TWIST VS VELOCITY?? TWIST AND VELOCITY?? WHAT SAY YOU?

[8x68s]

I haven't seen this question asked around the website. I want to build a rifle that will shoot heavy for caliber bullets. All specifics aside, does driving a heavier, longer and better BC bullet faster thru a "standard" twist stabilize that bullet the same as driving that bullet more slowly thru a faster twist? Or, is the faster twist the only solution for stabilizing the heavier bullet regardless of velocity? I understand pressures will be proportionally greater the faster a bullet is driven no matter the twist.

In the specific, I can purchase a 10 twist, 6mm barrel but pertaining to my question, is that enough twist for a 115 grain bullet.

 

[Edd]

Velocity will not compensate for twist.

A 10 twist is not fast enough for a 115 grain 6mm bullet.

 

[mwkelso]

If there isn't enough twist, but there is more velocity, you're left with an unstable bullet flying faster...

Berger has a stability calculator on their website that is a universal tool and very useful.
Anything with a stability factor less than 1 should not be shot, it is not stable.
Between 1 and 1.5 are marginally stable. They can be shot, but may or may not perform well.
Anything greater than 1.5 is considered stable to full effect and should perform well.

 

[adam32]

Velocity will not compensate for twist.

A 10 twist is not fast enough for a 115 grain 6mm bullet.

Not true... velocity and altitude can both compensate for lack of twist to a certain point. But overall, proper twist makes everything work correctly.

No, a 10 twist will not stabilize any 115gr bullet.

An 8 twist will at certain velocities, but a 7 would be ideal...

 

[sedancowboy]

The twist rate does not cause you to loose any significant amount of velocity.
Brian Litz in one of his books ran a test and determined that you only loose about 5 fps per inch of twist gain. So not much.
The other part of your question going really fast in a slow twist barrel will help but marginally so. And no a 1-10 will not stabilize a 115 at any speed or elevation. Well with in reason.

 

[Edd]

Not true... velocity and altitude can both compensate for lack of twist to a certain point. But overall, proper twist makes everything work correctly.

No, a 10 twist will not stabilize any 115gr bullet.

An 8 twist will at certain velocities, but a 7 would be ideal...

Maybe in your make believe world velocity can compensate for twist but not in the real world.

 

[8x68s]

I know I've asked my question succinctly when I get such concise answers. Thank you, gentlemen!

 

[Edd]

Krieger has a few 7.5" twist 6mm blanks in stock.

 

[adam32]

Maybe in your make believe world velocity can compensate for twist but not in the real world.

Math isn't your strong suit I see.

Go over and play with the Berger stability calculator, or better yet read up on this exact subject on the Blackjack bullets page.

You're wrong on this one Edd, sorry.

 

[Edd]

Math isn't your strong suit I see.

Go over and play with the Berger stability calculator, or better yet read up on this exact subject on the Blackjack bullets page.

You're wrong on this one Edd, sorry.

I'm comfortable with my math skills but I don't really need any to use the Berger calculator.

Since a 115 grain bullet and a 10 inch twist was specifically asked about and since Berger has a 115 grain bullet, lets see what the calculator says.

The 115 grain bullet has an SG of 1.52 with a 7.5 inch twist barrel at 3000 fps.

With a 10 inch twist barrel it takes a velocity of 16,000 fps to get to a 1.50 SG.

I'm sticking with you being in a make believe world.

 

[8x68s]

for cripe sakes you guys!! does everything have to be an argument. state your opinion and back the EFF off!! sick of the argumentative hijacking from you !! you do nothing but lose the respect of those on this site who participate without being combative. I hope to see you get jacked off this site!

 

[Edd]

for cripe sakes you guys!! does everything have to be an argument. state your opinion and back the EFF off!! sick of the argumentative hijacking from you !! you do nothing but lose the respect of those on this site who participate without being combative. I hope to see you get jacked off this site!

Well then, go ahead and buy that 10 twist barrel and see if you can get a 115 grain bullet going fast enough to be stable.

 

[aushunter1]

A lot of people are forgetting its not about projectile weight, its more about the overall length & bearing surface length in stabilization.

E.g I can shoot a 55gr nosler ballistic tip out of my .22-250 with 1:14 twist which most calculators will say is at the stabilization crest for the 1:14.

BUT I can successfully(and accurately) shoot a 70gr Speer spitzer out of the same 1:14 twist barrel.

WHY?

Both projectiles are nearly the same identical length, the Nosler is .810 long & the Speer is .808 long, so the heavier projectile is actually shorter by a whisker!
Not only that the bearing surface is almost the same.

So IF you could find a short 115gr projectile in .243 then it could theoretically be stabilised in a 1:10

It certainly will not work if the 115gr projectile is something like a VLD.

If you want to comfortably be able to shoot different/VLD projectiles in a .243 then I would be looking at a 1:8

 

[adam32]

I'm comfortable with my math skills but I don't really need any to use the Berger calculator.

Since a 115 grain bullet and a 10 inch twist was specifically asked about and since Berger has a 115 grain bullet, lets see what the calculator says.

The 115 grain bullet has an SG of 1.52 with a 7.5 inch twist barrel at 3000 fps.

With a 10 inch twist barrel it takes a velocity of 16,000 fps to get to a 1.50 SG.

I'm sticking with you being in a make believe world.

Wow, reading comprehension still isn't your strong suit either I see....I agreed with you about the 1/10 not being sufficient. I said velocity/altitude make a difference to a certain point. Holy moly Edd it's not going to make up the difference between a 1/7 vs a 1/10 but it can and will make the difference between a 1/7 and 1/8.

Run that 115gr in the calculator with a 1/8 twist at 7,000' and 3250fps and see what it says.