Question on Re-chambering from .40-65 to .40-70 SBn

[Dragoon 45]

Got this question today from a friend and I don't know the answer. He is thinking about re-chambering a .40-65 to .40-70 SBn. I assume it is not as simple as running a .40-70 SBn chamber reamer into the .40-65 chamber? My guess is the barrel would have to be set back at least a couple of threads? And then another thing that occurred to me is that it might actually be cheaper just to rebarrel the rifle with the desired chamber. It is an Uberti High Wall that has seen some hard use and it appears the chamber is damaged according to my friend. I don't know exactly what he means by damage although he said something about a flat spot that causes the cases not to eject so I assume he did a chamber cast to find that.

What would be the best recommendation to give him? Thanks

[2Tite]

It's probably doable. The SBN is longer and based on the 45-90 rather than the 45-70 as the 40-65 is. I'm considering going the other way on a rifle of mine which would require setting the barrel back. Depending on the damage he may not have to rethread the barrel. The extractor would be the same.

[Dragoon 45]

Thanks guys.

[country gent]

Keep in mind the .40 cal pilot wont be giving any support till the last of the chamber. The original chamber is bigger than the pilot and will "float" till it get to the barrel.

[EDG]

You can speculate a lot on this. Pulling the barrel and examining it would help.
Polishing the chamber might fix it without rechambering.

This is not a collector piece so it might be better to fix it by setting the barrel back and just rechambering with a 40-65 reamer.

[Dragoon 45]

Actually I think he has convinced himself he wants a .40-70 Bn. I suspect he is using the bad chamber as an excuse to rechamber it to what he wants. He would probably be better off if he just ordered a rifle chambered in what he wants, but he is somewhat of a tinkerer and is not hurting for money. So I expect to see him find a gunsmith to rechamber it. I was just curious as to how it could be done. I looked at the cartridge drawings for both and it was not clear to me how to do it.

You can speculate a lot on this. Pulling the barrel and examining it would help.
Polishing the chamber might fix it without rechambering.

This is not a collector piece so it might be better to fix it by setting the barrel back and just rechambering with a 40-65 reamer.

[Don McDowell]

If the bn reamer is speced for the modern (assuming he's going to use a current production 40-65) case neck for the larger bore and land diameter of the old 40 cals it should work ok. The bn case is fairly straight to the shoulder so the reamer should clean up the 40-65.
It would work best if the barrel was set back a couple of threads and the chambering work done in a lathe.

[Dragoon 45]

Thanks Don. I saw him today at our local matches and he says he has found a gunsmith who can get a reamer and rechamber it for him. It will be interesting to see exactly what the smith will have to do to rechamber it.

If the bn reamer is speced for the modern (assuming he's going to use a current production 40-65) case neck for the larger bore and land diameter of the old 40 cals it should work ok. The bn case is fairly straight to the shoulder so the reamer should clean up the 40-65.
It would work best if the barrel was set back a couple of threads and the chambering work done in a lathe.

[Don McDowell]

In your neck of the woods, there's Dan Zimmerman and Dave Crossno, either one could do that rifle for him, and it would be done right.

[Dragoon 45]

He found someone local here in Tulsa, don't know who it is yet. Steve Baldwin does some work like that also when he is not making sights. He has one really sweet set up in his shop.

Don't know how true this is, but I have been told Dave Crossno is having some health problems and stopped taking any new work for the immediate future.

I am trying to wait patiently for Dan Zimmerman's new scope line. What I am hearing from some of the shooters down in OKC, his scopes are showing some real promise.

In your neck of the woods, there's Dan Zimmerman and Dave Crossno, either one could do that rifle for him, and it would be done right.

[Don McDowell]

I too am waiting to see what DZ's scope is going to be.
Hate to hear that about Dave, heck of a nice guy to do business with, hope he gets on the mend soon.