Barrel twist

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Husa-Monster

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I've been running numbers in Bergers barrel twist calculator. Is there a point where the SG number is too high despite the calculator saying your bullet is still stabilized? I realize that over spinning a bullet can have less than desirable effects, but short of trial and error is there a recognized point of no return?
 
As you spin a bullet, or any object for that matter, variations in the distribution of mass in the object affect the motion. And the faster you spin it, the greater the effect. I suppose you could over-spin a bullet, but it will come apart long before that happens. Out of suitable fast twist barrels, you are already hitting 270,000 RPM with some cartridges, the forces exerted on the jacket are enormous.
 
4890 fps take a little 30 gr 22 cal berger apart at 60 yards
3690 take a 168 30 cal Sierra's apart I know
But isant that the fun part of reloading and doing stuff
 
A 3170fps round fired out a 1/7 barrel is spinning at around 325,000rpm...A mind boggling amount...I have only seen a couple varmint bullets spin to pieces before hitting the target...Also mind boggling.
 
I think I need to add some context. Currently shoot a 25 cal 100gr bullet for hunting thru a factory 10 twist (which the Berger calc says is too slow.) I want to try shooting a new 131 high BC bullet at steel but the company recommends a 7.25 twist. Im willing to rebarrel - faster twist would be better for small bullets anyways, but concerned they might be over spun despite the Berger calc determining they're still in the "stabilized" zone. I'm probably over thinking it all, but I'm new to all this and trying to learn.
 
I've been watching what Blackjack has been up to for the last little while an I think it's super interesting. With the 131 ACE, it appears that most guys are having great luck with 1:7-1:7.5" twists and I wouldn't overthink the Berger calculator numbers. I'm pretty sure all of us on here, at some point, have thought about trying a bullet that was too heavy for our twist rate (according to the calculator) and got it to work!

The biggest issues that you will run into is getting a barrel and those 131 gr bullets up here. I don't think there are any Canadian gunsmiths with a 25 CM, 25x47, 25 WSM, etc. reamer up here yet, so you will have to import all of your barrels and components, which just gets costly.
 
I load my 6mmbr Norma 1:8 twist. Bullet constuctuon is everything, I load a Hornady V-Max 5 8 grain bullet at 3400 feet per second. Bullet stays together and Pop's gophers well. I didn't think a 1/8 twist would stabilize a 58 grain bullet. Accuracy is still three quarter inch.
 
Just barely enough spin is where you will generally get the best accuracy under calm conditions, although it seems that spinning a little faster can help keep the round more stable in flight in windy conditions... So there is no one perfect answer.... But I always prefer a little too fast over a little too slow.

If the twist rate is too slow, then you'll need to run a hot load to get accuracy, or you'll be stuck running lighter bullets. If the twist rate is too fast you can run a more polite load and get good accuracy. If you want the optimum accuracy at maximum velocity, you might need to ask some hard core competitiors with experience what is best, or buy what you think is best now but expect to refine it with your next barrel. Don't ask a guy with a 6 Creed what to do with your 6x47, because obtainable velocities are cartridge specific.

As stated above, spinning faster can open the group by magnifying any imbalance in the bullet, but that can be overcome with high quality bullets. That's why guys get bad groups with mil surp 55 grainers out of a 1:7 twist. Groups would be good if they ran 69 grain SMKs... so it's not the barrels fault... just what they feed it.

If you think about terminal performance... the rotational energy must be significant for a round to fly apart in flight, so just under the ragged edge of destruction is where you will find the most explosive terminal performance.

I shot a 6x47 Lapua for a while and had a few 115 Bergers fly apart on me during match competition. I reported it to Berger and they started using thicker jackets. They still make the bullet with the thinner jacket but they now call it a hunting bullet instead of a competition bullet.
 
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Husa-Monster said:
I think I need to add some context. Currently shoot a 25 cal 100gr bullet for hunting thru a factory 10 twist (which the Berger calc says is too slow.) I want to try shooting a new 131 high BC bullet at steel but the company recommends a 7.25 twist. Im willing to rebarrel - faster twist would be better for small bullets anyways, but concerned they might be over spun despite the Berger calc determining they're still in the "stabilized" zone. I'm probably over thinking it all, but I'm new to all this and trying to learn.
Click to expand...

1/10 will work fine for 100 gr bullets in a 25 cal. - dan
 
Kudu said:
I've been watching what Blackjack has been up to for the last little while an I think it's super interesting. With the 131 ACE, it appears that most guys are having great luck with 1:7-1:7.5" twists and I wouldn't overthink the Berger calculator numbers. I'm pretty sure all of us on here, at some point, have thought about trying a bullet that was too heavy for our twist rate (according to the calculator) and got it to work!

The biggest issues that you will run into is getting a barrel and those 131 gr bullets up here. I don't think there are any Canadian gunsmiths with a 25 CM, 25x47, 25 WSM, etc. reamer up here yet, so you will have to import all of your barrels and components, which just gets costly.
Click to expand...

That's the bullet I want to try, but in my 25-06. If things look good maybe I'll try one of those 25 cal Wildcats someday and source a reamer from Blackjack if needed.

dan belisle said:
1/10 will work fine for 100 gr bullets in a 25 cal. - dan
Click to expand...

No complaints from my 25-06 so far. Just didn't want to walk away from my preferred hunting bullet if I decided to rebarrel.
 
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