I have 3 barrels in 300WM, all are 10” twist and all shoot the 215’s and 230’s just fine.
Sure, a 9” twist is probably a safer bet, but I have NEVER had an issue with a 10” twist.
I have a Palmer barrel in 300WM too, it has a 13” twist, IT WILL NOT stabilise ANYTHING above 168gr pills. PERIOD.
I always go a inch faster than needed to get the stability at extreme ranges. Also improves bc at distance. The extremely minor speed lose you get with a faster twist than needed makes up for its self at transonic and beyond
Yea I agree with the 9 but the 10 would suffice. The new 230gr smk .8 bc bullets supposedly requires a 1 in 8 twist. I don't know how fast you burn out a barrel but it seems the bullet manufacturers keep upping the ante. I may try out a 8 twist on my next 300 wsm barrel.
Seems like most bullets now are much better made than years ago. Used to be guys would talk about over stabilizing a bullet. Too fast a twist would cause asymmetrical bullets to not stay true in flight. Not so sure about this, but remember reading about it. More likely could be a problem of jacket core separation in flight. This should not be a problem with well made bullets particularly bonded bullets. If you are running mono's like ours it is never a problem. It is being proven by the elr guys that long range accuracy is aided by faster twist. Several years ago Nemo was installing 8" twist barrels on their 300wm not because they wanted to run extra long bullets but because they found better accuracy at 1000y and beyond.
From our testing, and as hunters, the faster twist will aid in proper terminal performance. In years past I hunted with marginal stability bullets because I wanted the higher bc. Accuracy was good so I never thought twice about it. Saw some questionable terminal performance and just chalked it up to poor bullet performance. I think many of the poor bullet performance issues that we hear about are due to marginal stability. Between marginal stability, hollow points plugged with tips, and tiny 1mm hollow points, it is a crap shoot whether the bullet will perform properly. When it comes to terminal performance it is more about the rpm's of the bullet vs the stability factor. We have found that an sg of 1.5 or higher calculated at sea level will result in better terminal performance. If you think of the bullet as a top spinning it will make more sense. A fast spinning top spins true for a long time if nothing touches it. As soon as friction is added to the top by touching it the rpm's degrade rapidly causing the top to wobble. The more rpm's the top has the more interference it can take before it starts to wobble. If a bullet is flying with yaw due to marginal stability, it can be very accurate, but the angel created by the yaw makes it harder for the hydraulics needed for expansion to get into the nose of the bullet. The more angle the bullet has the smaller the hollow point gets. In flight there almost no degradation of the rpm's. Once it impacts the rpm's rapidly degrade. As the rpm's degrade the bullet will try to tumble. This will cause the bullet to stop deforming properly and increase the risk of the bullet not tracking in a straight line. The higher the rpm's the longer the bullet stays point forward as it passes through the animal.
When discovering this in low vel testing of our bullets all of a sudden poor bullet performance from years gone by started to make sense. I am no longer willing to hunt with marginal stability and try to set my rifles up with what would be considered "over stabilized" bullets. Terminal performance is simply more dramatic on game. I will shorten my game for higher stability vs lengthening my game by using marginally stabilized bullets in order to get higher bc bullets. If shooting rocks or targets the only thing that matters is accuracy, so using altitude to calculate stability for external ballistics is all that is needed. Altitude adds stability for flight due to thinner air, but it does not add any rpm's to the bullet. So as soon as the bullet touches the animal and the rpm's degrade it allows the bullet to get off axis more quickly.
It is worth every hunters time to check this out. Our bullets are all listed with min twist rates for full stability at sea level or 1.5sg. This should be considered strongly for hunting.