Hi All,
I'd like to try something that may be a little unusual, and I'm inexperienced and don't know it it's safe to do.

I noticed I can drop a bullet into the breech of my Argentine rolling block and push a case onto it by closing the breech block.  It's doable with not a lot of effort.

I'd like to load fire-formed cases with black powder (like breech loading) so I can shoot with what I have on hand instead of waiting to find components for conventional reloading.  If this works out I can shoot for long enough to get the the other stuff together.

I'm concerned that the case doesn't go up very far on the bullet (.246") and that the case isn't very "tight" around the bullet as it might be if loaded in a press.

Is this likely to allow gases to escape from the breech?

In the attached picture you may notice that these bullets are intended for muzzle loading.  See any problem with using them in a case in my rolling block?

You do not really need dies. A lot of shooters do not size their cases. Just put a wad on top the BP and  put a bullet in and if necessary push the nose of the bullet against something to correct depth.

those hollow base Minie'-style bullets were often filled with grease.  You could fill them with lube and it might help keep the overpowder wad in place

So the bullet definitely touches the cork wad when you breech seat?  There's no air space between the bullet and the wad?
I'll be using 55grs of black with a filler of PSB which I'll fill to the case mouth and compress enough for the bullet to seat on it, and use the wet type floral foam to close the case, which goes to nothing when you press on it.  Here's the PSB:
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And here's where I learned of it:
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I have a very similar situation.  While not being strictly breech seated bullet, I have fixed ammunition that contains BP, .060 veggie wad and a paper patched bullet.  The bullet is stuck in the case about .030" and just nests into the rifling on loading.  Fine fit between bullet and walls of rifle's long (approx. .78") free bore.  Chamber has a 6 Deg leade.  45-90 Win.

Experiencing vertical stringing.  Little horizontal.  What's up?

Thanks, Boats.  Bore is cleaned every shot, no residue.  Powder is Swiss 1.5.  Neck tension is a small issue as the bullet base is in the case .030" and just snug enough to keep from falling out.  What I did not do was check COAL before shooting, there may be some variance.  Detail, Detail.....

" Consistency of powder charge and wad seating is key."  Boats