Hi,
Many times installing a bucking benefits from having the hopup wheel and or the hopup arm removed prior to inserting the barrel and bucking into the hopup.
As the lip of the bucking often gets pinched due to the nub itself. We've seen it many times and will cause the bucking to appear oval when inside the hopup. With a distincted sharpened 'oval' point at the top of the bucking.
Also a little grease on both the bucking and inner wall of the hopup helps to reduce friction when inserting it. We find it necessary to do so when installing on Prowins and Maxxpros.
Try giving that a try on your setup and see if it appears more circular as a result.
