What length bullet jump to start with?

Ammo Junky · June 24, 2006, 04:28 PM

What Bullet jump do you guys start with to select a powder charge with? .005? .025? Do you try to retune the charge after getting an oal set?

**Unclenick** · June 24, 2006, 04:44 PM

Start out just touching the lands. Run the powder charge down 0.5 grains (Glen Zediker's criterion) from normal for this, because it will raise pressure over that from firing a bullet that jumps, owing to static coefficient of friction being higher than kinetic coefficient of friction between bullet and bore. Then seat the bullet down 0.01" below the lands with the powder charge returned to normal. Continue down in 0.01" steps until you achieve best accuracy, reducing the charge 0.1 grains each time to keep pressure about the same (in .30 cal). See where you get to best accuracy? When you've found this spot, start the process of adjusting the powder charge alone until you get the tightest possible group.

Nick

June 24, 2006, 04:28 PM	#1
Ammo Junky Senior Member Join Date: March 11, 2006 Location: IL Posts: 537	What length bullet jump to start with? What Bullet jump do you guys start with to select a powder charge with? .005? .025? Do you try to retune the charge after getting an oal set? __________________ Will work for brass. I apologise in advance for spelling errors.

June 24, 2006, 04:44 PM	#2
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Start out just touching the lands. Run the powder charge down 0.5 grains (Glen Zediker's criterion) from normal for this, because it will raise pressure over that from firing a bullet that jumps, owing to static coefficient of friction being higher than kinetic coefficient of friction between bullet and bore. Then seat the bullet down 0.01" below the lands with the powder charge returned to normal. Continue down in 0.01" steps until you achieve best accuracy, reducing the charge 0.1 grains each time to keep pressure about the same (in .30 cal). See where you get to best accuracy? When you've found this spot, start the process of adjusting the powder charge alone until you get the tightest possible group. Nick __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle