Bullet Size and Nurling

[Sliver Shooter]

I have been doing way to much thinking about bullet sizes for my .303, 7.7 and 7.62x54. All taking basicly the same bullet. I have read other threads talking about nurling to increase the size of a bullet and so my thoughts are wondering, what happens to the cast bullet when it gets nurled by the rifling in a barrel. That lead that gets pushed down by the rifling has to go somewhere so if the boolit already fits groove size, it must lengthen it. SSSSOOOO, if one were to have a boolit that were, say .002 smaller than the groove size, when it gets nurled by the rifling, would it not fill the gap in the grooves? If that were true, my rifle, that has a bore size of .304 and a groove size of .314, if I were to use a boolit that was .311 or .312, would it not fill that space in the groove when it gets squeezed by the rifling, thus being a very good match for that barrel? does that make any sence????????:?:

[turbo1889]

The reason the theory you are proposing falls apart is that there is already massive pressure loads on the base of the boolit before it ever engraves in the guns rifling while the boolit is in the guns throat. Thus the damage is already done before an undersize boolit ever engraves in the rifling. This is why I have been sizing my boolits to fit the guns throat rather then the bore like one does with revolvers only I am trying my best to do it with all my guns especially my bolt action rifles.

[Bret4207]

I have been doing way to much thinking about bullet sizes for my .303, 7.7 and 7.62x54. All taking basicly the same bullet. I have read other threads talking about nurling to increase the size of a bullet and so my thoughts are wondering, what happens to the cast bullet when it gets nurled by the rifling in a barrel. Okay, first off, the boolit doesn't get knurled, which is an impressed pattern around the entire circumference of the boolit. It get's engraved lengthwise along portions of the boolit.That lead that gets pushed down by the rifling has to go somewhere so if the boolit already fits groove size, it must lengthen it.To an extent, yes, but it's a tiny amount. SSSSOOOO, if one were to have a boolit that were, say .002 smaller than the groove size, when it gets nurled by the rifling, would it not fill the gap in the grooves? No, probably not. It also likely won't happen over the length of the boolit and may happen more to one side more than another giving a lopsided boolit. If that were true, my rifle, that has a bore size of .304 and a groove size of .314, if I were to use a boolit that was .311 or .312, would it not fill that space in the groove when it gets squeezed by the rifling, thus being a very good match for that barrel? does that make any sence????????:?:

I think I understand your idea mostly because I had the same general idea 20 years back. In theory I suppose if you could really hammer the boolit and keep the pressure up till it was well in the barrel it would swage out fill the grooves. The problem is all the other damage you'd do to the boolit. Your idea of the rifling engraving the boolit and the displalced alloy filling the grooves was answered in your own post- it tends to lengthen the boolit. To get the boolit to swell uniformly along it's length you'd need the powder pressure pushing on the base and something blocking the nose (Like "bumping" in a sizer) or to mash the boolit into putty with pressure. That's a very, very hard thing to control.

So far all experience with undersized boolits and smokeless powder shows that the boolit will not act as you desire. The idea of the boolit "obturating" to fill the grooves is an iffy proposition at best. Alignment is lost, every shot gives different pressures, variations in boolit weight of charge may alter the effect....it's a lot to ask and to get gilt edged accuracy.

[Sliver Shooter]

Ok, that answers it nicely and eliminates that line of thinking. I guess then that the only way that anything like that would work is with the hollow base bullet and a charge of black, which acts differently than smokeless.