I have what was once a nice provincial English Boxlock (Damascus). Barrels started life as 2 1/2" but were lengthened to 3" (not a misprint). Is it feasible to sleeve the chambers to 2 3/4? Thank you, Gil

Yes, although typically it is done to reduce gauge, not sustain the current gauge, but before you do get the wall thickness measured by someone who knows barrels. Depending on the original wall thickness and how was removed you may or may not have a problem

Depending on who you reference a good working rule for wall thickness min wall at the end of the chamber varies but .105 is good, with the walls narrowing down to .045 nine inches from the breech. If you have more than.105 at the end of the 2 1/2 original and down through the end of the 3 inch chamber you maybe ok. C.I.P calls for lower minimums, but it becomes a mental confidence issue for some to get too close to the edge.

Measure the wall thickness. May still be thick enough to use lower pressure shells. If you sell it, let the buyer know.

It is done in the same gauge sometimes to repair a damaged chamber. I have a pretty nice boxlock that has had the chambers sleeved, I assume to repair pitting but it is hard to tell. Still has 2&1/2" chambers.

Why?

In order to replace lost or damaged steel with quality new steel.

It allows for the removal of pits then replaces that steel removed to ensure continued safe minimum wall thickness.

Why? This may be next
16g No. 0 L.C. Smith with chamber lengthened to 2 7/8"



Radiograph with the bulge and thin wall



or even worse, courtesy of Randy McCune; chamber also inexpertly lengthened to 2 7/8" and forcing cone lengthened. I don't unfortunately have the end-of-chamber wall thickness and the reload also showed evidence of over-pressure



Briley's same gauge chamber sleeving is $275
http://www.brileygunsmithing.com/c-879-full-list-of-shotgun-gunsmithing-pricing.aspx

I recently owned a Brit hammer 20ga, original 2 1/2", lengthened to 3". But it had the correct British reproof. I thought it odd that someone had the chamber lengthened to 3". But given the reproof, I didn't worry about it. Without a reproof, I'd worry a lot.

I am just reposting this from another thread where I posted the same response:

This is a short article on chamber sleeving by Diggory Hadoke. I considered it on a 10, but ended up selling the gun instead.

https://www.vintageguns.co.uk/articles/chamber-sleeving/

Briley can do the work although I am sure there are people who are more specialized.

https://www.brileygunsmithing.com/c-879-full-list-of-shotgun-gunsmithing-pricing.aspx

Edit: the chamber sleeving article is no longer available on Diggory's website.

My question was to Gil and was why he wanted a chamber sleeve down to 2 3/4”
Not why the barrels needed to be measured

OP .That must be quite a bit of work as you`ll have to remove the over extended cones won`t you to get them back to 2 1/2" spec ?

A dealer I use to see at the Great Southern Weapons Fair at Richmond back in the day had a No. 3 NID Ithaca Super-10 that someone had hogged out to Magnum-10, but he had, Briley I think, sleeve the chambers back to their original 2 7/8 inch.

I wouldn't. I'd just check the wall thickness and make a decision. I see no sense in worry.

SRH

Well . . . one reason to worry--given the fact that thanks to discussion boards like this one, people know a good bit more about proof rules than they used to--is that without a reproof, the gun is out of proof. Illegal to sell in the UK. And while you can sell it here in the US, you'll likely take a hit on value from anyone who knows much about British guns.

And having passed proof gives one a bit more confidence than simply measuring wall thickness. You know the gun has survived being fired with loads of far higher pressure than any you're going to use.