I learned about tight pins this past year; on my last build I drilled the front pin hole a little askew instead of 90 degrees, I slotted the pin hole but still had a pin that was hard to drive in. When I shot the rifle, it was a real dog, terrible accuracy. It was a Bobby Hoyt re-bore so I immediately blamed the barrel.
This was my pre-carve from hell rifle, looks didn't matter so tried redrilling the pin hole correctly just to see what happened. I could push the pin in and out with my finger after re-drilling.
I tested the rifle again, it shot a tight cloverleaf at 50 yards, nothing wrong with the barrel but the builder had a thing or two to learn.