Is putting grease in the chamber of a cap n ball a myth ? ...

I shot cap and balls for years. I started out putting Crisco
in the chamber because that was the advice I received
as a novice. But, apart from it being messy I figured
that it was more likely a chain fire would be caused by
a bad fitting cap than a spark passing by a tight fitting ball,
and going backwards to boot.
Plus, back when these revolvers were in vogue and were
carried on the hip, then if indeed the guys used grease, then
in the summer months their pant legs must have been
covered in grease stains.
I never had a chain fire either with or without Crisco.

I recall reading an article by Major G. Nonte, [possibly an early 1970's era, Shooters' Bible]. where he recommended sealing the open cylinder with crisco to prevent the possibility of flash-over.

Still think is a good idea.

Berdan Sharpshooter's were initially armed with Colt revolving rifles, and reports indicated flash=over were common.

Need to research documentation.

Never hurts to be safe. Besides, I don't carry mine all day in a holster.

I have never used grease or anything, never had a 'flash over'. I was aware of the warning. Cast my own balls and they always shaved thin piece of lead when chambered. The grease also helps to keep barrel fouling soft. To get a flash over you would need two loose loads next to each other. I doubt it happened often.

Just like a cast lead bullet for a modern revolver, the ball needs some lubrication. When I shot BP competition I bought a Ruger Old Army from one of the pistol shooters at a bargain price because it wouldn't group. I used .457 swaged balls with Navy Arms Pistol lube squirted around the ball, and the Ruger turned out to be very accurate. In many thousands of rounds never had another cylinder to fire.

That is what the grease was for, lub and as I said to keep fouling down. Crisco is for baking pies!

The only chain fire I ever had was caused by worn nipples.
American Pioneer fake powder said not to use any lube....so I went with naked balls.

Apparently, the flashover situation with the Colt rifles made shooters nervous enough about their left hands, wrists, etc. to contribute to the short usage of that model. Yes, there were other issues, but if the hazard factor could have been eliminated, workarounds could have been made to gain the benefits of five quick shots.

When shooters use oversized caps, or use nipples that are too small, they squeeze the caps to pinch the nipple tighter. This opens up the caps around the nipples other two sides allowing the flash to spread through the gaps and set the other chambers off. I’ve never used grease over the bullets. The oversized ball is swagged down tight within the cylinder and seals it from flash like it does with a bullet in a cartridge case.

When you seat an oversized ball & shave off that ring of lead, ain't NUTHIN' gonna get between that ball & the cylinder wall. All grease/crisco does is make a big mess that attracts & builds fouling quicker. I've used very lightly lubed felt wads, and more recently (past 5 years) a square of toiletpaper with a tiny dab of patch lube folded up inside. Cylinder & bore stays much cleaner much longer & Ive never had a problem with leading.