The Ruger #1 happens to be my personal passion and I can recommend one to anyone looking for a quality single shot rifle. Swampfox's article is a good one to read before buying one and, as he states, all of mine shoot under an inch with favorite loads. I have not had a problem with the barrel rib on any of mine as Swampfox mentions, but some rifles may have such a problem. Many people claim to experience vertical stringing of groups, usually caused by the forearm hanger, but there are several ways to remedy this also:
The first method is to install a Hicks Accurizer (available through Brownell's) that attaches to the front of the hanger and adjusts the barrel/hanger tension by means of a tensioning screw. Installation is relatively easy, but a fair amount of inletting of the forearm and glass bedding is required.
The second method requires either the services of a gunsmith or machinist to drill and tap the hanger just in front of the mainspring retainer. A 6 – 48 tpi setscrew is screwed into the resulting hole to contact a small steel pad placed against the barrel. By careful adjustment, the optimum tension setting for a particular rifle can be found. Again, glass bedding is essential.
The third method is a result of my habit of both trying things for myself and not having access to a gunsmith that I trust with my rifles. This method only requires a selection of small steel nuts or shims approximating the width of the hanger and of varying thicknesses. By wedging a shim of the appropriate thickness between the hanger and the barrel to create the required tension, accuracy is enhanced immensely. This method is cheap, easy for the average gun-owner to perform, requires no permanent alterations to the rifle (other than bedding) and works perfectly.
The first step, as in all work with a firearm, is to make 100% sure that the rifle is unloaded!
Next, remove the forearm while being sure not to lose the forearm takedown nut.
Using a wide-bladed screwdriver (wrap the blade area with tape to protect the rifle's finish) gently spring the hanger away from the barrel. Insert a shim to create a tension wedge exerting enough tension to hold it firmly when you allow the hanger to return to its former location. This additional tension will hold your shim without fear of movement.
How thick should the shim be? Only you can determine that for your particular rifle. I always start with a thickness that springs the hanger enough to create a gap about .052" (about the thickness of a dime) greater than it originally was and use thicker shims if shooting shows that they are needed. This thickness also generally creates the proper clearance between the barrel and the forearm to, in effect, free-float the barrel.
An easy way to tell how much tension is required is to shoot the rifle without the forearm and try various thicknesses while testing. All shooting should be from a bench and only the forearm hanger should contact the bags. If you elect this method, be sure to either remove the forearm takedown nut or securely tape it in place. It can be lost very easily.
Once you have determined the proper tension and installed the wedge, a few drops of one of the new "wonder" glues can help keep it in position even if the forearm is sprung slightly as when using a sling.
Any of the above methods should be followed by careful glass bedding as Swampfox outlines in his article. Don't let any of this scare you off. There are a lot of #1s out there that shoot just fine with no modifications. Good luck with your search and have fun!