Started rolling my own 38 Special ammo end of last year and have found a well working combination of 3.8 grain Accurate #2 under 158grain LSWC that gives in the 700 fps out of 2 inch snubbies. What I observe is an accumulation at the rear of the cylinder and the frame bridge. I assume it’s blow back from the primer. Primers are looking fine afterwards. I’m not sure if that also happens with factory ammo since I’m out of it and never shot more than maybe two cylinders per session but with reloads it gets more than 50 and more per session now.
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It’s not gun specific, all my snubbies show that. Is that an issue with primer seating or not enough/too much pressure?

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With low pressure, you would see soot on the side of the casing, extending back from the mouth. However, resizing sometimes leaves the case diameter too small, so you'll see a bulge where the bullet is seated, and probably one near the base of the case.

If the empty cases fit loosely in the chamber after firing, you may be able to reload without resizing.

Kind of looks like the pressure on that load is a little light and the cases are not fully expanding to the chamber walls and sealing, allowing "soot" to blow rearward. If the case bodies are showing signs of soot around the outside after firing that is your first clue. Might have to up the charge slightly or try a different powder to get a little better pressure/seal on your cases.

Looks like maybe one of your cases is cracked? That's not normal.

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Loading data for Accurate #2 and uncoated lead lists it at 3.8 max. With copper plated or coated bullets it could go up to 4.0 max. I understand that a snubbie isn't building a lot of pressure so maybe I could try more then what Hornady lists and see if it goes away.
On the other hand 3.8 gives me a good soft shooting round for a snubbie with ~700fps which seems to be nice for a short barrel. With a 4 inch gun I get around 800fps with the same load.
Leading shouldn't be too much since I seldom shoot more than 100 rounds per session and the gun get's cleaned afterwards.

Here the fired rounds from today. The marked ones might show some soot coming back
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On the other hand not all show it
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These are how the rounds look like. Some seem to be a little bit undersized and the bullet creates a little bulge in the casing but fits well in the cylinder.
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Low pressure and cases not sealing or the kind of lube on your cast bullets. Your first pic shows some soot coming from the BC gap also.

Not a primer issue, unless fired cases are showing blown primers, or signs of leakage around the primer pocket. I would think less than optimal case / chamber seal during firing.

Bear in mind that any lubed cast bullet load fired in a SS revolver is going to leave fouling that stands out on the SS finish. They are dirty by nature. Coated lead bullets have become popular in part for this reason. If the load otherwise works well for you, it's not really a big issue, as the gun should be wiped down / cleaned after a range visit anyway. As long as your reloads are reliable, accurate and not leading the barrel, I think you are good to go.

Wanted to ad that I am unfamiliar with your particular load. You mention "Dirt". If you are getting a large amount of unburned powder grains, especially around the rear of the cylinder / ratchet area, that could result in a reliability issue, and would probably steer me in the direction of a new powder / bullet combo.

Larry

What your seeing is pretty typical for lead/lubed bullets using standard 38spl/pressure loads. The fired cases look good, but I'd adjust your seating die so that:

The bullet isn't seated as deep, some of your loads rounds show the brass's top lip on the shoulder of the bullet. Use more crimp, it will increase the short start pressure of your load. Along with making it more consistent.

A picture of a s&w 686 6" bbl'd revolver after a 200 round range session.


The 200 rounds were cast/coated 158gr fn hp's (flat nosed hollow point) with a 3.3gr load of bullseye.

You can click on the picture above and save it. Then open it in any photo software on your computer and enlarge it. You will see that even though I'm using a coated bullet there's still powder fouling on the cylinder. On my revolver it's heavy on the front on the cylinder and migrates to the back of the cylinder & frame.

This is caused by the cylinder gap/bullet jump and the gasses that escape in that opening. All revolvers do this.

Why is yours heavier in the rear of the cylinder????
It has to do with where the front shoulder of the bullet sits in the throats of the cylinder. And the short start pressure of your load. A picture of a cut-a-way of a cylinder with the same bullet being seat short and then with a longer oal.

The bottom/longer oal puts the shoulder of the bullet out further into the leade of the cylinder. Doing this aids in increasing the short start pressure of your load. Along with sealing the cylinder by expanding the brass quicker. Right now your bullet is free boring/jumping that gap (same as jumping the cylinder gap) allowing gases to escape.

Back in the day we'd bring 30cal ammo cans full of cast bullet loads lubed with the old nra 50/50 lube to the range. After 200/300 rounds you'd have to wipe the revolvers down from all the soot/layers of half burnt lube on everything. And yes, the hands got washed also.

