What twist rate do you suppose is need for this Federal factory .280 Rem ammo?

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What twist rate do you suppose is need for this Federal factory .280 Rem ammo?

Federal Trophy Copper 140s:

https://www.federalpremium.com/products/details/rifle.aspx?id=974

Seems like it's a pretty long bullet, being all-copper, but I don't see any info on twist rate there at Federal's site.

My rifle is 9.5 and I'm guessing this would need at least 9.25, 9.0, or maybe tighter.

Anyone know the bullet length?

People say these are a variation of Nosler E-Tips, and the 140 E-Tip is 1.350" long.

http://www.nosler.com/e-tip-bullet/

If that is the length, then I actually get a stability factor of around 1.48 at 3500 feet and 45 F, which is just under is acceptable, to my surprise, but in reality would be acceptable - BC would be compromised a smidge, but it should be accurate. I thought it would be way under 1.5.

http://www.bergerbullets.com/twist-rate-calculator/

But the Federal bullet has body cannelures to the E-tips smooth body, so it can't be the exact same bullet - the Federal version may be longer.

If it's 1.375" instead, for example, my stability factor drops to 1.40 at 45 F and 3500 feet, which is even with a very optimistic 2900 MV.

This bullet has a BC of .489, and would be an ideal elk bullet for me in the .280, if it shoots - don't want to shell out to buy it unless it has a high chance of shooting - I could be anywhere from 3500 to 7500 feet when hunting, and anywhere from 10 F to 45 F. So the worst case scenario is 3500 feet, 10 F, in which case stability is at best 1.37, even if it's only 1.350" long. I'd like to stay over 1.4 at least. But most likely I'd be at higher altitude.

Thanks.
 
I think you'll be just fine. People shoot 160-175 gr lead bullets in 1:9.5 twist 7 mags all the time. The 140 gr copper bullets will be longer than a 140 gr lead bullet, but I'm betting you don't have any problems with it being stable. You'll just have to shoot them to see how accurate they are.

I found a video online a few days ago that a guy posted shooting 215 gr Bergers in a 308 with a 1:12 twist at 2600 fps. All the experts say that combo won't work, but he was making hits at 1800 yards.

In game the 140's will penetrate and perform like a 160-175 gr lead bullet as long as impact speed is fast enough to expand. While lead bullets will expand at slower speeds copper needs about 2000 fps for good performance. According to the chart listed on Federals website that gets you over 500 yards so I'd think you're good with that combo.
 
Most factory rifles in 7mm use between a 1:10" and a 1:8.66" to stabilize lead core bullets up to 175 gr, so I will go out on a limb here and say that whatever your factory rifle is equipped with will suffice to stabilize those 140 grainers.
 
Most factory 7mms are horribly under-twisted. 7mms really need a 1/8 twist. Personally I don't trust anything marginally stabilized. It may come out of the muzzle fine, and then go toes up before it gets to the elk.
 
Without knowing the specifics of their bullet and your rifle, I will just have to opine that it would be dumb of Federal to sell hunting ammo not suitable for common hunting rifles with the usual twist rate.

I guess a box of ammo to test would be wasteful.
 
The bullet resembles a Barnes 140 grain TTSX.

According to Barnes, that bullet is 1.361 inches long.

IMO, you are way overthinking this. It's important to not have a gross mismatch between twist and bullet length, but there is a much wider band of acceptable matching than you seem to think there is. Fretting over a quarter turn of twist is pointless.

A standard 30-06 barrel will handle bullets ranging from 110 to 220 grains just fine. I realize that an all copper bullet will be a bit longer than a lead core bullet, but a standard 7mm twist rate will handle bullets much heavier (and longer) than a 140 grain copper.

Buy a box of the ammo, shoot it and in the unlikely event you get keyholing, then let's talk about it.
 
The problem of course is that your test at the range and the conditions on the hunt usually aren't the same. As it gets colder, and the ranges get longer so the spin has more time to slow due to air resistance, the situation gets worse. It's very common to have a load that's rock solid stable at 70F at 100y, and very marginal at 300y at 0F.

That's how ammo makers get away with making ammo that isn't really stable, or alternately how rifle makers get away with making rifles that can't stabilize the ammo.

