Stick with the recomended OAL
If I understand what you are trying to do, you are trying to seat the bullet out farther to increase accuracy, and it is long enough that your dummy round won't eject. Is this right? Well, it is a short action and you are trying to load your ammo long. Actually not too uncommon, the entire action is designed around a certain length, and you are pushing the upper end. I don't know how much experience you have with the .300WSM and reloading, but use Nosler's OAL and vary the charge weight first before changing seating.
Anyway, in the May issue of Rifle magazine there is a good article on the .300WSM regarding seating depth. The author, Chub Eastman, and the plant manager for Nosler, Mike Lake ran a series of experiments with seating depths. For the article they used 180 gr. Accubonds. To conduct the test, they started out with factory loads, both Federal and Winchester load the 180 to 2.820". Then they took handloads and increased the length .060" at a time until they had an OAL of 3.00"
The part that is of interest in this was the pressure results.Using the same charge of powder for each load as they increased length, pressure actually rose; using 69.0 grains of H-4831sc it increased a total of 3,000 psi, and with 70.5 grains of RL-22 it went up 4,000 psi. And no they were not jammed into the rifling, they still had .005 till contact. The best accuracy was at the second load length, 2.880".
I don't know what powder or charge weight you are trying, but be careful with going longer if you are near max loads.
Another thing from the article, Nosler's ballisticians like the .300WSM enough that it is their cartridge choice when testing .30 caliber bullets.
hope this helps,