Obturate??

[russellshaffer]

I had to google this topic, as I've never seen a round ball obturate from being shot, I have however seen recovered round ball like these in the photo with the rifling marks.

Were these patched or fired from a revolver? I don't see how a patched ball could have such sharp rifling marks.

 

[Loyalist Dave]

Sounds like an interesting experiment, as so far, the patched round ball that I have seen after firing into gelatin, whether video online or in person eye witness, ..., while there was a mark on the ball from where it was compressed against the rifling with a cloth patch, and there was in some cases a deformation which appeared to be from impact with the gelatin. However, there was no evidence of any additional obturation from having been fired. I would have liked to have loaded a few patched round ball and popped them back out with compressed air, to see what the loading had caused. Then I would like to do test with recovered, fired patched round ball to see if further compression appeared on the ball, which could then be attributed to firing. Alas the fellow with the gelatine and rifle was testing for deformation when no bone was struck, not for obturation. However, no marks from lands or grooves have I seen in the past. The photo of the round ball with clear groove marks in an earlier reply is very much from a cap and ball system.

LD

 

[Erwan]

May be some people is talkin about the wedge effect of the patch around the bullet and, in that case, it makes think like a "clogging effect" between the bullet and obturate the bore with the compression of the patch in the rifling to ensure the sealing ...
I think more something like that than a real obturation stricto sensu...

 

[hanshi]

As a general rule tighter prb combinations are more accurate. If the patches have any holes, are scorched or burned then the patches are not thick enough or strong enough. I long ago polished the crowns on my rifles so tight loads could be seated with the wood, underbarrel rod. My .45, for instance, takes either a .440" or .445" ball and a canvas .024" patch and both load pretty easily. A lot depends on the lube as well. Liquid, slippery lubes make a patched ball seat the easiest with a thick patch. TOW mink oil, which I use for hunting, require (for me) just slightly more pressure to load with the wood rod but still easily doable. Hoppes BP Lube is my go-to for general shooting while mink oil is my go-to for the woods.

 

[smoothshooter]

I read in a post here that a ball and patch "obturate" as it's being loaded, or as it's being started. What exactly does this mean? The definition of obturate is "block, or close off". I think I know what it means in this context but I'd like to hear it from you guys.

“Obturate” means bullet expansion against the interior walls of the barrel upon powder ignition, in our context.

 

[Notchy Bob]

“Obturate” means bullet expansion against the interior walls of the barrel upon powder ignition, in our context.

That is a really good, working definition. Well stated!

Notchy Bob

 

[fishmusic]

The reason I asked this question Read what is because I've never been convinced that my ball and patch combination fills (blocks, obturates) the spaces between the lands and grooves. I think my ball is too big and my patch is way too thin. A gunsmith set it up for me that way, along with some other minor work, but I think he blew it on the ball and patch sizes. I want to avoid gases jetting past the load just after detonation. Unfortunately I've never found one of my patches down-range for examination. Maybe I can find a muzzleloading - savvy gunsmith within driving range.

Read what Woodnbow and Grenadier1758 say, You don't need a gunsmith to cure this issue. working up a load includes experimenting with lubrication, powder charge, ball size and patch thickness. Get a copy of Dutch Schoultz's black powder rifle accuracy pamphlet. Dutch presents a treatise on how to systematically work up a load and improving your rifle's accuracy by changing variables one at a time until voila, your rifle starts acting like it should. I have used his method to much advantage. His exact methods aren't necessarily gospel but the systematic work up is golden. See if this link works Black powder rifle accuracy system -

 

[Silent Walker]

Were these patched or fired from a revolver? I don't see how a patched ball could have such sharp rifling marks.

Unknown if they were or not, but no one has provided definitive proof that a patched round ball will obturate from being shot.