Copper Bullet Stability

[fishingstockwell]

Hello,

I have very little experience with all copper billets, so a little help would be very appreciated. Is there any reason that copper bullets, specifically Hammer Hunter Bullets, would be any less stable that lead core bullets with an equal BC? I am currently shooting Berger 230 Hybrids from a 30 Nosler with a 1-9.4" twist rate and have absolutely no problem with stability. The Bureger bullet has a G7 BC of .368. My father drew a once in a lifetime type of elk tag, and the regulations require an all copper bullet. I've read a lot of good things about the Hammer Hunter bullets and would like to shoot the heaviest Hammer Hunter bullet that will work in my gun. Their Hammer Hunter 199 says that a twist rate of 1-9.25 is necessary, and they also list the G7 BC as .299, which is lower than the Berger 230 Hybrid that have been shooting. Using the Twist Rate Stability Calculator on the Berger web site, the Hammer Hunter would be fully stable in my gun, with an SG of 1.54. Is there something ai am missing? Is there any reason that all copper bullets need a faster twist rate than lead core Bullets of an equal BC? I appreciate the input. Hopefully I can post pics of I giant Rosevelt, along with a great story, by mid September.

Thanks,
Matt

 

[Hand Skills]

Stability is a mainly a function of PROJECTILE LENGTH and Twist rate. Air density plays into it too (elevation and temperature)

Because copper has a lower density than lead, a copper bullet of the same weight and same caliber is longer than a lead based bullet, sometimes by a lot.

Stick with the recommended twist rates

Here are a couple of calculators if you want to play around;

Twist Rate Stability Calculator

Our newly updated Twist Rate Stability Calculator not only tells you what your SG is, but it also lets you know if you are reaching your optimized BC.

bergerbullets.com

JBM - Calculations - Stability

www.jbmballistics.com

SG of 1 is stable in flight

SG of 1.5 is recommended for terminal performance

SG of 2 or better is best practice IMO

 

[Southpaw Tikka]

It's not necessary to go heavy with monolithics, rather, it's often better to drop weight in order to increase the much needed impact velocity.

 

[FEENIX]

SG of 2 or better is best practice IMO

I have been doing this on C&C bullets now, too.

 

[FireFlyFishing]

and would like to shoot the heaviest Hammer Hunter bullet that will work in my gun.

Why?

 

[Koda_]

the Hammer Hunter would be fully stable in my gun, with an SG of 1.54. Is there something ai am missing?

Yes, an SG of 2.0 or even better.
Dont let the old school heavier is always better myth drive your bullet selection choice. You cant overspin or over stabilize a bullet.

 

[Shane Lindsey]

215 Berger/ 214gr Hammer Hunter.
You can get away with the hybrid tip on C/C because of mass. The Hammer has to make up for weight with material. I would look at the 150-168 class Hammer and run them at light speed.

FWIW I run a 150 Hammer in a 300 WM at 3400 FPS and the 181 was at 3198 FPS.

 

[Don Rackley]

Ditto on going to lighter bullet. Copper is less dense than lead, so an identical body will be lighter if all copper.

I am a fan of Barnes TTSX and in my 7PRC, I shoot 150gr. Remembr, expansion and weight retention are hallmarks of monolithic bullets.

 

[fishingstockwell]

Thanks for everyone's input. I guess I left out one of the puzzle pieces. I'm not looking for the heaviest bullet for the sake of energy, like we might with rapid expanding lead core bullets. I was looking for the heaviest bullet possible, because it would be the longest. My gun has an Extremely long throat!!! To load the Berger 215's close to the lands I didn't have enough bearing surface left in the neck. Maybe it was technically enough, but less than I like, so I had to switch to the 230s. Even with the 230s, the junction of the bow tail and bearing surface is above the junction of the shoulder and neck on the case. Factory shells have so much jump that I'm loosing pressure and velocity. My 230s shoot at 2980 fps. I tried factory copper bullets and was getting under 2800 with 180s. I need a long bullet and didn't understand why the 199 HH, with a lower BC than the 230 Berger, needs a 9.25 twist when 230 Berger's shoot fine out of a 9.4. I don't know if there is something other than the BC that I'm missing with copper bullets that requires the faster twist rate. The 196 will probably work fine. I just prefer the better BC of the 199 if it will stabilize in my gun.

