Thread: Another Vintage project and what happens when .....

For anyone interested in how this conversion was done here are some missing details on the process I used.

There are clearly a lot of little tips and tricks.
Just remember when epoxying in a liner that any soldering of parts needs to be done prior to final fitting the liner with epoxy.

I took a sulphur / carbon chamber and bore cast.
The 16 gauge chamber has a reasonable amount of straight taper and there is the forcing cone to replicate in reverse. I wanted a very close fit the casting was a very accurate way of getting both lengths and diameters.

The smaller bore plug was cast about 50mm forward of the forcing cone. Once it hardened I pushed it gently forward to the muzzle to check if the barrel was indeed parallel and where the choke ( if any ) started.
There was no choke as cylinder bored. But I still did intend shorting the barrel a little when finished to get the balance point further back



Then the task of turning down a new full diameter barrel blank. Lots and lots of swarf.
When the main bore section of the blank is very close to size the final fitting for a close slip fit is done in very light cuts and the tail stock is removed to check fit by slipping the barrel over the liner on the lathe.



Then on to the chamber area which was just a bit of following the numbers on the DRO and then use the smoke lamp to find the tight spots.
Lots of off and on with the tail stock to fit the barrel during this stage.
But well worth the effort because this liner ended up being very closely fitted in all points.

Usually liners are done with a "bore and line" on existing rifle barrels and there are only 2 diameters and a step between them at a known depth.
So lining an unmodified shotgun barrel is a little different.

This is the liner with smoke to slip barrel on and find the high spots where the smoke is rubbed off.



Liner fully fitted and breech space done. Chamber is not yet cut.



Cut the 45-60 chamber and then dry fit to barrel and check firing pin protrusion on a formed and primed case.



Not shown is having machined a section of the breech flange off the liner for where the extractor needs to be re fitted

And not shown is the new extractor extension fitted to the existing 16 gauge extractor.

Epoxy fitting the liner
There are no images of this stage as its messy and can be quite difficult.
You will need a hydraulic press to fully seat a stepped liner because liquids are uncompressable. You need to force excess epoxy out both ends from the step area.
Silicon tapered plugs are great to avoid lots of epoxy getting into the barrel.
You need to mix the epoxy accurately. Mix plenty and thoroughly to get the mix right.
Try and get some epoxy into the bore.
Coat the liner well as it goes in. There will be plenty coming out the breech as you gently turn it in,
Have the press set up ( dry run first ) so you can roughly clean up the mess and then press in the last few MMs
The epoxy puddle in the forcing cone area will go out both ends of the barrel / liner.
Its messy but you don't need to leave it in the press because once the excess is gone nothing will move.
And you don't need to rush because the epoxy has plenty of pot life if you mix it in a flat container. Never mix it in a small deep container.

Then you can clean up the sticky mess with acetone etc.
You can even fit it to the frame once clean and check the liner is fully in place and that your extractor rebate is perfectly in place.

Due to the tapered chamber area, forcing cone and stupidly close tolerance I machined this this liner to, there was vastly more surface tension when fitting it than i was used to.
So prepare for it to go into the press. Have everything set to go and there should be no drama.