Alpha OCD and Lapua Brass Comparison 6 Dasher

[Bryan Z.]

Results from testing Alpha OCD and Lapua brass in 6 Dasher

 

[Matt_3479]

Good video! Thank you

 

[RegionRat]

@Bryan Z. , really appreciate you sharing all your hard work. The Alpha OCD Laupa video was very well done. It led me to the quick look test on humidity, and I liked that one too.

Looking forward to the follow up tests!

Regards, Dino

 

[Tob5]

solid data !

thanks for putting all the effort towards this project!
Adam,

 

[DIBBS]

Interesting! Appreciate your efforts as I am considering this chambering.

 

[jobhopper66]

A very in depth video. So much better than unfounded opinions and speculation.

 

[One Eye Pete]

Great video. Thanks for sharing the research!
Was wondering about one thing. I know Lapua 6BR brass has a .059-.060 flash hole and Alpha 6BRA brass has a .080 flash hole as I use both brass types. Although have never used it I would assume that Alpha dasher brass also has a .080 flash hole. If my assumption is correct could the flash hole size account for the difference in the velocity, SD and group size? The only other thing I could attribute these differences to would be case capacity. I know that for the 6BRA, Alpha brass seems to have a slightly smaller case capacity than Lapua but I don't know if this difference also applies to Dasher brass.

 

[Bryan Z.]

A very in depth video. So much better than unfounded opinions and speculation.

Yes, the old saying that’s plastered on Lou Murdica’s test tunnel, “One test is worth a thousand expert opinions” has some merit. Now people can take the test data and interpret how they wish as they consider which brass to use.

 

[Bryan Z.]

Great video. Thanks for sharing the research!
Was wondering about one thing. I know Lapua 6BR brass has a .059-.060 flash hole and Alpha 6BRA brass has a .080 flash hole as I use both brass types. Although have never used it I would assume that Alpha dasher brass also has a .080 flash hole. If my assumption is correct could the flash hole size account for the difference in the velocity, SD and group size? The only other thing I could attribute these differences to would be case capacity. I know that for the 6BRA, Alpha brass seems to have a slightly smaller case capacity than Lapua but I don't know if this difference also applies to Dasher brass.

Flash hole size very well could account for differences. One way to test that is to make sure both flash holes are bored to the exact same diameter and then fire away with the same loads, rifle, atmospheric conditions, etc. I would be interested to see the data on that type of test. Without that data, I would guess that case capacity is what led to the difference in velocity - same charge but less case capacity in the Alpha OCD relative to Lapua would show higher pressure and velocity than Lapua. I did follow up analyses where I statistically matched velocity in the Alpha and Lapua data and then ran a paired sample t test on groups and standard deviations. The results showed that when velocity is matched, Lapua still has smaller groups and standard deviations relative to Alpha. I posted that data in the video description and comments sections of the YouTube video.

 

[Straightshooter1]

Yes, the old saying that’s plastered on Lou Murdica’s test tunnel, “One test is worth a thousand expert opinions” has some merit. Now people can take the test data and interpret how they wish as they consider which brass to use.

Excellent job there, Bryan.

I'd guess the reason for higher velocities on the Alpha brass is that they have less case volume???

If so and one is switching between the two brass, one would need to adjust the load accordingly to get performance between them closer the the same.

 

[BoydAllen]

There are a couple of things that I think are worth mentioning here. First of all, I believe that it is possible for identical velocities may have different shaped pressure curves, and that there is a possibility that different size flash holes could produce difference in pressure curves. Secondly, there seems to be a simple way to determine the effect of flash hole size on velocity. Drill out a few Lapua cases' flash holes to .080. Finally, if a smaller capacity case is loaded to the same velocity with the same powder, I think that it is likely that the pressure is higher that it would be in a larger capacity case. All in all, I think that this points to the desirability of simply tuning both cases to the best accuracy that can be obtained and testing them in a manner that minimized the effects of conditions. I probably should have mentioned that if accuracy was simply a matter of matching velocity, then any powder that gave that velocity would give the same accuracy.

 

[Bryan Z.]

Excellent job there, Bryan.

I'd guess the reason for higher velocities on the Alpha brass is that they have less case volume???

If so and one is switching between the two brass, one would need to adjust the load accordingly to get performance between them closer the the same.

Thanks! Yes, a big lesson in all of this testing is to expect changes if you swap brass and be prepared to go back to load development.

 

[AM_ARixon]

Great video. Thanks for sharing the research!
Was wondering about one thing. I know Lapua 6BR brass has a .059-.060 flash hole and Alpha 6BRA brass has a .080 flash hole as I use both brass types. Although have never used it I would assume that Alpha dasher brass also has a .080 flash hole. If my assumption is correct could the flash hole size account for the difference in the velocity, SD and group size? The only other thing I could attribute these differences to would be case capacity. I know that for the 6BRA, Alpha brass seems to have a slightly smaller case capacity than Lapua but I don't know if this difference also applies to Dasher brass.

Good question, in our testing we did see an increase in velocity due to flash hole size, though rather minor. We observed that velocity difference also changed dependent on primer/powder combination. The major difference in velocity comes from the internal capacity being slightly less in the dasher Alpha brass. It is very challenging to design tooling to perfectly match internal volumes.

 

[garandman]

A truly impressive, comprehensive test. As I'm newly into 6 Dasher, very timely.

I use Peterson brass, but still...

Maybe its just me, but the "Results" section seemed to largely omit N140 powder, which had smaller groups, as I recall. Any reason for that ? ...maybe I missed it in the video....

 

[BartsBullets]

Bryan,

Great job on the video and the information! Check your PM.

Bart

 

[Bryan Z.]

A truly impressive, comprehensive test. As I'm newly into 6 Dasher, very timely.

I use Peterson brass, but still...

Maybe its just me, but the "Results" section seemed to largely omit N140 powder, which had smaller groups, as I recall. Any reason for that ? ...maybe I missed it in the video....

Thanks for checking it out and commenting. I did include the N140 results in the larger analyses but i didn’t look at it individually because it was a very small sample size, therefore, the statistical method I applied to the Varget and IMR4895 analyses did not have the statistical power to detect any difference between Alpha and Lapua unless it was extremely large. Velocity had a large difference with the N140 so the stats detected that difference. If I would have shot the N140 about 5 more times (ie, 10 more 5-shot groups), I suspect that it would have showed a difference in standard deviation and groups.

 

[Bryan Z.]

Good question, in our testing we did see an increase in velocity due to flash hole size, though rather minor. We observed that velocity difference also changed dependent on primer/powder combination. The major difference in velocity comes from the internal capacity being slightly less in the dasher Alpha brass. It is very challenging to design tooling to perfectly match internal volumes.

Thanks for commenting and adding to the info. I suspected the flash hole variation was not a major factor and case volume was. I did not test this but suspected it. Looks like your test did point to case volume as a major factor in the velocity difference.