... is to try is upping the load some. I use a lot of light loads and have some blow back issues, but it's just soot and cleans up easy.

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Load is at book max per the OP. TO get a better burn you would need a heavier bullet. You might go with a different brand of bullet if bought or lube if fouling. If you like the load your just going to have to clean up after it.

I like AA2 and shoot a lot of it in semi-autos. I think you have a combination of lube blow pack and powder fouling. If you want to try for a better burn, select 24 pieces of the same brand brass, trim to the same length, and compare to your regular loads.

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I'm going with ... inconsistent crimping.

From the powders I tested before settling for this load Accurate #2 was the cleanest and fastest combination without excessive smoke and powder residues flying out the barrel. I was specifically looking for something for 2 inch barrels and this seemed to be it. Nice, controllable recoil, hitting to point of aim under 10 yards and no obvious leading or powder residues in bore in under 100 rounds. I will check if going 3.9 might solve it but after reading here it seems normal to show this more on SS guns then blued.

That's a lot of good input, thanks. Since I'm new to reloading I haven't experimented with seating depth. I try to keep them on the short side but that seems the wrong direction.
I will start experimenting with seating depth on the longer side of the 1.475-1.455 COL and see if it changes. It's not that the soot is easy to remove, I was just wondering why that happens and need to benchmark against some factory ammo.
Also I think I may have some inconsistent crimping and want to test out how that reacts.
Since I'm using fired brass and have no means as of yet to trim this would be the next step after COL and crimp tune.

I think Forrest pretty well nailed it but one other thought. Are you using range pick up brass? That may account for some brass being a smaller diameter. That would solve it self as you use them.

....gives the max as 4.0 gr of Acc #2. I see that a lot of the data is very close between the starting and max load. Not desirable from my perspective. However I really like Acc #7 as it is a great performer getting max out of some cartridges/loads.

The OP could try using coated SWCs. I've found them to be very clean to shoot, but I don't think this is a bullet problem. I use the Missouri version. Very consistent.

IF the OP thinks the cases might not be fitting well, he could try annealing the tops of a few of them. I think I would set them in about 1/4" of water to keep the case head strong. 650 deg F. is a good annealing temperature. Too hot is bad. I anneal bottleneck cases by heating the neck until I the rim gets hot to hold.

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"He was kinda funny lookin'"

I use AA2 with my Berrys 125 bullets and load to minimum loads. I get some soot too which is no problem and cleans up easily. Actually it’s carbon and helps lubricate the case in the resizing die. Once in a while I dump my cases in the polisher but generally I leave them as they are.

AA2 seems to be a cleaner powder around minimum loads compared to 231/HP38 which I used to use and is definitely less position sensitive and burns more complete in lighter loads.

In my 158 grain loads I’m using Accurate Nitro 100NF and get excellent low recoil loads. It’s a touch faster burning than Bulkseye and is very well suited for short barrels. I love snub nose and like these faster powders that are more efficient.

The odd thing that I'm seeing is that there is carbon fouling of the frame at the REAR of the cylinder, but little to no carbon deposits on the outside of the fired brass.

If the carbon fouling is due to low pressures allowing gasses to get past the brass because it isn't sealing to the chamber walls, how is it that the carbon isn't being deposited on the exterior of the fired brass? It is somehow "blowing by" but not leaving any traces?

Those two things just don't seem to add up to me. Seems like there may be something else going on here. But what do I know?

FWIW, when I first read the subject line of this post, I expected it to be all about the classic "symptom" of unburnt powder residues using reloads. This is something else altogether...

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If you take a close look at the pictures the op posted you can see finger prints in the "soot". That's consistent with bullet lube, hence my statement about the nra 50/50 lube.

The picture I posted of the 200 round count revolver with the "carbon" buildup is completely different.

The op's brass is sealing or you would see the soot marks on 1 side of the case by the case mouth.

With a 38spl/revolver reload the only thing holding the bullet in place is neck tension and crimp. When you hit the loud button (trigger) the hammer hits the primer and "BANG", the bullets off to the races. Well, not so fast. The primer itself can and will push the bullet out of the case and forward. The primer ignites the powder and as the burning powder builds pressure it is also pushing the bullet forward.

This is where that short start pressure thing comes into play.

When that bullet starts to move forward out of the case the case itself is also moving towards the rear of the revolver. Until the case hits the shield (reseating the primer) and the bullet enters the leade of chamber. There is a small window of opportunity for gas blowby. With a lead/lubed bullet part of the blowby contains partially burnt bullet lube.

