230gr Berger, 1-9 or 1-8 twist

[senna.bra]

Hi all,

I am currently using 1-10 twist, but I might be buying a new barrel in the next couple of months. I am shooting the 230gr exclusively in 300 Winchester magnum. Has anyone tried a faster twist rate, like 1-9 or 1-8 for the 230s? Of course there is nothing wrong with 1-10, I am just curios.

Thanks,

SC

 

[Darkker]

Few questions to ask here.
Which bullet? Hybrid, or Target Hybrid? They are different lengths, which is why twist is important, NOT weight.
The answer is that either is stable at a sedate launch velocity of 2400 fps, with a 10-twist.

The problem with faster twists become a question of destruction. About the strongest jacket out there is Sierra, they will withstand about 312,000 RPM. Velocity decay happens rapidly, rotational decay is VERY slow. So if a bullet was stable, but barely at the muzzle; it will gain stability down range. The RPM relative to velocity, will get stronger and impart more stability factor.

MV * 720 / Twist = RPM

JBM - Calculations - Stability

 

[senna.bra]

Few questions to ask here.
Which bullet? Hybrid, or Target Hybrid? They are different lengths, which is why twist is important, NOT weight.
The answer is that either is stable at a sedate launch velocity of 2400 fps, with a 10-twist.

The problem with faster twists become a question of destruction. About the strongest jacket out there is Sierra, they will withstand about 312,000 RPM. Velocity decay happens rapidly, rotational decay is VERY slow. So if a bullet was stable, but barely at the muzzle; it will gain stability down range. The RPM relative to velocity, will get stronger and impart more stability factor.

MV * 720 / Twist = RPM

JBM - Calculations - Stability

Very interesting. I decided to use the OMT exclusively because I want to load it from a magazine.

 

[DIBBS]

Other threads on the topic....

230 berger twist - Google Search

 

[senna.bra]

Other threads on the topic....

230 berger twist - Google Search

Thank you! I read some if not most of it. I was able to find most of the information on 1-10 twist, and some people inquiring about the 1-11. I am curious about the other direction, 1-8 or 1-9 twist.

 

[Darkker]

. I am curious about the other direction, 1-8 or 1-9 twist.

Do the math from my formula.
Assuming a smoking fast launch of 2800fps, an 8-twist will give you 252,000RPM.
That SHOULDN'T cause destruction, as most light jacket bullets (TNT, SXSP) have a limit of 230-250,000RPM. You may want to confirm that with Berger.

Couple of potential issues with a faster twist could be:
Match bullets aren't typically designed with surviving impacts and such. So when that much mass engraves the rifling, there can be core/jacket slippage. As the jackets may not be welded as stout as a hunting bullet. The difference in mass between the core/jacket can cause a slip. That isn't going to any thing good for accuracy.

The next issue can be with precession and nutation. Because a bullet will always gain more stability from spin as it travels, if you start with an exceptionally high spin, it can aggravate the potential for issues with the overturning moment. This is especially true if the bullet has a bad relationship between it's Center of Gravity Vs. Center of pressure. That specific issue, coupled with a stupid tail angle, is precisely why the original 168gr. SMK would overturn and tumble when crossing the Trans-sonic threshold.

Will any of this happen? Don't know, merely consider it.

 

[senna.bra]

Do the math from my formula.
Assuming a smoking fast launch of 2800fps, an 8-twist will give you 252,000RPM.
That SHOULDN'T cause destruction, as most light jacket bullets (TNT, SXSP) have a limit of 230-250,000RPM. You may want to confirm that with Berger.

Couple of potential issues with a faster twist could be:
Match bullets aren't typically designed with surviving impacts and such. So when that much mass engraves the rifling, there can be core/jacket slippage. As the jackets may not be welded as stout as a hunting bullet. The difference in mass between the core/jacket can cause a slip. That isn't going to any thing good for accuracy.

The next issue can be with precession and nutation. Because a bullet will always gain more stability from spin as it travels, if you start with an exceptionally high spin, it can aggravate the potential for issues with the overturning moment. This is especially true if the bullet has a bad relationship between it's Center of Gravity Vs. Center of pressure. That specific issue, coupled with a stupid tail angle, is precisely why the original 168gr. SMK would overturn and tumble when crossing the Trans-sonic threshold.

Will any of this happen? Don't know, merely consider it.

Roger. I will ask Berger. Again, this is just curiosity... I appreciate you taking the time to write this up. I learned something new today. Thank you!

 

[briang7511]

Hi all,

I am currently using 1-10 twist, but I might be buying a new barrel in the next couple of months. I am shooting the 230gr exclusively in 300 Winchester magnum. Has anyone tried a faster twist rate, like 1-9 or 1-8 for the 230s? Of course there is nothing wrong with 1-10, I am just curios.

Thanks,

SC

I have a broughton 1in 9tw on my 300wm. I use 230 bergers both the .743bc and .719 bc with great success. I also use 208 amax an bthp. My barrel is about 30 in, mv with the 230s is 2800fps. I wouldn't change a thing as the rifle is super accurate at 1k. Havent stretched it out further than that yet.