Blackpowder arithmetic

[David R. Pennington]

At our monthly match today we got in a discussion about how many shots it would take to shoot out a barrel to the point it would need to be recut. The fellow loading to my left was shooting a rifle he built 35 years ago and he still shoots very well with it. He has never done anything to the bore but clean it. (He beat my target on the mystery match.) The fellow on my right said he estimated his .45 cal. Bill Large barrel had around 22,000 rounds through it before it needed freshed out.
That got me thinking, at 22,000 rounds how many pounds of powder and lead did he use up?
He says he shoots about 65 grains 3f and a .440 ball.

[drago]

About 402 pounds of lead and 204 pounds of powder.

[David R. Pennington]

What would that be in dollar value at todays costs for powder and lead? I figure at the rate I shoot it would take me about 61 years to shoot out my rifle's bore.

[bob in the woods]

I have a target rifle with more than that through it. It's never been recut [ rifling ] but I did refresh the crown and where I used to shoot 60 gr of powder, I now shoot 70 grains. Otherwise, it's still a good shooter. Some of the old iron barrels were very very soft, so that was an issue, but I think corrosion rather than erosion was the cause of many being recut.

[Daryl]

As Monk has noted, loose loads contribute to erosion ahead of the powder chamber due to the gas cutting effect of the powder gasses rushing past the patched ball. This, along with rod wear, contributes to the need for 'freshing' or re-cutting the rifling- especially in iron barrels.  Steel barrels are more resistant to this type of erosion but are not immune to it, not even the 4140 & 4150 modern chromemoly barrel steels normally used in CF applications. I sincerely doubt, however, if cared for and cleaned properly, those barrels would EVER need freshing or re-cutting.
12L14, being quite soft in comparison, would likely need 'help' if shot a lot. 1075 or whatever GM uses, harder and more resistant, etc.
We have a fellow in our club who has over 10,000 shots fired from EACH of his flintlock guns. Aside from the odd main or feather spring and replacement frizzen, his guns keep on shooting well.  He documents EVERY shot fried from them, in that he knows EXACTLY ow many shots each has fired, to the ball.

[smylee grouch]

If I remember right, Roger Fisher had over 20,000 shots through some or at least one of his guns befor he had John or Don Getz fresh it out a little.

[Mad Monk]

Most of the barrels I looked at that were "shot out" had suffered numerous events of after rusting.  If the bore gets even a fine coat of rust on the surface it will wear quicker.  I don't know of any of the really gung ho target shooters I have ever dealt with were able to shoot out a modern steel barrel.  But I know from one of my .50 caliber powder testing rifles that if after rusting becomes a problem due to a lube that does not do what the mfg claims you can shoot one out eventually.

When dealing with the old wrought iron barrels seen on original rifles you would see a "glassing" of the surface of the bore back in the breech area.  The soft wrought iron was being subject to high heat as the powder burned and gasses rich in carbon.  That gave what amounted to a case hardening effect.  Trouble is that the soft wrought iron would flex slightly during the firing of the gun.  The carbonized surface metal would crack and flake off during the firing.  So the first step was to fresh out the rifling but after a bit the barrel would have to be bore to a larger size.

This thing about a hard surface cracking and then flaking off in a bp bore was seen in ml rifles and shotguns, made in Italy, that had chrome plated bores.  The hard chrome plating was supposed to stop corrosion and require less frequent cleaning.  But The soft steel barrels flexed while the triple layer of hard pure chrome did not.  At a Morgan's Rifles shoot at Winchester, VA one year I watched a gun shooting one of those chrome lined shotguns.  In the sun is was real pretty.  The smoke from the gun looked like it had sparkles added.

Mad Monk

[Daryl]

sparkles- how wonderful!

[Mad Monk]

sparkles- how wonderful!

Some time after watching the shotgun blowing out chrome flakes with each firing Chuck Dixon gave me a .50 caliber Investarms barrel that had a factory chrome lined bore.  Hack sawed it in half from the muzzle down through the breech plug.  Then placed it under a strong microscope.  The minute cracking and flaking could be seen under the microscope.  Exactly as the text books described the process.  Once the 3 layers of chrome start to micro crack you no longer have a barrier against powder residue corrosion.  The you start to see little stress cracks develop in the base steel under the chrome.  This barrel had bulged and opened a split in the bottom flat when the stress cracks reached the base of the holes holding the screws that held the under rib to the barrel.
The owner had fired not one short started maxi but two.  The first one left a ring in the chrome lined bore with a short tear centering on the one under rib screw hole.  Then he fired a second short started maxi parked about an 1/8 of an inch away from the first one.  That caused the lower flat to tear for about 6 inches

After I had looked at this I found some information that said the U.S. military had similar problem with the early versions  of the AR-15.  They had electroplated hard chrome bores and on full auto would "shoot out" fairly quickly as the chrome cracked and flaked.

Mad Monk

[Daryl]

After reading your words about the chrome cracking and flaking, I initially thought about the chrome lining of AR barrels in VN, then the Italian 12 bore SXS's that had chrome lined barrels, Monk. Glad I sold it - to LB. He didn't have it long and sold it to someone else who needed it.

[Mad Monk]

After reading your words about the chrome cracking and flaking, I initially thought about the chrome lining of AR barrels in VN, then the Italian 12 bore SXS's that had chrome lined barrels, Monk. Glad I sold it - to LB. He didn't have it long and sold it to someone else who needed it.

After looking at the chrome lined barrels I did some serious digging in the tech books.  They would chrome the bores by filling the bores with the source of the chrome.  That being chromic acid.  Then doing the electroplating in three layers, three applications.  The acid tends to corrode the surface under the steel during the process.  Making the metal more porous.

In Europe they came up with another way to deal with the chrome plating problems.  They would mix chrome with nickel in a fine powder.  Coat the bore with the powder and then use a plasma flame to melt it and bond it to the base steel.  The mix of chrome and nickel was not brittle like pure chrome so it does not crack with the firing of the gun and they base steel is not degraded by acid corrosion as is seen in electroplating.

Mad Monk

[Daryl]

Experimentation - that's what it's all about - for us, a much less grande scale, but experiment we must, or be happy 1st or 2nd losers - HA!