Dirty brass after firing.

I get the same thing sometimes in my 9mms. Factory and reloads. As far as I'm concerned, it's pretty normal.


Eventually, with reloads, it can be a sign that the brass is work-hardened and not expanding in the chamber to seal the gasses off.

 

I can only give you an opinion on what I have learned on my SR1911LW Commander. It really depends on which powder you shoot and the amount of velocity that the powder emits. My personal favorite is W-231 as I find it to be cleaner burning because the powder is slower. Titegroup is a little faster and will leave a little more residue on your casings and pistol. On a .45ACP the casing tolerance differs from .476 at the head and tapers to .473 at the bullet end. It takes so much gas to push to bullet forward and so much blowback in order for the bolt to eject and reset. Therefore you have that .003 tolerance that allows the bullet to discharge. The residual gasses work the bolt which is holding gasses in the barrel and chamber is giving you the soot. From personal experience I have found that the hotter powders tend to leave more soot or residue in the bolt/chamber area and the slower powders seem to use more powder to propel the bullet and less in blow back. I am shooting 230 Berry plated round nose with a .452 diameter and then taper crimped so I have quite a bit of room for the gasses. Power Pistol (BE86) is terrible powder for being dirty and I actually have flames come out of the barrel when firing. I could not locate your AA5 in the powder burning rate and that may be something you have to google. Here are some examples:
Fastest to slowest: Bullseye #4, Titewad #5, Titegroup #9 and W-231 #20. The book shows Power Pistol by Alliant as #30 however, with my experience, I thought it was faster. It is a hotter powder than the rest I have shot and I know that lately they have changed their formula in their powder manufacturing.
I hope I have not confused you and my study is by no means scientific. I just go by how dirty my pistol is when I am done shooting and how hard it is to clean. You might try some W-231 and see the results and check on the difference Titegroup.

Tommy

 

Tommy, sets of physical data can be interpreted in more than one way. I don't know how close to Right you are, but you are definitely entertaining.

It could be useful to examine case reaction to the firing process in a non-blowback design (like a revolver), just to eliminate having to look at some stuff. I know I sometimes get smoked cases, and some of those sometimes they are not light loads. I ciphered on that for awhile, and came to the conclusion that I don't understand what goes on there. Well, I don't understand what goes on in a lot of places, but never mind that.

Please think on it, Tommy.

 

Bob,
I did some bullet comparisons for you however remember to take this as food for thought. My studies are far from scientific and only from what I learn from the Lyman's book and what I have for fodder for bullet comparisons. The case length on a .38 special is supposed to be 1.155. I took some empty casings I had and measured them and they varied from 1.137 - 1.145. These were expended rounds. I then pulled apart a .38 special I had on hand. Casing length was 1.145 and the bullet was a 158 grn. lead single flange (ring) round. Seating depth of the bullet was approx. .435. The bullet had the rubber ring on it which I suppose is the gas ring. I could be wrong as I don't reload .38/.357 or at least it has been a long time since I have. The expended casings varied in length from 1.137 - 1.148. That variance is quite a bit. Max COAL for a .38 loaded round is 1.550. I do not know which powder you are using, nor the bullet, and seating depth. Since the .38/.357 is a straight casing, not like a tapered .45, it leads me to believe that, when the bullet is chambered, then fired that some gases are held in the chamber. The amount of gases depends on seating depth, bullet size, bullet configuration and powder used. A hot powder with a shorter bullet will expend the gases in the chamber thus leaving "soot" in the chamber and around the cylinder. I did not load the .38 specials myself, they were given to me by my brother so I don't know what powder he used. So in that context you would have a lot
of "empty" space for the gases to remain in the cylinder. According to Lyman's the best accuracy powders for vary according to the bullet used. For example a 125JHP uses Bullseye 3.2grn starting to 4.4 max. A 158grn JHP flies best using Unique 3.7 starting to 5.0 max. In summation I can only say that bullet sizing and powder are the 2 most contributing factors for having dirty casing and pistol when done shooting. I have shot about 200 rounds that my brother gave me and it was dirty after approx. 50 rounds. I am certainly no reloading expert by any means and the info I have given you is what I believe to be the closest idea of what is happening. Anyone who has more info, I would be happy to jump in on this conversation, and should I be wrong, I would greatfully appreciate their guidance. All ideas and suggestions would be greatly appreciated!!!

