Midas+ higher BC than Center-X?

[littlepod]

So this one is a odd one - I've always thought and I think the word around town is Midas+ is just the more consistent Center-X. But since I swapped to Midas+ I've been having issues with my Kestrel lining up.

I've been shooting Center-X for 2 years, running the Center-X AB Custom Curve and it's been spot on out to 350 and 2 NRL22 Nationals, and I've never had to use DSF. Then I get back some Midas+ from a recent lot test and I was having to bump the chrono'd velocity about 20 fps to get it to line up from 0-200 (this is my local range), it chrono'd at 1056, and I trued it at 1076 which made everything from 50-200 spot on.

So I was scratching my head, and I decided to create a new Vudoo profile in Kestrel, this time with the Midas+ Custom Curve, and lo and behold it lined up perfectly with my chrono'd numbers. So the Midas+ custom curve in AB has a slightly higher BC than the Center-X custom curve... what gives?

 

[6.5SH]

Less projectile deformation so higher average BC? How exactly does Lapua sort their lots to determine what is Center-X, Midas or X-Act?

 

[littlepod]

Less projectile deformation so higher average BC? How exactly does Lapua sort their lots to determine what is Center-X, Midas or X-Act?

That's an interesting thought. I had heard they just run it through their test tunnels and do it by group size / es / sd. Maybe there's a correlation to the bullet deformations causing those, thus ultimately higher BC.

 

[CommissarGrub]

That's an interesting thought. I had heard they just run it through their test tunnels and do it by group size / es / sd. Maybe there's a correlation to the bullet deformations causing those, thus ultimately higher BC.

That's what I read too.
Might be interesting to buy a couple recently made center x boxes and see how they perform at longer range compared to your older lot.

 

[justin amateur]

CenterX, Midas+ and X-Act, are made from the same components on the same machines.
Results on target through multiple fixtured barreled actions determines how they are labeled.
Best results from multiple samples of a batch become X-Act.
Second best is Midas+, CenterX is third. Because of the method of testing a small portion
from a batch and the fact that minor variations in assembly and components occur,
what is labeled third best can actually produce better results as they are graded from
a small sample. The sample tested may have had a few minor issues, but the rest of the
batch was very uniform in quality and muzzle velocity.

 

[grauhanen]

As justin notes, CX and M+ bullets are the same. (The third digit in a Lapua lot number indicates the bullet used -- in this case a "5" which will be the same for X-Act also.) Some of these "identical" bullets may have more consistent dimensions than others, but that's not possible to determine without actually measurinng and as a result destroying rounds.

All three Lapua standard "rifle" match ammos -- CX, M+, and X-Act -- are made on the same production run. That is to say, a single production run when completed can produce all three Lapua varieties. How they are graded isn't clear (it's not made public). But since some lots of "lesser" grades perform better both over the chronograph and on target than some "better" grades, it's not only, if at all, the result of test barrel performance.

All three varieities -- CX, M+, and X-Act -- are produced with various average MVs. That is to say, there are faster and slower lots of each. Furthermore, the average MV of any lot may be different between one bore and another, even on barrels from the same manufacturer.

In addition, chronographs themselves may not always produce accurate information.

 

[rick137]

It may be the composition of the bullet. Many years ago the Army lab determined the composition of RWS50 and Eley Tenex as part of program to aid Americans in the Olympics. Bottom line was there were differences and these differences produced differences in hardness of the bullet. Of course the exact composition is highly proprietary.

Perhaps Lapua has changed the composition and that in some way has changed the effective BC if the geometry of the bullets before firing are the same. But the geometry of the bullets after firing could be different, perhaps only slightly being enough to change the BC by amount observed.

 

[justin amateur]

Coffee's still hot, bacon's gone, had time to ponder the idea of lot grading.

How would I go about it?

Need an enclosed test range, no wind, big enough to minimize reflected shockwaves.
Floors, walls, cieling along flight path covered in shock/sound absorbing materials.
Controlled ventilation to pull burn gases out yet minimally affect projectile flight.
Computer recorded trajectories, documenting muzzle velocities and flight paths.
Heavy, reinforced fixtures to affix at least 5 match barreled recievers to.
At least 250 cartridges tested per batch, 50 taken from beginning, 1/4, 1/2, 3/4 and end of run.
10 cartridges from each 50 cartridge sample sent through each test barrel.
Muzzle velocity data recorded only for labeling purposes.
Only results on target at 50 meters matter as to quality determination.
How much spread occurs from the samples tested determines labeling.
12 mm outside to outside would be best, 14 mm second, 16 mm third.
10 mm spread and that batch would be stashed away for use by factory sponsored competitors.

 

[littlepod]

That's what I read too.
Might be interesting to buy a couple recently made center x boxes and see how they perform at longer range compared to your older lot.

That's a good point. I should get some newer Center-X packaging to test. My friends all got Center-X and I got Midas+ this last run so I'll have them test their Center-X with the new Midas+ curve. It might just be that the Midas+ curve has been updated more recently.

 

[rick137]

Coffee's still hot, bacon's gone, had time to ponder the idea of lot grading.

