Hey Kindy!
No luck with your grandfather and my Dad either.
As far as Gedmatch goes, from the main page, go over to "analyze your data." There are several options available there. The two most commonly used are the first two options 'One-to-Many' matches and 'One-to-One' compare.
'One-to-One' compare is the most basic search on the site. In this, you enter in the Gedmatch test numbers of two tests, and the search tells you if the tests match and for matching tests - tells you the exact DNA location of the match (the specific segment of the specific chromosome). I just did a one-to-one comparison of my Dad's A461940 and your grandfather's M446497 test, and the search returns that we do not match.
'One-to-Many' searches identify all of the tests on Gedmatch that match with your test. So - if you do a 'One-to-Many' search for your grandfather's test, you get all of the tests that match him on Gedmatch. I just ran this search for his M446497 test and you have some great matches there. When you look at the results, you will see that the strongest matches are at the top of the list (you are currently his strongest match). When I am first starting out with these results for a test, I usually focus on the "Longest cM" column and look for the longest segments, as long segments (anything over 25 cM - especially anything over 35 cM) tend to be evidence of a recent common ancestor. There are 8 different tests in his results that have a segment over 35 cM - so you should probably start with those. Be sure to always run a one-to-one search on tests from these results that interest you - just to make sure that you have a match.
Alright - looks good. Let me know if you have any questions, as I use Gedmatch all the time.
