Moly Coating Bullets

Sorry, Moly is one of the worlds most stable compounds. The temps that are required to break it down would melt the barrel. No, water does not case the moly to dissassociate and form other compounds.

Throw some moly in a cup of water and see what you get. if the theory above is correct, the moly will dissolve into the water just like salt.

If you have a bare barrel in the rain, well it is going to rust. Take care of the bore and it will take care of you.

Burnt powder is hydroscopic so whether there is moly present or not is moot. I find that wrapping the muzzle with a piece of electrical tape helps a lot as the barrel is sealed at both ends. However, if caught in a downpour or any high humidity situation, I dry the barrel as quickly as possible.

Jerry
 
HD, why did you have to clean it out of a barrel in the first place?

The power of moly is its ability to cling to the metal and form a consistent surface for the bullet.

The fact that it is hard to remove is a good thing. However, a few minutes with JB and it is gone. It is not easily removed with chemical solvents (again the whole point of being).

Using moly has its benefits and must be treated in its own ways. Nothing is perfect which is what some expect moly to be.

Jerry
 
Part of the problem with these assessments is that most of the story is missing. I suppose it is possible for crevice corrosion to occur with the moly or even carbon deposits. The layering of either carbon or moly would likely promote accelerated localized corrosion when moisture, particularily excessive moisture or water (not to mention salt!) is present.

In dry Alberta I have yet to see (using a bore scope) this problem in my firearms or clients.

416R stainless still rusts.
 
I have heard this argument rage for years, it is almost like the Ford /Chevy debate. Some barrel makers will not warrant a barrel if there is any trace of moly, other do not care.
I have experimented with it and was less than impressed with the results. Some of the barrel makers I use are against the use, so as a result ALL of my custom rifle work come with the disclaimer that if moly is used in the barrel the warranty is void. Several other makers have adopted this stand as well.
There are a great many products on the market that can do damage to a barrel, some solvent and brushes can destroy a barrel in short order, but some people still swear by them
 
mysticplayer said:
I find that wrapping the muzzle with a piece of electrical tape helps a lot as the barrel is sealed at both ends.

Jerry
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Hey Gerry... This will also keep those sneaky bore snakes from crawling up your bore and taking residence and wreaking havoc overnight when you are not looking. :)

NormB
 
Moly is one of the worlds most stable compounds
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Yes, at room temperature.

The temps that are required to break it down would melt the barrel.
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The Handbook of Chemistry and Physics cites molybdenumdisufide to decompose at 750 C; that temperature is far surpassed upon firing; most of the moly will escape decomposition, but small amounts will most assuredly decompose into its elements molybdenum and sulfur. In the high temperature (2500 C) oxidizing environment of smokeless powder deflagration, the liberated sulfur will be oxidized to SO2 and SO3. These oxides of sulfur are then free to react with whatever moisture is present to form both sulfurous and sulfuric acids; trace quintites mind you, but still available to react with steel (barrel material) over extended periods of time usually being detected as crevice corrosion.
 
Any idea what compounds are formed when smokeless powder burns?

Any of them potentially corrosive in the presence of moisture?

considering the amounts of powder burning vs moly on the bullet, I am very surprised that there could be enough of anything from the moly alone to cause problems.

I have recovered moly bullets where the bullet is still grey except from the lands (similar to what you have seen in advertising). The amount that starts on the bullet is almost zero for weight and most is still on the bullet when it leaves the barrel.

If the temp around the bullet exceeds 750C, most of this would be 'burnt' off. Obviously, it doesn't. The base of the bullet will get hot but the rest of the bullet is (should be anyways) sealed off from these very hot gases. The base of the boattail were still grey so how hot did it really get?

The bullet acts as an insulator and for the few microseconds the bullet is exposed to the burning powder, the bullet can't heat up that fast. We know that lead melts at pretty low temps and the cores don't fail in bullets.

Just doesn't have the time to get that hot. So I question that any moly burns beyond the very little from the base and what is scraped off by the lands. That leaves so little material to develop acidic compounds that this is a nice urban legend.

Jerry
 
Any idea what compounds are formed when smokeless powder burns?
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Single base smokeless powders are mostly nitrocellulose, double base powders are nitrocellulose and nitroglycerine; both coumpounds contain only the chemical elements carbon, hydrogen, nitrogen, and oxygen. Upon deflegration smokeless power yields mainly carbon dioxide, nitrogen, water, some carbon monoxide, and some free carbon (some of the free carbon is due to the graphite coating on most powders). These products are not normally corrosive towards steel, the water is of course, expelled from the barrel in the vapour state.

Bullet travel time down the barrel is in the order of two milliseconds, this not a long time on an individual basis, and the low bulk material temperatures that the barrel or bullet attain are not the issue; it is the temperature attained at the surface layer of atoms where the activity of interest occurs. This is exactly what is responsible for throat erosion. The high gas (flame) temps (order of 2500 C) and high turbulence impart a high enough temperature to the suface layer(s) of barrel atoms, causing the steel to sublimate one or more atomic layers at a time during each firing. The amount of energy available to cause this sublimation of barrel steel in the throat area increases exponentially with the flame temperature, this is why large capacity cases with small bores experience the greatest rate of throat erosion. Small amounts of moly will be similarly affected:)
 
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