G7 BC 200 SIERRA.
- Thread starter dkhunt14
- Start date
rijndael
Silver $$ Contributor
That's the G1 BC, not G7.
M995
T SNOOK
It's appx. 1/2
Toolbreaker
Gold $$ Contributor
Hi Matt. Litz has the G7 at .285 in JBM's software.
Thanks. I searched for it and couldn't find it. Matt
Thanks. Matt
But what about the new one with so high G1 BC? Does anyone know its G7 BC? It should be more than 0.320
If it’s 285 may as well shoot juggernaut
Ned Ludd
Silver $$ Contributor
Based solely on BC analyses via both drop and LabRadar for a single [different] Sierra bullet, the average G1 BC should be approximately 97% of the high velocity band G1 BC as given by Sierra. However, if you compare high G1 BCs to the average G1 BCs listed for several older Sierra bullets listed in Bryan Litz' text, "Ballistic Performance of Rifle Bullets", a correction factor for converting high band G1 BCs to average G1 BCs of about 93% is probably more appropriate. The average G7 BC will be approximately 51% of the average G1 BC, as noted above. These approximations should work reasonably well for most purposes.
For the new Sierra 200 gr .308 bullet (Cat.# 2231), the high band G1 BC given by Sierra for this bullet is 0.715. Using the 0.97/0.51 conversion factors, this value translates to an average G1 BC of approximately 0.694, and an average G7 BC of about 0.354. Using the 0.93/0.51 conversion factors, the 0.715 high band BC translates to average G1/G7 BCs of approximately 0.665 and 0.339, respectively.
Note that these values are only approximations, not written in stone. However, they are probably quite decent "working" BC values until more actual user test data becomes available. Anyone shooting one of Sierra's new bullets with a LabRadar can collect sufficient data in only a few shots to generate a G7 BC estimate.
For the new Sierra 200 gr .308 bullet (Cat.# 2231), the high band G1 BC given by Sierra for this bullet is 0.715. Using the 0.97/0.51 conversion factors, this value translates to an average G1 BC of approximately 0.694, and an average G7 BC of about 0.354. Using the 0.93/0.51 conversion factors, the 0.715 high band BC translates to average G1/G7 BCs of approximately 0.665 and 0.339, respectively.
Note that these values are only approximations, not written in stone. However, they are probably quite decent "working" BC values until more actual user test data becomes available. Anyone shooting one of Sierra's new bullets with a LabRadar can collect sufficient data in only a few shots to generate a G7 BC estimate.
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A .339 or more or less is an outstanding BC for a 200gr .30 cal!
ranger0787
Gold $$ Contributor
My .308 load on 30" barrel in SoFla is 44.20gr Varget MV es:22, sd of 8.2. -.040" jump, palma brass, cci-450 primers CBTO: 2.236, COAL: 3.098, avg mv is 2636'/sec with G7BC over Labradar & RSI Shooting Software is 0.341
XTR
F-TR obssessed shooting junkie
These have been on the market now since at least 2017, and not a single shooter that I know of is using them in F-TR, there is a reason for that. If you are looking for a 1MOA bullet this will do it for you, if you need a bullet that will give you .5MOA vertical at 1000 yards this isn't it.
About 2015 to 2017 there were several 200gr class bullets released targeting the F-TR market. The only one that provided the precision needed for the game was the Berger 200.20x.
The Sierra looks a whole lot like the KP Ballistics 200 Jack (Canadian bullet) from the same time frame....
Both have a high BC and a short bearing surface
Both are factory pointed
Both need faster than a 1:10 twist to take full advantage of the BC (last time I checked anyway)
Both will shoot flyers to the edge of the 10 ring on 20% of your shots, and that's the best you'll get them tuned.
I shot up a bunch of both in a 1:8 twist barrel trying to get them to work. Even at 100 yards I could never get a 5 shot group w/o a flyer that was more than just a little out of the group.
About 2015 to 2017 there were several 200gr class bullets released targeting the F-TR market. The only one that provided the precision needed for the game was the Berger 200.20x.
