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Discussion Starter · #1 ·
Been reading about the transitional period from black powder to smokeless.

The original smokeless powder loads caused severe bore erosion. It was thought this was due to the powder, and Springfield Armory undertook a study, trying different bullet jacket materials, none of which eliminated the problem.

Then it dawned on them-it was the mercury in the primers that was the culprit! Why did mercury suddenly start eroding bores, after being in use for nearly a hundred years? The culprit now was smokeless powder~it did not foul the bore with the protective coating as did black powder.

So, Frankford Arsenal came up with chlorate primers. And a new problem: Chlorate primers left salt deposits (sodium chloride) in the bore when fired. These salts attracted moisture, which rapidly led to rust forming in the bore. Since salt is water soluble, a thorough cleaning with soap and water was mandated, followed by a good oiling.

Current primers are lead styphnate, supposedly as corrosion free as possible.

Bob Wright
 

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Mercuric primers did affect the brass of fired shells and did not have a long shelf life, but never heard they corroded the bore.

Ordnance originally thought that the combination of the fired primers and smokeless powder formed an acid which eroded the bore, but they found that the actual culprit was the priming compound containing potassium chlorate formed potassium chloride when fired, and if the humidity was greater that 50% the potassium chloride, which is very similar to sodium chloride (table salt) attracted moisture and rusted the bore.

Once they knew the cause of the corrosion and the cleaning required after firing, the military continued to use the "corrosive primers" in all small arms other than M1 Carbine ammo until the early 1950's.
 

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Discussion Starter · #4 ·
I have examined several old cap lock rifles that were in the family, each had an octagon barrel. The "flats" around the nipples were eroded away so that the barrel was partially rounded in that area. Yet the bores of these rifles were in very good condition.

Bob Wright
 

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A pretty good read on primers.

Primer Composition
One ingredient that proved to be a great source of trouble in early priming compounds was fulminate of mercury. Easy to manufacture and very sensitive, fulminate of mercury was the basis for most early percussion caps and primers. The real problems began when brass cartridge cases and smokeless propellants began to see widespread use. Upon firing, the mercury in the primer amalgamated with the brass, chemically attacking and weakening the case. As long as black powder was the primary propellant used in small arms ammunition, this effect was minimized by the milder primers then in use, and the lower operating pressures inherent to this type of propellant. When smokeless propellants became more prevalent, the damage caused by mercuric primers immediately began to create major difficulties. While the mercury caused no damage to the firearm itself, cases fired with this type of primer became brittle, rendering them useless for further reloading. The damage was caused instantly upon firing, could not be prevented, and could not be corrected afterwards. Mercury was soon identified as the culprit, and was promptly eliminated. Virtually all commercial primers have been made without fulminate of mercury since around the turn of the century, and are still clearly labeled as being “non-mercuric.” The U.S. military completely suspended the use of mercuric primers around 1898, so the likelihood of running into mercuric primers in anything other than extremely old, or some foreign ammunition is remote.
Corrosion was also a major problem in black powder firearms, due in part to the nature of the propellant itself, but largely to the qualities of the priming compound used in most early percussion caps and primers. Potassium chlorate, used as an oxidizer, was a primary ingredient in most of these mixes. Upon firing, some of this is deposited in the bore in the form of potassium chloride. Being very similar to ordinary table salt, potassium chloride is extremely hygroscopic, which is to say it attracts and holds moisture.
 

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Had an old friend, who sold me the Woodsman he bought new in 1928, wax enthusiastic about the year 1927. This marked the introduction of Remington Kleenbore priming to the benefit of shooters everywhere. Prior to that time he made the extra effort to keep his firearms' bores clean with Winchester Crystal Cleaner but he said that corrosive priming compounds were a chore. Winchester Crystal Cleaner apparently worked as I also have a Winchester Model 1890 and a Winchester Model 1907 that he owned since they were new and which predate 1927 by several years.

I'd love to have a bottle of Winchester Crystal Cleaner for Cres' guns' sake.
 

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...Corrosion was also a major problem in black powder firearms, due in part to the nature of the propellant itself, but largely to the qualities of the priming compound used in most early percussion caps and primers. Potassium chlorate, used as an oxidizer, was a primary ingredient in most of these mixes. Upon firing, some of this is deposited in the bore in the form of potassium chloride. Being very similar to ordinary table salt, potassium chloride is extremely hygroscopic, which is to say it attracts and holds moisture.

Winner, winner chicken dinner.
 
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