BP Granulation size and bore erosion?

Hey Guys,

Finally getting back into BP shooting and I am seeing a trend from what I am reading and it has changed since the last time I was on the forums etc.

Today's shooters seem to be using 3f in bores 50 and above without concern of bore erosion. Have thoughts on this changed, did they have it all wrong or whats the deal? Just curious because I am finding it really interesting hearing about shooting 3fg in a .62 cal etc. Yeah I bet it will get more zip but at what price if any?

Thanks in advance for you input and advice!

Billy

 

[Walks with fire]

When I bought my TC their book stated that 2f should be used in the 50 caliber so that's what I use. It works for me.

 

[roundball]

Hey Guys,

Finally getting back into BP shooting and I am seeing a trend from what I am reading and it has changed since the last time I was on the forums etc.

Today's shooters seem to be using 3f in bores 50 and above without concern of bore erosion. Have thoughts on this changed, did they have it all wrong or whats the deal? Just curious because I am finding it really interesting hearing about shooting 3fg in a .62 cal etc. Yeah I bet it will get more zip but at what price if any?

Thanks in advance for you input and advice!

Billy

The industry rule of thumb when substituting 3F in place of a 2F load is to simply reduce the charge by 15% to stay in the same pressure range...ie: instead of 100grns 2F, use 85grns 3F.

These aren't .264 Winchester Magnums were talking about...just simple muzzleloaders with very low pressures...vents in Flintlocks would wear out before a barrel would and vents are not commonly replaced.

 

[MikeChapin]

Up until I switched to KIK, a year or so ago, I used GOEX 3F in everything from .32 to .58. Don't know where the bore erosion story came from but I have never seen any in the 20+ years I was using 3F. It's the same story from other people I know that still use it.

 

FFF will ot ERODE but failure to properly clean will CORRODE!

The only damage to bores that I have seen in 40 years is when folks fail to care properly for their guns.

 

[Mad Monk]

This depends a good deal on how soft or how hard the steel is that was used in the barrel. Also how tightly one patches the ball.

Episodes of after rusting will result in bore erosion with fine grain powders.

 

[paulvallandigham]

I don't think you can expect much if any bore erosion from powder in the steel barrels that you find these days, and have been standard for more than 60 years. The metallurgy is very good post WWII. You won't find iron barrels until you go back before WWI( 1917) , and then for most guns, you will have to go back before 1880 to find iron being used to make many barrels. Iron is much softer than steel, and there, you might see erosion.

As Mad Monk. you should be much more concerned with rust, due to failure to clean the gun properly after shooting. The residue contains both carbon, and Sulfates. There are also potassium compounds, and Nitrogen is always present. Sulfuric Acid can be formed with the pressense of moisture in the barrel at any time that sulfur is present. Nitric acid can also be formed. These and other acids can eat stell and erode the chamber.

All acids can be neutrlaized by flushing the barrel with plain water. Thow in a little soap, and the crud will come out in the wash. But, you cannot skip a good cleaning of the gun if you want the gun to maintain good accuracy. Our problem today is that way too many shooters don't want to take the time to clean everything, even smokeless powder guns. These guys are who keep gunsmiths in business. More than one smith has told me that at least half his business consists mostly of just cleaning dirty guns to make them work right. There really is nothing else wrong with the guns.

When I was an asistant public defender, many years ago, a friend from one of the police departments told me the average working life of a gun that is stolen is only about 30 days. That is because the bad guys don't know anything about gun maintenance, or storage, and they often hide the guns in burlap sacks which they bury. Within 30 days, a brand new gun will have no finish, and cannot be opened or fired in those conditions. He recovered a Browning Superposed O?U shotgun taken in a burglary 30 days after the crime. It had been buried in the RR embankment across from the city Train Station in a gunny sack. It had no finish, and he could not even open the action, much less get the trigger to fire. He cried. It was an expensive shotgun most of us have only drooled over in gun store display cases.