 

[Shane Lindsey]

BC has nothing to do with twist rate.
Twist rate is determined by the length of the bullet alone. Your twist rate is right in the weird spot for long cup and core and short monos.

The Hammers are very insensitive to jump. In fact, all I have used, seem to prefer a good bit.

 

[fishingstockwell]

I've got a few boxes of the 181's. They seemed short for the long throat in my gun, but I'll give them a try. I'll probably order some 196s and try them both. I have h1000, Retumbo, N570, rl 26. I'll probably start with the H1000, unless I can find some starting numbers for N570, which I have a lot of. I don't mind torching the barrel with N570. I consider it reasonable to replace every few years and round count is still fairly low. I had a good load with 215 Bergers at 3150, so I would imagine I can push the 196s and 181s to some light night fast speeds.

 

[Koda_]

Thanks for everyone's input. I guess I left out one of the puzzle pieces. I'm not looking for the heaviest bullet for the sake of energy, like we might with rapid expanding lead core bullets. I was looking for the heaviest bullet possible, because it would be the longest. My gun has an Extremely long throat!!! To load the Berger 215's close to the lands I didn't have enough bearing surface left in the neck. Maybe it was technically enough, but less than I like, so I had to switch to the 230s. Even with the 230s, the junction of the bow tail and bearing surface is above the junction of the shoulder and neck on the case. Factory shells have so much jump that I'm loosing pressure and velocity. My 230s shoot at 2980 fps. I tried factory copper bullets and was getting under 2800 with 180s. I need a long bullet and didn't understand why the 199 HH, with a lower BC than the 230 Berger, needs a 9.25 twist when 230 Berger's shoot fine out of a 9.4. I don't know if there is something other than the BC that I'm missing with copper bullets that requires the faster twist rate. The 196 will probably work fine. I just prefer the better BC of the 199 if it will stabilize in my gun.

Your worrying too much about jump. Accuracy nodes can be found at any jump to lands. Just pick a bullet you want thats appropriate for your twist rate and load it and done.

 

[Hugnot]

My thinking would be to shoot a lighter & shorter solid copper Hammer bullet. The Berger stability calculator uses altitude to determine pressure.

Some info:



The 197 gr, Hammer bullet would be "marginally stabile" with a 9.4 twist if used when barometric pressure greater than 27.7 or lower than 2000 ft. above sea level and temps less than 45 F. Marginal stability being less than Sg = 1.5.

I think the actual barometric pressure would be a more accurate input value vs. altitude as stuff happens like a high pressure low temp situation (arctic high) or a warming trend with rain & wind (storm). The term "blue norther" comes into mind.

I would go with the JBM Sg calculator that uses the Miller Sg estimator as shown above.

The Berger 230 Hybrid is a real pointy bullet having a sharp meplat (point) & the Hammer 197 (AKA 199 Hammer) has a more open meplat. Back then my grand parents, who did not smoke or own horses, had an ash tray having 8 mm Lebel (solid brass spitzer WWI) bullets soldered on the rim to hold smoking cigs. I was fascinated with the sharp points & grandmere told me that the sharp points made the bullet go thru the air better.

A 180 or so grain Hammer bullet at over 3 K fps should kill elks real good and be stabile in your rifle. Copper is less dense than lead and solid copper bullets are longer than lead core bullets of equal weight.

 

[Russ-T]

I've been using Barnes bullets for years and have never lost an animal at any distance with any cartridge. There is talk about copper bullets not shooting well unless the barrel has been cleaned and then fouled with all copper bullets, as the gilding metal's differing make up (zinc) has some effect on the bullet as it travels down the barrel. I have not found this to be the case, although some people seem to think it's a thing.

The TTSX and LRX are great choices.

Try the 212 gr bore rider.

0.308" 30 CAL LRX 212 GR BT Bore Rider

Pioneering the world's most effective all-copper hunting bullet. For over 30 years, we've been engineering the most advanced hunting bullets, trusted by the world's best hunters and shooters.

barnesbullets.com

It has a special ogive that can handle seating the bullet super long. This way, you can choose a slower powder for higher velocities. You'll essentially have an ICBM in that cartridge.

Keep us posted!