Bushnell 300mm 5.5 M42 lens

[Chasr]

I have this lens and it is very very sharp on my T1i,,all searches on it came up empty,,cant find anything about it,,from what I've seen from other Pentax Vivitar and all the rest but they can't touch it,,will be getting a 1.4 times for it and have made up bean bags for the roof of mu truck and it is held solid,,just wondering if anyone has any information on it,,dammed if I know Bushnell really made it,,have many M42 lenses and a few good Canon ones,,any help would set my mind to rest,,thanks guys in advance.
chas