Is it time to panic about my twist rate being too fast?

[TacosGigante]

Here is the situation - I live in Virginia but am going to hunt in Montana the first week of November. I am using a 300 WSM with a 1:9 twist and handloaded 175gr Federal Terminal Ascents going about 2900. I had thought about stability before and looked up Montana's average November air pressure, plugged it into the bison ballistics calculator, and things looked good.

Turns out where I will be hunting the air pressure is a good bit lower, and the ballistics stability calculator is now showing the bullet significantly overspun (Sg 2.65). Is it time to panic? I could do a quick order barrel from PVA, but would need to do more load workup. I could hope I can find some factory loads that work, I could be freaking out over nothing.

What should I do?

 

[Supersubes]

Put the credit card down. You’re fine, forget about it. The only problem with “over spinning“ is bullets failing mid flight. If you’re not having bullet failures, reduced barometric pressure isn’t going to cause your bullets to fail. I bet that bullet would hold together in a seven twist, it’s a rather stout projectile.

 

[TacosGigante]

Put the credit card down. You’re fine, forget about it. The only problem with “over spinning“ is bullets failing mid flight. If you’re not having that issue, you are fine, and a lower air pressure isn’t gonna make bullet failures more of a thing.

From your mouth to God's ears! I'm not having the problem now, but I am shooting in the apparently soupy Virginia air, not the whispy Montana stuff.

 

[MK20]

You have been sold some type of ballistic whiz bang calculator which is probably a good calculator, but wherever you learned to use it gave you bad info. Overspinning bullets really isn't a thing until they start blowing up. Air density has nothing to do with this and I don't really know where you got this idea.

Don't worry. You will be fine.

 

[Supersubes]

From your mouth to God's ears! I'm not having the problem now, but I am shooting in the apparently soupy Virginia air, not the whispy Montana stuff.

You’re thinking about this the wrong way though. Your slightly high SG will result in a slightly higher BC, the lower air density is going to further increase performance.

 

[TacosGigante]

Thanks all. It looks like the bullet will be doing under 240k rpm, so that should be safe in terms of it spinning apart(?)

 

[Kwtaylor]

Depending on what you’re hunting, the kill zone is the size of a 5 gallon bucket at 100 yards just go shoot it!

 

[Supersubes]

Thanks all. It looks like the bullet will be doing under 240k rpm, so that should be safe in terms of it spinning apart(?)

Yes, you're not even close.

 

[Railguner]

Here you are, go watch this. If I recall, he is in the mountains of Washington state.

See the 4:45 mark....

 

[Kickin45]

You’ll be fine, but step up to a 185 and have your peace of mind.

 

[JR1200W3]

Thanks all. It looks like the bullet will be doing under 240k rpm, so that should be safe in terms of it spinning apart(?)

Yes. You're not even close to needing to be concerned.

Stability calculator isn't the issue. It's RPMs. You want to stay under 300K rpms. Formula is MV(12/twist)60= rpms. So 2900(12/9)60= rpms. 232K rpms . Ridiculously safe.

 

[mkollman74]

Here you are, go watch this. If I recall, he is in the mountains of Washington state.

See the 4:45 mark....

Not the mountains, the foothills. Mountains have snow on them 365 days per year. Just being super picky... Good video.

 

[trob]

You’ll be fine, but step up to a 185 and have your peace of mind.

Yea geez, I’d switch to a heavier bullet before I bought a quick-order new barrel.

I shoot the 200gr terminal ascent in a 1:10 300wm

 

[TacosGigante]

Yea geez, I’d switch to a heavier bullet before I bought a quick-order new barrel.

I shoot the 200gr terminal ascent in a 1:10 300wm

If you know where I can get 200 gr TA bullets shoot me the link.

The only reason I was worried about the barrel is the hunt is coming up and I might not have time to do load workup. If this was two months ago I would have just used a larger bullet.

 

[db2000]

Stay away from Hornady ELD-M’s just to be safe

 

[roostercogburn98]

Thanks all. It looks like the bullet will be doing under 240k rpm, so that should be safe in terms of it spinning apart(?)

Start thinking about it when your RPMs hover at 300k or higher

 

[Baron23]

If you know where I can get 200 gr TA bullets shoot me the link.

The only reason I was worried about the barrel is the hunt is coming up and I might not have time to do load workup.

Friend, I get it....big hunt of a lifetime and you don't want no bueno stuff happening.

But you asked and have been told at least 4 times that your RPM is well withing the envelope and nothing to worry about. So, stop and enjoy your hunt

Good luck

 

[Ronws]

i learn something new, every day. Even though I have read about the ability to stabilize over time as a function of spin rate, I had not thought about the different environments. Having read about and seen people do set-ups for elk hunts in places in Montana while doing their work in Tennessee or Georgia, I had not seen or considered what setting up in the humid and thick deep south might affect what the performance is in the higher elevation and somewhat thinner air.

From what I see here, it is not really an issue. Which is good to know. I guess I figure that by using Hornady 4DOF, I can account for the change in environmental factors. I choose to find zero angle and that is where you put in all the initial conditions of the system. Then, on site, input the real time environment in the HUD. Other solvers have similar abilities. For example, where I have the rifle zeroed is about 574' above sea level, station pressure 29.81, 52 % RH. 1:8 twist rate for my 7 PRC, a heavy for caliber bullet.

Then, again, I am hunting 400 yards and in and many of the finer variables are just not having much affect at closer distances. That is why I like the Texas Plinking series. Anyone can look really good at 100 yards. 1,000 yards is another story.

 

[TacosGigante]

Friend, I get it....big hunt of a lifetime and you don't want no bueno stuff happening.

But you asked and have been told at least 4 times that your RPM is well withing the envelope and nothing to worry about. So, stop and enjoy your hunt

Good luck

Oh, I know. I just want some 200gr TAs, that would have been my preferred loadout if they had been available.

*edit* not for this hunt obviously, but just in general.

 

[trob]

If you know where I can get 200 gr TA bullets shoot me the link.

The only reason I was worried about the barrel is the hunt is coming up and I might not have time to do load workup. If this was two months ago I would have just used a larger bullet.

just buy a couple boxes of federal 200g TA ammo and be done with it. I don’t reload.
300wsm 200gr TA - on sale too

 

[bohem]

Here is the situation - I live in Virginia but am going to hunt in Montana the first week of November. I am using a 300 WSM with a 1:9 twist and handloaded 175gr Federal Terminal Ascents going about 2900. I had thought about stability before and looked up Montana's average November air pressure, plugged it into the bison ballistics calculator, and things looked good.

View attachment 8785438

Turns out where I will be hunting the air pressure is a good bit lower, and the ballistics stability calculator is now showing the bullet significantly overspun (Sg 2.65). Is it time to panic? I could do a quick order barrel from PVA, but would need to do more load workup. I could hope I can find some factory loads that work, I could be freaking out over nothing.

What should I do?

I'm happy to make you a rush, but it's not needed. You're fine. There's nothing to worry about with that bullet, chamber and twist rate.


Again though, if it makes you sleep better at night we can cut you a rush replacement with a slower twist rate