Load Workup Method on 6mm Bullets for 6BR Match Rifle

A. Determine COAL to Lands with Hornady Lock-N-Load Overall Length Gauge

· Seat bullet with gauge under firm pressure.

· Recover bullet, place in gauge and measure overall length (COAL) and length (COMP) with Hornady Lock-N-Load bullet comparator using Mitutoyo digital caliper.

· Repeat 5 times and calculate mean values for COAL and COMP

· COMP value is used for loading since meplat variations provide unreliable variations in bullet seating.

B. Initial Powder Load Ladder

· Load initial test cartridges with form-fired, re-annealed Lapua brass

· All powder charge ladders started with bullets at 0.015 inch jump to lands except for Berger 105gr VLD bullets which were started with 0.015 jam into the lands.

· Powder charges were determined with default QuickLoad settings using case volume of form fired Lapua brass at 38.7 grains water so that predicted maximum chamber pressure would be between 51000 psi and 58700 psi in 0.3 grain variations in charge (e.g. 30.0, 29.7, 29.4, 29.1, 28.8 grains Varget for Berger 108gr BT bullets with COAL at 2.310 inches).

· Three, 3-shot groups were fired at targets at 200 yards for each charge

· Group size was calculated for each 3-shot group using center to center method (Maximum spread + maximum vertical + maximum horizontal / 3). MOA was calculated by dividing group size by 1.047 and adjusting for 200 yard distance by dividing by 2.

· The optimum initial charge for further tests was selected by the finding the charge with the smallest average vertical spread in the shots.

C. Best bullet distance to lands (Jump or Jam?)

· At the selected powder charge, two, 3-shot groups were fired at COAL’s provided for bullet jam (+0.015) or 3 jump lengths (-0.005, -0.015 and -0.025 inches).

· The COAL that gave the smallest average MOA at 200 yards was selected.

D. Refine powder charge

· Once an optimum COAL was determined, three, 3-shot groups were shot with powder charges at the previous optimum charge, 0.3 grains above and 0.3 grains below the previous optimum charge.

· The charge with the best average MOA was selected.

· On one test with V-TAC 103’s, the complete powder charge range was run when it was found that best results were obtained with jammed bullets.

E. Cartridge Reloading

· Lapua 6BR Norma brass that had been form fired was used. The brass was deprimed and was cleaned for 4 hours in corn cob media with polish (Frankford Arsenal).

· The brass was annealed after cleaning with an Annealing Made Perfect, Mark II annealer using cycles 0154 to 0157 depending on analysis results for the brass lot being annealed.

· Necks were resized with a Redding Competition Bushing Neck Sizer die (0.266 bushing) except for 5^th reload brass which was resized to bump shoulders back to first form fire conformation with a Whidden Gunwerks Click Adjustable FL Bushing Sizer die with 0.265 bushing.

· Powder was dispensed with an AutoTrickler V2 system (Adam MacDonald, New Brunswick, Canada) on an Entris Sartorius Balance. The AutoTrickler delivered powders within a 1-2 granule range of the target weight.

· Bullets were seated with a Redding Competition Seater die using a Redding T-7 turret press.