The Sierra looks a whole lot like the KP Ballistics 200 Jack (Canadian bullet) from the same time frame....
Both have a high BC and a short bearing surface
Both are factory pointed
Both need faster than a 1:10 twist to take full advantage of the BC (last time I checked anyway)
Both will shoot flyers to the edge of the 10 ring on 20% of your shots, and that's the best you'll get them tuned.
I shot up a bunch of both in a 1:8 twist barrel trying to get them to work. Even at 100 yards I could never get a 5 shot group w/o a flyer that was more than just a little out of the group.
ranger0787
Gold $$ Contributor
Agree completely; I use them now for fire-forming. I spun all 2000 over the Bullet Genie and had a LOT of deviation. So much that I was concerned about accuracy. I "Lent" them out to some newer shooters and they experienced many "fliers"; X, 10, 8??, 10, 9...
One of my previous posts...
"
Just received @ 1200 #2231 from Medic505 (Thank you, btw) and am trying to "will" these bullets to shoot great. First "aha" today was running them over my Bullet Genie to batch-sort them. I was a little alarmed at the large spread from all bullets spun; I have ES values from a low of "12" to a very large amount over "70" with some over "100". Without manually counting the and to guesstimate; I would say I have over 250 bullets that are way out of the bulk/norm.
When first using the Bullet Genie a few years ago, I first batch sorted 10 x #100 count matching lot number boxes of Berger 200.20x bullets. The spread with those bullets ranged from "5" to "35", with only 5 or 6 in excess of "40". I tried "improving" the BC on them by running them through the Whidden pointing die to close the meplats. Afterwards, I re-spun the same bullets and found I "knocked them" out of whack and the ES shot up into the 60-80 range. So I stopped doing that. The #2231's come factory pointed...That may be the reason for the large ES values. As long as I shoot within each batch, HOPEFULLY they will prove accurate.
Sierra may have tried increasing the BC of the new bullets at the expense of possibly ruining their consistency. Only range time will tell. I'll post my results whenever I'm finished. The image directly below is after using the Genie for several hours. The Sierra box on the left has all the >70 bullets in.
One of my previous posts...
"
Just received @ 1200 #2231 from Medic505 (Thank you, btw) and am trying to "will" these bullets to shoot great. First "aha" today was running them over my Bullet Genie to batch-sort them. I was a little alarmed at the large spread from all bullets spun; I have ES values from a low of "12" to a very large amount over "70" with some over "100". Without manually counting the and to guesstimate; I would say I have over 250 bullets that are way out of the bulk/norm.
When first using the Bullet Genie a few years ago, I first batch sorted 10 x #100 count matching lot number boxes of Berger 200.20x bullets. The spread with those bullets ranged from "5" to "35", with only 5 or 6 in excess of "40". I tried "improving" the BC on them by running them through the Whidden pointing die to close the meplats. Afterwards, I re-spun the same bullets and found I "knocked them" out of whack and the ES shot up into the 60-80 range. So I stopped doing that. The #2231's come factory pointed...That may be the reason for the large ES values. As long as I shoot within each batch, HOPEFULLY they will prove accurate.
Sierra may have tried increasing the BC of the new bullets at the expense of possibly ruining their consistency. Only range time will tell. I'll post my results whenever I'm finished. The image directly below is after using the Genie for several hours. The Sierra box on the left has all the >70 bullets in.
Attachments
That's been the experience of GB 'Effers' too and also with a good friend who tried the Canadian KP Ballistics Jack in lieu of the Berger 210 LRBT that he'd otherwise used in F/TR almost from Day One.
I've no experience of the 308 SMK, but have tried the 0.284 183gn new-form model in 284 Win, and gave up on that after a reasonable amount of effort. As best I can see looking at Bryan Litz's measurements in his Ballistic Performance of Rifle Bullets 3rd edition, the new super-BC SMK range members are a single design 'scaled' up and down by calibre. They have inordinately long nose sections with 27.84 calibres radius in the 7mm model's case. Meanwhile, I plod on with older shorter nose SMKs very happily with good results in 7mm at least with the 175 and 180gn models even if their BCs are modest.
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