Why the unburned Bullseye in .38 Spl?


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UnderDawgAl
November 12, 2007, 05:50 PM
I loaded about 100 rounds of ~2.6 gr. Bullseye (cavity .30 in Lee Auto Disk) under a Speer 148-gr. HBWC. I used a light roll crimp on the shoulder of the bullet in my FCD.

I also loaded about 100 rounds of ~2.9 gr BE (cavity .32) under the same bullet. Same crimp as above.

At the range today, I noticed that the 2.6-gr loadings often had some unburned powder after firing. Would a tighter crimp ensure that the powder all burns? I didn't notice the issue with the 2.9-gr. loading.

If it's the crimp that's the problem, then it seems that I should either use a tighter crimp on the 2.6-gr rounds or just stick with 2.9 grains as my load. Note that, because I'm using the old Auto Disk powder measure, I can't load the classic 2.8 grains of BE under my wadcutters, unless I manually do it one round at a time.

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CSA 357
November 12, 2007, 07:20 PM
IT may not be unburnt powder, it could be powder skeletons , i have seen this with blue dot , see if it will burn, csa

UnderDawgAl
November 12, 2007, 08:14 PM
Will give it a try next time around, CSA. Thanks for the idea. I'll have to see. It looked, though, just like fresh, clean powder flakes, fresh out of the bottle.

Steve C
November 13, 2007, 12:49 PM
The charges listed on the charts for Lee volumetric measures with preset inserts or the dippers are generally optimistic about how much powder they throw. Without a scale its just an approximation and probably the absolutely largest charge you can throw so you can almost be assured that you're charge is actually a couple 1/10ths less.

The first load using cavity .30 is probably a bit light and doesn't produce enough pressure to fully consume the powder.

If you where to weigh the actual charges thrown, I'd guess that the average throw weight of the .32 cavity is actually closer the the classic 2.6gr load.

UnderDawgAl
November 13, 2007, 01:03 PM
Good response, Steve. I have been weighing every 5th round, and, in line with what you noted, the Lee volumetric amounts are optimistic to say the least.

On my scale, with this particular 1-lb bottle of Bullseye, cavity .30 weighs between 2.6 and 2.7 grains. We'll call it 2.65, and it weighs that consistently.

Using cavity .32, I get a weight just over 2.9 grains consistently. Again, let's call it 2.95.

I'm inclined to agree with you that the rounds from cavity .30 probably are underpowered. I think I'll do a few more at that level and put a tighter crimp on them, so that I'll have some additional empirical evidence. Because I'm new at reloading, I didn't want to start out with too much of a crimp and risk having any issues. Better to err on the side of caution.

Also, a tighter crimp, if the same brass is used over and over, will weaken that end of the case, right? I figured that less crimp would extend the life of the case.

redneck2
November 13, 2007, 08:17 PM
Smokeless powder burns by building heat and pressure. The more heat, the higher the pressure, and the faster the burn. The faster the burn, the more heat and pressure, etc.

If you don't get enough initial heat and pressure, the bullet moves at the initial burn and/or when the primer pushes it out. In any event, the fire "goes out" and the powder doesn't burn.

Using a harder crimp forces the bullet to stay in place, which allows the heat/pressure to build before the bullet can move and relieve the pressure. Easier method is to increase the powder charge which reduces the volume (which raises the pressure).

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