How important is it to have part of the full diameter portion of the bullet in the cylinder throat with a loaded round? I would think that this is like a rifle cartridge being snug on the lands, it helps keep things centered. Failing this sort of fit the bullet lies on the bottom of the chamber, to an extent, and may not enter the cylinder throat straight or on center.
Neither rifle nor revolver bullet noses should be relied upon to center the bullet during static fit any more than you would trust Stevie Wonder to safely pilot the next plane you take. If the case lies in the bottom of the chamber, or if the bullet nose cannot free-float dead center to begin with you have already made a mistake. Try focusing on the parts of static fit that absolutely cannot go to hell when the primer goes off, the things you CAN count on.
WHAT? Ok, think about this. In the first ten thousandths of an inch of bullet travel, the bullet can already be going 20 to 40 fps at that instant! Now, you tell me, if you take one of your bullets and throw it as hard as you can, about the same speed as that bullet is moving in ten thousandths, at an oblique angle against hardened steel, is it not going to get dinged pretty badly? If you allow the brass to point the bullet off-center or crooked at the start, is there any hope that the bullet alignment can be corrected by the throat without damaging the bullet on the side that contacts first? The answer is yes and no, or really, "it depends". Whether the nose pre-pilots on center or not is also fairly irrelevant, any piloting on the lands in a rifle is weak support at best, sort of a "feel good" thing people do because it helps band-aid other things at low velocity. In a revolver, the bullet is moving even faster when it hits the taper, and has less nose to align much less anything to really "pre pilot" against other than the cylinder throat. What you need to do is simple, just POINT the bullet in the right direction and make sure that the part of the brass holding the bullet releases evenly all the way around and the same way every time.
But wait, there's more. The Noble gas laws tell us that pressure within the system will find equilibrium. There are wave fronts within the case where pressures are initially fluctuating, but the origin and case shape direct them evenly upon the bullet base....usually. The pressure NEEDS to be uniform on the base, anyway. This is why primer/powder/charge weight/density is so important, it creates uniform pressure on the bullet base. If the gas is pushing evenly, and the bullet is pointed in the right direction in the first place, then the bullet HAS to go straight since it's considerable inertia, even after a few thousandths of an inch of travel, must obey Newton's laws of motion. The only thing that can re-direct the bullet is a force stronger than the bullet's inertia during launch, which will of course be the steel of the throat or forcing cone. But we already know that vector forces strong enough to re-direct the bullet's flight in the throat are high enough to damage the bullet's shape on one side, and since we don't live in a perfect world, there must always be some damaging going on. So how to contend with that? First, nobody shoots one-hole, one caliber groups, so perfection is unattainable. Second, this is where your alloy, bullet shape, powder choice, and static fit will save you. It's the dynamic thing again. The bullet must self-align BEFORE velocity is so high that the bullet sustains damage from that alignment, so you see proper bullet shape/toughness DOES get you some wiggle room if you allow for it when you select components and create the cartridge. But you can only get away with just so much self-align capability before you have to rely on something else, the BUMP. The bump is a swage-to-perfect-fit operation which occurs IN the gun, and since the gun is what we're trying to fit, nothing can do it better, especially right in the big middle of a violent launch. Your components need to be selected to work together so that this bump/swage/DRAW thing occurs at the time it can do the most good, which is the time when the bullet can be out of alignment, which is in the throat/forcing cone, or whatever restriction we're forcing it through to get fully into the parallel dimensions of the barrel. We aren't extruding the bullet enough to completely re-form it, otherwise it wouldn't matter how crooked it was launched, it would still come out a straight slug of spaghetti. We only get a little bit, and although it's not enough to straighten out deformation from a bad sideways blow, it can be enough to correct the tiny misalignments that turn a half-inch group into a three inch group once high rotational forces start acting on the bullet. Success relies on a combination of every little thing we can do to get that bullet going straight, and just supporting the nose on the lands or in the cylinder throat isn't enough. This is what I have meant all the times I've written things like "the bullet must be given 'absolutely straight' as the path of least resistance, because it will always follow the path of least resistance". You create that path to begin with and guide it the whole way.....unless you give them a hard enough skin, make them hard enough to withstand ricocheting off of the various insides of the gun until they finally funnel into the middle of the bore, or accelerate them slowly enough that they just sort of wiggle into place when fired. Really, I think most of the time we're doing a little bit of all of this with a proper load. Another thing is the noses of the bullets, particularly rifle bullets, don't affect the flight all that much, particularly with revolvers. If the pointy tip of a bullet isn't perfectly straight with the rest of the bullet, it doesn't matter all that much. My M1A with all the mechanical problems it has STILL shoots 2" groups at around 2200 fps with bullet noses so mangled most people would fear pulling the trigger. If the rifle was right I'll bet it would do an inch with the same bullets, we'll find out soon enough. Single-loading perfect bullets didn't make a noticeable improvement in groups any more than letting it chew them up self-loading hurt them. That's just one example of the "fudge factor" we have with nose concentricity after the "bump" event.
The nose alone isn't strong enough to keep the bullet guided straight all by itself, so like I already said, it's just a bonus if the nose is supported when the cartridge is chambered. With revolvers you can get away with a lot because most bullets are basically cylinders to begin with, rifling twist rates are low, and velocities are comparatively low. Get consistent bang-bump from the case to the throat (repeatable jump created by consistent case neck tension and consistent ignition) and you'll get repeatable bump/swage/draw in the forcing cone so that the bullet can recover from any cylinder or other alignment problems by re-swaging to a balanced shape as it passes through the forcing cone area and into the barrel.....all provided that your alloy and powder pressure are correct when the bullet gets to the forcing cone, and provided your bullet left the confines of the brass pointed directly at the center of the muzzle.
Some things you can't force. Some things need to be forced more than you might think they do. I say that as I sit looking at some little 26 bhn gremlins for one of my rifles and try to figure out how much powder and how fast it will have to burn in order to bump them enough to shoot straight.
