Took my new magneto speed out today, It functioned flawlessly. I did have to play with it a little to have it fit properly with the sized barrel I was shooting. I found when I added all the spacers needed it tended to have some raising up at the end of the bayo. The point of impact was changed by about 1+ inch but it did not affect the group size. My main reason for buying this unit was to have constant speed reading and it has accomplished that.