Gas sealing with PRBs in rifled barrels

[roundball]

A few years back some documentary about muzzleloaders (I think it was on the History channel) happened to include some slow motion footage of a PRB being fired out of a ML rifle. It was demonstrating that a couple feet of flame exiting the muzzle before the patched ball ever even appeared.
I unfortunately didn't bookmark the link or info to find it again...does anyone recall that documentary and have any links to it...or similar demonstrations and links?

 

[Rifleman1776]

That would be interesting to see. And it would be a revelation if correct.
My guess is this might occur with a very loose fitting, undersized, ball.
The physics of shooting a projectile are better left to the guys that can do advanced equations.
The old large cannons could shoot a ball great distances and those were undersized with no patching. Always a puzzlement to me.

 

[Larry Pletcher]

An NMLRA safety film made quite a while back showed this if viewed frame by frame. This probably is not the one you're talking about though.

I may have seen others too but will have to look. I'm thinking it was made by a German photographer. If you find it, would you please share your source? I'm always interested in this stuff.

Regards,
Pletch

 

[ApprenticeBuilder]

Here is a Link to a couple vids, think that the kodiak is prb

 

[Rifleman1776]

That .72 Kodiak sure had the bullet/ball in front of the fire. No doubt about it.
Do wish that guy would put a shirt on though. :haha:

 

[Vaino]

Seeing the "seal" w/ a PRB is only tangental, the pressure could force the gas past the "seal"....which is only cloth. Logical conclusion....a tighter patch/RB fit is better at sealing. But, even w/ a very tight patch/RB combo, is a 100% seal possible? Perhaps not.

Seeing round bottom rifling doesn't have the hard to fill corners of normal rifling, would it be better sealing?

Another factor to consider....Is the usual PRB rifling cut too deep? The weakest seal is in the grooves and many shooters pick combinations of patch/ball that don't even fill the grooves....plenty of gas blow by.

Don't really know why the rifling depth is so deep on modern bbls, eg...015 depth requires a thicker patch to seal. Perhaps .012 rifling depth would be better?....Fred

 

[Billnpatti]

There was a day when I used to have a 6 pack like that. Ah, for the good old days! :haha:

 

[dave524]

That .72 Kodiak sure had the bullet/ball in front of the fire. No doubt about it.
Do wish that guy would put a shirt on though. :haha:

Strange, I did not see any rise of the barrel with recoil with that Kodiak :shocked2:

edit: OK I compared an early frame to a late frame and there is movement but not anything like I expected , must have been a very light charge.

 

[Wes/Tex]

I posted some comments a while back, but briefly:
Back in the dim, dark past(mid-late 60's) a group of us at NASA, that were into muzzleloading, managed to get the use of one of their high-speed cameras for a weekend, though we coughed up film money....expensive, even then, and especially at several hundred frames a second. Over a two day period we tried every ball and patch combo we could get into several different guns, including an original .55 caliber Hawken rifle one guy owned. Some of the loads were so tight that we had to pound them down with a mallet. We didn't care about accuracy, we were trying to find ONE load combo that didn't allow smoke and blast effect beat the patched ball to the muzzle. We used 'natural' material for patching, cloth & leather, and rendered bear fat or lard with beeswax for lube. Not one load stopped the smoke getting out the muzzle first. Granted, modern lubes and materials might make a difference now, I don't know. But basically it proved to us that patches transmit rotation to the ball but can't form a totally tight seal against the blast pressure of black powder, the only powder we used as well. Original notes I made got lost to one of the hurricanes that knock the stuffings out of the Houston/Galveston area every few years, but think we were playing with 70 to 90 grains of FFg, if memory serves.

For Roundball: Among my old books is a story with photos about a similar experiment. I'll try to find it this evening.

 

[galamb]

I am going to ask an honest question here, so please don't read anything into it.

What is the basis for attempting to obtain a perfect or near perfect gas seal?

Is it simply to try and squeeze maximum velocity (and thus accuracy - maybe) out of the shot?

Is there any evidence that historically it was a concern for the average owner/user of a long rifle?

Or is it more of "now we have the technology" and we are trying to squeeze every bit of performance out of the rifle??

 

[Wes/Tex]

Don't have all the answers for your question but the remarks about sealing the bore has been around since muzzleloading was rediscovered in the 40's or 50's(though that really isn't a good analogy since it never was really lost)and probably for many centuries before that. I've always heard it used but it always made me wonder as well...if it's sealing the bore so blast pressure doesn't get though, why are patches found with scorch marks beyond where it should be sealing off the bore? When we got the chance to use a camera that fast, it just got to be one of those "neat" things to try out. don't consider what we did as scientific, by any means, just one of those things one is fortunate to get to try out and scratch your head over the results. :thumbsup:

 

[Clovis]

OK warning, I am likely out of my league here, but I thought I would relate what I am currently doing and what I am finding as it seems to relate to the subject but forgive me if I am way off.