How would I go about it?

Need an enclosed test range, no wind, big enough to minimize reflected shockwaves.
Floors, walls, cieling along flight path covered in shock/sound absorbing materials.
Controlled ventilation to pull burn gases out yet minimally affect projectile flight.
Computer recorded trajectories, documenting muzzle velocities and flight paths.
Heavy, reinforced fixtures to affix at least 5 match barreled recievers to.
At least 250 cartridges tested per batch, 50 taken from beginning, 1/4, 1/2, 3/4 and end of run.
10 cartridges from each 50 cartridge sample sent through each test barrel.
Muzzle velocity data recorded only for labeling purposes.
Only results on target at 50 meters matter as to quality determination.
How much spread occurs from the samples tested determines labeling.
12 mm outside to outside would be best, 14 mm second, 16 mm third.
10 mm spread and that batch would be stashed away for use by factory sponsored competitors.

@justin amateur:

Do you know if the LPTCs meet your specs for a test range?

Secondly, an issue to which I have posted in the past and which has fallen loudly on deaf ears, the ammo which gives the best performance in a rig with one support system may not give the best with another support system. A few indications that is true but only indications since all variables not stated. In a best case scenario, absolute accuracy/precision for a given ammo depends on the support system but relative accuracy does not.

 

[justin amateur]

Rick, no idea if they match my idea of a test facility.

Will ammunition produce different results in different barrels?
If the muzzle velocity fits optimum exit timing/barrel harmonics, I'd say yes.
With rimfire, differences in components and assembly have more to do
with results on target, than a rifle's "likes". Thinking rimfire cartridges are all identical
is a lapse in the shooter's understanding regarding the manufacture of ammunition.

I've never found a favorite brand of 22lr.
For my rifles it has always been about tight muzzle velocities and cartridge uniformity.
What has produced great results in my Lilja has done the same in my Shilen
and my factory barreled 22's. What shot well from last month's purchase,
didn't from this month's. Eley, Lapua, SK, RWS and Fiocchi Italia have all
delivered great results, and also delivered boxes that were disappointing.

It's the lot to lot, box to box, variations that make the difference in my results.
Not the brand name on the label.

 

[Jefe's Dope]

So this one is a odd one - I've always thought and I think the word around town is Midas+ is just the more consistent Center-X. But since I swapped to Midas+ I've been having issues with my Kestrel lining up.

I've been shooting Center-X for 2 years, running the Center-X AB Custom Curve and it's been spot on out to 350 and 2 NRL22 Nationals, and I've never had to use DSF. Then I get back some Midas+ from a recent lot test and I was having to bump the chrono'd velocity about 20 fps to get it to line up from 0-200 (this is my local range), it chrono'd at 1056, and I trued it at 1076 which made everything from 50-200 spot on.

So I was scratching my head, and I decided to create a new Vudoo profile in Kestrel, this time with the Midas+ Custom Curve, and lo and behold it lined up perfectly with my chrono'd numbers. So the Midas+ custom curve in AB has a slightly higher BC than the Center-X custom curve... what gives?

What are the BC's for both?


Edit: Strelok Pro has all three the same @0.172 and 1073 fps.

 

[littlepod]

What are the BC's for both?


Edit: Strelok Pro has all three the same @0.172 and 1073 fps.

This is using AB's custom curve which is variable BC throughout the velocity. I know using the exact same settings in my Kestrel, my 200 yard dope is off by 0.2 mils when looking at the CX custom curve vs the Midas+ custom curve. Which is about 20 fps difference at the muzzle.

 

[rick137]

Rick, no idea if they match my idea of a test facility.

Will ammunition produce different results in different barrels?
If the muzzle velocity fits optimum exit timing/barrel harmonics, I'd say yes.
With rimfire, differences in components and assembly have more to do
with results on target, than a rifle's "likes". Thinking rimfire cartridges are all identical
is a lapse in the shooter's understanding regarding the manufacture of ammunition.

I've never found a favorite brand of 22lr.
For my rifles it has always been about tight muzzle velocities and cartridge uniformity.
What has produced great results in my Lilja has done the same in my Shilen
and my factory barreled 22's. What shot well from last month's purchase,
didn't from this month's. Eley, Lapua, SK, RWS and Fiocchi Italia have all
delivered great results, and also delivered boxes that were disappointing.

It's the lot to lot, box to box, variations that make the difference in my results.
Not the brand name on the label.

@justin amateur:

Agree with all your points but I obviously didn't state well what I had in mind. So a unrealistic scenario that we will call it a thought experiment. Send your rifle to Lapua Performance Test Center and have them test lots of Center-X, Midas+ and X-Act. That is not unrealistic. The results come back with Center-X having the best performance, Midas+ second and XAct last. That is presumably unrealistic but does not contradict the laws of physics which are the ultimate arbiter. You buy cases of the best lots of CX, M+ and XA. That is unrealistic. You shoot all rounds of all three in whatever why gives you the most enjoyment, with accurate measurements of precision or accuracy or both perhaps on all 15,000 rounds under the exactly the same conditions, which are possible because this is a thought experiment. By whatever measure or measures of accuracy you want, determine which ammo performed best, middle and least. Then compare that with the LPTC results.

