Dirt around rear of cylinder with reloads

[darg]

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.

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.

 

[darg]

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 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

 

[.38SuperMan]

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.

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.

 

[darg]

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.

 

[.38SuperMan]

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.