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Rolandr
Guest
What twist and powder is recommended for a 6br using a 62 gr. Barnes green bullet?.
Thanks
Thanks
David Sengelaub
New member
I agree with Randy I'm guessing 1-12
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Larry Elliott
Guest
Contacting Barnes might be the best option, but those bullets are likely as long as a lead core 75 gr bullet which would make a 1 in 12 twist a safe bet. If they're good bullets a twist that's a little fast won't hurt, but one that's too slow will not work.
As for powders I'd check the manuals for powders used for conventional 65 to 70 gr bullets.
As for powders I'd check the manuals for powders used for conventional 65 to 70 gr bullets.
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Stonewall
Guest
Email Berger .
Technical Support
Walt Berger
Founder & Chief
Technical and Load Data
Consultant
bergerltd@aol.com
Bryan Litz
Ballistician
bryan.litz@bergerbullets.com
Technical Support
714-447-5458
Book:
Applied Ballistics for Long Range Shooting by Bryan Litz
Hardcover, 536 pages. Includes measured BC data for over 175 long range bullets. Also includes a ballistics program on CD for desktop computers
http://www.appliedballisticsllc.com/
Glenn
Technical Support
Walt Berger
Founder & Chief
Technical and Load Data
Consultant
bergerltd@aol.com
Bryan Litz
Ballistician
bryan.litz@bergerbullets.com
Technical Support
714-447-5458
Book:
Applied Ballistics for Long Range Shooting by Bryan Litz
Hardcover, 536 pages. Includes measured BC data for over 175 long range bullets. Also includes a ballistics program on CD for desktop computers
http://www.appliedballisticsllc.com/
Glenn
V
Varmint-Shooter
Guest
Barnes recommended twist rate of 1:10 or faster for 62 gr Varmint Grenade
http://www.barnesbullets.com/products/rifle/varmint-grenade
http://www.barnesbullets.com/products/rifle/varmint-grenade
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nhkuehl
Guest
Twist
You can also figure out the twist you need with an on-line calculator at: http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi
Barnes recommends a 1:12 for the .224 36 gr Varmint Grenade (and says a 1:14 will work), but I found they shot best in a 1:9 twist after trying them in a 1:12 twist barrel. They were reviewed favorably in The Varmint Hunter and had been shot in 1:8 and 1:9 twist barrels.
I shot some of the 6mm 62 gr VG in my 1:10 twist 6mm BR and wasn't impressed. I'll try them again when I have a 1:8 twist barrel. nhk
You can also figure out the twist you need with an on-line calculator at: http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi
Barnes recommends a 1:12 for the .224 36 gr Varmint Grenade (and says a 1:14 will work), but I found they shot best in a 1:9 twist after trying them in a 1:12 twist barrel. They were reviewed favorably in The Varmint Hunter and had been shot in 1:8 and 1:9 twist barrels.
I shot some of the 6mm 62 gr VG in my 1:10 twist 6mm BR and wasn't impressed. I'll try them again when I have a 1:8 twist barrel. nhk
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Pitchfire
Guest
I am curious how accurate twistcalc @ JBM & Field Firing Solutions is? Anyone have any experience on the edge of stability that has or can model their results there? Nhkuehl you mentioned the 62 gr VG @ 1:10, what was/is the stability factor (below 1)?
Sorry if this is a sidetrack...
Sorry if this is a sidetrack...
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nhkuehl
Guest
Stability factor
Using the Don Miller twist rule unadjusted the Sg for the .243 62 gr VG (0.975" length) was 1.12, using a velocity of 3200 fps it was 1.17, or still under 1.2 Sg. I looked back and my load was 28 grs of X-Terminator and I didn't chronograph it. I shot three different loads of X-Terminator at 100m and 28 grs was the lowest and gave the best group at 5/8". I try to select bullets of at least 1.4 Sg, but found I have my best results at around 1.7 Sg. That would take a 1:8 twist for the 62 gr VG.
I also shot the .224 36 gr VG at 3600 fps in 1:12 (1.09 Sg) and 1:9 (1.94 Sg) barrels and the best groups at 100 m were 1.38" and 0.56" respectively. Over a range of 5 loads (2 nodes) each. I also shot a known accurate control load in each rifle to check myself and conditions that day.
