Case "blow by"

P

Prof Young

New member
Revolverers:
A buddy let me shoot his S&W 357. The brass went in shinny and came out shinny. No black marks from "blow by" in the chamber. In both my Taurus revolvers (The Judge and a 44 mag raging bull) I put shinny reloads in and most came out with black marks of "blow by" on them. Is that just the difference in quality of handguns? Is the S&W chamber more precise so the brass fits tighter and the burning powder won't blow back across the brass? Does my shooting reloads have anything to do with this. He was shooting new ammo.
Still like my Taurus handguns and wouldn't hesitate to buy another . . . but . . .
Live well, be safe.
Prof Young
 
Different powders burn "cleaner" or "dirtier" then others. I find Unique to be dirtier then some other powders and WAY dirtier then factory ammo

A1680 is another really dirty one. Cases come out covered in soot:o
 
Does my shooting reloads have anything to do with this. He was shooting new ammo.
Click to expand...

I suspect that is it.

Some thoughts:

I know, in particular, Bullseye shoots filthy.

To do the test right, run the same round, factory or handloads, in both guns.

it may be that the handload is not loaded hot enough for the case to obturate.

Still like my Taurus handguns and wouldn't hesitate to buy another . . . but . . .
Click to expand...
 
Prof - I reload 38 spl and only shoot cast. I use Bulls Eye for powder. I have 7 different revolvers I shoot - Ruger, Colt & Smiths. I always seem to get some "dirty blowback" - BE is known for it. The loads are lighter target loads - WC, SWC & RN slugs - sized to .358. I just don't like shooting "hot" loads nor "magnums" - too old for all of that. The loads I use are accurate and I only tumble lube my slugs in Alox and Paste Wax - all but the SWC I use have conventional lube grooves.

I just accept the "dirt" as part of the process in what I'm doing. Maybe I could eliminate it a little by loading a little hotter, but why? They do what I want them to which is punch paper, kill cans, etc. :D

Right now, I'm laid up with some foot problems but when I can get back to it, I'm going to try some AA2 and Unique "just for fun" and see how they work. I'd also like to try some Red Dot as well. Maybe I'll get the same dirt with them since I'm loading light? Only time will tell. I clean my shooting irons after every shooting session so it's not a big issue to me - and like I said, I really like BE. If you handgun is shooting accurately, I wouldn't worry about it too much. Good luck to you and have fun! :)
 
Prof - I reload 38 spl and only shoot cast. I use Bulls Eye for powder. I have 7 different revolvers I shoot - Ruger, Colt & Smiths. I always seem to get some "dirty blowback" - BE is known for it. The loads are lighter target loads - WC, SWC & RN slugs - sized to .358. I just don't like shooting "hot" loads nor "magnums" - too old for all of that. The loads I use are accurate and I only tumble lube my slugs in Alox and Paste Wax - all but the SWC I use have conventional lube grooves.

I just accept the "dirt" as part of the process in what I'm doing. Maybe I could eliminate it a little by loading a little hotter, but why? They do what I want them to which is punch paper, kill cans, etc. :D

Right now, I'm laid up with some foot problems but when I can get back to it, I'm going to try some AA2 and Unique "just for fun" and see how they work. I'd also like to try some Red Dot as well. Maybe I'll get the same dirt with them since I'm loading light? Only time will tell. I clean my shooting irons after every shooting session so it's not a big issue to me - and like I said, I really like BE. If you handgun is shooting accurately, I wouldn't worry about it too much. Good luck to you and have fun! :)
 
Sounds like light handloads without enough pressure to seal the chamber.
Maybe try a faster powder or heavier charge to generate more pressure so the brass seals the chambers.
 
l n. field said:
it may be that the handload is not loaded hot enough for the case to obturate.
Click to expand...
This was my first guess, as soon as I saw that the professor is shooting reloads. I have some case blackening with my reloads in 1911s, and it doesn't matter what pistol I shoot them through. I know my loads are on the light side but I get acceptable accuracy and the pistols all cycle, so I'm not going to increase the load just to keep the brass a little cleaner.
 
There is a term, "obturation", which means the expansion of the case to seal off the chamber. If the load is light, the case will not "obturate" enough to fully seal the chamber and keep gas from coming back around the case, resulting in blackening at the case mouth. It generally does no harm except to leave carbon in the chamber that will eventually have to be cleaned and to leave soot on the case that will also have to be cleaned off before reloading as it is an abrasive and can harm the sizing die.

Jim
 
Thanks.

Loaders and Shooters:

Thanks for all the thoughts and info. Yes, this makes a lot of sense. I haven't been worried about my dirty brass, but was impressed with the shinny brass that came out of my friend's 357. I use unique powder, titegroup, some blue dot and H-110. I never thought about some powders being more dirty than others. So much to learn in this game.

Thanks again.
Live well, be safe.
Prof Young
 
Some powders just seem to like to be loaded hotter. For example, I used to load my .44 Magnum ammo with 17-18gr of Alliant 2400. While these loads shot well enough, they left the gun and cases filthy and I had a good deal of unburnt powder. Nowadays, I've bumped my charge up to 20gr which is just as accurate if not more so and much, much cleaner.
 
While blackened case mouths are often the sign of incomplete obduration, they can also happen on cases that seal properly.

If you are using a smokey powder (and cast bullets add to it), there may be enough of a "cloud" remaining after the pressure drops enough for the brass to spring back away from the chamber walls, and crud can be deposited on the case then.

It usually comes from a light load, but doesn't have to, under the right conditions.
 
Different powders burn "cleaner" or "dirtier" then others. I find Unique to be dirtier then some other powders and WAY dirtier then factory ammo
Click to expand...
Unique burns much cleaner when you push it harder. It's really only a dirty powder in light loads.
 
Sometimes it is a tradeoff. A good example is Bullseye; it burns "dirty" but it is very consistent in light target loads and, with loads around 2.7 grains, it is very economical.

Jim
 
When I used to shoot Remington UMC .357 the cases would literally come out almost black. In fact, just about anything Remington I have found to be the dirtiest ammunition out there.
 
I'm not sure if this is a factor in your reloads, but the final step of my reloading process is using paper towels and removing any excess case lube left over from the reloading process. With light loads especially, I've found that leaving any case lube on is super messy. This just amplifies the "obduration" problem.
 
You must log in or register to reply here.
Back
Top