Warner Flatline 30 cal 180 grain FTR: BC test results

Discussion in 'ELR, Ballistics & Bullets Board' started by bsl135, Nov 11, 2015.

  1. bsl135

    bsl135 Site $$ Sponsor

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    We got the Warner Flatline 30 cal 180 grain FTR bullets tested for BC. We shot them from two barrels: 1:8” 308 Win 24" barrel, ave MV ~2300 fps, and a 1:9” 300 Win Mag 26" barrel at 2950 fps. These were both 'nominal' loads, not pushing pressure limits. Normalized results of both barrels for the average speed band 3000-1500 fps.

    Results for G7 BC’s are: 0.341 and 0.342; nearly identical for the two barrels. Both cases produced SG’s over 1.5, so I’ve got confidence in the results being accurate.

    Warner Tool Co advertises G1 and G7 BC’s for two different velocity bands: 3000-100 fps and 3500-1500 fps. I'll focus on the 3500-1500 fps band, as taking it to 100 fps can highly skew an average. WTC advertised performance for the 3500-1500 fps band is 0.348. If I calculate the G7 BC for the same band as WTC (3500-1500 fps) based on my testing, it's 0.347.

    In essence, when BC is averaged for common velocity bands, my measurements are nearly identical to the WTC advertised performance of this bullet.

    Some analysis for FTR.

    For the following analysis, we'll consider the G7 BC and form factor (http://www.bergerbullets.com/form-factors-a-useful-analysis-tool/ ) averaged over 3000-1500 fps because that's what all comparable bullets have their BC's figured for, and it's a more likely velocity range for the FTR application.

    Here are a few other bullets with their G7 BC's and form factors for comparison (3000-1500 fps averages).
    Code:
    Bullet							G7 BC	G7 form factor
    WTC Flatline 180 gr FTR					0.342	0.793
    Berger 200 gr Target Hybrid (unpointed)			0.316	0.954
    Berger 200 gr Target Hybrid (pointed*)			0.329	0.917
    Berger 215 gr Target Hybrid (unpointed)			0.354	0.915
    Berger 215 gr Target Hybrid (pointed)			0.368	0.880
    
    * Assuming nominal +4% BC increase for pointing.

    As you can see, the Flatline FTR bullet has about an 8% higher BC than the Berger 200 grain Hybrid, out of the box. Point the Berger 200 grain Hybrid and you close the gap to within 4% of the Flatline bullet. Now consider the 215 grain Hybrid. It's got a higher BC out of the box, and quite higher pointed, but it's also heavier which will affect the MV and ultimately, the wind performance.

    Next step of this analysis is to figure the '10-mph crosswind deflection' for each bullet, and see how it plays out on an FTR target at 1000 yards.

    Consider the muzzle velocities that are achievable with the different bullets; that will play a part in addition to the BC's.

    Solid bullets have some flexibility in their bearing surface/drive band design which often allows for higher velocities at the same pressures compared to conventional bullets which need to engrave the full length of the bearing surface. It's unknown exactly how much extra velocity is possible with the Flatline bullets. For this analysis, we'll assume +50 fps for the solid bullets compared to the conventionals. We'll base everything from a 2650 fps MV for the 200 grain conventional bullet. So we have:

    Code:
    Bullet						G7 BC	MV	wind deflection in 10-mph crosswind at 1000 yards (inches)
    WTC Flatline 180 gr FTR				0.342	2843	59.4
    Berger 200 gr Target Hybrid (unpointed)		0.316	2650	74.2
    Berger 200 gr Target Hybrid (pointed*)		0.329	2650	70.2
    Berger 215 gr Target Hybrid (unpointed)		0.354	2556	67.5
    Berger 215 gr Target Hybrid (pointed)		0.368	2556	64.2
    
    Now that we've got the BC's, likely MV's, and calculated wind performance of each bullet, we'll consider the effects on a shooters score in an FTR match, based solely on wind performance.

    In the book: Applied Ballistics for Long Range Shooting, I present a series of tables that estimates a likely score for: various classes of shooters (beginner, average, elite), levels of wind performance in terms of inches of wind drift at 1000 yards in a 10-mph crosswind, and what score would result from various levels of wind uncertainty (+/-1mph, +/-2mph, etc). These tables are generated by modeling the various shooter skill levels and simulating the various ballistic performance. The tables track surprisingly well with reality. We'll use them to look up the average scores for elite shooters (averaging 1/2 MOA groups) in easy vs. difficult conditions.
    Code:
    Bullet						G7 BC	MV	wind	 easy	hard
    WTC Flatline 180 gr FTR				0.342	2843	59.5	198-12	189-10
    Berger 200 gr Target Hybrid (unpointed)		0.316	2650	74.2	196-5	185-5
    Berger 200 gr Target Hybrid (pointed*)		0.329	2650	70.2	196-11	188-8
    Berger 215 gr Target Hybrid (unpointed)		0.354	2556	67.5	197-12	187-4
    Berger 215 gr Target Hybrid (pointed)		0.368	2556	64.2	197-12	189-0
    
    Reality check; during the recent 2015 FCNC, I was shooting pointed 215 grain Hybrid bullets. From the best to worst conditions, my scores ranged from 198 to 191. This tracks with the predictive model within a point. Not saying it's 100% accurate (being based on statistics, it's just a 'most likely' scenario), but it passes the sanity check.

