So in a previous post I was talking about locating ammo sample packs to see what my T1x likes best. I have rounded up a few different ammo choices and have more on order, so that is set. And yes, I acknowledge the fact that lot numbers play a big part in the process, however some basic testing will let me know what ammo my rifle likes, and from there I can delve deeper.
So now a new question comes to mind and that is pertaining to cleaning the barrel during testing, specifically in between groups/ammo types etc. My intent is to thoroughly clean the barrel prior to taking the rifle out, fire a couple of groups to foul the barrel, and then commence my testing which will consist of multiple five round groups (of each ammo type) at 50m and at 100m.
What I am wondering is if I should clean the barrel prior to firing the next ammo to be shot (ie shoot Eley Match, clean barrel, shoot SK Standard) as well as if I should fire fouling rounds between ammo types or if I am altogether overthinking this.
Thoughts?
EDIT: Feel free to discuss barrel cooling between groups as well as I know it will come up...
Barrel heating not an issue because .22LR ammo simply doesn't heat up a barrel like magnum rimfire or, even more, centerfire. Shooting in colder temperatures along with cartridge temperature variations can contribute to accuracy issues, but barrel warming because of shooting will not. According to a detailed study of barrel temperature, "the total temperature increase does not exceed 5°C after taking 40 shots and does not affect the position of the hitting point on a target". Shooting in colder temperatures will likely result in a smaller temperature increase. See h t t p s://www.ncbi.nlm.nih.gov/pmc/articles/PMC3944560/
A good maxim to remember is a clean bore shoots better than a dirty bore.
As suggested by other posters, it's a good idea to clean the bore between different ammos. This is especially important when changing between ammos made by different manufacturers. The bullet lubrication can be very different, and results can be affected particularly for the first couple of groups if no cleaning occurs between makes of ammo. For example if switching between Eley and Lapua/SK ammos, clean the bore.
When shooting different varieties of ammo by the same maker -- SK ammos, for example -- it is less important to clean than when switching between ammos from different manufacturers. Of course if a lot of rounds are shot, it's a good idea to clean to keep everything on a level playing field.
Cleaning doesn't have to be complicated. Use a cleaning rod and a jag with a patch and a bore guide. Put some solvent on a patch and run it through the bore, followed by a couple of dry patches. That will clean the bore adequately for testing with ammos by different manufacturers. If you don't have a cleaning rod, and are using a bore snake, order a one piece cleaning rod and use the bore snake until you get the rod. The bore snake will be better than nothing. When testing for the best accuracy with different ammo varieties or lots of ammo, having a cleaning rod and bore guide should not be avoided because they may be considered too expensive.
Shoot a few foulers after cleaning. A clean bore often does not put the first bullets where a fouled bore will. Above all, make sure to shoot enough groups to get enough information. Sometimes one really nice group suggests a good ammo has been identified, but it's important not to confuse a random act of act of accuracy with repeatable consistency. Shoot at least five 5-shot groups before concluding an ammo is good. Lousy ammo can often be identified with fewer than five groups.
Finally, unless a shooter is experienced enough to consistently shoot well at 100 yards, it's a better idea to test ammos at 50 yards. Why? At 100 yards there is much more room for shooter inconsistency to influence results as much as or more than ammo inconsistency. Find the ammos that produce the best results at 50 yards and then try them at 100 yards. No ammo will improve in accuracy MOA-wise as distance increases. In other words, if an ammo can't shoot well at 50 it won't self-correct and do better (MOA-wise) at 100.