the scope mount is one of those t/c 2 piece rails
and separate rings, so there is lots of places to have little issues
then i bought a 6-18x 50mm bushnell and it was lacking about 20 thousands to clear the barrel
so i cut a shim out of a piece of that blow moulded plastic packaging to make the shim...
it worked for a time, however it was not the thing to do.
the other day i found the rail loose, so i retightened it, and didn't notice that the plastic shim was crushing, which makes things bad...
because the t/c mount and the omega holes are drilled so closely there is no way to move the scope back or forward more than about a quarter inch, the rings are only about 2inch apart center to center.
so any tiny issue with a plastic shim makes for several inches of elevation problems down range.
so i removed the shim, made one out of aluminum sheet and then worked some aluminum foil folded to add about 5 thousands of taper back to front, in order to pick the barrel up a touch and hopefully put the scope adustment so that i have more elevation up than down.
anyway, i am about 98% sure of the mount now, that is if i guessed the elevation correction toward more lift, and i am much more sure that it will stay tight now.
it was just odd as heck that this setup was holding zero and doing an excellent job out to 100-120 yds prior to the use of bh209...
now that i think about it, the bh209 runs hotter, and i bet it was this heat that softened my plastic shim! the mount screws are just about right over where the powder is fired, so there is more heat there than elsewhere along the barrel.
i fired enough of the bh209 to get the outlet end of the barrel noticeably hot.... i never checked the breach end, i bet it was much hotter there!
that makes sense to me!
lesson learned, don't use plastic for a scope rail shim!
thanks for asking about the scope, it is in answering the question that maybe i stumbled onto the problem and more importantly the cause and solution.
bob g