Any quick and easy way to remove the rifling on an old .22 single shot so I can have a smooth bore .22 for shot shells?
My understanding is that the rifling effects the pattern of the shot.

You might try shooting some shotshells from the rifle before going to the trouble of removing the rifling, but yes, in my experience the rifling does pretty much ruin the pattern and make it useless at any distance.

There are ways of boring out a barrel to permit relining it with a new rifled insert, so that would be one way of removing the rifling. That would leave an oversized bore, though, and might reduce the effectiveness of what you have in mind. But that’s just a guess, and I have no basis of knowledge for it.

Using a deep drill or whatever is involved with relining a barrel would not, however, be cheap or easy unless you could find a gunsmith who was already equipped for the process. If using that process, though, it would be necessary to avoid removing the chamber from the barrel, and I don't know how that would work.

Perhaps smoothbore liners are available.

Another possibility that occurs to me would be to use an abrasive on something suitable like a cleaning jag chucked onto a power drill and see how that works. Older rifles chambered for 22 LR are reputed to have been made of softer steel, so it might be feasible. If that worked for me I’d start with something coarse and aggressive, and then finish with finer abrasives to achieve a smoother finish. If using that method, again it would be necessary to avoid damaging the chamber.

Added: Your question prompted me to search the question online. There are many discussions about the same topic, and one mentioned Urban Rifle Supply in Idaho as offering the service. It seems, though, that the company is no longer in business, but perhaps a more detailed search would turn up alternatives. One thing that was mentioned, though, is that shotguns (which a smoothbore .22 would be, I believe) must have 18 inch barrels to avoid the NFA restrictions. A lot of older rimfire rifles had ~16 inch barrels.

Thanks Sigfreund;
Good point about the short barrel, I will have to measure it.
I know you can get a long bit for running bell wire but I think the smallest is 1/4".
I will pattern my rifle with shot to check, but I have shot at some chipmunks from pretty close and missed.
Maybe some coarse lapping compound and a brick of 22s will do it

The right drill for the job is actually called a “gun drill”. It is special in that it drills an exceptional smooth bore. To get it to drill a straight bore the barrel needs to be rotated in a lathe, with the drill not turning. The bit will then naturally center itself in the barrel. It would also be normal to have a flood lubricant system that flows chips out of the barrel, lubricates and cools the barrel.

Non of this is “home shop” or even “average” gun shop kind of work.

In this case it would be an extremely fine cut. A few thousandths of an inch at the most.

22 long rifle shot is pretty marginal as far as payload and effective range. It is really only useful for rodents snakes or very small birds inside about 20 feet max. Just my opinion, but outside of use on snakes at under ten feet, not much useful for anything

Brownells sells the barrel sleeve and drill bit for installing a new 22 sleeve. But the diameter is bigger than .22.

Try patterning the current rifle with rat shot at differing ranges