When the case is against the shield and can't move anymore & the bullet is entering the narrow leade of the chamber. The pressure of the load will start to build ending the short start pressure cycle.

At this phase the building pressure is applying pressure to the bullets base. This pressure collapses/compresses the lube groove forcing the lube outward. Some of the hot gas gets by the base and pushes the lube forward as it keeps burning it. The bullet enters the forcing cone and encounters it's first real mechanical resistance. This resistance allows the pressure of the load to compress the bullets base until it bumps up to the diameter of the leade of the chamber sealing the chamber. As the bullet moves forward the bullets base jumps the forcing cone/cylinder gap and more soot is thrown everywhere. Once the bullets base is past the forcing cone and in the bbl. The pressure of the load is still compressing the bullets base forcing the lube outward and forward with hydraulic pressure. Some of the hot gasses/pressure gets past the bullets base/bottom drive band and pushes the lube forward lubing/sealing the forward drive bands.

Myself, I always viewed bullet lube as a gasket more then an actual lube.

I've showed this picture before, it recovered cast bullets. I received this from a member on another website years ago. We were discussing the difference between round vs square lube grooves.


If you look closely you at the lube grooves of the recovered bullets you can see that they are compressed/smaller than the unfired bullets above them. This is that compression and the lube thing I was talking about.

I haven't seen Bullseye in shops since starting to reload and hope to find some in the future but it looks meek here in AZ right now.
From my limited testing of other powders faster powder is better for snubbies and Bullseye would be on the wish list.
I was quite disappointed by HP-38 since it was recommended a lot but was giving out of 2" inconsistent fps and smoked like crazy. However it was OK with loading to max and shooting it out of a Marlin 1894. I will revisit it when I load WC loads.

My uncoated lead SWC are lubed. I ran out of copper XTreme bullets but have some now on hand and will see if I load up more to see if the sooting is the same. I only had a couple for snubbie shooting since I loaded them mostly for 357Mag and shooting them from my Marlin lever.
Maybe going to the max of the COL might help with the lead SWC.

The Nitro 100NF sounds great, I will keep an eye out for this.
What confused my in regard to burn speed was that my Titegroup loads did not performed as well as ACC#2 even when Titegroup is much faster then ACC#2. Let's see how a step up even faster works out

I like 231 for 45acp and heavier loads but in 38 spl light loads it was extremely position sensitive. I tested light loads, within Hodgdon recommendations, and had two rounds fail to ignite the powder. The primer ignites but not the powder. I was shooting with a model 10 2” and a Cobra 2”. In both cases the primer didn’t ignite the powder and the bullet didn’t make it out of a 2” barrel. I know there was powder in the case because when I opened the cylinder the powder poured out of the barrel.

I was chronographing loads when that happened. I observed over 200 fps difference in speed if I tilted the gun up before firing the round vs tilting it down before firing the round. I also observed this with 45 acp. The data was so erratic I thought my chrono had failed. Medium to heavy loads I haven’t experienced that.

Interesting observation. I have some loads with WIN231 and HP-38 that show huge variation in speed between 350 to 700. I wasn't paying attention to what I did with the gun before I fired the rounds that came out fast or slow but you mention gun orientation might give me a hint. I was assuming the chrono might have had a hiccup since I never chorno'd before and though it had issues detecting the bullet.
On the other hand out of a 4 inch gun it both loads never had the same issue but again, no idea how I held the snubbie in comparison to the 13.

The first time I observed this issue was with 45acp. I would have to go back in my notebook but thik I was shooting a government model with 6” barrel. Again I was chronoing loads and thought my chrono had had a stroke. I fired one round that registered 60fps. I thought that can’t be and thought I can throw the bullet that fast. Was it a fluke? I don’t to think so. I think the powder didn’t ignite properly because the volume was very low. I don’t remember my load at the moment but also observed large variations in velocity on the light end of my loads. Again I was within Hogdons recommended data.

In addition to position I know temperature can be a factor. I do r remember conditions but need to make notes of temperature. I’ve been loading over 40 years and have a degree in chemistry and know temperature, pressure and humidity can influence reactions. Perhaps I was found a set of conditions that resulted in these results. I’m also curious as to whether I could reproduce these results and might attempt to recreate it at some point.

My concern is too little powder resulting in an explosive detonation. I saw a documented case where too little powder in a 45LC cartridge resulted in an explosive detonation in that chamber and split the cylinder in two pieces. The article stated too little powder can be as dangerous as too much powder. The article I read was from a science journal back in the 60’s. Yes I’m that old.