ORIGINAL: UncleNorby
Eldeguello explained the higher impact from the "duds" exactly right.
But I didn't see anyone address the higher velocity of the heavier bullets, that you attribute to the sloppy bore fit.
I don't beleive it is the sloppy fit that allows them to gain more velocity. If anything, a sloppier fit would result in less pressure generated, and less velocity. BUT other factors are also at work. Because you did get higher velocity I'm sure the heavier bullets are upsetting properly and sealing the bore, allowing perhaps even a more efficient burn of the charge resulting in higher velocity.
Uncle Norby,
I am using a wad with the flat based BB 410. One thing I noticed is that the velocity keep falling off with the 410's each consecutive shot. First at 1620 and the final at 1391 (a distribution of 229 fps). I'm not sure what to attribute that to, but I suspect that the barrel, in getting hot, expanded enough that each consecutive shot let more breech gas blow by.
The GPs are the only bullet, apart from the BB 270 Ballet, that I have achieved three touching holes at 50 yards, so I think the tight fit of the GP's are a good thing for accuracy, albeit it seems to inhibit muzzle velocity.
Another nice thing about the GP's is that their velocity distribution was very tight, tight at least for what I've been used to. If one throws out the slow one where I did not swab, the distribution only ranges by 24 fps. Weighing charges and a little more care in loading, I could probably narrow that, which would I think, extend my range.
In reading the GP pamphlet, the GP bullets are .509 diameter. My Sidekick is .510. I think the Hawken is .512, which must explain why I don't recall the GP's being so hard to load in my Hawken. I figure that by the time Iget them crowned, the GP's top band is snug with the bore. I do not feel that to be the case with Buffalo Bullets. Seems like B.S.was saying he would swage his Buffalo Bullets in apiece of extra barrel to assist with the bore fit.
I would like to try a 12 shotsample with the 410's allowing ample time for the barrel to cool between shots, just to see if I can tighten its velocity distribution and test four 3-shot groups for accuracy.
Happy Hunting, Phil