230 gr in a 10 twist

[Hugnot]

The Berger stability calculator uses the Miller method that is very conservative and provides Sg numbers that are on the safe side with a qualifier to the effect that "good groups might be obtained but...." Another site, JBM, has a stability calculator that uses the same Miller method,. I have played around with this stuff using a spread sheet that duplicates both Berger & JBM calculations.



The math is shown on the top line.

I have shot down silhouette chickens at 880 yards (half section) with a 10 twist .22-.250 using 68 Hornady hpbt bullets at 3250 fps., 2000 ft. elevation, 75*, dry day. The Sg for this combo is Sg=1.10 for this .987 inch long 68 grain .224 diameter bullet at 3250 fps from a 10 twist. Should not have been this good but was. All my .22-.250's now have 7.7 twists. I have a 10 twist .300 WM and intend to try some of this stuff out should anybody donate some real long pointy .30 bullets.

 

[B.C.]

The Berger stability calculator uses the Miller method that is very conservative and provides Sg numbers that are on the safe side with a qualifier to the effect that "good groups might be obtained but...." Another site, JBM, has a stability calculator that uses the same Miller method,. I have played around with this stuff using a spread sheet that duplicates both Berger & JBM calculations.

View attachment 297296

The math is shown on the top line.

I have shot down silhouette chickens at 880 yards (half section) with a 10 twist .22-.250 using 68 Hornady hpbt bullets at 3250 fps., 2000 ft. elevation, 75*, dry day. The Sg for this combo is Sg=1.10 for this .987 inch long 68 grain .224 diameter bullet at 3250 fps from a 10 twist. Should not have been this good but was. All my .22-.250's now have 7.7 twists. I have a 10 twist .300 WM and intend to try some of this stuff out should anybody donate some real long pointy .30 bullets.

Agreed,

156 Eol in my 6.5 saum for example, by bergers numbers I should have issues in my 1-8 twist when then temp falls come winter Their calculator shows a 4% bc penalty at -20 C w marginal stability However i haven't encountered any issues what so ever

 

[Shane Lindsey]

Not a 230 so take it as it is.
270 win With a 165gr Martrix from a 10 twist. At sea level, I would have amazing groups one day, then next time out with cold temps, I would have keyholes.

308 win with 181gr monos from a 10.5 twist would keyhole as well. It does well with the 215 though.

After that I have decided overspin, is better than under.
FWIW…not much.

 

[B.C.]

Not a 230 so take it as it is.
270 win With a 165gr Martrix from a 10 twist. At sea level, I would have amazing groups one day, then next time out with cold temps, I would have keyholes.

308 win with 181gr monos from a 10.5 twist would keyhole as well. It does well with the 215 though.

After that I have decided overspin, is better than under.
FWIW…not much.

I have chosen that route in my most recent build choosing to go 1-8 in a big 30 cal

 

[L.Sherm]

I dont think you can use bergers in a 8 twist 30 cal and then complain about them blowing up.

 

[B.C.]

I dont think you can use bergers in a 8 twist 30 cal and then complain about them blowing up.

Hopefully I don't detonate them, it's a short barrel, and I don't plan on getting crazy on maxing it out. If they do, I won't complain, it's my experiment lol

 

[L.Sherm]

Hopefully I don't detonate them, it's a short barrel, and I don't plan on getting crazy on maxing it out. If they do, I won't complain, it's my experiment lol

Its not just in flight that I'm just talking about.

 

[Cliffhunter]

is anyone shooting 230 bergers in a 10 twist ? I know its not optimum, but will it stabilize 230 otm s ?

 

[Cliffhunter]

I assume you're shooting 300 ultra mag. That is what I use. And I have the same situation custom built lap barrel tremendous accuracy touching at 100 m. Go to Berger's website and they have a twist rate chart based on your velocity. That is the key. How far do you want to have terminal velocity?. You are on the weak end of twist rate.
Let me know how it goes I want to do the same thing. True it at 1200 yards. Good luck

 

[L.Sherm]

That is the key. How far do you want to have terminal velocity?. You are on the weak end of twist rate.

With an 8 twist? Weak end guess I dont understand.

 

[VLD Pilot]

With an 8 twist? Weak end guess I dont understand.

Think he means with a 10 twist. It's still not weak in the 10 twist at 1.6 stability.

 

[VLD Pilot]

Think he means with a 10 twist

An 8 twist isn't too much twist for the 230s and I've never seen any come apart either running at 3100 fps using one. The 9 IMO is ideal unless it's a .308 win then an 8 may be needed. Around 280,000 RPMs running an 8 twist with 230s at 3100 fps won't spin jackets off the Berger bullet, or at least I've never seen it done. Maybe in the lower-mid 300,000 range. Not sure what speed you'd need to make for that to happen.

 

[B.C.]

An 8 twist isn't too much twist for the 230s and I've never seen any come apart either running at 3100 fps using one. The 9 IMO is ideal unless it's a .308 win then an 8 may be needed. Around 280,000 RPMs running an 8 twist with 230s at 3100 fps won't spin jackets off the Berger bullet, or at least I've never seen it done. Maybe in the lower-mid 300,000 range. Not sure what speed you'd need to make for that to happen.

Agreed I've seen the hard data and results, 300rum, 20" 8 twist 215 bergers over 3k all day long

 

[L.Sherm]

Agreed I've seen the hard data and results, 300rum, 20" 8 twist 215 bergers over 3k all day long

Have you shot anything with an 8 twist running 3100fps