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BULLET DATA

What detail and technical bullet data on GS Custom bullets do we get from the manufacturer on their website?
Apart from the basic data like Bullet Number, Bore Diameter, Groove Diameter and Suitable for Calibres (Subject to twist) detail, we also get the following technical data on the bullet which are essential for the reloader.

With the 308130HV bullet as example, let's look at the available technical data.

(a) The bullet's dimensions, i.e. Length (total bullet length) as well as it's Nose Length only, are given to us in both millimeters (mm) and inches (").
(b) Three different bullet speeds are indicated in both m/s (meters/second) and fps (feet per second); also
(bi) Three different BC values for each of the above three bullet speeds.
This comes in very handy when fed into a ballistic program to calculate the bullet's trajectory over different target distances.
(bii) Minimum Impact Speed in m/s and fps at which the HV bullet will expand reliably, is also given in the technical data.

These are important data for the reloader in order to know what to expect when using the specific bullet. As an example, if the specific bullet does not yield the minimum required impact speed over the planned hunting distance in your trajectory calculations, then obviously you should select another bullet that will yield at least the minimum impact speed over the planned hunting distance in order to achieve the best terminal ballistic results.

In the ballistic table below, this specific bullet still yields a velocity of 2548.7fps at 500m distance (Minimum impact speed = 1600fps.). Reliable expansion will therefor still take place at this distance and beyond, although normal hunting distances are most of the time well below 500m.

.308W
Altitude: 3000 ft    Temperature: 78 °F.
Bullet Weight:    130 gr    BC: 0.365.
Muzzle Velocity: 3150 fps    Zero Range: 250 meters.

Then we also get Guidelines for Stability Factor & Twist Rate which are explained in a lot of detail and accompanied by a chart giving SF values for the particular bullet when launched out of a rifle with a specific twist rate.
Once again, if the required SF cannot be achieved with your rifle and it's twist rate over your planned hunting distances, please follow the advice given in the columns below, i.e. either select a shorter or longer bullet to achieve the SF requirements indicated for the specific hunting distance.

How do I know what is the minimum/maximum cartridge overall length (COL) that I can use with this bullet?
Follow the instructions in the COL columns below - simply add the minimum/maximum values given, to your cartridge case length.
In doing this exercise, you can determine the maximum COL that will fit your rifle's magazine best, as well as ensure proper feeding of the cartridge out of your rifle's magazine.

Finally, what is the minimum/maximum seating depths with this particular bullet?
With a little easy calculation one can easily get the answer to that question!

Minimum seating depth = Bullet length (1) or 29.6mm/1.17" minus Maximum value 21.0mm/0.83" (3) = 8.6mm/0.34".

Maximum seating depth = Bullet length (1) or 29.6mm/1.17" minus Minimum value 18.0mm/0.71" (2) = 11.6mm/0.46".

The barrel's vibration can be fine tuned by adjusting the COL between the above minimum and maximum seating depths of the bullet in the brass case. In so doing you should be able to achieve the smallest possible group on the target with the particular bullet, after having complied with your rifle's specific preferences on COL.

 

Bullet Number		Bore Diameter		Groove Diameter		Suitable for Calibres (Subject to twist)
308130HV080		7.62mm	0.300"	7.82mm	0.308"	308 Win, 7.62 UKM, 7.82 Warbird, 7.62 Nagant, 30 Picra, 30-06, 300 Mag H&H, Lapua, RUM, Wea, Win, WSM, 30-284, 30-30Win, 303 Sav, 300 Sav, 30-40 Krag, 307Win, 308EH, 308 Norma Mag, 30Fl N.E., 30R Blaser, 30 Super Fl H&H.
Length (1)		Nose Length		Weight
29.6mm	1.17"	16.0mm	0.63"	130gr	8.4g
Speed		1006m/s	3300fps	747m/s	2450fps	488m/s	1600fps	Min Impact Speed
BC		.370		.355		.352		488m/s	1600fps
Guidelines for Stability Factor, Twist Rate and COL:		Choose a bullet length best suited to your rifle twist and type of hunting. Note that S/F increases as twist tightens.  A 1:10" twist is tighter than a 1:12" twist.		Bush and dangerous game hunting S/F greater than 1.6 is required. There is no upper limit to the S/F here. If this bullet does not meet the requirement, use a shorter bullet.		General hunting to 500m/yds S/F greater than 1.4 is required. There is no upper limit to the S/F here. If this bullet does not meet the requirement, use a shorter bullet.		Long range beyond 500m/yds S/F greater than 1.1 is required but more than 1.5 is not desirable. If this bullet S/F is too high, use a longer bullet. If too low, use a shorter bullet.
		COL: To determine the minimum and maximum cartridge overall length with this bullet, add the minimum or maximum values to your cartridge case length.				Minimum		18.0mm / 0.71" (2)
						Maximum		21.0mm / 0.83" (3)
On the chart to the right: 1. Select the twist rate of your rifle on the horizontal axis and read the S/F on the vertical axis. 2. Use the guidelines above to determine suitability for your application. 3. Check the calibre list for your calibre.