No responses so I'll take a stab. Velocity would be second of importance on your questions. For me, it wouldn't even have been a question. People who buy on published velocity will undeniably pass on some lots that would have shot really good, if they had tested them, because they didn't have the same or close to the same velocity as a former lot that shot really well. That former lot was just a good lot.
I would go with the same machine (loader as you put it) in the same year. Be very much aware though, certain machines in certain years will produce a good volume of good ammo, but not all lots are going to be great. The only way to find out is testing different lots, even if the same machine. There are several reasons for this, but they are not relevant to the question. Once the machine goes through maintenance and rebuilding, it may go down in the quantity of good lots and another machine may be better. Historically with Eley, some machines in certain years produce the bulk of the good lots for that year. Back in 2018 and early 2019, the 6 machine cranked out an impressive number of good lots. It didn't produce every lot that was a winner though. When I do buy test lots of Eley, I always buy more lots from machines that have produced winning lots recently, but still buy some other machines to test as well. I also buy through the range of speeds. If you don't buy that way to test, you limit your chances of finding something special. No brand/type, no speed, no machine should ever be ruled as the best, or the one you THINK doesn't work, in your barrel. Only lots matter.
While your question has some merit, it still comes down to lot testing, no matter what 'hot' machine is involved, or what someone perceives is best for their barrel.
JME........Scott
