have found with this condition, (a lot), have gotten firelapped. It is safe, easy, and has worked in every single instance I have tried it.

I did slug it myself before sending it to be reamed (hornady round ball) but with the 5 groove rifling I couldn't get a good number (which is why I asked him for a better measurement). I do not remember any resistance by the frame but it was a few weeks ago. He is waiting on a reamer so it may be a bit before it is figured out.