Found These on ebay, and it made me wonder.

I have a.308 barrel I pulled off that is rough inside.

How high a pressure can a relined barrel tolerate?

I was under the impression that only low pressure cartridges were suitable for relining, but now I’m curious .

Just looking at it mainly as a skill building exercise on the lathe that I will likely screw up, but at that price I could afford a couple screw ups.

Doable? No?

Unlike a rim fire or some other small caliber liners, big bore liners come in multiple flavors.  Some are basically 1/2 to 5/8" in diameter to contain the cartridge, others like these are only for the barrel in front of the cartridge.  They only replace the rifled portion of an already chambered barrel, leaving the chamber intsct.  But thanks, I just bought two.

Doubletap.

Question:
Are these retained the same way a .22 rim fire liner is, with solder ?
If so, I wouldn't use one in a rifle that can lay down a lot of rounds quickly.
Would hate to see the solder get too hot, and let the liner go down range.

I could see oven brazing, but that would require a kiln of some sort.

But none the less, going to grab a couple

Brazing or soldering could kill that liner's strength properties, and those of the outside portion.  The original AR-10 tested during the M14 rifle trials had a stainless steel rifled liner shrunk-fit into an aluminum sleeve, and it failed spectacularly for obvious reasons.   I would not recommend trying that.

Today, soft solder is not much used to bond in barrel liners.
It was used in the past because that's all that was available.

These days an anerobic locking compound is used, and some people use a high strength epoxy.
Epoxy is a little more difficult to work with since it requires a very careful mix of the components and any excess will harden and make a mess to clean up.
These anerobic liquids only cure in an airless space.  Put some out on a glass plate and nothing happens.
Put it on a part that's a tight fit that excludes air and the liquid cures.

Loctite makes these in various strengths for various uses, including one for use on shafts.

The liner is slightly roughened up and the hole in the barrel is slightly roughened to give a better bond.
One way to do this to the liner is to leave the lathe marks.  These look like ultra fine screw threads.
You often see these marks on military rifle barrels like on AK rifles.
You can also use wet or dry sand cloth to roughen the liner.

The parts are carefully degreased and cleaned, then both are covered with the compound.
Put a piece of plastic or wood in the muzzle to exclude the locker compound from getting in the liner bore.
You have to work quickly because these start to set up fast in tight areas so you need to get the liner in place before it starts to harden.

As the liner is pressed in, the locker compound excess will run down the barrel.  Simply put down a pad of paper towel and newspaper to catch it.  While it's exposed to air it won't harden and can be cleaned up later.
After 24 hours cure time, simply clean off the uncured excess that is exposed and won't harden.
Then you can finish the chamber and crown the muzzle.

In most cases the best results are to lathe turn the liner so there's a flange on the rear and a corresponding recess in the original barrel.
This flange will positively prevent the liner from de-bonding and sliding forward.

In the case of a high power rifle you have to use some common sense as to whether a liner will stand up.
In most cases, this comes out to actually be a new barrel covered by a thin barrel shroud, similar to the Dan Wesson and S&W two piece barrels.
In short, the original barrel is machined to a fairly thin shell and the liner is left as thick as possible.

Again, you have to use common sense when dealing with an original barrel that's a thin contour.
In those cases this won't allow having a thick enough liner to stand the pressure.

I would not trust a liner not thick enough to
work on its own in a modern center fire cartridge.

There a ARE going to be skips in the joining of the liner to the old barrel.
Unless the liner can hold the pressure at that point it is going to work with every shot.
This will eventually cause it to crack.

I've lined a few real sewer-pipe barrels over the years. Once you epoxy the liner in place it's a very good idea to touch up the chamber with a finishing reamer to remove any step where the existing chamber meets the liner.

ETA: While I've also lined plenty of rimfire barrels I'm specifically talking about centerfire barrels. I've had success on multiple bolt action rifles. Of course you can also get approx. 18" 30cal barrel blanks from Sarco for all of $20 each.

ETA2: Thought about it overnight. Dug around one of my project safes this morning and came up with another handful of sewer pipe guns that could use a liner. I'm supposed to receive the liners in the next three weeks or so. We'll see how they work out but I don't expect any issues.