door closer question

I purchased a 40-079 door closer from Swisco to replace a worn out S-B Manufacturing Storm King Model 105. Installation was easy and thankfully you offer this product as it resembles the design of the old closer. However, I have a problem with just the last few inches of door travel (see attached video), because it stops retarding and then closes with a bang. Turning the adjusting screw all the way in slows the closing but does not alter the final retardation. I realize you'll notice that I haven't installed the last two retaining screws on the jamb, deciding not to drill the holes quite yet if I can't get this one to work. I bought two of these, just in case, as I have another storm door with another original Storm King that still operates. I believe they both are 60+ years old but the one that is still doing its job has had much less frequency of use.
Do you know a solution for my problem?