I've been loading for 50+ years and I've always been super cautious and safety minded. I always moved up gradually with different loads watching for pressure signs using manuals as a guideline.
But what caught my eye, after owning a couple 300 win mag rifles, is having one in an Encore pistol! I had a BFR in .45-70 which was a handful even though it was a heavy gun. But an Encore in 300 Win mag - Geez Louise....I sure hope it is at least ported.
That does not sound like a fun gun to shoot.