You must unload it just as the old-timers did:
1. Remove the cylinder.
2. Remove the nipples.
3. Using a brass, aluminum or hardwood pick (to avoid sparks), scratch out the old powder.
4. Using a hammer and a short length of brass rod that fits in the hole, tap out the ball. A short length of hardwood dowel may also work.
5. It's best to use a scrap of 2X4 with a 1/2" hole drilled into it to receive the ball when it leaves the cylinder. This makes tapping-out much easier.
But really, unless you stoked that Remington with a full load of Hodgdon 777, which generates greater pressures than black powder (used on equal volume with black powder, which should never be done with 777), I'd just shoot it out.
If you loaded that Remington with 35 grains or less of real black powder, there shouldn't be a problem firing out the loads.
Yes, the larger ball will create a wider bearing band for the rifling to grip, but not nearly as much total surface area as a conical bullet.
If you have concerns about the greater bearing area of a .490 ball, then put a few drops of vegetable or olive oil over each seated ball before firing, to help lubricate its passage down the bore.
Incidentally, through the years I've occasionally loaded a conical bullet with too much powder, and couldn't seat it deep enough for the cylinder to turn.
The Colt is easily remedied: shoot it without the barrel attached. Even with a maximum charge, the projectile (ball or conical) apparently doesn't have much velocity, and projectiles bang out of each chamber easily.
The last time I did this, I aimed the barrel-less Colt 1851 .36 at a cable spool. The conical bullets hit with a thunk but didn't penetrate its wood.
Curious, after reloading the revolver and replacing the barrel, I shot the wooden spool again from the same distance (about 30 feet). Every ball plowed deep into the wood.
Amazing what 7-1/2" of barrel can do!
