A couple questions about re-lining

[srf]

A couple questions about guidelines for re-lining:
• Is there a minimum wall thickness of the original barrel that should be left when relining?
• If the liner would infringe into existing dovetail cuts, is it better to touch-up the dovetail after installing the liner, or to step the OD of the liner so it doesn’t infringe into the dovetail?

I would like to install a 38-55 liner (with .609 outside diameter) into an octagon barrel which is only .680 across the flats at the muzzle (the barrel currently is 45-70). There are dovetails at the muzzle on top and bottom, for front sight and magazine tube hanger.

I am thinking that stepping the liner down to .562 or .500 about 8 or 10 inches behind the muzzle would be prudent.

I would sure like to hear the thoughts of someone who has been there and done that.

[MtGun44]

I have not done it -- but - here's my mechanical engineering opinion. May be worth
what you are paying for it.

I think you would be in trouble with that thin a barrel shell. Can you get a smaller
liner, or have it turned down? I think you would need a follower rest to turn that
without flexing it badly. Not sure how well it would work to step the hole and
liner - what if they are slightly off center from each other? Does the liner kink
at the step? May work just fine, good luck with the project.

Bill

[country gent]

You are only going to have around .035 wall thickness on a side of the original barrel left if you go size for size, any clearence will make this even thinner. Thats a pretty thin cross section to work with may buckle or bend pretty easy installing the sleeve. Also on that small thickness warpping will become an issue. Most of the dovetails will be cut into the liner due to this also. Another issue will be any threaded holes will be thru both barrel and into liner. Recatching those threads on that thin section may be tricky as there will only be one thread or so left. On the plus side the dovetails and threads will also help to hold the liner in place. How long is this barrel and liner? Maybe turn to .560 and drill and ream to .562. Epoxy liner into place with a good long cure epoxy working liner thru barrel rotating and half strokes to work epoxy thru and relieve air pockets. If the drill dosnt track straight and true or the barrel it self warps things may go south real fast.

[John Taylor]

T.J.'s has a 38-55 liner that is .531", 1 in 18 twist .375 groove. I use quite a few in this size. I have installed the bigger liner, sometime turning it down and sometimes recuting the dovetails. I don't like turning the liner down, it may cause the bore to be uneven because of the stress in a hammer forged liner.

[srf]

T.J.'s has a 38-55 liner that is .531", 1 in 18 twist .375 groove. I use quite a few in this size. I have installed the bigger liner, sometime turning it down and sometimes recuting the dovetails. I don't like turning the liner down, it may cause the bore to be uneven because of the stress in a hammer forged liner.

Good point about stress due to the hammer forging!

If I do this particular barrel, I am stuck with the larger OD liner, because the barrel is currently 45-70 and I need to fill the existing chamber.(Oops, my mistake. .531 would be large enough to fill the existing chamber. SRF) Also because I am kind of partial to the .379 groove diameter. I realize that I will need to set the barrel back a thread or two in order to get the hood at the chamber entrance to come out right.

It is a 26 inch barrel, and I have the liner on hand (T.J.'s). I still need to make or buy piloted drills.

[John Taylor]

Don't set the barrel back. Solder a bushing on the end of the liner to fill in the rim cut.

[Hooker53]

Srf. No you don't have enough barrel thickness to do that even if you do step it down. With that size .cal, you will have expansion and contraction at detenation due to heat and presure. With this in mind, this first problem cancels out the dovetail problem.

I've tried to "come in under the wire" on rebuilds like this and your just better off to take the safe road here. If you consider the thickness on the Cyl of a wheel gun wall you wonder how it can hold the pressures and most do but with this liner operation it's not the same properties here. You have a liner at your chamber position that will be working against what barrel wall you have left. Do you have enough Dimentions on your action to increase your barrel size??

[johnson1942]

john taylor is a proffesional expert and listen to him and if you want more just to cross check talk to norm johnson of high plains at turtle lake north dak. these guys are experts in barrel relineing. relined barrels usually shoot better than the original barrel. better harmonics.

[srf]

Yes, I know several people that have old guns that John Taylor has relined, and have heard nothing but good things about his work and experience. I greatly respect someone who has been around the block many times, and has a good reputation. And I certainly appreciate his willingness to help those of us who have little experience.

Regarding the safety comment, since I am starting with a factory barrel which has a .450 bore, and lining it to a .372 bore, it is not obvious to me that I am necessarily reducing the pressure capability. If I do step the liner down to be close to breaking into the dovetails, I believe that I will probably end up with greater wall thickness at the dovetail locations than the original barrel. Near the chamber, I believe that I can leave the liner at full diameter. I suspect that the hammer forged liner material is at least as strong as the original barrel material, but that is only an assumption. However, perhaps I am missing some detail.

Does anyone have recommendation on reference books which discuss technical aspects of re-lining?

Thanks for all the suggestions,
Steve