I think the lower groove you are referring to is actually the lube groove if the bullet was not powder coated. I used those bullets for rifle and handgun. I used 13.0 of 2400 as my starting and I want to say it got me around the 900 or so fps in my 6". I lost quite a few of my notes not to long ago and that load was among them. Coal that worked for me was 1.615. I used Oregon Trail Rifle data for these loads. Same bullet from what I can tell. As with any loads on a forum your mileage may vary. One of the best investments I made years ago was to join Loaddata.com. For a yearly rate you get all published manuals, and published load data out there. The data is copied right from the actual manuals and published articles. Its great.