There are three reasons for more English guns being sleeved than US guns. Cost of the job, versus value of the gun, and the lack of any Proof laws in the US and parts interchange more easily for US guns with a ready supply of spare parts.
If we had proof laws here that made it a crime to sell a out of proof gun, with the number of lawyers we have in this country, more guns would get sleeved. We do not so they do not. Many a British gun that gets sleeved was bought for a few dollars before it was sleeved beacuse it was out of proof and just a parts gun unless sleeved.
Think of sleeving as an investment to bring a worn out or damaged gun back to life. It has to make sense from a money viewpoint. Think of it like an upgrade. The gun has to be worth a certain amount before any upgrade is economically feasable. If the upgrade is a $1,500.00 sleeve job, the gun has to be worth the investmet and should sell for at least more than the investment of the sleeving. So figure the sale price needs to be $1,750.00-2,000.00 or more after sleeving. Now look at all the American doubles field grade guns, those that sell for less than a $1,000 in 50% or less condition include, Ithaca NID and all models before the NID, LC Smith, Fox both A grade and Sterlingworth, Lefever, all the hardware store guns. Only the Parker would be much out of this price range and sleeving is the one thing that will make most Parker collectors cry.
The mid to high grade guns begin to have enough value to warrent the investment of sleeving. A few guns get sleeved because they have personal value far beyond money. But out of the million plus American double guns made, only maybe 20% are canidates for sleeving.
On top of that it is so easy to fit a second set of barrels from a low grade gun to a high grade gun that there is very little demand for sleeving here. It is cheaper to buy a second set of barrels or even a complete gun and use the barrels by fitting to a graded gun than to have the original barrels sleeved. Economics are againt sleeving here in the US.
Right now there is a 20 Fox on Gunbroker with a blown tube. If it would cost $1,500.00 to sleeve the gun and the gun is now at $700.00+ is it reasonable to do? Only at the curent price, because it is an ejector gun. But if the price goes much higher that it is now, the repair would make the gun into a money pit. Too easy to tie up $2,500 to 3,000.00 in a gun that you can not get that much out of it. And the left barrel has to be measured to see if it too is too thin. I suspect that a total sleeve job may be needed, not just one tube.
I looked real hard at it, as a progect gun, but passed. By the time you put a nice stock on it, re-did the barrels and metal and finished the sleeving it would have been a mistake. Now if I had an extra set of ejector barrels on hand it would have been easier. But then you have a mismatched numbered gun which is only a shooter, not an original ejector. This gun is a very tempting money pit, if you are not careful and lucky. Most other guns, that need sleeving, fall into the same pit unless they are worth a lot more than a small bore Fox ejector. Think about it.