I recently worked up loads for a friend's 1:12 6X47SM. He gave me 13 different moly coated bullets, several powders and a couple different primers. Before I loaded anything I ranked the bullets by Sg and started with the highest one (1.61 Sg) which was a 75 gr Sierra flat base HP and I shot 5 loads and the first four were 0.25" and the fifth was 0.375", so I selected the one with the lowest ES and SD. Last week he shot a 0.25" group at 200 m with that load. Of the 13 bullets he gave me, 8 were at or above 1.4 Sg. - nhk
Using the Don Miller twist rule unadjusted the Sg for the .243 62 gr VG (0.975" length) was 1.12, using a velocity of 3200 fps it was 1.17, or still under 1.2 Sg. I looked back and my load was 28 grs of X-Terminator and I didn't chronograph it. I shot three different loads of X-Terminator at 100m and 28 grs was the lowest and gave the best group at 5/8". I try to select bullets of at least 1.4 Sg, but found I have my best results at around 1.7 Sg. That would take a 1:8 twist for the 62 gr VG.
I also shot the .224 36 gr VG at 3600 fps in 1:12 (1.09 Sg) and 1:9 (1.94 Sg) barrels and the best groups at 100 m were 1.38" and 0.56" respectively. Over a range of 5 loads (2 nodes) each. I also shot a known accurate control load in each rifle to check myself and conditions that day.
I recently worked up loads for a friend's 1:12 6X47SM. He gave me 13 different moly coated bullets, several powders and a couple different primers. Before I loaded anything I ranked the bullets by Sg and started with the highest one (1.61 Sg) which was a 75 gr Sierra flat base HP and I shot 5 loads and the first four were 0.25" and the fifth was 0.375", so I selected the one with the lowest ES and SD. Last week he shot a 0.25" group at 200 m with that load. Of the 13 bullets he gave me, 8 were at or above 1.4 Sg. - nhk
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nhkuehl
Guest
3 more bullets/twist I use:
.224 55 gr. Nosler BT in 1:9, Sg 1.77 (3100 fps) 1/2 MOA load/rifle
.243 107 gr. Sierra MK in 1:8, Sg 1.62 (2955 fps) 1/4 MOA load/rifle
.308 168 gr. Hornady A-Max in 1:10, Sg 2.06 (2800 fps) 1/2 MOA load/rifle - I thought I had a 1:12 twist which would have been Sg 1.43. - nhk
.224 55 gr. Nosler BT in 1:9, Sg 1.77 (3100 fps) 1/2 MOA load/rifle
.243 107 gr. Sierra MK in 1:8, Sg 1.62 (2955 fps) 1/4 MOA load/rifle
.308 168 gr. Hornady A-Max in 1:10, Sg 2.06 (2800 fps) 1/2 MOA load/rifle - I thought I had a 1:12 twist which would have been Sg 1.43. - nhk
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Pitchfire
Guest
Thanks for that, I have had some confusion as to where stability is actually achieved. German Salazar's weblog writeup: stated both that Tom Tamas soundly dominated with an Sg of 1.14, and that at 1.33 in his experimentation, he couldn't notice any yaw at 300 meters with a scoring plug...etc..., yet asserted that 1.4 was the safe minimum as per Litz. Whether Litz asserted that as a safe margin of error or the edge of good stability is of course at the heart of the matter.
I notice that with my 1:10 twist .243, the 80 gr. 1.083" long Barnes TTSX isn't theoretically very stable under fall field conditions (today is 54deg here with 29.89"Hg for an Sg of 1.09), yet a 105 gr. Speer cup and core bullet is much closer to that theoretical minimum (1.09" long spitzer same conditions Sg of 1.35).
And in fact the Speer is a longer bullet (not by much). Which leads me to the conclusion that either (in this case) the calculator does not model the situation accurately enough or that real density (not sectional density) is the real factor and not length per se, as is so oft repeated.
Other people tell me that 1.15 Sg is a good bet for the border regions of stability and yaw. That seems more in line with Tamas' results and it looks like yours as well?
With a very common 1-10" twist rate .243 barrel no one could utilize bullets with poly tips or any of the lead core bullets above the vicinity of 80 grains if we stuck to the 1.4 Sg requirement under fall early morning field conditions.
I think I'm going to pick a bullet on the edge of theoretical stability and try pushing it back and forth with temp., velocity, and maybe barometric pressure as well and see if I can find the actual barrier for that bullet under those conditions. Maybe AlinWa has already done so in his research?
I notice that with my 1:10 twist .243, the 80 gr. 1.083" long Barnes TTSX isn't theoretically very stable under fall field conditions (today is 54deg here with 29.89"Hg for an Sg of 1.09), yet a 105 gr. Speer cup and core bullet is much closer to that theoretical minimum (1.09" long spitzer same conditions Sg of 1.35).
And in fact the Speer is a longer bullet (not by much). Which leads me to the conclusion that either (in this case) the calculator does not model the situation accurately enough or that real density (not sectional density) is the real factor and not length per se, as is so oft repeated.