My hypothesis would be the results for 100 boxes would be statistically significant to best, middle, least. However, which ammo performed best at the LPTC may not the one which performed best in the field. Secondly, to your point, if you ordered the accuracy/precision of each box for each of the three types of ammo, for example the fifteenth least accurate box for the three types, any one of the three types could be the winner.

Conclusion: rimfire ammunition is at best biased roulette or at worst a total crap shoot, figuratively and literally.

 

[justin amateur]

I think I follow you.

It all leads back to the method of testing.
What's the metric that determines the sample size in order to have confidence in y'er purchase?
How many shots does it take to determine if 3 cases of ammunition are worth purchasing?
How many shots did it take for the factory to label those 3 cases as CenterX?
Can't test fire them all or there'd be none to sell.
If the testing sample is too small, you can draw an incorrect conclusion.
Too large you affect y'er profit margin.

It's rimfire, welcome to the assembly line lottery.

 

[rick137]

I think I follow you.

It all leads back to the method of testing.
What's the metric that determines the sample size in order to have confidence in y'er purchase?
How many shots does it take to determine if 3 cases of ammunition are worth purchasing?
How many shots did it take for the factory to label those 3 cases as CenterX?
Can't test fire them all or there'd be none to sell.
If the testing sample is too small, you can draw an incorrect conclusion.
Too large you affect y'er profit margin.

It's rimfire, welcome to the assembly line lottery.

@justin amateur

With apologies to Werner Heisenberg, call the situation you describe the Rimfire Uncertainty Principle. To adequately test a lot of rimfire ammunition requires so many shots the remaining number of shots in the lot are not sufficient to generate the requisite profit when sold.

 

[jbell]

I'm sure they were correct, but could the actual atmospherics have been different than what the software was using? Have you tried to repeat the test including chronographing again? Or did you also try your known good center x to confirm the algorithm and also check there velocity with the same chronograph to confirm all that is correct?

Just a few thoughts...

 

[littlepod]

Yep I still have the same lot of my ammo since I was able to get 4 cases back then, and that curve still works perfect for it. Even with the new rifle 22" Benchmark was shooting it at 1051 vs 1076, it was spot on at 200 again throughout the different atmospherics which also causes it to vary.

When I switched to Midas+ from the new box of ammo the chronoing and the curve didn't line up. I had to speed up the bullet by 20fps to match the curve.

 

[Boxerglocker]

Did you happen to check the G1 difference in the AB library on the Kestrel Elite? Center X G1 is listed at 0.121 Midas Plus G1 is listed at 0.131 therefore what you are seeing would make total sense being they list different G1s for each the CCs will be different as well.

 

[grauhanen]

Did you happen to check the G1 difference in the AB library on the Kestrel Elite? Center X G1 is listed at 0.121 Midas Plus G1 is listed at 0.131 therefore what you are seeing would make total sense being they list different G1s for each the CCs will be different as well.

Despite BC differences that may be found, the manufacturer uses the same bullet on both CX and M+. Of course, any two lots of CX and M+ can have different MVs and the result of this will be different BC figures. Slower rounds will have a slightly higher BC than those that are faster.

 

[Boxerglocker]

Despite BC differences that may be found, the manufacturer uses the same bullet on both CX and M+. Of course, any two lots of CX and M+ can have different MVs and the result of this will be different BC figures. Slower rounds will have a slightly higher BC than those that are faster.

We aren't talking about random resources here though but BCs taken from the AB library which are specifically derived from their testing with each specific bullet. If you go to Lapua they list both Center X and Midas Plus as 0.175 BC.

 

[grauhanen]

We aren't talking about random resources here though but BCs taken from the AB library which are specifically derived from their testing with each specific bullet. If you go to Lapua they list both Center X and Midas Plus as 0.175 BC.

Indeed. The point remains that, despite whatever values are given in any library, the bullets used for both CX and M+ are the same.

As a result they ought to have the same BC for a given MV.

 

[littlepod]

Indeed. The point remains that, despite whatever values are given in any library, the bullets used for both CX and M+ are the same.

As a result they ought to have the same BC for a given MV.

Agreed, so not sure why in AB's testing Midas+ shows a higher BC. And yes the BC is not a static number, which is why I use the AB custom curve which is constantly changing based on velocity.

Swapping from my 18" Vudoo to my 22" Vudoo I lost 30 fps on my Center-X ammo and my Kestrel AB custom curve accounted for that perfectly, no issues. So it handled from going 1085 to 1055. And then with Midas+ which shot at 1055-1075 depending on barrel, the CX curve didn't map as it was too high, which when trueing for velocity I had to add an additional 25 fps. AB recommends truing velocity <= 200y and using Cal-DSF for > 200.

I'll do more testing, but it's just interesting that switching to the Midas+ curve everything lines up. I'll need to try this with the new CX ammo, maybe the Midas+ test is more recent, so it is looking at the new boxed ammo, and if I had some new boxed CX ammo the curve would also fit.