LDC for .30-378 & GS-Custom Bullets

Caliber

30-378

Load Data for GS-Custom .308 Cal. HV Bullets

Bullet	Weight in Grains	Required Twist	Maximum FPS	Propellant	Start Load in Gr.
308150HV.079	150	1:11" / 279mm	3850	H4831SC	103 Min. to 106 Max.
BC	Diameter	Length	Min.Impact fps	H1000	109 Min. to 114 Max.
0.480	7.825mm	32.8mm	1900	H870	122 Min. to 127 Max.
Momentum/Energy	100	200	300	400	500
83 / 4938	79 / 4543	76 / 4171	73 / 3822	69 / 3493	66 / 3185

Bullet	Weight in Grains	Required Twist	Maximum FPS	Propellant	Start Load in Gr.
308160HV.078	160	1:10" / 254mm	3700	H4831SC	101.5 Min. to 102.5
BC	Diameter	Length	Min.Impact fps	H1000	103 Min. to 110 Max.
0.515	7.825mm	35.0mm	1900
Momentum/Energy	100	200	300	400	500
85 / 4865	82 / 4599	80 / 4344	78 / 4099	76 / 3864	73 / 3639

Bullet	Weight in Grains	Required Twist	Maximum FPS	Propellant	Start Load in Gr.
308173HV.074	173	1:9" / 228mm	3600	H4831SC	99.0 Min. to 103 Max
BC	Diameter	Length	Min.Impact fps	H1000	108 Min. to 110 Max
0.650	7.825mm	38mm	1900
Momentum/Energy	100	200	300	400	500
89 / 4980	87 / 4737	85 / 4502	83 / 4277	80 / 4059	78 / 3850

Notes:

Most important is to choose a bullet that is matched to the twist rate of the barrel or that is shorter (lighter) than indicated. Longer (heavier) bullets than indicated, will not perform well.
Always use magnum primers.
Maximum f.p.s. is for a 24" barrel. Higher speeds are possible in longer barrels.
Start loads may produce maximum f.p.s. in some rifles. Develop loads with a chronograph.
Develop speed first by loading two cartridges at the start load and two each increasing in half grain increments (one grain increments if the bullet is over 100 grains) until the desired speed is reached.
Load the bullet touching the rifling to start with, if possible. HV and FN bullets do not cause pressure spikes when loaded touching the rifling.
Once the desired speed is reached, load 15 rounds with that propellant charge and still at the maximum length possible in the rifle, preferably touching the rifling.
Fire three for group. Seat the next three 0.5mm (0.02") deeper and fire for group. Repeat the process until the best group is obtained. Use 1.0mm (0.04") steps if the bullet is over 100 grains.

Troubleshooting:

If pressure signs occur at substantially lower speeds than the maximum f.p.s. indicated, try a propellant that is more bulky in order to reduce air space in the case and make sure a magnum primer is used. If pressure signs are still present at low speeds, have the headspace of the rifle checked.

Notes:

Chart Data provided by GS-Custom Bullets, SA. Actual Load Development performed by C. James for the above chart using GS-Custom Bullets and quality new brass. COL Data not currently available or posted.

173Gr. HV Bullets performed best in a modified 27.5" Custom Shilen Barrel. Stock Weatherby Barrel noted poor accuracy with the GS-Custom Bullets and did not properly stabilize the 173 Gr. HV Bullets properly at 100-200 yards.

Recommendation is to use the above loading data with 180 Grain Nosler Winchester FailSafe Bullets or 180 Grain Barnes X-XLC XBT Bullets. 150 Grain HV's performed best with H1000 loaded at 110.5 grains with a CCI250 Magnum Primer, 2.903" Trim.