270149HV293 Technical Profile ©   Application: Long Range Hunting

Barrel Bore Diameter: 0.270 " 6.860 mm The diameter of the barrel from land to land.
Barrel Groove Diameter: 0.277 " 7.040 mm The diameter of the barrel from groove to groove.
Bullet Weight: 149 gr 9.7 g Bullets are guaranteed to weigh within 0.25% of the stated weight.
Bullet Length: 1.61 " 40.900 mm
Secant Ogive Length: 0.82 " 20.815 mm These dimensions are critical to consistent external ballistic performance and are held constant to within 0.005 mm (0.0002")
Meplat Diameter: 0.06 " 1.650 mm
Min Bullet Protrusion: 0.89 " 22.690 mm Add the case length to these numbers to determine the maximum and minimum cartridge overall length that is possible with this bullet.
Max Bullet Protrusion: 1.22 " 31.000 mm
Bullet does not conform to CIP and SAAMI for magazine length. Check the magazine length of your rifle for suitability with this bullet.
Maximum M/V: 4000 fps 1,219 m/s If the maximum muzzle speed is exceeded, dynamic stabilty problems may be encountered.
Short Range Twist: 6.3" / 161 mm or tighter 23.5 Cal/length or tighter Twist recommended if average hunting distances are 310 yards or 290 m. A tighter twist can be used.
Twist: Sg = 1.5: 7.0" / 177 mm 25.9 Cal. in length General hunting twist for average distances to 640 yards or 590 m.  A tighter twist can be used.
Minimum Twist: 8" / 203.2 mm 29.6 Calibers in length The twist required for stable flight and good terminal performance further than 640 yds or 590 m.
Minimum Impact Speed: 1600 fps 488 m/s At this impact speed, the bullet will open to at least double caliber.
Calculated Ballistic Coefficient - G1 profile
BC = 0.638 4000 fps to 2800 fps 1,219 m/s to 853 m/s BC values are calculated at standard Metro values and serve as a comparison between GSC bullets.  Any comparison with the BC values of other manufacturers is not valid as there is currently no standard method in use between manufacturers.
BC = 0.560 2800 fps to 1600 fps 853 m/s to 488 m/s
BC = 0.549 1600 fps to 0 fps 488 m/s to 0 m/s

Suitable Cartridges, with consideration of the above specifications:

270 LRH

NOTES
A Gyroscopic Stability (Sg) greater than 1.1 is required for stable flight with HV and HP bullets. For hunting at average 640yds/590m , an Sg of up to 1.5 or more can be used. For longer distances the Sg can be decreased but never less than 1.1.
*Note that Sg increases as twist tightens.  *A 1:10" twist is tighter than a 1:12" twist within a given caliber only. *Twist rates given in caliber lengths can be compared across calibers. *Choose a bullet length best suited to your rifle twist and type of shooting.  *When a bullet is specified for a given twist rate, it can also be used in any twist that is tighter.  Using it in a slower twist than specified, is not advisable. *Some experimentation will be required to determine exact drop tables for your equipment and location.