Great accuracy investment (4.10.2012)
A quick, easy way to get better accuracy out of any rimfire you own. Whether you're shooting top-of-the-line match ammo, or the "weekly special" from the hardware store, segregating your ammo by rim thickness helps to one degree or another.
One benefit is the ability to judge the consistency of your ammo. The best match ammo I've tested so far showed that rim thicknesses grouped almost 50/50 into two different thicknesses, less than .001" apart. GOOD digital calipers make it much easier to read the results, and are a good investment in themselves for many tasks.
Match ammo is very consistent, but if you shoot a 10-shot string with nine rounds of one thickness, and the other different, that 10th round will look like a flier. I used to kick myself for messing up with an occasional "bad" shot, until I started sorting the rounds by rim thickness. Many of those "fliers" went away, and not because I suddenly became a better shot.
Also, some rimfires will shoot well with almost anything, while others can be quite finicky. My CZ453 shoots almost any quality ammo well, although all brands group slightly better when sorted. My Ruger 10-22 heavy barrel wasn't that great with any sorted ammo, except ONE combination of rim thickness and bullet diameter, where it produces .600" ten-shot groups at 25 yards (my testing protocol), beaten only slightly by the CZ bolt action. Who knows what the next Ruger off the assembly line liked?
All the more reason to test your sorted ammo with every one of your rimfire weapons. I'm still testing with Federal Match, methodically eliminating variables. My first Ruger likes .0415" rim thickness, so I assembled a supply of them, along with the other thicknesses, to check out my other Rugers.
For plinking ammo, you may find a favorite weapon/ammo combo, or the most consistent brand, and get some idea of how much effort to put in the project.
For match ammo, I'm finding I need about 1000 rounds for testing in multiple rifles. About 500 rounds for the various combinations and permutations, and the other 500 to size and sort into the best performers.
This might not be everyone's cup of tea, but it's a soothing way to spend a winter evening at the work bench with some good music playing.