Originally Posted by AJ Peacock
I'm not overly concerned with the aiming error for any individual shot, as a group of shots can be shot that will mathematically smooth out those errors in the data. Simply shoot a group, find the center and measure the vertical distance to the aimpoint. This is how I test loads and have documented this process with associated spreadsheets correlating velocity spreads with the vertical dispersion.
The thing I wonder about is the measurement method used to find the actual drops. I looked at the reticle you said you are using "NP-1RR" and couldn't figure out exactly how you were measuring 10.3-10.5 MOA since the Nightforce reticle pdf doesn't show a spacing that would easily allow you to measure to that precision.
In my estimation, this measurement method along with the aiming error could easily introduce more than 1moa of error into the the entire drop board/measurement process.
According to Exbal, a 1moa error in measuring a 300SMK at 338Edge speeds at 928yds is equivalent to a BC variance of .13. If the actual BC of the HAT bullets is .9, this measurement error could more than account for the reported BC's of >1.0. Even a 1/2moa error in drop measurements would account for the BC variance that some very knowledgable ballisticians on this board have questioned.
I don't doubt that these bullets have a BC of .9 or even .93 given the math that I've studied over the last couple of days (although it's been a couple decades since I've done any serious math). I also don't believe there are free lunches in physics. I expect that one of the following 2 reasons, or a combination of the 2 are responsible for the measured drops of these bullets.
1) They have a high BC (around .9+) and the math should be pretty easy to understand.
2) They are flying with a nose up attitude that causes them to shed velocity to support their better drop numbers. I hope this is not the case, as this will cause them to be more sensitive to headwinds/tailwinds/updrafts than other bullets. This will also cause them to impact the target with less than expected downrange velocity. Some downrange Chrono numbers would be a great help in determining if this is indeed the case.
ps: Noel, I read some of the stuff you've been focusing on with super high twist barrels and lathe turned bullets. Very interesting and complicated stuff. I for one appreciate your opinions on this board.
What you say is possible and that is specifially whay we choose the aiming point that we do. Additionally, we do not read the center of the group or even the highest point in the group in an attempt to funish extra sunshine to the posterior of shooters and hunters..... We read the worst shot in the group. We advertise the worst case scenario vice the average or even the best...... That way when it is performed by others with their equipment and conditions, they should get more impressive results than ours.
The aiming error and reticle error would be the same for any bullet tested using the same equipment and that levels out the error of one bullet over another during side by side comparisons since the same equipment is used.
Since the last group was 3.5" then that equates to a resonable and acceptable shot dispersion and aiming ability for that amount of distance. FWIW, we have already discounted the potential group dispersion by only using the lowest shot in the grouping. Another good reason to use the worst case impacts.....
I don't know how they are flying that flat, but they do.... I am just reporting the RAW DATA for those who wish to calculate numbers to be used for comparison.... Folks that are truly interested (beyond the desire to merely debate) will respond by getting some and test them in their own equipment under the conditions that they see in their locale. The customer is the most important tester that uses these..... The danger is that all customers do not have the same equipement or ablities as each other and therefore they will see different results from one shooter to another.
Sometimes you have to interprelate scales.
The NP1RR has 13 moa of continuous elevation (+3 to -10) indications. It then has a break to the -15 moa mark.... So to prevent from having to read the impacts below the 10 moa point, we do not aim or read from the center of the reticle. If the projectile yields a trajectory less than 13 moa, it can be easily seen and recorded. Specifially, when the value is greater than .25 and less than .5 and that is what we reported. Specifically, we used numbers rounded to the nearest .1, that comes up to .3 to .4 as I have posted.
For example you can read a 10.5 moa drop using the +3 moa point and the area between -7 and -8 moa... You can also use this reticle to measure the size of inteneded targets at specific ranges. We do this to grade animals and to size up the antlers during our hunts.
As I posted above, these were the lowest shots in the groups.
I don't know how much experience you have with the NP1RR, but our experience started with them in 1994 when I traded some of the 338 Lapua precursor (30 Snyper) cases to Bill Shehane (Nightforce distributor) for a 12-42 Benchrest scope.
Another point that has not been broached so far and I will answer it in advance is "how do you know you are exactly on the same calibrated power level to read the shots in the reticle"... The answer to that is simple..... Instead of aligning the "dots", we use "scribe marks on the power ring and the scope scale. This allows for a much closer alignment of the numbers..... We got this idea from the vernier scale on micrometers. So all the testing is performed using the same marks on any scope that is not 5-22x. I typically try to use the 5-22s for all the target readings since they are the most repeatable and accurate...... Nightforce calibrates the 5-22x to the stop of the rotation of the power ring vice the actual mark on the power ring..... This is very advantageous when in the field under low light conditions. Just dial to the stop and you are exactly at 22x.
Your scope inquiries bring up another good point for shooters and hunters to consider..... Scope A at the 10 moa point MAY not be the same as scope b-z at the 10 moa aiming point. It is crucial to ensure you are using reticles that are either properly calibrated or their values verified by the end user...... As you can probably tell, I have a lot of interest in calibration..... Without it, the data (from anyone) on any subject is not as useful or accurate as it could be when using calibrated instruments that can be traced back to the associated prime standards...... I personally own two sets of Starrett-Webber Croblox gage blocks (grade 2) that are cablibrated. I verify my instruments before each and every critical measurement. I also eliminate measuring variables by using spring loaded comparator equipment whenever it is possible as this minimizes the affects of random and uncalibrated pressure on measuring instruments.
AJ, please do not take offense to this, but if you want some down range velocity numbers then you will have to shoot them out of your equipment. I don't have acoustic targets and when shooting at longer ranges you are just one undetectable wind condition away from a chronograph disaster.
I do know that some have armor plate at extended ranges to protect their equipment, but I do not. I have been flirting with the devil (chronograph) during the last few months. Nicking the chronograph is actually how we got started conversing with the DR. Ken. He was interested in our testing and made some suggestions that actually cost him some business. So, we feel that his recommendations were ethical in nature and we really appreciate his insight. He is a nice guy.
You will not find us "quoting" BC numbers of the Gen II bullets since we cannot get them directly from an instrument(s). However the Gen Is were easily determined by instrumentation and they were .770 for the 265s and .878 for the 280s...... As prevously stated, the newer Gen IIs are more sleek than the Gen Is and we expect better trajectory performance from them.
Buy them, test them, hunt with them, kill with them.