 

[Mad Monk]

Paul,

I have cut a number of ml barrels in half from the muzzle through the breechplug with a hand-held hacksaw. How hard it is to saw and the "song" the cutting makes gives some idea of how hard the steel is. I can tell you from experience that there is a good bit of variation in the hardness of the steels used in ml barrels. Investarms barrels are fairly soft. T/C barrels are harder.

Some years back I had discussed this 2F versus 3F business with Jim Fulmer. This caused him to think a bit.
He commented that what he was seeing in this was the loss of the accuracy he would see in a new broken in barrel. A loss of accuracy that the average shooter would not notice.

In 1998 I was shooting 9 lots of Elephant that had just arrived in the U.S. Using my GPR flinter that I had purchased in 1983. That rifle had seen only Ox-Yoke lube and mainly charges of 3Fg powder. My "standard" test load was 80 grains.
As I shot the lots of 3Fg Elephant in the 1998 shipment I shot them in lot number order. I noted that as the day went on each lot would average about 15 to 20 fps slower than the previous lot. A puzzle at first.
The folloowing day I took the same cans of powder and my other .50 cal. to the range and ran them all through that rifle. Did not see the same steady drop in velocity. All of the lots closely matched the others in velocities.
I had also noted that the GPR barrel was getting a bit loose in the breech area.
So that barrel was pulled and sawn in half from muzzle through the breech plug.
At first I could see nothing really wrong. Then I got out the magnifier. Then did some sectioning of the barrel. Looking at ridge height. Under the magnifier I saw that the circle formed on the top of the land no longer matched the circle formed by the base of the grooves. The tops of the lands appeared to be canted.

When you move a projectile up the bore via gas pressure you have a "driven side" of the land and a "slack side" of the land. You have pressure against the side of the land since you are trying to rotate the projectile while moving it foreward in the bore. There is very little pressure on the "slack" side of the land. You get gas escaping on the slack side of the land.

In dealing with gases at very high temperatures they may be erosive if the velocity of the escaping gas is much greater than the velocity of the accelerating projectile.

This was before I switched over to the #40 cotton drill patching and had problems with the Ox-Yoke patch material I was using.

After looking at the condition of the lands in the cut up barrel I went back into my collection of recovered patches. Tiny shredded areas and places where little holes had formed I was able to match those up against the slack side of the lands.

All this did was to back up military papers from the late 1800's on bore erosion in guns.

I usually do not get into this stuff on the Internet anymore. The typical response being that it doesn't to me then any who claim it does are full of you know what. But I know what has come through Dixon's shop over the years relative to this.

Without rusting problems in a barrel it would take a lot of shooting to wear out a barrel to the point where the "average shooter" would notice it. With after-rusting problems a barrel can go in very short order.


As far as corrosion with bp goes.

When you subscribe to the idea of sulfuric acid and nitric acid being formed in the bore you might want to take an actual look at the chemistry of bp fouling verus some of the nonsense that has been published.

If you have a properly made black powder you will see no nitric acid in the powder prior to combustion nor in the post-combustion residue. I have done that work as part of a forensic chemistry project with an ATF lab.
When GOEX produced bp at the Moosic plant the drought production lots of BP would show up as a strong positive for free lower oxides of nitrogen in the powder and the post-combustion residue. Lots made during periods of high rainfall in the area would be a very faint positive for free lower oxides of nitrogen. Once they moved to Minden the powder comes up negative as does WANO, Swiss, KIK and Schuetzen.
My work on this was prompted by work done at a university in Kansas City, MO. Two profs claiming that they had devised a test to prove if smokeless had been used in a ml bp gun.

While black powder residue will sometimes smell strongly of sulfur compounds keep in mind that the first thing formed would be an SO3. Sulfurous. That would then auto-oxidize to SO4, sulfuric. To have the sulfur compounds form the acid you would need water present. Most of the solid material produced by bp combustion is potassium carbonate, or potash. A mid-range caustic.
So if you had enough moisture present in the bp residue to form either nitric or sulfuric acid you would have enought water present wherebuy the caustic potash would neutralize, or kill, any acid present.

