When I first heard and played the long Gibson PC I too felt it was a different animal somehow. In looking at the reed I saw it was designed more like an NSP reed than a Highland PC reed. About the bore I don't know, I've not measured the bores of various PCs. But whether due to the reed alone, or a combination of the bore and the reed, the Gibson to me sounded and played more like a mouthblown NSP chanter than a traditional Highland PC.

For those who've not played NSP (Northumbrian Small Pipes) the bore on an NSP chanter is much like the bore on a Highland PC, a straight (cylindrical in music-speak) bore, quite narrow.

The reeds are very different. The traditional Highland PC reed is narrow and long, the NSP reed is short and wide, more square. The Gibson PCs I have came with short wide NSP style reeds, though plastic. NSP pipe chanter reeds are nearly always cane.

About my Cocobolo Dunbar pipes, I've owned two ABW and one Poly Dunbar and all were great. I don't have those others any more, so I don't have an ABW Dunbar to hand to compare to my Cocobolo Dunbars. My PM does have ABW Dunbars so I need to get together with him sometime for an ABW/Cocobolo comparison.

As presently set up our pipes sound very different, his with Rockets, mine with Kinnairds. He's getting the sound he wants, very bright, and I'm getting the sound I want, warm.