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Posted: 3/9/2014 12:22:51 PM EDT
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OK, so I've never had a problem with 5.56 and .308 but 300 Blackout is kicking my ass for some reason. Brass converted from LC and checks out fine using a Sheridan Engineering gauge. Trimmed to 1.36 length. Using SMK 125gr bullets and Lee Dies I can seat the bullet fine and get it to the right depth (by "feel") but no matter how I adjust the bullet seating die there is about 3/64" gap between the shell holder and the bottom of the die. If I complete the ram stroke, the shoulder on the case collapses.  Any ideas? It almost feels like the bullet seater is "catching" on the neck and thus collapsing the neck while not seating the bullet in any further. |
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If I remember right the seating die gets screwed in until it touches the shell holder and then backed out three full turns. Use the seating stem to adjust bullet seating depth.
I just checked my 300 black out die, also a Lee. It is a little less than half an inch away from the shell holder. |
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My seating die instructions say place an empty case in the shellholder and raise the ram. Screw the seating die down until you feel resistance on the empty case. Then adjust the seating stem separately. If you do not want to crimp and seat at the same time, follow the above process but back the die body off half a turn and then adjust the seated stem.
Could be something else but really sounds like an adjustment issue. |
Ok, figured it out. Yes, set-up issue. Did not have the ram completely bottomed out before adjusting the die. I will go hang my head in shame for a bit. So, got that part taken care of. Now to figure out why they are no-go on the Sheridan gauge after seating when they were good prior.  |
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That would probably be a result of some diameter being out of spec afterwards. You have the headspace set right on the brass, so it gauges good beforehand. One common issue with the 300BLK when using reformed 223, is the brass wall at the neck being too thick, so that it is out of spec when you seat the bullet.
Another common issue is what you already saw in the pic where the shoulder collapsed. If there is too much force transferred to the brass when you seat the bullet, you can cause the brass to bulge below the shoulder. |
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Quoted:
Ok, figured it out. Yes, set-up issue. Did not have the ram completely bottomed out before adjusting the die. I will go hang my head in shame for a bit. So, got that part taken care of. Now to figure out why they are no-go on the Sheridan gauge after seating when they were good prior. you checking before or after crimp? |
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This is what happens when the crimp is applied prior to the bullet being at the full depth. As crimp is applied and the bullet is still trying to seat deeper it crushes the shoulder. Do your seating and crimping two separate steps.
As to your failure of case gauging, check your neck thickness. 0.002" is where it needs to be, any thicker you will fail. What headstamp are you loading? |
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