Anytime I get a new powder to test one of the things I do is to check the pH of the powder and the pH of the fouling left in the bore.

Some years back, up until 2000, GOEX powder was based on a source of potassium nitrate that contained a small amount of potassium chloride. The potassium nitrate having been made by reacting potassium chloride with nitric acid.
In my work on the nitric acid in certain lots of Moosic GOEX I also checked samples of potassium nitrate produced by their supplier. Finding no free residual nitric acid in the potassium nitrate.


I mentioned potassium carbonate, or potash, as being the main component of the solids left by bp combustion. Roughly 3 parts of potassium carbonate to 1 part of potassium sulfate.
Potassium carbonate is in itself slightly corrosive. Working with powdered technical grade potassium carbonate on brass and steel.
There is a critical range in relative humidity where the potassium carbonate picks up enough moisture to bein eating away at brass or steel. Low R.H. gives no effect. Very high humidity where the potassium carbonate becomes rather wet gives no effect. But within a certain range in humidity the effect on the base metal is highly noticeable in just a few hours. I did some time lapse photography with the computer microscope on this.

What it showed me was that cleaning the barrel is very important as far as preventing after-rusting goes.

 

What it showed me was that cleaning the barrel is very important as far as preventing after-rusting goes.

10,000 words condensed into the one sentence that had already been made.

 

[J.D.]

10,000 words condensed into the one sentence that had already been made.

Yeah, but now you why.

 

[paulvallandigham]

So, the pits I have found in old guns that have been neglected are more likely to have been made by the Potassium Carbonate, than the potassium sulfate, and the fact that i smell sulfur in these old barrels is simply a by product of the sulphur trioxide? That is very interesting. I only wish the old gunsmith who told me what ate barrels was still alive for me to share this with. Who says you don't learn something new every day??

I still am going to tell shooters to clean their barrels after shooting each day, and do a good job at it. Your testing proves the importance of finding the best patch thickness for your bore, and not just using something " pretty good ", as you have proven that it allows gases to cut the lands and will eventually affect the general accuracy of the gun. The guy who just plinks with his gun off-hand all the time is never going to notice half the stuff we talk about here. But a guy who fires his gun off a bench rest ever year or so to see how well his loading components are doing will notice the changes. Thanks for the detailed information. Its easy to ignore the presense of alkalies, and think only about acids, when in fact, both can be harmful to barrel life.

 

[Runner]

Do you by any chance know the chemical properties of pyrodex fouling also?

 

Hi Mad Monk! Thats the reply I was looking for thank you!!!!! Hey did you ever come out with that book you were working on?

I still have some of that old "good" elephant powder.

Will follow your advice and stick with the larger granulations in the larger bores. I had a used 58 that you could actually feel it get loose about 2" from the breech when running a tight dry patch down the tube. Original owner was a competitor back in the 70's.

Thanks again!

Billy

 

[paulvallandigham]

I don't on Pyrodex, but Mad Monk, or someone else may. I watched a good shooter try to get consistency out of Pyrodex when it first came out many years ago. He shot off the bench, and was shooting tight groups with black powder. With pyrodex, he could not find a combination that would shoot as accurately at 50 yds. We changed loading and cleaning procedures to see if that was the problem, and nothing worked for him. He did not have a chronograph, because they cost way more than the gun in those days, and no one outside a lab had one. Now you can buy darn good machines for less than $100, and for just a little more get a chronograph with all the features you want on the older lab models, including hooking it to a Portable computer.

 

[TANSTAAFL]

Ditto, I use 3F from priming to .62, no problems, others mileage may vary.

 

[Mad Monk]

Paul,

BP subs are not usually noted for the really good accuracy you can get with black powder.

