What causes ammo to be 'dirty'

[BugI02]

Apologies if this is found to be the wrong place to post but it seemed too non-technical for ammo and reloading. I was thinking about how some ammo is dirtier than others in everyday use and realized I don't know why. Could someone school me on the differences causing this effect. Is it a slower burn rate on the powder, something different about the powder chemistry, something added to the powder to increase/decrease its volume or in order to enable controlled granulation, differences in primers or even quality of ingredients? I would think manufacturers would not want to be noticeably dirty so perhaps there is a financial incentive such that cheapening/altering the product improves their bottom line. Get technical if you wish (I'm an engineer) but I'd really like to know why this happens and what the residue (the dirt in dirty) is. Thx

 

[throttletony]

Cheaper powders tend to burn dirtier or not get a complete burn... but they are priced cheaper and generally function fi e, so the low price keeps them popular.
NO ammo is totally clean, even if the best quality powder and appropriate burn rate matched to your barrel length, etc. So, enojoy it for what it is (contained explosions of awesomeness...and bacon)

Older mil surp and some import ammo can also be corrosive, so firearms should to be cleaned after shooting (but thats a separate question altogether )

 

[Dead Duck]

What causes ammo to be 'dirty'

It's only natural.
Maybe if ammo wasn't always stored together in such close quarters it wouldn't be as dirty.

 

[Mgderf]

Just a guess here as a new reloader.
I have found some loads have been "dirtier" than other loads with the identical powder, leading me to believe it's how efficient the powder burns.

Another cause CAN be an under-powered round.
If the charge is not enough to fully expand the case and seal to the chamber you will get more blow-by into the chamber making it appear "dirtier" than a round that seals completely.

This is my guess.
Someone else may come along with a definitive answer.

 

[BehindBlueI's]

I've found that inconsistent burn is usually the issue. Powder that is not well suited for the caliber and didn't fill enough of the case volume, for example.

 

[BogWalker]

Completeness of combustion. Think of a campfire versus a wood burning stove. They both burn wood, but the campfire leaves behind more ash and cinder per amount of wood burnt as the combustion isn't as complete.

 

[drop45]

Completeness of combustion. Think of a campfire versus a wood burning stove. They both burn wood, but the campfire leaves behind more ash and cinder per amount of wood burnt as the combustion isn't as complete.

So it WOULD be okay to cook bacon over gunpowder then.

 

[Indycar:v1.1]

It's a combination of the nature of the powder, type of bullet, velocity and bullet lube.

For example;

Bullseye tends to be dirtier than Unique.
The type of bullet. A totally encased jacketed bullet tends to leave less debris than jacketed bullet with an un-jacketed base.
Lead bullets take into consideration the formula of the lead, whether the lead is cast or swagged, the bullet lube and the velocity the cartridge is loaded to.

 

[Bennettjh]

So it WOULD be okay to cook bacon over gunpowder then.

Heck yeah!

 

[Drail]

Some powders make a lot of ash and some don't. Unique used to be MUCH worse than it is now. That stuff was one step up from black powder. The cleanest pistol powder I have found is Winchester Super Target (a shotgun powder). The now discontinued WW 452AA (another shotgun powder) was the cleanest stuff I have ever used. Most shotgun powders made for light target loads also work well in handgun cartridges up to medium speeds.

 

[BugI02]

Great Info as usual INGO. Thanks all. Keep it coming. Bacon grease for bullet lube?

 

[AA&E]

Just a guess here as a new reloader.
I have found some loads have been "dirtier" than other loads with the identical powder, leading me to believe it's how efficient the powder burns.

Another cause CAN be an under-powered round.
If the charge is not enough to fully expand the case and seal to the chamber you will get more blow-by into the chamber making it appear "dirtier" than a round that seals completely.

This is my guess.
Someone else may come along with a definitive answer.

I have the same thoughts about case expansion within the confines of the chamber. An inspection of the cases after firing can provide a good indication of gas seeping back toward receiver.

 

[LarryC]

A lot of the commercial ammo is pretty dirty, leaving quite a bit of residue. I can only surmise but it appears this ammo is loaded to keep the pressures low to prevent damage (and lawsuits) when the ammo is used in a old firearm that has lower quality steel or badly worn firearms. In my experience reloading and shooting most if not all powder burns more completely when the "pressure" is closer to the high end of the SAAMI spec.. I can't prove whether this is due to more complete sealing of the cartridge to the chamber (I personally doubt this) or the powder just burns more completely at the high pressure. I do know that certain bullet weights and powder charges of the same powder do have much different amounts of dirty residue left in the firearm - and even is evident in the "smoke" evident when the cartridge is fired.

However much or most of what we call dirty residue is actually the unburned graphite that is used to coat the powder granules. As far as I know almost all powder is coated with Graphite. The "coatings" used to cover the grains determine the burn rate of the powder. I'm sure there are other materials used in addition to the Graphite to coat the powder to obtain the proper burn rates, but I doubt anyone will tell what these are as they are proprietary to the manufacture. By the way the Graphite residue is not a problem in firearms, it is actually a lubricant and will also wipe off the metal parts easily without solvent.

 

[Tactically Fat]

To turn the thread a bit to something that generally comes up about steel/aluminum cased ammo:

Powder combustion aside, case material can also play a small role in the PERCEPTION of ammunition being "dirty" or not. Aluminum and steel don't expand/contract under firing like brass does. This can, and often does, allow plenty of crap to blowback into the chamber of the firearm. This crap gets noticed more with certain ammo because there IS more. If it all blew out the barrel - it wouldn't be noticed as much, though the same amounts are still produced.

 

[HoughMade]

Lack of a strong male role model and/or abuse.

 

[GodFearinGunTotin]

Lack of a strong male role model and/or abuse.

 

[rob63]

Another thing that could be a factor is something that came out of the investigations of the early jamming issues with the M-16 in Vietnam. Different powders can have different levels of calcium carbonate in them, which contributes to the amount of residue after firing. The calcium carbonate is added by the powder manufacturer to neutralize any acids remaining from the manufacturing process, some add more than others. It would kind of make sense that an ammunition manufacturer that was using steel cases would be extra careful to make sure the powder didn't have any acids.