If I had your problems I would find someone that knows what they are doing help you with some proper handloads. They would measure your chamber to get the right length for the bullet that is to be loaded. The SAMMI standard lengths may not be the best fit for your chamber. A couple of different bullets along with a couple of different powders and a couple range days should eliminate any concern about ammo being the problem.
Handloaded ammo is usually much better than factory, and much less expensive to boot.