One of the driving goals behind the BP subs is to do away with what the inventors call the very dangerous traditional method of making black powder.
Generally, the subs could best be described as little more than large agglomerations of the ground ingredients.
The ingredients are not ground as fine as the ingredients in BP.
Then they simply agglomerate the ingredients in a damp state.
The so-called grains are usually low in density. Pyrodex for instance has a loading density of around 0.75 g/cc while BP should run anywhere from 1.00 g/cc up to 1.10 g/cc.
The grains with the subs lack the mechanical strength found in bp produced by the traditionalo methods of production. With BP the powder press densifies the powder and imparts a high degree of mechanical strength.
Then with BP you have the glazing/polishing step where you form a thin but very hard surface on the powder grains.
With bp, the grain hardness and degree of grain surface polish promotes uniform ignition from one charge to the next.

Think back to the late 19th century. Where they talked about "diamond grain" powders. That might aptly describe the degree of powder grain strength and surface polish and hardness. It did not describe the shape of the grains. Simply how hard they were. Diamond grain powders being then considered to be almost inherently accurate.

You might say that the concepts used in the production of the subs runs counter to all the rules of thumb in black powder manufacture. Even though the subs and BP are both compounded explosives.

It is tough to get real competition accuracy out of any of the subs.

 

[Mad Monk]

Pyrodex uses potassium perchlorate as part of its oxidizer system. About 17 parts of potassium perchlorate.
Powder combustion converts that to potassium chloride. This will be found as minute crystals in the bore.
Along with potassium carbonate, some potassium sulfate.

 

[Mad Monk]

Paul,

Here is a gem that will get you laughing. Sort of up your alley in your real life work.

From:
Analytical Chemistry, Vol. 57, No. 3, March 1985

Article titled:
The Analytical Approach
Darwin B. Dahl and Peter F. Lott
Chemistry Department
University of Missouri - Kansas City

The Differentiation of Black and Smokeless Gunpowders

"HERE'S THE PROBLEM. We are being sued for millions because this black-powder gun blew up. We are certain smokeless powder was used, but how can we show it? Our situation is made worse by the fact that we did not test-fire the gun before it left the plant. You know, of course, that the U.S. has no proof laws. I know, I know, don't tell me - we should have proof-fired the gun. The crucial point in the litigation is whether or not smokeless powder was used."

"if at all possible, the testing should be performed by two independent methods so as to produce unquestioned results, Ideally, the initial screening should also be quickly performed using a simple method with minimum equipment."

So the lab had at it with a simple screening test. A burst barrel, or their test rifle, would have the bore washed out with "dry" acetone. The idea being that black powder is not soluble in acetone while smokeless powders are.
The acetone bore washing is then evaporated. Reconstituted with sulfuric acid. Diphenylamine added to the sulfuric acid.
If smokeless powder had been used in the gun, either alone or as an admixture with black powder, you would get a blue color develop in the solution of sulfuric acid with diphenylamine.
This test actually detects any lower oxides of nitrogen or nitric acid.

What caught my eye was that in some parts of the test they would use GOEX black powder. Other parts they would use old Du Pont bp.
Really fishy. We are talking early 1980's here. The idea that a new bp shooter would go into a gun shop and buy a brand spanking new T/C Hawken and be handed a can of Du Pont bp simply did not wash.

So in the lab I set up to duplicate their work. Quickly found out that GOEX BP gave a very strong positive for smokeless. Based on their test method. But other brands of BP, including 100 year old samples, gave no blue color or only very faint in the range of 2 or 3 parts per million.

So in their initial; screening test they simply could not prove thaqt smokeless had been used in the gun at some point in time.

Their second "confirming" test was when they evaporated the acetone bore washing down to dryness. They described a lace like film in the watch glass used to evaporate the acetone. This lace-like material was claimed to be nitrocellulose.

Trouble is that black powder usually has between 0.50% moisture and 0.75% from the can. Then bp bore fouling will contain moisture in varying amounts as long as the R.H. is over 30%. So the acetone picks up the moisture (water) from the powder or the bore fouling. The mineral matter in the water forming a lace-like material in the watch glass used to evaporate the acetone.

These guys proved utterly nothing in their work.
In two tests some drought period production GOEX gave a more intense blue color than my IMR smokeless used to reload .223.

 

[brubincam]

JUST LOAD IT AND SHOOT IT.... :v :v :v