Single-shot rifles and accuracy ...

Well, mine's a Ruger #1-S in 300 H&H (26" barrel). It's now sub-MOA @ 100yds with Federal's 180gn Noslers. Still working on various handloads, presently Hornady 220gn RNSPs and RL22.

It didn't start out that way, of course. Best groups initially were 3"-4" @ 100yds.

The following "tricks" worked for me. First, my gunsmith did a fine trigger job, light and crisp, but not unsafe. Second, he channelled and bedded the fore-end, essentially free-floating the barrel for most of it's length (except the bedded portion).

From Brownell's I got a Hick's "Accurizer" for #1s, which he installed. This is a small unit with a protruding screw. The unit fits up under the barrel on the hanger, inside the #1's fore-end. Only a little relieving of the wood up in there is necessary for fitting.

Then you basically dial-in your chosen load by turning the screw a little at a time, shooting groups and watching them shrink or expand. Once you shoot your smallest group, you've found the "sweet spot," or the pressure point at which the tension exerted by the tightened screw has created favorable barrel harmonics FOR THAT LOAD. On mine, shooting the factory 180gn Noslers, it took just under 2 full turns for the group to shrink to .75" @ 100yds, which is good enough for me.

What the Hick's unit actually does is tune your rifle to a particular load (factory or handload), which is the opposite of handloading where you're developing, through trial and error, a load tuned to your rifle.