Obviously, muskets can be loaded this way since that’s the only way to load them. But, excluding firearms which are designed to be loaded via the barrel, what would happen if you did this to other guns like a glock or a colt 45?
Wouldn’t work. The cartridge case is larger than the bore.
And if you tried with just a bullet, there’s no place that will contain the powder and the primer. That’s what the case is for(and to seal the firing chamber).
A Glock or Colt .45 are *by design *breechloaders, as mentioned the case itself is what makes the chamber gas-tight in back, and it has to provide for a way to extract it after firing. Also I believe something of sufficient diameter to be rammed down the barrel from the front would not stay in place for the firing pin/striker to set off the primer, it would just get knocked forward. For a modern muzzleloader I could see a design based on some sort of caseless round with a latter-day, likely electrical, “pan” for triggering the charge.
I wonder about the big guns on the very old Battleships. It seems to me that if you loaded the primer at the breach. the cordite and payload, which were loaded separately anyway, could have been bushed down the muzzle (by a team of sailors with a very large ladder).
At what stage did they stop loading the propellent seperately from the primer?
Some percussion revolvers could conceivably be loaded by jamming gunpowder and a bullet down the barrel, and I suppose maybe someone might try that in case the cylinder got stuck or something, but I can’t imagine it would be a very reliable way to use them. Normally the chambers would be loaded from the side, as shown here: https://en.wikipedia.org/wiki/Caplock_mechanism#/media/File:Loadseq.jpg
You could insert a 357 mag. into the bore of a 45 colt. If somehow you were to insert it tight enough that the firing pin would actually detonate the primer and not merely push the smaller cartridge out of the way, you would end up with a ruptured case stuck in the chamber of the 45. The bullet would likely exit the bore however, inaccurately.
For a very forgiving definition of “firearm” : that’s how mortars are fed and fired.
- Propellant and projectile *could *have been pushed down the bore. But the whole point of the invention of breech loaders was to avoid having to do so.
Pulling the cannon far enough inboard to get access to the muzzle end ensured the gun was misaligned for the next shot. Getting it realigned was a matter of guesswork. So there was no ability to fine tune aiming from one shot to the next. And it took time to move and then re-place the gun. This was a *huge *disadvantage to muzzle-loading naval cannon.
As well, feeding the main charge in from the breech was dangerous. The barrel was hot, any leftover powder fragments from the previous shot might trigger premature detonation, etc.
Last of all, ramming the projectile in from the breech end meant it either took a huge amount of force, or else the fit between projectile and bore had to be very loose. As in so loose the barrel couldn’t be rifled (much).
Bottom line: Not much point in designing a half muzzle-loading, half breech-loading weapon. Cap and ball revolvers were such a device, but they were an example of evolutionary transition from pure muzzle-loader to pure breech-loader. Once pure breech loading was perfected on handguns the process only had to be scaled up to ever larger guns.
2. AFAIK primers and propellant were and still are separate on cannon which fire non-unitary rounds. Any mortar, howitzer, or naval gun that accepts differing charges is going to have a separate primer. Or else a potent electrical ignition system to fire the charge with no primer at all. I’m going from memory here and a cursory Google / wiki was uninformative on the details of modern or early 20th century primer practice.
But it is still the case that some remaining large guns fire non-unitary rounds. I doubt such guns are still being designed, and may not even be being produced anymore.
Clear now it’s been pointed out to me 
Thank you.
I hadn’t thought through the mechanics of landing a ballistic shell on target.
The question asked about pushing a bullet down the bore, not a cartridge, and yes this is doable, You’d need to pour in powder first, and the primer is carried in the rear of the cartridge, so you’d still need to insert at least a primed rim via the breech in order to fire the gun, but really you need the full case, as that is what seals the hot gasses at the breech.
You will be limited to fairly modest pressure and velocity, because the bullet must be soft enough to start and drive down the barrel without breaking the ramrod, and such a soft bullet will strip out on the rifing if modern velocities are attempted, and best if it is a short light bullet, because the lower velocity will reduce the spin rate, and a long bullet may not be stable enough.
It is rather important to get the bullet well seated on the powder. Excessive space can lead to misfires, or worse, pressure spiking in the barrel, at least with black powder.
Mossberg, and possibly others sell replacement barrels for their pump action shotguns that convert them into .50 cal. muzzle loading rifles, so it is nothing new to at least use the lock mechanism of a thoroughly modern firearm in a muzzle loading capacity, and many modern muzzle loaders use modern mechanisms as well.