That's a very good press with high degree of repeatability and virtually no springiness. There are factors that can easily influence OAL that are not readily apparent, especially with short cartridges. Rims often get nicked during firing, for instance, which can raise or tilt a short a case such as a .45 ACP on the shell holder by more than a couple of thousandths.
The greatest offender is with regard to variations in bullet shape that occur in shipment and handling, or even with mixed lots from different swaging or casting dies. Your seating stem will sit differently on a narrower profile than a stouter one, even if the difference is only discernable under an optical comparitor. That's why some competitors shoot in competition with Sierra bullets or the like that hold to such absolute standards. But I must tell you that a .45 bullet gets battered around pretty easily when a fork lift lays a pallet of bullets down with a ton of bullets on top of it.
There is also the human factor, which relates to how fully you exert the press linkage on each stroke with uniformity.
In any case, .45 ACPs, are not the sort of cartridge class that is critical of OAL to absolute standards. Far more important than OAL for that round is bearing surface that affects resistance, and cartridge case insertion that affects internal pressure; neither of which is affected by slight variations of forward profile (ogive). You should be in good shape.
