Decided to go back to the drawing board with a different powder that has published data from Barnes. With the case volume being dramatically reduced by the longer all-copper bullet, and the relatively quick burn rate of N320, there is too much risk of generating unpredictable pressure spikes. So, I am moving on to test with Ramshot Silhouette.<s>
I am working on understanding Quickload calculations and have a couple of questions about velocity, pressure and adjustments to the program. For a 45 ACP load I am working up, I adjusted inputs for actual case volume, case length, and temperature. My goal is ~ 950 fps for a Barnes 185gr tac-xp in a 4.25" barrel, ideally not a +P load. I worked up from 4.0 to 5.0 grains in 0.2 gr increments and chrono'd 5 rounds for each load.
Quickload calculates
5.0 grains VV N320 = 958 fps @ 21,212 psi (!)
CED M2 Chronograph field measurement
5.0 grains VV N320 = 855 fps @ ?? psi.
Back at the ranch, Quickload calculates
4.3 grains VV N320 = 853 fps @ 15,466 psi
Would it be safe to conclude that in my field test measuring 855 fps, the pressure was slightly more than 15,466 psi?
In an attempt to get Quickload calcs to match my field results....a rock-solid internet source indicates that you can alter the Burning Rate Factor (Ba) and Bullet Weight to match your field velocity measurements. Doing this to match my field measurements, I adjust Ba from 3.5542 to 3.00 (~16% reduction) and increase bullet weight from 185 gr to 190 gr (2.7% increase). New calculations match all of my field results from lowest charge to highest charge within 1%. Using these new settings:
Quickload calculates
5.5 grains VV N320 = 948 fps @ 19,649 psi
Am I doing this right, or am i going to lose some fingers? I understand that powder lots can vary by ~10%, but a 16% reduction in Ba seems like too much. Also, I am not confident that the relationship between velocity and pressure is that direct.
Any advice would be much appreciated.
</s>
JD
I am working on understanding Quickload calculations and have a couple of questions about velocity, pressure and adjustments to the program. For a 45 ACP load I am working up, I adjusted inputs for actual case volume, case length, and temperature. My goal is ~ 950 fps for a Barnes 185gr tac-xp in a 4.25" barrel, ideally not a +P load. I worked up from 4.0 to 5.0 grains in 0.2 gr increments and chrono'd 5 rounds for each load.
Quickload calculates
5.0 grains VV N320 = 958 fps @ 21,212 psi (!)
CED M2 Chronograph field measurement
5.0 grains VV N320 = 855 fps @ ?? psi.
Back at the ranch, Quickload calculates
4.3 grains VV N320 = 853 fps @ 15,466 psi
Would it be safe to conclude that in my field test measuring 855 fps, the pressure was slightly more than 15,466 psi?
In an attempt to get Quickload calcs to match my field results....a rock-solid internet source indicates that you can alter the Burning Rate Factor (Ba) and Bullet Weight to match your field velocity measurements. Doing this to match my field measurements, I adjust Ba from 3.5542 to 3.00 (~16% reduction) and increase bullet weight from 185 gr to 190 gr (2.7% increase). New calculations match all of my field results from lowest charge to highest charge within 1%. Using these new settings:
Quickload calculates
5.5 grains VV N320 = 948 fps @ 19,649 psi
Am I doing this right, or am i going to lose some fingers? I understand that powder lots can vary by ~10%, but a 16% reduction in Ba seems like too much. Also, I am not confident that the relationship between velocity and pressure is that direct.
Any advice would be much appreciated.
</s>
JD
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