B
bsl135
Guest
Guys; this is the real thing!
I generally advocate against deriving BC's from drop because it's too easy to be lazy, shoot 3 shots at 1k, note the scope adjustments and run a trajectory with 'standard atmosphere' and best memory of average MV from a 9 year old shooting chrony, and derive a 'true' BC. Most of the time, it's no more 'true' than my 9-year-olds story of why he got in trouble on the bus.
If it's done right (as in the linked report) BC's can be derived from drop quite accurately, but it takes the kind of effort and attention to detail that K has put into it.
Here are a few observations I have of the testing and report:
1. He says that his BC's aren't true, but according to the JBM derived BC's, for the 3 bullets, the differences in BC for the Berger, Lapua, and Sierra bullets are +1.5%, +0.4%, and +1.1% respectively (compared to my measurements). That's a very small difference, easily eclipsed by normal shot-to-shot variations in muzzle velocity. I don't consider our (mine and K's) measurements of BC to be significantly different at all for these bullets.
2. I'm very interested to know if the scope 'come-ups' are verified true MOA. Since in this experiment, most of the drop is corrected for with scope adjustment, it's very critical that the adjustments are true (consistency with my results indicates they are, but a question to ask non-the-less).
3. The JBM derived BC's produced results much closer to my measurements than the PSSF software. I suspect this may be due to a feature of JBM that allows a 'muzzle velocity' to be given as the value measured some distance from the muzzle, as in the case of a real world 'instrumental reading' from a chronograph. If the PSSF software doesn't have this feature, the drop in velocity between the muzzle and chrono could explain why PSSF predicted higher BC's than JBM. (All of the ballistics programs I write match very closely to JBM, that program (JBM) is golden).
4. It was very interesting to see the relative chamber pressures and resulting muzzle velocities. This is a metric that we rarely get insight to.
Overall I think this was a very well done test and report. It's refreshing to see a truly scientific approach taken and result in genuine information that's useful to the masses.
Although the test was done with a tactical 'flavor' in mind, I'm sure there are many other shooters; Palma and F-TR guys in particular, who would find this test and report very interesting.
Great work K, we look forward to more of your testing in the future.
-Bryan
I generally advocate against deriving BC's from drop because it's too easy to be lazy, shoot 3 shots at 1k, note the scope adjustments and run a trajectory with 'standard atmosphere' and best memory of average MV from a 9 year old shooting chrony, and derive a 'true' BC. Most of the time, it's no more 'true' than my 9-year-olds story of why he got in trouble on the bus.
If it's done right (as in the linked report) BC's can be derived from drop quite accurately, but it takes the kind of effort and attention to detail that K has put into it.
Here are a few observations I have of the testing and report:
1. He says that his BC's aren't true, but according to the JBM derived BC's, for the 3 bullets, the differences in BC for the Berger, Lapua, and Sierra bullets are +1.5%, +0.4%, and +1.1% respectively (compared to my measurements). That's a very small difference, easily eclipsed by normal shot-to-shot variations in muzzle velocity. I don't consider our (mine and K's) measurements of BC to be significantly different at all for these bullets.
2. I'm very interested to know if the scope 'come-ups' are verified true MOA. Since in this experiment, most of the drop is corrected for with scope adjustment, it's very critical that the adjustments are true (consistency with my results indicates they are, but a question to ask non-the-less).
3. The JBM derived BC's produced results much closer to my measurements than the PSSF software. I suspect this may be due to a feature of JBM that allows a 'muzzle velocity' to be given as the value measured some distance from the muzzle, as in the case of a real world 'instrumental reading' from a chronograph. If the PSSF software doesn't have this feature, the drop in velocity between the muzzle and chrono could explain why PSSF predicted higher BC's than JBM. (All of the ballistics programs I write match very closely to JBM, that program (JBM) is golden).
4. It was very interesting to see the relative chamber pressures and resulting muzzle velocities. This is a metric that we rarely get insight to.
Overall I think this was a very well done test and report. It's refreshing to see a truly scientific approach taken and result in genuine information that's useful to the masses.
Although the test was done with a tactical 'flavor' in mind, I'm sure there are many other shooters; Palma and F-TR guys in particular, who would find this test and report very interesting.
Great work K, we look forward to more of your testing in the future.
-Bryan
bill larson
Member
bullets
Dam good work.... Thank You...
Bill Larson
Dam good work.... Thank You...
Bill Larson
C
cybersniper
Guest
your report is not available
please send me a link to it
Thanks
edu
please send me a link to it
Thanks
edu
K
kombayotch
Guest
Unfortunately, geocities closed and I'm looking for a new host site. Send me your e-mail and I'll send it to you.
T
Tony Shankle
Guest
I would appreciate a copy also.
Last edited by a moderator:
F
Frank Green
Guest
That was nice!!!!!!!!!!! Easy to read for the average guy and good clean information.
Later, Frank
Bartlein Barrels
Later, Frank
Bartlein Barrels