WTB: .177 pellet gauge

If you have the tooling you could use a reeming tool for exact size.
There are just tins that sux.
Ive had some huge variations in tins. Enough so that i wonder sometimes if they just do runs of mixed reject pellets into tins because its cheeper than remelting and recasting them and distribute them amongst cans of good pellets.
Speculation only, on my behalf.
Buy im guessing you got a bum tin or two. Use em for plinking or take them back.
H&N FFT come in three sizes in .22
Hence my theory.
Yet to find nz shop suppler who
A: even knew this.
B: even cared or would try to order in the tins of a specific size.
I was after 5.53mm as those were the size that gave the tightest group and one of the sizes fft come in.

Have you poked a pellet through the barrel and measured the final size it came out?

Im not sure on that. But the pellet has to go through the choke so its going to end up that size.
As skirt flare is what seals for push so don't see that being a issue if the skirt is larger than usual. Its also the thinnest part of the pellet so pretty maliable.
Maybe just push one in enough to engage the rifling for a pellet length then back out and one all the way through to see what choke takes it down too.
There will be more onto ppl on site who can give advice from more experience.( For all i know you are one) Depends how fussy you want to get.
I just tend to sort pellets. Target shoot to find what sizings shoots tightest, then stick to that sizes for hunting and the rest for plinking and correcting faults in my technique.
So there aren't many out of spec I don't use. 😆