the method you described can work but it normally gives you about .020-.050 bullet into the lands. That is normally what is called the "jam"
If the gun has a magazine and you want to use it, then the mag length will determine COL.
has a seating depth tool for under $30 that allows you to accurately measure exactly where a particular bullet touches the lands. That way you can determine what seating depth your gun likes as far as on or off the lands.
Depending on the exact bullet you are using, you may have to adjust your COL (if shooting single shot) to the desired point. Not all bullets are the same length from the ogive to bullet tip.