Boxer:

Outta da Poor Boy 6-284. Never had a Green OEM 243Win spout that wouldn't pinhole 105's,but this one punched out to 6-284 is a Keyholing Machine. Should whistle a rod through it,if only as a twist curiousity confirmation.

I know you don't need "help", but there are good and bad green barrels and the "bad" ones won't shoot the 105's in even in a 243 mode. It's hard to wrap your mind around, but increasing rpms only makes a bad barrel worse. Had a f'up green 243 that key holed 105 AM on the lands, but shot them just <OK seated 35 off and backed of a grain. I'm talking keyhole to 1" so it's a 6cm now and wearing an 8 Brux from Gre-tan. Point is good QT cut barrels shoot every thing, others don't...and it's a crap shoot as you know.
Jacket thickness matters in a marginal barrel

Try an 100 gr Interlock and if it won't shoot pitch it.

Not judging here just what I know..(grin)... does that help?