Tried installing a new scope mount on a rifle for someone this weekend and I cannot get the screws to start in a couple of the mounting holes, but they fit in others, tightly but they do get started so i believe they are the correct size/pitch, it's a dnz mount for an axis. Is a rough tap common with the cheaper rifles that they're rushing through? should i give it a try with a drop of oil and a little pressure? They include grade 8 screws so of it's just some burrs it should just cut some nice clean threads i would think.