Another trick to protect your rifle is take a piece of plastic off a milk jug. Cut a slit in the plasticand put that over the blade of the front sight. Then when you slip with the file and you will, and youhit the barrel, you will not mark up the bluing. The masking tape is a way to mark the sight so you can keep track of how much of it you have removed.

Instead, I take the file and rifle right to the range. I shoot a round and take about four strokes off the sight. Then shoot again. Make sure you do at least two shot groups. When you get the POI close... STOP. This is where you really have to concentrate on sight picture target acquisition. Now startthinking about what range you want the rifle sighted in at. Move to that range and then start shooting and doing one file stroke at a time...

By the way thats a nice group but before I do any filing, I would increase the powder charge to say 80 - 90 grains and see if that does not pick up your POI a little while still giving you a good tight group at the 25 yard line. While 70 is a fine hunting load, I like to max out my powder charges. Then again, that is just my way. If you're happy with a 70 grains charge and ball, then by all means change the site. Just don't be in a hurry. It would not hurt to change it s little though.