In general, there should be no special treatment needed for 22 LR compared to traditional rifle bullets if they are not being damaged during feeding. Since 22 LR projectiles are generally constructed of plated lead, they are soft and can deform easier than a traditional copper jacketed bullet during feeding or handling. If this is the case, I can believe that there would be observed differences between prediction and actual point of impact. 4DOF will handle any normal projectile dynamics that exist due to possible projectile dynamic instability that may occur at low mach numbers (transonic / subsonic).
Unfortunately, some 22 LR projectile shape’s are more prone to having dynamic instability issues than traditional copper jacketed projectiles. If the dynamic instability is severe enough (dependent upon shape, mass layout, twist, and angle of attack), it becomes impossible to predict the effects from a point of impact standpoint. Based on what I have observed with the RADAR it is possible that 22 LR projectiles will experience dynamic instability that will result in erratic point of impact results after certain time of flights that will not be able to be corrected by the shooter. The shooter is looking for a trend, I’m always hitting high or always hitting low to be able to troubleshoot, identify, and fix a problem that exists between the ballistic prediction and the observed point of impact. Unfortunately though, if impacts at 300 yds with a 22 LR are “all over the map”, this cannot be fixed by a ballistic solver.
The recommended process with rimfire would be the same as any centerfire system.
- Measure and input an accurate muzzle velocity.
- Ensure all inputs are correct pertaining to the rifle and bullet picked from the library.
- Conduct the find zero angle process.
- Shoot at distances equating to time of flights of .5-1.3 seconds (100-350 yds for most 22 LR). If there is a difference between the point of aim and point of impact, conduct the axial form factor calibration to account for the difference observed.