Bergara HMR Pro Load Development

[stevieb92]

Hey all. I just wanted to share the results from load development for my girlfriend's Bergara HMR Pro in 6.5 Creedmoor. This is the heavy barrel variant. It's her primary bolt rifle and has approx 250 rounds of Hornady 140 ELD and 120 Amax ammo down the barrel before we started the load development process. She is a US Army Reserves Veteran originally from Idaho and is no stranger to shooting, but she is still learning precision rifle skills. We run a YouTube channel together called Life, Liberty and Adventures, so feel free to peruse our content. We are not professionals at it, just having fun in our spare time. We both have full time careers and the YouTube thing is only something we do in our spare time. Neither of us are pro shooters, just having fun, learning and expanding our skills along the way.

Initially, the HMR Pro passed the accuracy requirements from Bergara which is sub moa for two 3 shot groups with Hornady 140 ELD-M factory ammo. I shot those March 2022 during less than ideal temps (below 30F and snow). Those two groups went into about 3/4 moa, so, I'll call that a win under those conditions. She declined to shoot those groups since her hands were frozen. Mine were too, but I went for it anyway. lol



For the load development on this rifle, I ran through a ocw style methodology. The components used for load development are Hornady brass, Hornady 140 ELD-M, H4350, and CCI standard large rifle primers. I wet tumbled the brass, full length sized, annealed, trimmed to length, deburred and chamfered the case mouths and finally used an expander mandrel for final neck sizing. The first range session was eight charge weights from 40.3 to 42.4 grains of H4350 in 0.3 grain increments with five shot groups for each charge weight. These were shot in a round robin fashion with 2 minute cooling time between each shot and 5 minute cooling time between each shot string. Here are the target results.


Group# / charge weight / avg velocity / es / sd
#1 / 40.3 / 2631 / 51 / 20
#2 / 40.6 / 2661 / 32 / 14
#3 / 40.9 / 2676 / 43 / 17
#4 / 41.2 / 2687 / 16 / 7
#5 / 41.5 / 2690 / 22 / 9
#6 / 41.8 / 2713 / 27 / 11
#7 / 42.1 / 2725 / 22 / 10
#8 / 42.4 / 2746 / 22 / 10

HMR_Pro_Load_Dev_Round_01.jpg

After reviewing the velocity data, I decided to investigate the charge weight range from 41.1 to 41.8 in more detail, specifically 0.1 grain increments. These were shot in a round robin fashion with 2 minute cooling time between each shot and 5 minute cooling time between each shot string. The target results are below.


Group# / charge weight / avg velocity / es / sd
#1 / 41.1 / 2698 / 28 / 11
#2 / 41.2 / 2704 / 27 / 13
#3 / 41.3 / 2707 / 27 / 11
#4 / 41.4 / 2712 / 17 / 6
#5 / 41.5 / 2715 / 33 / 12
#6 / 41.6 / 2720 / 44 / 16
#7 / 41.7 / 2724 / 22 / 8
#8 / 41.8 / 2713 / 50 / 20

HMR_Pro_Load_Dev_Round_02A.jpg
HMR_Pro_Load_Dev_Round_02B.jpg

The first round data indicated that there was a node in the 41.2 to 41.5 range based on the velocity, group size and point of impact on the targets. The second round showed two nice groups in the 41.3 and 41.4 grain loads which also had low SD numbers. So, the final load I've selected is 41.3.

I realize there are other methods. This is the method I have used on multiple rifles and continues to guide me to what each rifle likes. Rosann did a great job shooting all of these groups in the round robin fashion. Overall, we're very pleased with the Bergara. Out of all 16 groups, only two were over 1 moa (barely). For a factory rifle, it's more than satisfactory.

Rosann_Shooting_Load_Dev.jpg

[Mr_themissile]

Nice write up. I almost bought an HMR, but decided on a savage 110 precision