Sorry if I sounded like I was being a d*ck about it.But i still disagree with your statement even if you have owned them. Having a 10fps variance and having a rifle that should just be binned is a totally different thing.
As I said 90% of people that use a bolt action are not like us, in the fact that we are anal about having the best tolerances, fps variance and best ammo.
Most guns even when upgraded rarely have a variance of 1fps and I would say a lot are worse than 10fps but still people use them happily and get plenty of kills.
My tanaka may have a variance of 10fps but I have not problem hitting a target at 80m 8 out of 10 shots.
There are so many variables with bb guns that fps variance isn't the only problem.BB weight variance can make just as big a difference and even the best bbs have variances,in weight and size..So do you hand pick all your bbs to be the exact size and weight as each other,I think not.
I use a gas rifle not for the best accuracy as I know my vsr will preform slightly better, i use it as its more of a joy to use,there quiet and minimal bolt movement helps a lot in concealment.
As for HPA, I would definitely advise getting one, as it will improve the rifle greatly.I would expect that a lot less sites would have a problem with it now a days as long as you can be trusted not to mess with it mid game.Here in the UK its still very much un used.