Anyone using PVA Cayuga bullets?

codyadams

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Southwest Wyoming
Nobody has said anything about these for a while, you're all still out hunting perhaps, but I'm curious if anyone had any further successes or failures with the Cayugas? I have a 7mag and thinking about trying them, I have a 9 twist, so I might be stuck with 151s but I'd sure love to run the 170s. Stability calculator shows marginally stable to almost comfortably stable for 170s, comfortably stable for varying conditions for the 151s.
My cousin just killed an elk with the 127 .277 bullets going 3425 fps from a .270 Sherman, and we recovered the bullet. Wasn't the greatest hit, he was in about a foot and a half of snow on a really steep hillside on a 620 yard shot, the large cow was at a hard quarter away as she was moving out quick and stopped to rest from running through the snow. A perfect hit at that angle would have been an entrance behind the ribs, so pretty hard quarter. He hit about 6-8" or so back, and made a direct hit to the femur bone. Did a ton of damage as would be expected, impact velocity was still 2530 fps, bullet was under the hide up in the rib area on the off side I believe. She went down hard on impact, then stumbled/fell to the bottom of the drainage, and he was able to put another one through the back of her head to finish her. So overall, not much of a terminal performance takeaway possible on this one, other than it seemed like a lot of energy was dumped into her, she was able to go down hill slowly and that's about it, but when I get a pic of the bullet, I'll post it up.
 

Laguna Freak

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South Central Texas, just north of the Wall
Nobody has said anything about these for a while, you're all still out hunting perhaps, but I'm curious if anyone had any further successes or failures with the Cayugas? I have a 7mag and thinking about trying them, I have a 9 twist, so I might be stuck with 151s but I'd sure love to run the 170s. Stability calculator shows marginally stable to almost comfortably stable for 170s, comfortably stable for varying conditions for the 151s.
I ran the .284 x 170 Cayuga data through JBM Ballistics Sg calculator at 9 twist, 55 F, 25” Hg, 2990 fps and got 1.407 stability factor. That is money!

I used 25” Hg based on my common barometer observations in Powell, WY. 25 being high.
 

archangel485

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Sep 17, 2016
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Wyoming
I ran the .284 x 170 Cayuga data through JBM Ballistics Sg calculator at 9 twist, 55 F, 25” Hg, 2990 fps and got 1.407 stability factor. That is money!

I used 25” Hg based on my common barometer observations in Powell, WY. 25 being high.
Nice. Yeah about what I was seeing on Berger. You haven't shot any 170s have you?
 

codyadams

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I ran the .284 x 170 Cayuga data through JBM Ballistics Sg calculator at 9 twist, 55 F, 25” Hg, 2990 fps and got 1.407 stability factor. That is money!

I used 25” Hg based on my common barometer observations in Powell, WY. 25 being high.
1.4 is not good proper stability, especially for a mono. Berger themselves recommend a minimum of 1.5, and monos are even more picky. It's not just to do with accuracy, but terminal performance. The twist rate and stability are critical for proper bullet performance. I went with a 1-7.5 twist to be able to run the 170 reliably, the slowest I would go is 1-8. Stick with the 151 Cayuga for a 9 twist, otherwise be aware that if you have poor terminal performance, that's on you.
 

Laguna Freak

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1.4 is not good proper stability, especially for a mono. Berger themselves recommend a minimum of 1.5, and monos are even more picky. It's not just to do with accuracy, but terminal performance. The twist rate and stability are critical for proper bullet performance. I went with a 1-7.5 twist to be able to run the 170 reliably, the slowest I would go is 1-8. Stick with the 151 Cayuga for a 9 twist, otherwise be aware that if you have poor terminal performance, that's on you.
Being monolith ignorant; I’m curious, if Sg 1.5 is the approximate minimum, is there a maximum Sg factor?

Is it possible to spin them fast enough to cause the rifling to excessively distort the bearing surface? Such would likely destroy accuracy and foul the bore in short order. Is it possible to spin fast enough to cause meplat petals to open before impact? I suppose that depends on the specific copper alloy used. Or would pressure get too high before that many rpm is generated?

Every system has its limits.

Seems the bullet manufacturers might have some applicable R&D experience. I’m looking for physical sciences or personal observation based responses. I have not researched monolithic bullets beyond reading personal observations on LRH.
 

FEENIX

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Great Falls, MT
Being monolith ignorant; I’m curious, if Sg 1.5 is the approximate minimum, is there a maximum Sg factor?

Is it possible to spin them fast enough to cause the rifling to excessively distort the bearing surface? Such would likely destroy accuracy and foul the bore in short order. Is it possible to spin fast enough to cause meplat petals to open before impact? I suppose that depends on the specific copper alloy used. Or would pressure get too high before that many rpm is generated?

Every system has its limits.

Seems the bullet manufacturers might have some applicable R&D experience. I’m looking for physical sciences or personal observation based responses. I have not researched monolithic bullets beyond reading personal observations on LRH.
Yes, there is a max RPM. However, don't overcomplicate it unnecessarily, follow the recommended SG as recommended (mono or not), esp. from ballisticians, and you are GTG.
 

Laguna Freak

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South Central Texas, just north of the Wall
1.4 is not good proper stability, especially for a mono. Berger themselves recommend a minimum of 1.5, and monos are even more picky. It's not just to do with accuracy, but terminal performance. The twist rate and stability are critical for proper bullet performance. I went with a 1-7.5 twist to be able to run the 170 reliably, the slowest I would go is 1-8. Stick with the 151 Cayuga for a 9 twist, otherwise be aware that if you have poor terminal performance, that's on you.
Dang! Now I have to look at monoliths to see what kind of Sg the mfrs are recommending. If any are other than the Sg 1.5 you posted re; Berger.

For anyone who is interested in calculating for local conditions, I ran the Cayuga 30 cal 178 and 210 through JBM Sg calculator. I input PVA published data and my common local conditions (S TX). They both yielded Sg of 1.7+. That is 13% greater than Berger’s 1.5 Sg minimum.

Haven’t looked at the Hammer or other monoliths yet but now I’m intrigued to see if there is any divergence in Sg by mfr. Or, if there is an applicable standard.
 
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