Howdy
I have never tried chambering a 44 Special in a 45 Colt revolver, but I am going to. The 44 Sp brass is considerably smaller in diameter than the 45 Colt, so I will be interested to see how far off center the cartridge sits in the chamber and whether the primer lines up well enough to be fired when struck by the firing pin. Don't worry, I am not going to actually try shooting a 44 Sp in a 45 Colt revolver, just going to eyeball the possibilities.
In answer to your question about tension and all that, yes, a bullet should be constricted not only by the barrel but by the chamber throats, so that expanding gasses remain behind the bullet and do not sneak around in front of it. Without being contained behind the bullet, the gasses do not build up as much pressure as they are supposed to.
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But in a related subject, I have fired 44-40 cartridges out of a 45 Colt revolver. No, I did not do it by accident, I did it on purpose. If you are not familiar with 44-40, it carries a 44 caliber bullet, usually between .427 and .429 in diameter, but the cartridge has been necked down from a diameter close to the same as the 45 Colt cartridge. I'll pop in a couple of photos when I get the chance. Bottom line is, a 44-40 cartridge will chamber in a 45 Colt chamber, and although it is not a perfect dimensional match to the chamber, it will center well enough that it will fire.
I had heard for so long that if the .427 bullet of a 44-40 was fired in the .451 barrel of a 45 Colt that it would 'rattle down the barrel', an exact quote from many sources, and not hit anything, that I finally decided to try it. It so happens that I load both 44-40 and 45 Colt with Black Powder for Cowboy Action Shooting. One day at the end of a match, while everybody was packing up, I put five 44-40s into one of my 2nd Gen Colts, chambered for 45 Colt. I aimed at the center of one of our typical steel targets and fired all five shots. Typical Cowboy targets are a piece of steel maybe 16" square or so. From typical Cowboy distance, about ten yards, I hit the target with all five shots. No great feat of course, but so much for the bullet 'rattling down the barrel' and not being able to hit anything. No the gun did not blow up and no the brass did not split. The front end of the brass mushroomed out to the chamber diameter, so it was pretty well ruined, but nothing split and nothing let go.
I repeated the experiment again a couple of weeks later with the same results. Yes, these were Black Powder rounds, so the pressure was not as high as it would have been had it been Smokeless, but frankly, I don't think it would have been a problem if I had done the test with SAAMI sped Smokeless either. The simple fact is, once the bullet leaves the cartridge, if the bore is not well sealed, pressure will never build up as high as it is supposed to. Gas 'leaking' around the bullet will keep pressure down nowhere near what would be required to damage the gun. I actually reported this on the Ruger Forum a year or so ago, and from the responses I got might have thought I had been playing with nuclear weapons. I was told I was lucky the gun did not blow up and that I was lucky the bullets did not go over the berm and strike a house someplace downrange. These comments were made by people obviously unfamiliar with the two cartridges, people who believed every thing they read on the internet, rather than actually trying something themselves.
I used to work for an old grizzled mechanical engineer. When he was a young man in the Army he was attached to Aberdeen Proving grounds, and he did a lot of work with artillery ballistics. Most of what he was doing was wading through mud, recovering shells that had been fired. Anyway, he told me about some tests the Army did with 45ACP ammo. The old thing about what happens if you throw a cartridge in a fire. What they discovered was if ammo cooks off without being confined in a close fitting tube (like a barrel) the bullets did not achieve enough velocity to puncture a layer of corrugated cardboard.
As far as accuracy with a bullet that does not get a good bite on the rifling is concerned, sometimes we forget how things were done a long time ago. The American Revolution was fought mostly with muzzling loading smooth bore muskets. Although their accuracy was obviously no where near as good as a rifle, they could still hit targets with surprising accuracy. You certainly did not want to be standing 25 or 50 yards in front of somebody with musket. The ball was not that inaccurate, you would probably be hit.
I used to have a Lee/Enfield 303 British that keyholed with everything I put through it. Cast bullet handloads or factory Full Metal Jacket stuff, it did not care, I could not get a bullet to leave that bore without tumbling. But the surprising thing was, at 25 yards, even though the bullets went through the targets sideways, they were still on paper, and not very far away from the bullseye. If I had been shooting at a man, I would have hit him every time. So really no surprise that my 44-40 bullets hit the targets when fired from a 45 Colt revolver. Just not enough time and distance for drag to really take effect and send the bullets spinning off into space. Fifty yards would probably have been a different story, but not ten yards.
