A question was askes a little further up the thread to the effect of how can a gun just increase in power without doing anything to it?
Besides the mechanical tolerance \ wear side of the argument, there is a significant variable in the pellets we use. I get through a fair few throughout the year, buy in bigger batches etc, but do lots of batch testing to get the best out of the kit.
All the testing is done weighed, with a tolerance of 1\10th gn, so regardless of batch, i test with 8.40 to 8.49.
What can be seen is even pellets from the same maker, head size, type can vary quite alot from one batch to the next. I proved this as recently as last saturday, witnessed at a rfd \ gunmakers premises on his chrono. The batch i use are towards the faster end of the scale, but set to run just touching 780fps at the highest, average 777fps.
I also put through a different batch to show the extent of variance, the other batch averaged 750, so a full 30fps lower.
From the gun builders side, if they set power with a slow batch at lets say mid 780s, and you have and do your own test with a fast batch, your gun will be almost certainly too high mv.
If the manufacturer happens to use a fast batch for initial set up, again 780fps how is the customer going to feel when they do thier own test which returns 750fps.
Its a bit of a no win situation for the manufacturers without a more defined and reliable test procedure and pellet. But, the variables that are built in to the current system do allow the law a certain element of a stretchy tape measure to catch any undesirables if required.
I do not agree with AT, but the people within the industry see it necessary even though not a legal requirement.