300 Blackout Case Capacity?
- Thread starter mattri
- Start date
Jager
Gold $$ Contributor
SAAMI specs the exterior dimensions of cartridges. But because different manufacturers make their brass of different thickness, actual case capacity will vary from headstamp to headstamp. So, no, there's no published spec.
In the case of the .300 Blackout, the headstamps I've measured tend to be between 24 and 25 grains of water. The one notable exception is X-TREME brass, which comes in at a much smaller 21.6 to 21.9 grains. That's enough of a reduction to get someone into trouble very quickly if they were using load data based upon a more typical case capacity.
In the case of the .300 Blackout, the headstamps I've measured tend to be between 24 and 25 grains of water. The one notable exception is X-TREME brass, which comes in at a much smaller 21.6 to 21.9 grains. That's enough of a reduction to get someone into trouble very quickly if they were using load data based upon a more typical case capacity.
As Jager noted there is a SAAMI Spec for the case dimensions. However, depending upon the case manufacturer the internal dimension may vary, such as wall thickness and case web thickness (bottom of case). Even with the cases from same manufacturer, the internal case dimensions can vary from year to year. Most of the discussion around variation in case capacity for 300BO is the result of .223 cases and 5.56 cases being converted into 300BO.
Do a search on headstamps that are good for converting into 300BO. There is an older list that users pulled together to identify headstamps were good to convert into 300BO. The primary determinant of "Good" was that the necks on newly formed 300BO cases had correct wall thickness (not too thick) to provide adequate clearance in the chamber. Some of the material might also include associated case capacity for these formed cases... I can't remember off-hand, but might be worth investing 30 minutes searching. Good Luck
Do a search on headstamps that are good for converting into 300BO. There is an older list that users pulled together to identify headstamps were good to convert into 300BO. The primary determinant of "Good" was that the necks on newly formed 300BO cases had correct wall thickness (not too thick) to provide adequate clearance in the chamber. Some of the material might also include associated case capacity for these formed cases... I can't remember off-hand, but might be worth investing 30 minutes searching. Good Luck
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