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**Unclenick** · October 25, 2011, 04:49 PM

Qtiphky,

Your results are what QuickLOAD predicts using 24" barrels.

QuickLOAD says the .308 with a Winchester case should send the Barnes bullet out at 2813 fps, right at 60,500 psi, getting 33.2% ballistic efficiency. The .300 WSM with 52 grains of H4895 it predicts to get 2762 fps from the Nosler BT, peaking at 45,600 psi and getting about 27.7% ballistic efficiency. It's in good enough agreement with the real results to consider the model's analysis valid.

So, 16% more powder is trumped by 20% more efficient use of the powder. The WSM case is only 79% filled with powder under the bullet, so the pressure is lower which burns the powder less quickly. This is what makes the powder usage less efficient in the WSM load.

October 25, 2011, 04:49 PM	#7
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Qtiphky, Your results are what QuickLOAD predicts using 24" barrels. QuickLOAD says the .308 with a Winchester case should send the Barnes bullet out at 2813 fps, right at 60,500 psi, getting 33.2% ballistic efficiency. The .300 WSM with 52 grains of H4895 it predicts to get 2762 fps from the Nosler BT, peaking at 45,600 psi and getting about 27.7% ballistic efficiency. It's in good enough agreement with the real results to consider the model's analysis valid. So, 16% more powder is trumped by 20% more efficient use of the powder. The WSM case is only 79% filled with powder under the bullet, so the pressure is lower which burns the powder less quickly. This is what makes the powder usage less efficient in the WSM load. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle Last edited by Unclenick; October 25, 2011 at 09:47 PM. Reason: typo fix