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Ive noticed that when I reload toward the bottom of the fps range with its corresponding lower pressure, that the cases exhibit alot of burn residue around the neck/ shoulder. Given that I am loading/shooting the same bullet wt., same brass, same rifle, same bullet sizing and that the only variable is the powder charge I am wondering if there is a point at which the pressures are not great enought to expand the brass and seal the chamber??
Whether or not you are loading for rifle or pistol, you can get too low in powder charge and NOT seal the case to the chamber . You will get sootie necks first then sootie cases.
If you get too low with some slower powders you risk detonation rather than powder burn. pressures will sky rocket and bad things may happen to your firearm.
When beginning to load with cast Boolits use a reliable reloading manual and stick to their minimums. After you are comfortable with those then venture into the "Unknown". The folks here on this board can answer questions on boolits and powder charges and they have "Been there, done that, got the "T" shirt". Ask any question about powder/boolit /case /firearm and someone will have blazed a trail for you to follow.
If you venture out on a limb, on your own, Please at least have a crony and know what the readings mean.
It's a great big world of reloading out there and some guidance is good for your well being, at times.
Have fun with a great hobby , but Please be safe.
In my paper patching episodes, I got a lot of carbon/soot/bits of paper, on the case neck and sometimes the case itself.
Upping it 3gns and no carbon.
I think there is a fine point where it expands enough to seal. I suspect, the sealing takes place anyway, just not as fast as if there is enough powder to expand the case also.
I load to minimum load data for jacketed bullets. Just under that, and I get soot. I mean 3gns on a 30gn load.
Example, my 7.62 paper patch load calls for 38.4gns of 4895. I loaded up 50 at 34.3, and it was soot city! When I fire my .303 British at 38.4gns, no soot whatsoever. At 34.3, soot city.
The 4896 acts like 4064, so it is already a light load.
I guess I found my sweet spot with those two calibers, but light, it will soot like crazy.
The first time I loaded some cast boolits I was in for a surprise. This was back when I was buying bulk boolits. I bought a box of 500, and began researching load data. Well, soon enough I found a load that was listed as a starting load. Was recommended by several people on several different forums as a "sweet" load out of their 4" 38s and 357s. So I figured,"Ok, thats where I will start."
Well, as it happens, once I had found this load I began loading up 500 Rem brass with 158g SWCs and 4.0g Unique, the "sweet" load. Well about a week went by, and I got out to the range. Got all set up with an ammo can half full of 38spl loads, loaded up a full cylinder, pointed down range and gently squeezed the trigger.
It was at that moment I got a HUGE surprise. The load smoked as if it was a BP load. After a couple of cylinders full were sent downrange I checked out my empty brass and gun. The two had soot all over them. Went down range to take a look at my targets and noticed that I had a load that would shoot "minute of barn." I had 500 of these loaded up.
Next time I was smarter and only loaded a box of ammo to test before going all out. Increased the charge to 4.3g and sooting stopped, and I had good accuracy. If you getting sooting, increase the charge. It was at the point that sooting stopped that I found "my sweet spot."
It doesn't have to be too light a load, it can be an unsuitable powder. Many years ago, the first rifle I ever reloaded for was a 303-25 built on a Lee Enfield Mk III* action. I guessed that 748 would be well within the right powder speed range, and started load development. I got sooty necks, extending well back down the case body. Kept raising the load waiting for it to go away. Eventually I got stuck cases, but they still had sooty necks. I made a powder change to the predecessor of BLC(2) (it was called AR2201, and had been developed for 7.62 NATO ball) and suddenly results made sense - no soot, and pressure rose smoothly with load, but had just about no effect on accuracy. The burn rate of AR2201 is only about half a whisker faster than 748, but it fixed the problem. My guess was that the heavily moderated ball powder didn't work in that fairly heavily bottlenecked case, but the stick powder did. I've never found out the actual reason, but I learned a timely lesson about being careful, and not expecting everything you try to work.
Ditto on what's been posted so far.
Anyone who has tinkered with cast or even some low pressure Jbullet loads for very long have dealt with sooty cases. Usually wrong powder or low pressure. However, for my preference in cast bullet shooting it is a fact of life to be dealt with since I almost exclusively load at low pressure.
A couple of other possibilities for correction could include:
Neck sizing or partial full length sizing so the case better fits the chamber.
Annealing the case neck. The caution of course is that in short cases like most handgun cases great care must be taken so as not to soften the body or base of the cartridge.
Grumpy, it's the timing and location of the pressure excursion(s). I've seen cases expand over a specific personal limit and produce less velocity than those that do not at that same location. ... felix
Thanks felix. My guess was that the heavy coating of graphite on the 748 caused it to be relatively slow to light up, in relation to its burn rate. Hence the pressure rose slowly for a short time just after the bullet left the case neck, and during that time it sooted the outside of the case.
It could just have been an errant batch of 748, perhaps with too much graphite coating - I'm still using the same batch, and still getting weird results, but now I'm getting them in 30-30 and 30-06. The symptoms seem consistent with variations in early burn rate. Whatever is causing it, it sounds like a form of what you've described.
If the "pressure" in the time/pressure curve isn't sufficient to expand (obturate) the case in the shoulder-neck area to seal against the chamber walls by the "time" the bullet has cleared the case mouth gas and thus soot will flow back between the case and the chamber walls giving you sooty cases. Ma ny slower burning ball powders and slow extruded powders give this problem. This problem also is frequest in straight walled pistol/revoler cartridges when loaded with light loads of even fast pistol powders. Solution is a faster powder, heavier charge of powder, heavier bullet use of well fire formed cases that are minimally neck-sized for such loads.
Larry Gibson
As initial pressures during engraving have a large effect on boolit deformation, low pressures initially are desireable. This in view of what has been said creates a dilemna. Too low of pressures can also cause inconsistent burning, as well as the sooting that is the subject here. Therefore, if slower burning powders are used the loads should not be too light, both to get better case sealing and more consistent burning. Some powders like 4350 are plain dangerous when under loaded, and other powders like 4831 will burn consistently even in situations where they shouldn't. Powders must be chosen with this in mind.
Also, the crimp has some to do with the case expansioin especially with low power loads. Try a heavier crimp or a FCD. A heavier crimp will allow the pressure to build within the shell before the bullet exits the shell thus allowing the shell to expand and seal properly...
Unique and no crimp at all is another bad choice for light loads. Its a smokey load. I've always had people tell me they love Unique and just smooth out the bell, but i've had problems with it being real dirty....................... Now is there other factors involved, i'm not sure.... BTW i'm talking about 45 acp loads and the forty cal. One more possiblity is too much case lube left on the brass when you size them.
Along with everything else mentioned here, you might think about brass from different mfgs being different weights, and, some guns just have over-size chambers.
I have loads that shoot great in one gun and not worth snot in another.
Aint reloadin fun? :lovebooli
I have a pal who had trouble with this in a 6.5X55 chamber. No matter what suitable powder he used- 4895 is his standard- he'd get soot. Even with neck sized brass. Same load in his other Swedes, no problem.
So you never know. There's some variation from gun to gun as well.
great posts all !!!
Im also thinking that brass if not properly annealed (i.e. too many reloads without annealing) won't expand as it should....