Witch Doctor: Alpha OCD Lapua Brass Comparison
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- Опубликовано: 29 окт 2021
- The purpose of this video is to present data from comparison testing regarding Alpha OCD (Trademark) and Lapua brass in 6 Dasher. Overall, Alpha OCD exhibited higher velocity relative to Lapua (average of 27.1 feet per second). Lapua exhibited lower standard deviation and groups size. Of the three powders utilized in testing (Varget, N140, and IMR4895), IMR4895 exhibited the largest difference in velocity with Alpha being 29.9 feet per second faster than Lapua, and Lapua showed smaller standard deviation and group size. When it comes to differences within Alpha, there were no differences regarding standard deviation and group size between Varget and IMR4895 and this was the same for Lapua. With Alpha brass, lower velocities were associated with higher standard deviations; this trend was not present with Lapua given that Lapua exhibited small standard deviations along the entire range of velocities.
UPDATE: due to requests to assess for differences regarding groups and standard deviations while controlling for velocity, I performed "yoked control" statistical analyses. I paired velocities shot with the Lapua and Alpha OCD brass that were within 10 feet per second of each other and was able to pair 28 sets of 5-shot groups. When I ran the same t tests as the above-mentioned analyses, the same pattern emerged whereby Lapua had a statistically significantly lower standard deviation (p=.028; Lapua average = 6.35, Alpha OCD average = 8.09) relative to Alpha OCD and smaller groups (p=.020; Lapua average = .5718, Alpha OCD average = .6900). This follow up test suggests that controlling for velocity does not change the results of the primary analyses. 
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Another well organized, informative presentation using the scientific method.
UPDATE: due to requests to assess for differences regarding groups and standard deviations while controlling for velocity, I performed "yoked control" statistical analyses. I paired velocities shot with the Lapua and Alpha OCD brass that were within 10 feet per second of each other and was able to pair 28 sets of 5-shot groups. When I ran the same t tests as the above-mentioned analyses, the same pattern emerged whereby Lapua had a statistically significantly lower standard deviation (p=.028; Lapua average = 6.35, Alpha OCD average = 8.09) relative to Alpha OCD and smaller groups (p=.020; Lapua average = .5718, Alpha OCD average = .6900). This follow up test suggests that controlling for velocity does not change the results of the primary analyses.
Great work! And thanks again for sharing it!
Thank you Bryan !!
Thanks for sharing your hard work. That set of components is very popular and there are going to be many users with an interest in your results.
Do you think that the difference in group size of the Alpha would have been a closer match to the Lapua if the velocity was matched?
I just saw your comment as well as Alpha’s comment at around the same time and will comment on this in reply to Alpha. Please see that comment. Thanks for checking the video and commenting.
So for some reason I cannot find the post made by Alpha to this video. I recall it mentioning the same idea regarding matching velocity. In the scientific community, we call this a "yoked control" study design. At the outset, I did not consider matching on velocity and opted instead to make the independent variables the powder and powder charge. After a few firings, it became apparent that there was a notable velocity difference and so I considered changing the methodology to a yoked control design. However, the logistics of making it a yoked control design was considered in relation to the idea that I could do a post-hoc yoked control design. With that in mind, I went ahead and continued the test as planned and decided that if there was interest, I could conduct a post-hoc yoked statistical analysis. Well, it looks like there is an interest so I plan to conduct one in the very near future and either post the results here or in a new video. Basically, what I will do is take the exiting data and "yoke" based on velocity. Once the velocity is matched (to a reasonable degree), I will conduct the t-test analyses on standard deviation and group size. Some data will be lost in the analyses but I should retain enough to have decent statistical power to detect a mild to moderate degree of difference if it truly exists. Thanks for the comment!!
@@WitchDoctorPrecision Looking forward to seeing if the ES/SD and Group stats start to match up if the speed is matched. Also would be good to hear your opinion on brass weight and internal volume difference between these two sets after they have been fully formed. Great work and thanks again.
Thanks Bryan - interesting article. I shoot Alpha OCD in 6 Dasher and also noticed some loosening in the primer pocked after a few firings on a small number of brass (no more than ~6 our of 100). I did not notice differences on paper for those, but have not done rigorous testing. I use CCI Primers (BR-4 and #450) and they insert smoothly without any hard initial push on fired cases. (I forgot how it felt on virgin brass though.) Primer depth is consistent for me, but I do not 'hard crush' the primers. I am curious whether you measured and/or trimmed the brass to consistent neck lengths across Alpha and Lapua, and any differences after firings you may have observed. Also curious of the weight load of Varget you used. Thanks again for the time and effort put in this test!
I shot 32-32.5 Varget. I forgot to mention this but the brass was trimmed 15-20 thousandths of an inch from max length and I only needed to trim twice. Since I didn’t mark when I trimmed to what spec during the testing, I cannot proffer any conclusions regarding the impact of trim length…I treated trim length as a constrained constant rather than an independent variable. You could easily make it an independent variable and I actually did test that variable in my 6PPC and made a witch doctor video out of it.
@@Eric-qu3ht this is exactly what I want to test next. I do partial neck sizing (roughly 80%) on my 6PPC but never wonder about anything because the bullet seats into maybe the top 30% of the case. However, I did wonder if you partially neck size a long bullet that has to go beyond the sized portion like you mention. I think this is ripe for a test!
@@WitchDoctorPrecision Thanks Bryan - I look forward to your testing!
If sizing the full neck length makes a positive, measurable difference, I would invest in a FL body + neck custom die (no bushing) set at my desired neck diameter. I don’t think doughnut forming is an issue with quality brass on a 6 Dasher from my experience so far and from what I've heard from others.
FYI - Norma makes a 6 Dasher brass with a longer neck (and a small flash hole!). I have a box of Norma (which I never used) and it looks like the neck length is about 0.28 Inch. From my estimate, this should be long enough to seat bullets with a standard FL + Bushing dies, within the sized portion of the neck up to roughly 15 tho off lands. A new brass and smaller flash hole size would not compare to Alpha but should still be relevant for a test in isolation of other variables. If you want to test some of my virgin Norma cases, I can send you cases, just let me know..
@@Eric-qu3ht appreciate the offer to send the Norma brass. I really like the idea of a longer neck for dasher brass so that you have plenty of room to test seating depth without breaking into the shoulder-neck junction and then potentially crushing powder, etc.
@@WitchDoctorPrecision Let me send you a PM on Accurate Shooter to get a mailing address for the Norma brass.
@Witch Doctor
do you happen to know what powders lou murdica or your self uses for 308win for f class?
And as commented above great information A+
Thanks for watching! Varget is the typical powder of choice.