I was seeking to improve accuracy and tried various things with limited results and finally tried adding a wonder wad between the powder and patched ball, found accuracy improved markedly and for the heck of it tried two wads and greatly improved accuracy.

To the point also found something else, with two wonder wads over the powder on the first shot the recovered patch is spotless no burn through no sign or any darkening. Subsequent patches show slight darking from the groves but the wads seem to scrub the barrel on the way down and recovered patches only show small amounts of dark areas in the rifling area.

My feeling is I am getting a good seal and wiping out the bore with this and getting consistant shot to shot accuracy. If you are looking for a good seal I would suggest trying this direction as it may be what you are looking for.

Course, I could be completely wrong and it would not be the first time, likely not the last. :idunno:

 

[George T.]

I don't have a real interest in adding wads or wasp nests to my loading procedure. I patch thick enough that they will hold up to the abuse. It's odd but I have always viewed it as a compromise between tight loading and acceptable accuracy.

One thing though I have a 58 musket with shallow mini ball rifling that simply shreds a .015 patch but shoots 1 1/2 to 2 inch groups at 50 yards. If I move up to .018 the parches look great but there is very little improvement in accuracy and it is very hard to start the ball.

Geo. T.

 

[Kapow]

I came across this article the other day. Note item 6 under "Secrets" where it is suggested that the patch traditionally did nothing to seal the bore but rather the packing material between powder and ball did that job.
http://www.chuckhawks.com/flintlocks.htm

I also note several other items of interest such as using lead over leather to hold the flint to give a more positive strike and weakening the mainspring on the lock to avoid excessive flint wear. I made the assumption that the author is well respected?

 

[roundball]

Don't have all the answers for your question but the remarks about sealing the bore has been around since muzzleloading was rediscovered in the 40's or 50's(though that really isn't a good analogy since it never was really lost)and probably for many centuries before that. I've always heard it used but it always made me wonder as well...if it's sealing the bore so blast pressure doesn't get though, why are patches found with scorch marks beyond where it should be sealing off the bore? When we got the chance to use a camera that fast, it just got to be one of those "neat" things to try out. don't consider what we did as scientific, by any means, just one of those things one is fortunate to get to try out and scratch your head over the results. :thumbsup:

Right...round balls don't deform to seal a bore and a patch is not a gasket...a little bit of cloth patch material down in a groove does not seal pressures in the 7000-10,000 PSI range. Similar to the project you referenced, videos have been made showing this in slow motion. Just trying to locate / get links for some easy to understand visuals that are out there to help others starting out get a better understanding of the dynamics.

 

[Wes/Tex]

I think your observation and that of Clovis are both very much the same. I will readily admit that any sort of wad, cloth, filler or whatever could very well protect the patch and even be compressed up against the patch to the point it might even provide the wanted 'perfect seal'. What we were attempting to prove was, would a patched ball actually physically 'seal' the bore. Must also admit, I did't hear of using any additional patching or wad between powder and patched ball until recent times. It may have been something used since earliest times but I don't recall encountering it in print or practice until recently(last couple decades)...maybe Texans just haven't kept up! :wink:

 

[Rifleman1776]

a patch is not a gasket...a little bit of cloth patch material down in a groove does not seal pressures in the 7000-10,000 PSI range

Can't argue because I simply do not know one way or the other.
But intuitively.....OK, my gut...I have always 'known' the lubed patch seals the bore to prevent gas blow by allowing max pressure to propel the ball.
But, this thread is interesting. Another jug drainer for the campfire. :stir:

 

[BrownBear]

Right...round balls don't deform to seal a bore and a patch is not a gasket...a little bit of cloth patch material down in a groove does not seal pressures in the 7000-10,000 PSI range.

Never shot for the camera, but I share your skepticism. It's hard enough to get a seal while expecting lead conicals to obturate, no amount of obturation in a round ball could seal all the gaps in a fabric patch.

 

[crockett]

Gas "cutting" is generally viewed as detrimental to accuracy. One reason a wad over the powder and under the PRB may be great in one rifle and immaterial in another is the type and depth of rifling. Gnerally a tighter fitting PRB is more accurate. So, the best seal obtainable is a desired thing.

 

[George]

Must also admit, I did't hear of using any additional patching or wad between powder and patched ball until recent times.

It was mentioned in 1808 in a book by Henry Beaufroy, "Scloppetaria". This was in England, not this country.

Between the powder and the ball, it is usual to put either a patch or a stopple. The former is that adapted for military service, on account of its greater facility in loading; yet, for purposes of amusement, it frequently occurs that the latter only, or sometimes both, are used.

..... when firing for amusement, and where ample time is afforded, many, before ramming down the ball and patch, put between it and the powder a piece of circular card or felt, accurately fitted to the bore, just as is commonly done with shot guns”¦

He didn't say what they thought the advantage of doing it was.

Spence