When shooting on Orion air rifle or air pistol targets, it is always best to use lead wadcutter pellets. Orion scoring process is optimized for this type of ammunition; however, some teams and clubs are forced to use non-lead pellets. For these shooters there will be small differences in Orion scoring accuracy but much greater differences in the accuracy of the rifles that use lead verses non-lead pellets. The short answer to the question is that the scores of shooters who use non-lead pellets won't be degraded because of Orion scoring, but they may be degraded because of the inherent inaccuracy of non-lead pellets. Here is a more detailed explanation:
1.Scoring Accuracy: When used properly, Orion will score shots fired with wadcutter lead pellets to within +/- 0.1mm (one-tenth of a millimeter). Orion does not guarantee that shots fired with non-lead pellets will score to this same level of precision because non-lead pellets do not cut clean holes like those we see with lead pellets. The difference in scoring accuracy, however, is probably only about a tenth of a millimeter (total +/- 0.2mm). This slight additional difference in scoring precision will, on average, balance the in/out scoring decisions on close shots. Thus, you can use Orion to score all targets, whether fired with lead or non-lead pellets, and be confident that all competitors are being treated equally and fairly. Since there is a small but measurable difference in scoring accuracy, we have to warn Orion users that they cannot expect the same standard of scoring precision when shooting non-lead pellets. The difference is small and in most instances will not influence the final ranked results.
2.Rifle-Pellet Accuracy: This is where shooters could be facing an unequal situation. The Civilian Marksmanship Program has conducted extensive accuracy tests with lead and non-lead pellets. Their testing has shown that there are no non-lead pellets that shoot as accurately as lead pellets. In their tests, rifles with lead pellets shot many controlled test groups that would score 100x100 on the 10m air rifle target. The best non-lead pellets the CMP tested would probably not produce scores better than 96-98x100 on the 10m target. If you want more information on this testing contact Brad Donoho at the CMP (firstname.lastname@example.org).
How much of a disadvantage this accuracy difference would cause for a shooter depends a lot on the level of scores they are firing. If they are firing precision air rifles or sporter class air rifles and producing scores of 260-275x300 or higher on the 3x10 course of fire, then the teams that shoot lead pellets will have an advantage. If they are shooting lower scores, the teams shooting lead pellets will not have any real advantage because the larger shot groups fired with non-lead pellets will yield both gains and losses that tend to balance each other. The caveat to this general rule is that the teams shooting non-lead pellets must not be shooting really bad non-lead pellets. The CMP testing showed some non-lead pellets to be so inaccurate as to be practically useless for target shooting.
In general, it is not worth worrying about the scoring accuracy issue since scoring accuracy differences are small; however, on targets fired with non-lead pellets it may be necessary to make occasional "obvious error" corrections for badly torn shot holes (see Sec. 5.7 and Sec. 5.8 in the Orion User Manual). If a shooter score averages are below 250, he or she should be able to continue competing without making special adjustments; however, the shooters using non-lead pellets may want to conduct some accuracy tests with their pellets to make sure they are using pellets that produce reasonable accuracy.