Federal Terminal ascent required twist rates

FEENIX

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Berger twist calculator not work for tipped and mono bullets.
Did you plug in the right information?

Below is Cayuga 117 bullet information (https://patriotvalleyarms.com/cayuga-hunting-projectiles/)

Length: 1.365"
Optimal Freebore: 0.160"-0.210"
G1 BC average = 0.580*
G7 BC average = 0.282*

*The average BC was measured using 7tw 5R rifled barrels and being shot at approximately 2970fps. Different rifling geometry and muzzle velocity will affect the BC in a nominal manner.

257 cal Cayuga 117 requires a 1:8tw barrel.


... when plugged into Berger's SG calculator...

Cayuga 117 on Berger SG calculator.JPG


As you can see, it does work if the right information is plugged in.
 

Mikecr

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It worked in that case but the stability of the 117 from 1:8tw would actually be higher than Berger's 1.40sg result (where tipped).
 

FEENIX

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It worked in that case but the stability of the 117 from 1:8tw would actually be higher than Berger's 1.40sg result (where tipped).
So I do not misconstrue your statement. Are you saying if the Cayuga 117 is a tipped design, the SG would be higher than 1.40? If that is the case, yes, I agree that the SG would be higher.

Altitude is your friend comes to SG when it. If I ran the same numbers in #15:

- Range altitude of ~3333' SG = 1.58
- Average hunting altitude of 5500' SG = 1.72
 

257Tony

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They are showing the .308, 175 grain bullet is only .787" long, Gotta be wrong. That's the same length as a 110 Speer HP.

175TA.png
 

Laguna Freak

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So I do not misconstrue your statement. Are you saying if the Cayuga 117 is a tipped design, the SG would be higher than 1.40? If that is the case, yes, I agree that the SG would be higher.

Altitude is your friend comes to SG when it. If I ran the same numbers in #15:

- Range altitude of ~3333' SG = 1.58
- Average hunting altitude of 5500' SG = 1.72
The issues I’ve found with Berger’s stability calculator are:

1) no factor for bullet c.g. when comparing plastic tipped bullets to non-tipped. I assume because Berger makes zero tipped bullets

2) Berger attempts to use some sort of proprietary calculus in their elevation or altitude coefficient. Which, in my opinion, is bound to be less accurate than using actual barometric pressure and air temperature. Because their coefficient must assume a standardized pressure and temperature at the input altitude/elevation.

I’m sure Berger has their economic motivations. They are in the business of selling bullets. And they are fine bullets, no doubt.

I prefer the JBM Ballistics stability calculator because of the measurable inputs it requires for the above referenced “Berger deficiencies”. IMO.
 

257Tony

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Looks like the TA bullets are almost exactly the same length as the Barnes LRX of the same weight.
 

Mikecr

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Are you saying if the Cayuga 117 is a tipped design, the SG would be higher than 1.40? If that is the case, yes, I agree that the SG would be higher.
Yes. For a given weight-length with a plastic tipped bullet, more of the mass is in perimeter.
This, generating higher gyroscopic forces than a same weight-length non-tipped.
It is often surprising (to me) what twist you can get away with using tipped bullets.

I also agree with you about altitude (lower air density) being our friend.
 

Swamplord

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Those of you who wanted to try the Federal Terminal Ascent can get the 30 cal 175 gr from Midway right now via the "factory overrun" discounted sale at $59.99 per hundred pcs, last fall they were $42.99 per box of 50 pcs and Midway has jacked the price up to $69.99 per box, so the 100 pc bulk unmarked box sale is kind of a deal, limit 2 per customer

1B9351B2-77A4-4CA9-839E-B6A545E3F302.jpeg
 

General RE LEE

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Those of you who wanted to try the Federal Terminal Ascent can get the 30 cal 175 gr from Midway right now via the "factory overrun" discounted sale at $59.99 per hundred pcs, last fall they were $42.99 per box of 50 pcs and Midway has jacked the price up to $69.99 per box, so the 100 pc bulk unmarked box sale is kind of a deal, limit 2 per customer

View attachment 271762

I scored these last night. My Tikka .308 likes the Federal Terminal Ascent factory ammo and I kept the nickel brass so I can load up a bunch of these with Accurate 4064 powder.
 

General RE LEE

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Aug 21, 2020
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Those of you who wanted to try the Federal Terminal Ascent can get the 30 cal 175 gr from Midway right now via the "factory overrun" discounted sale at $59.99 per hundred pcs, last fall they were $42.99 per box of 50 pcs and Midway has jacked the price up to $69.99 per box, so the 100 pc bulk unmarked box sale is kind of a deal, limit 2 per customer

View attachment 271762

***PSA***

I ordered these and when they showed up they were not the Terminal Ascents, they were the short lived Edge TLRs. I went on Midway and other folks that received their order also noted they were the Edge TLRs. It appears Midway used the Terminal Ascent stock pic and specifications for this item but is shipping out the Edge TLR. I’m returning my order.
 

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