Patch thickness &RB Dia VS Cal. & Rifling depth

[zimmerstutzen]

After considering this for a day, I had some questions If the initial powder ignition is sufficient to obturate the ball, ie flatten it out somewhat, is it not also true that that pressure from behind would find the path of least resistance around the patched ball, is the place where the patch and ball seal is the narrowest, the band around the ball where it contacts the lands and grooves. And wouldn't force enough to flatten the ball somewhat from behind also be enough to constrict the ball slightly where it can force it's way past the ball in the grooves.

I seem to recall reading a post here about two years ago, with a photo of flame escaping the muzzle just ahead of the ball and it was a tight combination patch and ball.

And yes, I realize that Dan'l and Davy probably never concerned themselves with such considerations, but then again, they shot guns made by others who did consider things such as twist, groove configuration, etc. ie, they relied on the technical engineering of others.

 

[Vaino]

Hi....I don't think the low pressure generated by BP behind the PRB will "flatten" the RB by an amount that would be of consequence. It does so w/ a thin skirted conical which then becomes the bore seal.

The only path of gas blowby for a suitably thick patch and RB, would be through the grooves.....the lands because of the compression of the RB at loading and the patch also being compressed offers no gas path.

The culprit is the excessively deep grooves which are hard to seal off.....010 deep grooves would be a lot less prone to gas blowby and would still impart the spin to the PRB......Fred

I usually load a fairly tight RB/patch combo for all my MLers and they're not that difficult to load...using a short starter.

 

[zimmerstutzen]

The low pressure of 75 grains behind a hollow base Minnie can blow the skirt out at the Muzzle. If it can do that with an 1/8 inch skirt of lead, it can squeeze a couple thousandths to pass a prb.

 

[Khufu]

I have cleaned up sone .490 and .440 round balls recovered from deer and inspected them closely.
the ones I have recovered had the weave pattern of the patch imprinted on the powder side of the ball, but it looked very round, I did not measure it. the impact side was badly deformed, and were larger than a nickel (.490) the weight was in the high 160s and low 170s with the exception of the balls that passed through solid bone, some of those fragmented. concidering the balls were round on the powder side, I do not think the balls are deformed much if any by the act of firing them. perhaps firing into a water trap would be a better test and be more reliable information.

 

[Vaino]

If in fact a PRB could be compressed by the low pressure of BP, the expansion of the RB would only be tangental and in my opinion wouldn't fill the grooves to any degree. When the pressure of the expanding gas increases to overcome the inertia of the PRB {highest pressure that would be generated}, the PRB would move and once moving, the presuure would decrease and the PRB would be affected a lot less. At any rate, any slight compression/expansion {if in fact there is some} of the RB would have minimal effect as far as sealing the grooves which is where any gas blowby would occur......Fred

 

[hanshi]

I buy either blue or brown mattress ticking. I use my caliper and roll the jaws as tight as I can. Then I squeeze the jaws with thumb and forefinger several times and it springs back. Eventually the spring back will measure .024". Just using the wheel to close the jaws as tightly as possible gives something over .030". Applying pressure with thumb and forefinger compresses it even more. Measuring it at the store with a caliper usually gives about .035". Washing it tightens and strengthens the weave. At this level of tightness the bore stays relatively clean and no wiping is needed. A tight prb is the "secret" to all day shooting.

 

[Larry Pletcher]

Hi Fred,
I'd like to add a comment about burning patches and sealing the bore. I appreciate your calculations. In my .54 Rice (round rifling) I always wiped between shots. I was trying a ball/patch combination that was probably marginal because I wanted easy loading. I was getting small burnt holes and thought I should use a thicker patch. A shooting buddy said, "Don't wipe between shots."

I tried his advice. When I didn't wipe, my next patch was pristine. Every time I wiped, the next patch was burned. So, if I'm loading informally I'd use the thinner patch and not wipe . My conclusion was that fouling the ball pushed down the bore was protecting the patch.

Regards,
Pletch

 

[Vaino]

Hi Pletch...a lot of "unknowns" when shooting MLers. I have never wiped after every shot....in fact when the PRB requires more than normal force to seat, I use a wire brush and dump the debris.

Perhaps you could go to a thicker patch and wipe after every shot and see if the patch is burned through?

Also....if you have high speed photography equipment that could "freeze" the PRB leaving the muzzle and try different thicknesses of patches to see if it's possible to completely obturate the bore.....the absence of flame preceding the exit of the PRB would indicate that.

Why such deep rifling in the modern MLing bbls? Harder to seal the grooves and shallower rifling would still spin the PRB......Fred

 

[pinemarten]

I was very interested in the fact that the patches weren't burning through after fouling built up in the patch as the ball was pushed down the barrel! Really makes sense! But...then I thought about the fact that I am shooting my rifle for hunting (practice for it or roving with it with the goal of killing game). My first shot needs to count. That shot will come from a barrel that was clean and it will probably be the first prb down the barrel the morning of the hunt ...so, no fouling to biuld up and protect it. The rather tight combo I started shooting in my new rifle leaves a good looking patch with no burn holes. But, I have trouble starting it and want to develop a load I can use hunting with my wood ramrod. Maybe grease acts like your fouling to protect the patch from burning through?

Daniel

 

[Larry Pletcher]

Fred,
I know more experiment is needed to see if wiping at intervals could work. The idea of the high speed photography is cool, but the sources I've checked involves a chunk of money. In the early stuff i did was with borrowed equipment from Olympus Industrial. I may have lost that chance.

Daniel,
With an earlier gun, I had the same problem you mentioned. In that gun, .50, I loaded a .495, tight patch, etc in my garage. The balls carried for the second shot was .490. That left me with a tight first load, but a backup that was easier to load. I don't know if that will help in your case, but helped me.

As a 70 year old shooter with bad hands and shoulders, I have actually tried combinations easier yet. I'm loading a patch/ball combination that can be thumb pressed into the muzzle. I'd bet that it doesn't seal anything; but it means I can still shoot instead of watch others. Sometimes we make concessions to keep on playing.

Regards,
Pletch

 

[Vaino]

Easy loading PRB combos might have been used a lot years ago....sacrificing efficiency for speed of loading. I still don't know if short starters were used "back then"....or they're a modern thing. Your opinions are always welcome and your "dirty patches" surprised me. Someone asked if patch lube would do the same as the fouling on the patch. I don't think so....patch lube can burn while fouling is the remnant of already burnt powder and probably wouldn't burn again. Again...a lot of unknowns.....Fred