GS CUSTOM USA - Bullet Technical Profile

HOME

PRODUCTS

GALLERY

THEY SAY

408385SP144 Technical Profile © Application: Target/Tactical

Barrel Bore Diameter: 0.401" 10.185 mm The diameter of the barrel from land to land.

Barrel Groove Diameter: 0.408" 10.362 mm The diameter of the barrel from groove to groove.

Bullet Weight: 387gr 25.1g Bullets are guaranteed to weigh within 0.25% of the stated weight.

Bullet Length: 1.99" 50.550 mm

Secant Ogive Length: 1.08" 27.482 mm These dimensions are critical to consistent external ballistic performance and are held constant to within 0.005 mm (0.0002")

Meplat Diameter: 0.04" 1.019 mm

Min Bullet Protrusion: 1.16" 29.460 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: 1.54" 39.000 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: 3000fps 914 m/s If the maximum muzzle speed is exceeded, dynamic stabilty problems may be encountered.

Twist: Sg = 1.5: 13.0" / 323 mm 31.8 Cal. in length The twist required to give a calculated Sg 1.5

Minimum Twist: 14" / 355.6 mm 34.9 Calibers in length The twist required for stable flight and the best long range tractability more than 530 yds or 490 m.

Calculated Ballistic Coefficient - G1 profile

BC = 0.772 3000 fps to 2100 fps 914 m/s to 640 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 = 0.712 2100 fps to 1200 fps 640 m/s to 366 m/s

BC = 0.515 1200 fps to 0 fps 366 m/s to 0 m/s

Suitable Cartridges, with consideration of the above specifications:

All .408" cartridges, subject to the above specifications as well as bores including the .408" LRB.

NOTES

A Gyroscopic Stability (Sg) greater than 1.2 is required for SP bullets. For use under 530yds/490m an Sg of up to 1.5 or even greater can be used. For distances beyond 530yds/490m, the Sg can be decreased with a slower twist, but never less than 1.2 for GSC SP bullets.

*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.

408385SP144 Technical Profile © Application: Target/Tactical

Barrel Bore Diameter:	0.401"	10.185 mm	The diameter of the barrel from land to land.
Barrel Groove Diameter:	0.408"	10.362 mm	The diameter of the barrel from groove to groove.
Bullet Weight:	387gr	25.1g	Bullets are guaranteed to weigh within 0.25% of the stated weight.
Bullet Length:	1.99"	50.550 mm
Secant Ogive Length:	1.08"	27.482 mm	These dimensions are critical to consistent external ballistic performance and are held constant to within 0.005 mm (0.0002")
Meplat Diameter:	0.04"	1.019 mm
Min Bullet Protrusion:	1.16"	29.460 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:	1.54"	39.000 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:	3000fps	914 m/s	If the maximum muzzle speed is exceeded, dynamic stabilty problems may be encountered.

Twist: Sg = 1.5:	13.0" / 323 mm	31.8 Cal. in length	The twist required to give a calculated Sg 1.5
Minimum Twist:	14" / 355.6 mm	34.9 Calibers in length	The twist required for stable flight and the best long range tractability more than 530 yds or 490 m.

Calculated Ballistic Coefficient - G1 profile
BC = 0.772	3000 fps to 2100 fps	914 m/s to 640 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 = 0.712	2100 fps to 1200 fps	640 m/s to 366 m/s
BC = 0.515	1200 fps to 0 fps	366 m/s to 0 m/s
Suitable Cartridges, with consideration of the above specifications:

All .408" cartridges, subject to the above specifications as well as bores including the .408" LRB.


NOTES
A Gyroscopic Stability (Sg) greater than 1.2 is required for SP bullets. For use under 530yds/490m an Sg of up to 1.5 or even greater can be used. For distances beyond 530yds/490m, the Sg can be decreased with a slower twist, but never less than 1.2 for GSC SP bullets.

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.