The fact it's tossing that shot out by 8 inches eliminates most possibilities. There just aren't very many ways it is possible to have a shot go 8 inches out of the group.
Eight inches out is not a "cold bore" issue.
If FRP is throwing a shot 8 inches I'll eat a coyote.
Mount... Not impossible I guess. But 8 inches, that is baffle strike territory. I can't think of any possible way the mount consistently throws only the first shot - and more importantly, throws it EIGHT freaking inches. That, is an insanely big number.
Don't know how a scope, or scope mount, only does that on the first shot and only the first shot either though. But I can't think of anything else, on any rifle, capable of throwing a shot off by such an incredibly huge amount, other than the sighting system.
Taking for granted of course that bullets are stabilized and no baffle strikes and all that happy kinda crap.
I'm kinda betting it's not only on the first shot? The 8 inch number is just too huge. Something is way loose/jacked up to throw a shot out that far and if so, it's not going to be on just a first cold bore shot. That might be the only time it's been noticed so far, but something that out of whack is going to show itself more than that.
- DAA