Berger's 105 gr Hybrid match bullets are now labeled with an optimal twist rate of 7. The older boxes stated 8 or faster. I have 2 barrels for my dasher and one is an 8 twist and the other is a gain twist 8.25 to 7.75. Most of the dasher shooters that I know are shooting 8 twist with a few shooting a 7.5 twist. Are we missing out on some extra performance by not shooting faster twists with this hybrid bullet? Thanks, James Mock
Berger's new "Optimal Twist" ??
- Thread starter JDMock
- Start date
I have felt my 7.5 shot better at 1000. If 7 is optimal 6.75 should work . More barrels to try Larry
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But till I try a 7 then I will know . I do know the 7-5 is better then the 8 at 1000. Paper hole show that . Larry
My experience:
I tried the hybrids in my 6XC with a 1/8 barrel. Once I zero'd the scope I went to 300 yds. Groups were ok, not great but not bad. Played with seating depth, powder charges and primers. Groups were ok, not great but not bad. This was with my F-Open rifle.
So, I'll heed Savagedashers advise. Till this barrel goes south I'll be shooting 107SMK's or 105VLD's. My barrel likes these.
Judd
Gold $$ Contributor
I'm on my 3rd barrel that shoots 105 hybrids pretty darn good. I'm running 8.5 twist barrels. I'm not real sure what prompted the change for faster twist but I basically have just ignored them. These barrels shoot and I've got 2 more that haven't been chambered yet. I'm sure at some point I'll try the faster twist but I don't know when.
Yesterday I won our local 600 yard Bench Rest match with 105 hybrids launched at around 2815 fps out of a 28" Shilen Select Match 6mm BR Norma barrel with 1:8 twist.
It was far from a world record, but not bad for an old half-blind guy and good enough so that I'm gonna' shoot them again next month.
Wait a minute. After typing the above, I went to the Berger site and input the data to discover a calculated SG of 2.42 which is way over the SG minimum of 1.5. It also says I'm enjoying max BC and optimum twist rate.
Are you sure the new boxes say 1:7 twist?
It was far from a world record, but not bad for an old half-blind guy and good enough so that I'm gonna' shoot them again next month.
Wait a minute. After typing the above, I went to the Berger site and input the data to discover a calculated SG of 2.42 which is way over the SG minimum of 1.5. It also says I'm enjoying max BC and optimum twist rate.
Are you sure the new boxes say 1:7 twist?
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Berger put out a press release about the new published twist rate recommendation on their boxes... one thing it clarified is that they are rounding down to the nearest whole number.
Their twist rate calculator is still the more definitive source as to whether you are stable with your chosen twist rate/bullet in your shooting conditions.
Their twist rate calculator is still the more definitive source as to whether you are stable with your chosen twist rate/bullet in your shooting conditions.
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I think you forgot to select the "Calculate Stability" button after you selected your variables. The SG 2.42 is the default number when the Berger Calculator is first brought up on your computer. I think you will find your real SG is around 1.34 which is Marginal Stability. It says your Minimum Twist Recommendation is 1:7.5
Had to open my last shipment . Yes it says 7 is optimal . I don't know if the bullet is changed but the write is ? Larry
Duh..........guilty as charged. Thank goodness there are smart folks on this forum to put idiots like me back on the correct path. Thanks for setting me straight.
The old G7 278
G 1 547
New G7 275
G-1. 536 Larry
G 1 547
New G7 275
G-1. 536 Larry
Berger has changed all of its recommendations recently because recent research has shown that while a bullet with the long-time recommended minimum stability coefficient (Sg) value of 1.40 stabilises bullets fine and they may group brilliantly, they give up something in terms of their ability to cleave through the air with minimum drag. To achieve the full listed BC value, the bullet needs to be spun up to an Sg value of 1.50 now.
If you take the 105gn 6mm Berger VLD and Hybrid, Bryan Litz gives their OALs as 1.235" and 1.292" respectively. Run those through the Miller Twist Rule spreadsheet at 2,900 fps in an 8-inch twist pitch rate and you get exactly 1.50 for the VLD, and 1.32 for the longer Hybrid model. That's under 'standard conditions' (59-deg F; 29.92 inches mercury atmospheric pressure). Shoot the Hybrid on a day with 90F temperature and say around 2,000 ft ASL altitude when 29.92 pressure actually applies at sea level, the Hybrid's Sg value improves to 1.49. Shoot at sea level in a mid winter cold snap in temperatures below freezing in a high-pressure weather pattern (say 20-deg F; 30.5 inches mercury), and its basic stability / grouping ability risks being compromised, never mind its BC at an Sg value of 1.19.
Berger's formula says you lose the following % of the effective BC value with each of the above examples:
Winter ............................... 9-10%
Standard conditions ............ 5%
Hot summer, high altitude ... Nil
If you take the 105gn 6mm Berger VLD and Hybrid, Bryan Litz gives their OALs as 1.235" and 1.292" respectively. Run those through the Miller Twist Rule spreadsheet at 2,900 fps in an 8-inch twist pitch rate and you get exactly 1.50 for the VLD, and 1.32 for the longer Hybrid model. That's under 'standard conditions' (59-deg F; 29.92 inches mercury atmospheric pressure). Shoot the Hybrid on a day with 90F temperature and say around 2,000 ft ASL altitude when 29.92 pressure actually applies at sea level, the Hybrid's Sg value improves to 1.49. Shoot at sea level in a mid winter cold snap in temperatures below freezing in a high-pressure weather pattern (say 20-deg F; 30.5 inches mercury), and its basic stability / grouping ability risks being compromised, never mind its BC at an Sg value of 1.19.
Berger's formula says you lose the following % of the effective BC value with each of the above examples:
Winter ............................... 9-10%
Standard conditions ............ 5%
Hot summer, high altitude ... Nil
Corey Schwanz
Site $$ Sponsor
The bullets have not changed, just the information surrounding them. Some of the recommended twist rates were sped up in order to achieve an SG of 1.5 or greater. This does not mean you can't shoot them through a slightly slower twist like you have in the past. It just means you are potentially hurting the BC of the bullet a little bit. As for guys who have had good results shooting certain bullets through a now slower than recommended twist, "If it ain't broke, don't fix it" 
If in doubt, run your particular setup with your own variables and see where it may fall: http://www.bergerbullets.com/twist-rate-calculator/
Here is a little more detail on the updated twist rates: http://www.bergerbullets.com/berger-bullets-twist-rate-recommendations-by-eric-stecker-bryan-litz/
If in doubt, run your particular setup with your own variables and see where it may fall: http://www.bergerbullets.com/twist-rate-calculator/
Here is a little more detail on the updated twist rates: http://www.bergerbullets.com/berger-bullets-twist-rate-recommendations-by-eric-stecker-bryan-litz/
I don't understand. If the bullet will not shoot the group size you want under the conditions your shooting in who cares why? You'll get to the point of burning out your barrel playing around with all the variables. Pick another bullet more suited to your barrel twist and move on. Less headaches, less mental strain, less ware and tare on the barrel. Sometimes you just gotta say "The gun don't like 'em".
I think gsyaylorg hit the nail on the head. Many of us travel many miles to matches. Conditions change from our home range, altitude, humidity, air density, all that stuff. If we pick a bullet that gives us the highest BC and SG the barrels twist can achieve at the start of our load development it will remove one headache from the list. Now the wind, well that's a whole nother story.
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