I'll admit my ignorance, I never knew 30-30 used large primers. Obviously I never owned one nor reloaded it. I had heard that they didn't have a problem with pointy bullets because the taper of the cartridges kept the bullet point from lining up with the primer in front of it. I don't know if that part is true at all or not. But thanks for edumacating me, Mako!
When I lay .30-30 cartridges out flat in a line (and I'm using factory cartridges for this test), the points don't line up with the center of the next primer (see picture below). They kind of straddle the edge of the primer pocket. I assume they'd be similar in a magazine tube, although it would be dangerous to take that assumption too far. For instance, spitzer points could still find their way into the outer part of the primer and set it off.
These also don't really have "flat points" although they are recent (a few years ago) Remington factory Core-Lokt loads. The box doesn't even say flat point (just "soft point"). About half of them seem to have a small flat meplat little more than half the diameter of a large rifle primer. The other half are really more of a round nose. Not a lot of consistency even in the same box of ammo. Obviously Remington doesn't consider this a long-range or target cartridge!
So a flat point doesn't seem strictly necessary for the .30-30, but that doesn't mean it isn't necessary for other cartridges.
And every .30-30 case I've seen (or noticed, anyway) used large rifle primers. But that doesn't mean that it always has, all the time. For example, we usually think of .38-40 as using large pistol primers, but I have some old Peters cases that are sized for small primers. But I also have a box of Peters .38-40 with large primers. I've also heard that .44-40 cases can sometimes be found with large rifle primer pockets, not large pistol. (After all, it started out as a rifle cartridge.) I've never seen or heard of that with .38-40 but it's probably possible.
But I digress. However, I would be pretty surprised to find a .30-30 with a small primer pocket, and that may be part of the reason they're safe with some round-nose bullets (provided they're not too pointy).