Personally with that gun for elk in factory ammo I would carry the Nosler 160gr. parition load or possibly the Federal 150gr partition load. Both are premium bullets suited to the game, and both are stable in that rifle at any temperature and elevation.
 
Actually, spin decay is not the cause of low temperature instability, but inadequate spin is. I'll explain: Spin decay happens much more slowly than forward velocity is lost because the rotational surface speed of the bullet is slower than its forward velocity, and therefore its rotational surface fluid friction with the air, which is proportional to the square of that difference in velocity, is much less. The presence of the rifling marks makes no practical difference, as they are shallower than the boundary layer of air at the bullet surface.

What actually causes the low temperature stability problem is just that cold air is more dense than warm air, so that for any given velocity the overall drag on the bullet is greater and exerts more torque on the overturning moment of the bullet, causing greater initial yaw making it more likely it will initiate tumbling faster than precession can correct the nose into the wind. So the bullet needs to spin faster in cold air to enjoy the same degree of stability it had in warm air. For that reason, if you are going to hunt in cold air you want to choose a twist rate that is faster than is strictly necessary in warm air.

To accomplish that there are two good online calculators that estimate the stability factor for a given rate of twist, bullet length, velocity, and set of atmospheric conditions. They don't always agree with one another exactly, but they come fairly close. The results are in units of gyroscopic stability factor, either numerically or on a plot. This is a number which equals 1 when the bullet is right on the edge of instability. Below a value of 1, the bullet is unstable. Above the value of 1, it is stable. Sierra recommends that for hunting accuracy you try to pick a bullet, twist, velocity combination that produces a stability factor of not less than 1.3 in your worst case cold atmospheric conditions for hunting accuracy, and not less than 1.4 for target shooting accuracy. They recommend not exceeding 3.0 for hunting accuracy and not exceeding 1.7 for target accuracy, though I have shot any number of their MatchKings with stability factors of over 2.0 that still drilled cloverleafs. The reason for not overspinning is to avoid introducing extra wobble in flight that is caused by small mass distribution asymmetries.

Don Miller's estimator on JBM ballistics page.

McCoy estimator on Geoffrey Kolbe's site.
 
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I think your rifle should shoot that bullet OK. The twist rate in my .280 is an unknown and efforts to determine just was it is have not been very successful. However, the long Hornady 175 gr. bullet gave decent groups on the first try. Currently I'm playing with the 150 gr. Nobler ABLR which is not only a very long bullet but reported to be very finicky about seating depth. With hat one I have the velocity but so far not the accuracy.
I've done a one time try with the Barnes TSX bullet and velocity is good but accuracy only fair, More games with seating depth. If I can get a reasonably usable load with either the TSX or ABLR, I'll probably take the .280 on my elk elk hunt later this year. I'm also trying those bullets in a couple of 7x57s to see how the do. So far, not all that good although I have the TSX hitting just under 1.5" now. Just the seating depth game with that one. I haven't tried any in the custom Mauser yet and I know it has a 1in9" twist. It also shows high pressure much faster than the M70.
If it was me, I'd just get a box and give them a try. That's really the only way you'll know for sure.
Paul B.
 
OK, thanks all. It sounds like it's LIKELY enough that it will work well to shell out for one box just to try it.

If my rifle was 9.0 or even 9.25 twist, I'd have no hesitation, but it starts to get pretty borderline with a 9.5, at least according to the experts at Berger, who do in fact seem to know a thing or two about accuracy. :)

Thanks again.
 
I don't see any sign that you you posted your barrel length. The Federal MV will be for a 24" SAAMI standard velocity barrel. You can adjust MV approximately as below for a tighter number in the GS calculators.

Note, too, in the JBM calculator there is an argument for the length of the plastic tip, which it seems to simply discount. In theory that tip contributes a little drag to the overturning moment, but not very significant mass to the centrifugal effects of coning motion and nutation. It seems to me some discussion about how best to compensate was in Precision Shooting before it went under. In any event, if the calculator you used does not have an allowance for the length of the tip, it will lower the GS result compared to what it actually is.

Barrel%20Length%20Velocity%20Approximation_zpsvmsocp0k.gif
 
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