Well if the larger one are too large they won't go to waste as I will use them in a .177 pistol I have. As for measuring with m,y calipers well I'm sure the Theoben's bore will be 4.5mm to the 1/1000 of a mm, this will be due to the Greman barrel probably Anshutz
just had a quick look round on the net mate all the pages i looked on said the barrel is made by Anshutz