I would not expect bullet seating depth to have that much effect on chamber pressures. Bullet depth and crimp can indeed increase pressures a bit, but unless the loads are reaching maximum spec for the cartridge, it wont have that result.
I'd be getting out my bullet puller and pulling one cartridge apart on both the Federal and the Remington, and do a visual examination of the powder, plus measure the charges for both, just as a comparison. If it was an isolated incident, then an over charge wont show in an inspection, but I'd still do it to answer my own curiosity. By reverse engineering the charge based on weight, and info Federal provided on fps of their ammo, you might see something that you wont know without dissecting the components.
