Tested @ 1k: New 155 Palma, 155.5 Berger, 155 Scenar
- Thread starter kombayotch
- Start date
Guys; this is the real thing!
I just registered for this site, allow me to introduce myself:
I'm the Chief Ballistician for Berger Bullets. Before this job, I worked for the US Air Force for 6 years as an air-to-air missile design engineer. I'm also a very avid long range (Palma/Fullbore) prone shooter.
I was very happy to provide K with some Berger bullets for his testing, below are my comments on the report linked above.
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 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 today.
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. For those wishing to re-create the drop calculations in their own software, you'll have to use a sight height of 1.95". This detail was left out of the article (no big deal).
2. 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.
3. 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).
4. 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).
5. 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. Might I suggest posting a link to this report over on LongRange.com and Benchrest Central under the F-class page.
Great work K, we look forward to more of your testing in the future.
-Bryan
I just registered for this site, allow me to introduce myself:
I'm the Chief Ballistician for Berger Bullets. Before this job, I worked for the US Air Force for 6 years as an air-to-air missile design engineer. I'm also a very avid long range (Palma/Fullbore) prone shooter.
I was very happy to provide K with some Berger bullets for his testing, below are my comments on the report linked above.
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 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 today.
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. For those wishing to re-create the drop calculations in their own software, you'll have to use a sight height of 1.95". This detail was left out of the article (no big deal).
2. 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.
3. 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).
4. 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).
5. 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. Might I suggest posting a link to this report over on LongRange.com and Benchrest Central under the F-class page.
Great work K, we look forward to more of your testing in the future.
-Bryan
Great reading - enjoy seeing people like you who take the time to systematically determine what's going on with a specific component. Interesting to compare BC's in the real world as opposed to simply taking them from a man'f manual. Good work!
wolf300H&H
CGN Regular
- Location
- Cabin in central Alberta
wholly shi tttttt!!!!!!!!!!!!!!!!!!!!!!!!!!!!, bryan litz is on here and i just found it out now. thats crazy cool . oh man ,do i wanna pick his brain , i gotta find a vulcan now to arrange ameeting and do the mind meld thing..........LOL.
