Quote
Is a compressed load more prone to greater pressure spikes as the load is slightly increased?


No.

Quote
Could seating the bullet slightly deeper with a compressed load create a pressure spike?


No.

Compressing powder does not in itself increase pressure.


Give a man a fish and he eats for a day. Give a man a welfare check, a forty ounce malt liquor, a crack pipe, an Obama phone, free health insurance. and some Air Jordan's and he votes Democrat for a lifetime.