Not sure how the Hornady O.C.L. works, but I use the Comparator. Is this the Comparator that Sinclair makes?...
You may be using 2 different methods of measuring O.C.L.
My method: Take a wooden dowel that is about the size of the .308 bore—maybe 5/16th , ain’t sure…
Close the Contender up and insert the dowel into the bore—PLEASE BE SURE THE CONTENDER AIN’T LOADED!!!...
Then with a sharp pencil, mark the dowel where it is just at the junction of the crown and the bore. I put the pencil there and turn the dowel. I get a nice circle around the dowel…
Then, make a dummy round with the bullet you are going to use. USE A CASE THAT IS NOT PRIMED, THAT WAY YOU know IT IS A DUMMY ROUND…
Seat the bullet a little at a time and put it in the Contender. It shouldn’t close when the bullet is seated to minimum depth in the case to just hold it. (If it does, then I really won’t matter as you have a long chamber and seating near the rifling will be out of the question)…
Keep seating the bullet a bit at a time until the Contender will close and allow the rifling marks on the bullet. Coloring the bullet with a black magic marker will help to see this…
At this point let the dummy round in the chamber when it is closed. Insert the dowel again and do the circle thing with the pencil again…
Measure the distance between the 2 circles and you have the O.C.L. for that particular bullet when seated to the rifling…
Subtract what you want and then seat the bullet to that O.C.L…
Remember, that length will only be for that bullet. You can use the Comparator, if it is the Sinclair one, and that will give you the cartridge length to whatever distance you wish to stay away from the rifling. The measurement will be the same for all bullets when seated…
I seat all of my bullets to just touch the rifling or a 0.001” from them. In the Contender, this may not be possible as T/C make long chambers to prevent stupidity with reloaders that ain’t got it figured out yet…
Good-luck…BCB