Berger Updates Bullet BC Data and Recommended Twist Rates
Berger has released two important informational updates for its line-up of bullets. First, the Ballistics Coefficients (BCs) have been updated for the vast majority of bullets Berger sells. In addition, G7 model BCs are being provided for most of the bullets. You will want to use the updated BC data, which is based on actual testing of recent production lots of bullets.
Second, Berger is now providing a dual twist-rate recommendation for most bullets. Berger is now lists a “minimum” barrel twist rate as well as an “optimal” twist rate. To get maximum long-range performance from your bullets, use a barrel with the “optimal” rate of twist.
CLICK HERE for the latest Berger Quick Reference Sheets with updated BCs and new Optimal Twist Rates. Eric Stecker, Berger President says: “We have tested every lot of bullets produced in the last several years to bring you these updated numbers for all of our bullets.”
Ballistic Coeffificent (BC) Updates with G7 Data
Berger notes: “We have updated all of our Ballistic Coefficients to be even more accurate.
Prior to 2008, all of Berger Bullets’ BCs were calculated using a computer prediction. Early in 2009, we began measuring BCs with live-fire testing. As a result, Berger’s BCs were updated and G7 BCs were also made available. This represented a dramatic improvement in the accuracy of performance data at that time. Since 2009, the BCs assessed for Berger Bullets have not been updated. As part of our ongoing effort to provide shooters with the best information possible, Berger has been testing every lot of bullets produced for the last several years. The result is updated and highly accurate running averages of BCs for recent production lots.
| Description | New G1 BC | New G7 BC | % Change |
| 22 Cal 80gr VLD Target | 0.455 | 0.233 | +2% |
| 22 Cal 90gr VLD Target | 0.534 | 0.274 | -3% |
| 6mm 95gr VLD Target | 0.467 | 0.240 | -3% |
| 6mm 105gr VLD Target | 0.517 | 0.265 | +5% |
| 6mm 105gr Hybrid Target | 0.536 | 0.275 | -1% |
| 6mm 115gr VLD Target | 0.563 | 0.289 | +3% |
| 6.5mm 130gr VLD Target | 0.562 | 0.288 | +2% |
| 6.5mm 140gr Hybrid Target | 0.607 | 0.311 | -2% |
| 7mm 180gr VLD Target | 0.683 | 0.350 | +4% |
| 7mm 180gr Hybrid Target | 0.680 | 0.349 | +1% |
| 30 Cal 155gr Hybrid Target | 0.478 | 0.245 | -1% |
| 30 Cal 185gr Hybrid Target | 0.576 | 0.295 | +1% |
| 30 Cal 215gr Hybrid Target | 0.691 | 0.354 | -1% |
CLICK HERE for Complete Table with all bullets on Berger Website
G7 Form Factor Addition
Berger also added the G7 form factor to the Ballistics Quick Reference Sheet. The analysis of form factors can be very useful when considering a bullet’s long range performance potential. Going by BC alone can be deceptive since BC includes the weight and caliber of the bullet. Form factor indicates how much drag the bullet has, which is a very important consideration for all bullets of all calibers.
NEW Dual Twist-Rate Recommendations
Recommended twist rates for bullets are commonly listed as a single value, such as 1:12” (one rotation in 12″ of barrel travel). This may be overly simplistic. There is a big gray area of marginal stability in which bullets can fly with good accuracy, but with a reduced (i.e. sub-optimal) Ballistic Coefficient. Recognizing this reality, Berger is now listing two twist rates for each bullet it makes. The first is the minimum twist needed for good accuracy, which Berger has always recommended. The second is the new optimal twist rate, which is the twist that will stabilize the bullet to a level which achieves its full performance (BC) potential. CLICK HERE For more information.
Similar Posts:
- Berger Updates Free Online Bullet Stability Calculator
- Ballistics Tip: Understanding Bullet Stability (Twist Rate and MV)
- Figuring Optimal RPM with Berger Twist-Rate Stability Calculator
- Find Optimal Barrel Twist-Rate with Berger Stability Calculator
- New 7mm 184gr F-Open Hybrid Target Bullet from Berger
Share the post "Berger Updates Bullet BC Data and Recommended Twist Rates"
Tags: Ballistic Coefficient, Barrel Twist, BC, Berger Bullets, Erik Stecker, G1, G7, Twist Rate
The new twist rate, “Optimal Twist Rate * or Faster” (column heading)is, at best, confusing. At worse, its misleading.