    As you can see, the result of the BC, MV, and wind performance on score is such that the WTC Flatline bullet is definitely a contender among the other options currently being used to win FTR matches.

    This analysis focused only on the performance aspect. Precision/grouping/recoil/shoot-ability is another issue which hasn't been fully explored yet. As more of these bullets fly downrange, I'm sure a clear picture will form as to their suitability for FTR competition in general.

    -Bryan
     
  2. gstaylorg

    gstaylorg Silver $$ Contributor

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    Very informative analysis, Bryan, thanks for posting. In consideration of the merit of enhanced ballistic performance, a reduction in recoil would almost certainly be evident as well. It seems as though the major potential challenges to using these bullets would be their comparative ease/difficulty of reloading and load development, as well as the faster twist rates necessary to achieve stability. Do you have any thoughts on how 9-/8-twist barrel life might come into play, or whether an effect of aerodynamic jump at the faster twist rate might be considerations?
     
  3. wboggs

    wboggs

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    Bryan. Thanks for the analysis. I have some I'm going to try in a different application. Plan to load in a .300RUM with a 29 1/2" barrel with a .20" throat using Retumbo/?R33. Expect velocity of close to 3500fps based on my results with the Berger 185 Hybrid. Hope to test at extended ranges.
    Bill
     
  4. Jeffvn

    Jeffvn

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    interesting analysis; thank you for taking the time to do the analysis and publish your results.

    Am I correct in thinking that your wind deflection analysis of the solids was based upon a velocity of 2,700 fps (2650 from the jacketed projectile + 50 fps).

    Assuming that is correct, then the actual wind deflection gain from using the solids is even greater if you run them at velocities that can be expected, more like 2,950 or 3,000 fps from a 30" tube.

    JeffVN
     
  5. bsl135

    bsl135 Site $$ Sponsor

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    g,

    The faster twist rate required to stabilize the longer solids can exacerbate any imbalance or misalignment more so than a slower twist. However if the bullets are well made and carefully seated, the precision may be unaffected.

    Aerodynamic jump is proportional to the stability factor (SG) of the bullet, not twist rate. So if a longer bullet needs a 1:9" twist to achieve a stability factor of 1.5, and a shorter bullet needs a 1:12" twist to achieve the same 1.5 SG, the aerodynamic jump will be the same because the SG is 1.5 in both cases.


    Jeff,

    Here's how I arrived at the velocity for the 180 solids:

    1. Baseline MV of 2650 for the conventional 200 grain bullet.
    2. Scale MV for 180 grain bullet at the same pressure: sqrt(200/180)*2650 = 2793
    3. Add 50 fps for solid possibly being faster with the same pressure: 2793+50=2843 fps.

    To suggest a velocity of 2950-3000 fps for the 180 would imply its more than 100-150 fps faster than conventional bullets with the same pressure. I don't have hard data on this yet, but that seems a bit optimistic.

    Fair comparisons of different weight/BC bullets and their MV's should always assume equal chamber pressure (equal muzzle energy is the same thing). It's reasonable that the solid would gain some advantage thru it's bearing surface design, but how much is yet to be seen. If/when someone does the chamber pressure/MV analysis, then we can re-do the performance analysis above with corrected MV's. Till then it's anyone's guess.

    -Bryan
     
  6. Jeffvn

    Jeffvn

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    Bryan

    Thank you for the fast response regarding the tested muzzle velocity. I look forward to hearing more as you continue with your tests.

    JeffVN
     
  7. gstaylorg

    gstaylorg Silver $$ Contributor

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    Bryan, about aerodynamic jump, got it, thanks very much for responding. Several years ago, I had a .308 built with a 9-twist barrel specifically for the purpose of shooting a different manufacturer's monolithic solid. The performance with regard to wind resistance was very good, but I just didn't get the precision necessary for F-TR and ultimately had a different barrel chambered for the rifle. I still have the 9-twist barrel and it has a low round count, so the idea of trying these out is intriguing. Their design is quite different from the ones I tried previously and they may be much easier to load, better precision, etc. However, I doubt any bullet made could ever completely lure me away from the 90 VLDs; what a fantastic bullet! Anyhow, thanks very much for the informative post.
     
  8. Scott Harris

    Scott Harris Gold $$ Contributor

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    Checked pricing on these: $1.44/bullet for the 200s. If these take off in f class, I'll be looking for another hobby. :(
     
  9. 6BRinNZ

    6BRinNZ

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    Is the SG of 1.5 for a 10tw? Reading Warners site they list 10tw as recommended.
     
  10. gstaylorg

    gstaylorg Silver $$ Contributor

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    Scott,
    This is why God gave you two lungs, two kidneys, and two eyes. You really only need one of each to shoot; therefore the "extras" have some potential resale value ;).
     
  11. Jay Christopherson

    Jay Christopherson sun's out, guns out Administrator

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    Are these bullets going to be legal for competition? Someone mentioned that they are illegal (being solid copper/monolithic) under the ICFRA rules. It would suck to have a kick *** load that you couldn't take to international competition, if that is the case.
     
  12. JRS

    JRS Silver $$ Contributor

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    Unless something has recently changed, ICFRA rules on ammunition clearly state bullets of monolithic construction are prohibited.
     

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