Based on some limited data, it looks like MV decreases about .9%, (of the larger MV), per inch. Call it 1%, then from a 24" bbl at 1800 fps, a 20" bbl MV would be 1800 - (18 X 4) = 1728 fps.
Based on some limited data, it looks like MV decreases about .9%, (of the larger MV), per inch. Call it 1%, then from a 24" bbl at 1800 fps, a 20" bbl MV would be 1800 - (18 X 4) = 1728 fps.
Attached Files
Ballistics by the inch has some good source data on this...
And a quick analysis there confirms what I expected. This is going to be geometric, not linear. They log datapoints at 18, 16, 14, 12, 10, 8, 6, 5, 4, and 3 inches in 223. And the data does show a geometric relationship between barrel length and velocity.
Attached Files
The BBTI data covers 223 Rem bbl lengths from 3" to 18", see below:
Attached Files
I don't know what a "geometric" relationship is. The bbti graph looks like an exponential relationship, such as capacitor charge E vs. time, or diminishing marginal returns, (economics). Example below:
Attached Files
In any case, the relationship is pretty linear above 10" bbl length, and estimates using my data are PROBABLY reasonable.
Below 10" is uncommon. The relationship is probably kinda parabolic since mv starts to drop at some bbl length, maybe 6' or so.
Thanks;
joe b.
Attached Files