Tommy

I had to re-write this topic twice as I had some of my dimensions wrong. I wrote it and thought about it and after a couple of hours realized my mistake. If you had read this earlier, please disregard the former info. I do NOT encourage anyone to use this as verbatim, this was my findings only and recommend that you fact check yourself prior to loading. My wish is that this is a guideline and don't want anyone to suffer any injury.

 

Tommy, you did some good work there. I have never paid attention to soot inside the cases, as long as tumbling removes most of it. Soot in the gun is another story, but I have only considered the powder I was burning. For instance, I consider both Unique and H110 to burn much better when they fill most of the available room in the case. The amount of crimp may be a factor too, but I have no hard data.

My main interest in this particular thread is in regard to smoke on the outside of the case. I know that light loads are supposed to be a factor, but I have seen it with non-light loads too. Mechanically, it seems like the case mouth would be the last part of the case to experience gas pressure, but it ought to get there as the bullet leaves the case, and expand the case mouth to block gas blowback. ??

 

Bob,
Think of it in this way. When the bullet leaves the chamber and enters the forcing cone of the pistol you have gases expanding outward and backwards which would encircle the brass casing. When a rocket leaves the ground, you have propulsion gases that give the rocket the thrust to rise into the air. It also has repelling gases exhausting back towards the ground. For every action there is a reaction. If your casing happens to be shorter than the specific amount as listed by Lyman's, you will have more gases being expended sideways and backwards. A good example of this is not placing your support hand in the proper place and get powder burned. I am probably not making myself entirely clear but I am not good at putting things into words like I can if we were talking face to face. Does this make sense and does it help answer your question? Again, powder and bullet size will still have an effect on this synopsis. Try some different powders and see what happens and then some different bullets also.

Tommy

P.S. The case mouth expanding will not stop all the gases. If it expanded that much, then how could you get the brass to eject?

 

^^that makes sense. Also, it makes sense that the brass wouldn't expand that much, just enough to cut back on the amount of gas coming back out.

 

Thanks Savage,

I get tongue tied and I know what I want to say but have a hard time putting it into words. I don't know if it's old age or just can't relate messages.

Tommy

 

One reason for the use of brass in cases - the case walls will expand to seal the chamber, then contract to allow extraction. And do this multiple time before fatiguing to failure. If the case is properly charged, the case will expand all the way to the chamber wall - safely. If the chamber is dimensioned too large, the case will still try to get there, fatigue or no.

I read that in a book somewhere.

 

Low pressure = lack of case expansion to seal the chamber = soot on the case.
.45 Auto is low pressure to begin with and a light target load is even lower in pressure.
Bullseye shooters have been shooting very light target loads for decades without issue.
Don't manuals cover anything any more?

 

There were only 10 posts before you. You could have read them.

 

VThillman: did I do something wrong or are you just not feeling well? Hope all is well.

 

It seems that sometimes I ask too much of my co-inhabitants of Earth. Sorry.

 

Although you may be correct on crimp affecting clean burn, you don't want to damage the bullets shape affecting accuracy.

 

More crimp may help but if it doesn't also try a slight increase in powder charge. Some powders have a definite minimum pressure level before total clean burning kicks in ( unique is one ). Some brass is harder than others and thus allows that soot on the outside.
I had to anneal some 41 magnum brass to stop that problem with light loads and cast bullets in those stiff magnum cases.
Just keep working with the powder type , load and crimp to hit a winning combination.
Gary