Other people tell me that 1.15 Sg is a good bet for the border regions of stability and yaw. That seems more in line with Tamas' results and it looks like yours as well?
With a very common 1-10" twist rate .243 barrel no one could utilize bullets with poly tips or any of the lead core bullets above the vicinity of 80 grains if we stuck to the 1.4 Sg requirement under fall early morning field conditions.
I think I'm going to pick a bullet on the edge of theoretical stability and try pushing it back and forth with temp., velocity, and maybe barometric pressure as well and see if I can find the actual barrier for that bullet under those conditions. Maybe AlinWa has already done so in his research?
Last edited by a moderator:
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nhkuehl
Guest
RE: Stability
I think German concluded that at 100 yds you could get away with a lower Sg than you could at longer ranges. I go a little higher Sg and don't don't worry about temperature, etc. The longer lighter bullets require more stabilization than you calculate with the Greenhill or Velocity formulas. Those formulas are based on the density of lead. Some people still resist the idea that length matters and insist it's all about the weight. I wasted a lot of powder and bullets trying to make things shoot that should have according to the Greenhill formula. Now I won't bother unless it checks out with the Don Miller twist rule. There is probably a margin of error that isn't accounted for with polymer tips and HP cavities(?).
The .243 87 gr V-Max (Sg 1.32 in 1:10) shoots very well at 2800 fps in my 6mm BR with W748, but I only shot that above 70 deg because of the powder. Same thing with the .224 40 gr Nosler BT (Sg 1.14 in 1:12) shoots very well at 3500 fps with W748, at least at 100-200m in warm weather. I wonder what affect the balance point of the bullet has. Is a bullet more stabile if the balance point is at the center of the length, back or forward?
Life was simpler when I only had a .22 LR - nhk
I think German concluded that at 100 yds you could get away with a lower Sg than you could at longer ranges. I go a little higher Sg and don't don't worry about temperature, etc. The longer lighter bullets require more stabilization than you calculate with the Greenhill or Velocity formulas. Those formulas are based on the density of lead. Some people still resist the idea that length matters and insist it's all about the weight. I wasted a lot of powder and bullets trying to make things shoot that should have according to the Greenhill formula. Now I won't bother unless it checks out with the Don Miller twist rule. There is probably a margin of error that isn't accounted for with polymer tips and HP cavities(?).
The .243 87 gr V-Max (Sg 1.32 in 1:10) shoots very well at 2800 fps in my 6mm BR with W748, but I only shot that above 70 deg because of the powder. Same thing with the .224 40 gr Nosler BT (Sg 1.14 in 1:12) shoots very well at 3500 fps with W748, at least at 100-200m in warm weather. I wonder what affect the balance point of the bullet has. Is a bullet more stabile if the balance point is at the center of the length, back or forward?
Life was simpler when I only had a .22 LR
- nhk
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Pitchfire
Guest
I personally suspect that it is both weight in terms of density and length in terms of the leverage effect of the COG at odds with the tip, hence length. Otherwise polymer tips should be excluded from the stability calculation. I have run the various calculations found at JBM and Field Firing Solutions. They use the Don Miller calculation.
Nosler assures me that the 90 grain .243 Etip (1.18") will stailize in a 1:10 twist barrel. The JBM calculator gives me an Sg of 0.947 at 55 degrees and 29.85" HG. Should I believe Nosler or the calculator? At 0.947 that bullet would likely tumble. If I disregard the plastic tip, the length changes by a good .125" and changes the Sg to 1.277. That should be stable in close as per Nosler. So is the plastic tip moot? Or does it's length matter?
Nosler assures me that the 90 grain .243 Etip (1.18") will stailize in a 1:10 twist barrel. The JBM calculator gives me an Sg of 0.947 at 55 degrees and 29.85" HG. Should I believe Nosler or the calculator? At 0.947 that bullet would likely tumble. If I disregard the plastic tip, the length changes by a good .125" and changes the Sg to 1.277. That should be stable in close as per Nosler. So is the plastic tip moot? Or does it's length matter?
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nhkuehl
Guest
More stable the further it goes....
The rpm doesn't drop as fast at the velocity, but I think what German Salazar found contradicts that(?). If it isn't already stable, it isn't going to get stable is what I'd interpret that to mean. Some of the published Berger twists seem too slow to me, but then they probably have the results to justify it. I'd rather error on the side of caution. - nhk
The rpm doesn't drop as fast at the velocity, but I think what German Salazar found contradicts that(?). If it isn't already stable, it isn't going to get stable is what I'd interpret that to mean. Some of the published Berger twists seem too slow to me, but then they probably have the results to justify it. I'd rather error on the side of caution. - nhk