Dirty powder

Have any handloaders out there noticed that some smokeless powders burn dirtier than others?
Last night I cleaned the barrels on 4 of my rifles. I noticed that two of them were significantly dirtier with powder residue fouling than the others. It just so happens that I used the same powder for these two rifles, and I haven't used that powder in the other two. Besides the common powder, the two dirty barrels were from military surplus rifles, so I'm wondering if it could have something to do with the barrel rather than the powder. Before you ask, yes, I have cleaned these two milsurps thoroughly in the past, and they have probably seen fewer rounds down the pipe since the last cleaning than the two rifles that I am comparing them to.
The powder in question is IMR4064, which seems to burn much dirtier than H4350 and W760.

I've never tried 4064 but HS6 in my shotguns and .44-40 was filthy!​

I use 4064 and don't notice that it is dirty compared to others good point ill have to look at mine closer oilman

Cleanest powder I shoot is H335 and IMR4064 is not as bad as W748.

Quite often if you are using light loads, the powder will not burn as clean. Sometimes you can go to magnum primers to solve this, especially with ball powders, but your load book will specify which primer they use... . Some powders are just dirtier burning than others and some need high pressure to burn. Some ball powders are hard to ignite with a cigarette if you put a spoonful in an ashtray.

Any big differences between the different rifles barrel lengths?

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Originally Posted by skypilot

Any big differences between the different rifles barrel lengths?

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There's no pattern. The one using H4350 is 22", the one with W760 is 26" I believe. The ones with IMR4064 are a Husqvarna M38 and a K31. I'm not sure how long the barrels are on those, but they are not short.

Some powders are just dirtier burning depending on their composition , single or double based, and how much retardant they are coated with to control their burning rate.

The afore-mentioned POWDERS are relatively clean-burning . Have you ever tried UNIQUE ? --- Especially the older version , the newer type burns cleaner . --- I use it behind cast-bullets (handgun and rifle) . --- It's a good powder (for light loads) but leaves the bore looking like a smokestack .

I guess "dirty" is all relative then. IMR4064 does seem to be the dirtiest of the powders I've used, but maybe I'm using relatively clean burning powders. I have never used Unique.
Pat32rf has an interesting point - I was doing load development, so I was going from light loads up to more potent loads. Maybe it was the light loads that resulted in fouling?

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Originally Posted by Gunner 38

The afore-mentioned POWDERS are relatively clean-burning . Have you ever tried UNIQUE ? --- Especially the older version , the newer type burns cleaner . --- I use it behind cast-bullets (handgun and rifle) . --- It's a good powder (for light loads) but leaves the bore looking like a smokestack .

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Quote:

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Originally Posted by Gunner 38

The afore-mentioned POWDERS are relatively clean-burning . Have you ever tried UNIQUE ? --- Especially the older version , the newer type burns cleaner . --- I use it behind cast-bullets (handgun and rifle) . --- It's a good powder (for light loads) but leaves the bore looking like a smokestack .

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Not sure if this applies to rifle cartridges (I only reload shot shells) but cold temperatures will also make for dirtier burning, especially in low-pressure loads.