With ammunition, accuracy is affected by automated mass production. Sharp shooters hand load their ammo so that the powder charge can be controlled with much more consistency. Bullet seating, etc. are also factors, but the powder charge is a biggie. I'm sure the various Mabel decedents are good, but because they are automated, fast, and rely on mechanical, pneumatic, and or hydraulic processes to charge and press propellant, there are going to be inconsistencies. I have a feeling that the charges thrown into mass produced ammo are held to a higher degree of accuracy than MR motors, so I could easily see a considerable difference in performance from motor to motor. I suppose you could check the mass of each motor to try to find consistency, but you don't know if the few grams difference comes from propellant, delay, ejection charge, clay, or even paper casing material. We have often seen incredible differences in ejection charges, which are sometimes easily gauged with the naked eye and ear.

This doesn't count the slight breeze variations that will affect rod friction and weathercocking. Even tiny variations would cause several feet of altitude change. There is also the 1-2% altimeter error. A foot or two by itself it isn't much, but tacked onto other variables, it adds up. Even with extremely consistent motors, I'd be shocked to see every flight fall inside a 10' window.

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