1. Why the asterisk (*) without any explanation of what the * means – does it mean anything? [Same problem as prior, not fixed here.]
2. BOTH “optimal” and “or faster” – is “faster” the same, less, or more “optimal” than “optimal”?
Berger/Bryan – please unconfused us.
Not surprised from shooting these bullets the .22 caliber 80 went up and the 90 down some.
Hmm, all their target 6 mm suitable for the 6 mm PPC now aren’t stable in the standard 1:14″? Better tell the benchrest guys that they all need to rebarrel to 1:11.4 to 1:10.8″. What a load of tosh.
ELR,
You’re right about the asterisk. That should not be there. It’s from an earlier version that we decided to change. I’ll have it removed. Twist requirements are such that you need to reach a minimum threshold in order to achieve levels of stability. Anything ‘greater than’ is ok, but less than is not ok.
Neil,
The twist requirements that we provide are conservative so that they will work in all scenarios. Furthermore, the stability formula used is especially conservative for flat base bullets.
The minimum twist requirement is the minimum required to achieve optimal precision. However the minimal twist requirement does not produce maximum BC. In order to fully stabilize the bullet and achieve maximum BC, you need the optimal twist or faster. Short range Benchrest shooters who choose flat base bullets typically are not concerned with maximizing BC, so the minimal twist is more applicable. However,this calculation of the minimum twist is especially conservative for flat base bullets.
The article linked in the bulletin above explains where we are coming from with our stability requirements. Here’s the link to that article again
http://www.bergerbullets.com/the-state-of-the-art-in-rifle-bullet-stability/
The important thing to understand is that you can achieve enough stability for full precision with a bullet, and not be maximizing its BC. You need a faster twist to realize full precision and BC. If you don’t care about BC, then you can get away with a slower twist and less stability. The complication is that you’re always in a different environment and shooting bullets at different speeds. So it’s very difficult to determine what conditions a manufacturer should recommended twist rates for. If we are conservative and base our recommendations on the worst case scenario, then the twist rates we recommend will not be realistic for most average conditions. However if we base our recommendation on average conditions, then there will be some cases which the bullets won’t fly well. The best thing to do if you want to understand the stability requirements of your specific bullet in your environment, is to use the Berger stability calculator and decide where you want to be on the stability spectrum. And to reiterate, the stability calculation is very conservative for flat base bullets.
We understand that shooters appreciate simplicity. However, there are a great deal of rifle shooters who choose Berger bullets, who are interested in maximizing performance and understanding the details of their shooting. We choose to support these shooters with a higher level of information, and supporting educational materials to explain the realities of spin stabilized projectile flight.
-Bryan
Bryan:
Thanks for clearing up the asterisk. Appreciated!
Comment and interesting finding…
Comment: Not trying to be picky, but the definition of “optimal” is “best or most effective” (Merriam-Webster dictionary). “Best” and “Most” indicate “whatever” you are considering will not be improved by varying from that “value”. I suggest a more appropriate column heading would be, ” BC impacted if twist slower than”.
Interesting finding: Berger’s SG calculator has gone well beyond determining whether the projectile will be “stable”. That tool also calculates the impact on BC – to the point of recommending a specific minimum faster twist if the calculated SG is not at least 1.5. [So the user is not simply “stuck” with the static “optimum” value in the published table.] An example, I selected the Berger 338 Cal 300 gr Hybrid OTM Tactical (33109) and varied the muzzle velocity from 2800 (SG = 1.50) to 2650 (SG = 1.47). With the 2650 velocity the calculator ALSO displayed:
Bullet BC (G7): .421
Adjusted BC for 1 in 10.5″ Twist: .417
Your BC is being compromised by: 1%
Minimum twist recommended: 1 in 10.3″
Now that, IMO, is worthwhile info! [And it shows that “optimal” is not always optimal. Also, regrettable, it also shows that the column titled “Minimum Twist Rate (of faster) also needs some help. For this example it reads 1:12″.]
Thank you Bryan and Berger!
From the new table…
Berger 6mm 105gn VLD hunting. G1BC 0.545
Berger 6mm 105gn VLD Target. G1BC 0517
If this is true then I might have to start using the VLD hunting pill for F-Class instead of the Target pill.