This afternoon I managed to escape work early, again, and head out to my mates farm and complete my load development. I wrote a post about load development a few days ago so you can take a look at that post here if you like. I have also added a couple of links at the end of this post which will take you to two further posts that may give some more clarity to those who are interested.
Anyway today I shot three batches of ammunition I'd made, the three that shot the best last week, and found a clear winner. Below is the rifle and my shooting position looking down range. In the very distance of the left side photo you may see a little white thing...That's my target at 207m away. You can see below for the actual target page.
Below is the 4 shots that won the day and will be the load I use for the rifle when I make the ammunition. This group was shot at 207m, just like the eight initial load-development test-batches from last week. That's 226 yards for you non-metric people. I am doing this particular load development at the greater distance (I would usually use 100m as the distance) to allow a little more time for the bullet to fly, hopefully showing up inconsistencies...Which it did.
I tested 40.9 grains, 42 grains and 42.5 grains of gun powder, the ADI 2209 I mentioned last post, and the clear winner was the 40.9 as below. That group you see there, shot at 207m, is a head shot on a rabbit every day of the week so once I range out further to say 700-800m the group would expand exponentially but still be enough to impact on umm...Let's say a rockmelon sized object. (Rockmelon is what we call cantaloupe here in Australia if you're wondering.) The round could range out past that distance however accuracy and bullet energy suffers of course. Bullet energy is important to dispatch things quickly.
I haven't trued up the data yet but I should be getting a muzzle velocity of around 2950fps (feet/second) from the round. That's the speed at which the bullet exits the muzzle and at the ranges I cull feral animals at, let's call it 500m maximum, the time of flight is 0.70 seconds rifle to target with an impact pushing some 654ft-lbf (foot pound force) into the intended target.
You'll note in the image below a curious looking ruler. It's called a shooter's ruler and enables a shooter to determine the group size of a string of rounds in MOA (Minute of angle) and MRAD (Milradian) measurements. I've explained these before so please don't ask me to do it again...It's complicated. This rifle, with these particular rounds, the 40.9 grain loads, is a 0.5 MOA rifle.
In lineal measurement 0.5 MOA is 14.54mm (0.57 inches) at 100 meters. That means a half inch group essentially. The further the bullet is fired the bigger the group gets, although it will still be a 0.5 MOA rifle. The MOA measurement diverges with distance but is still called 0.5, or 1 MOA, or two etc. Google it.
Maybe to make it easier let's just assume that 1 MOA at 100m is a 1 inch group, at 500m a 5 inch group and at 1000m a 10 inch group. Obviously it's not exactly an inch but most shooters will call it so as it's so very close the difference doesn't matter. I won't go into MRAD as I always use MOA for this particular purpose. The scope's I shoot with are all MRAD though.
So, now I've found the load it's back into my workshop to make about 40 of those rounds. I will verify my zero on my scope at 100m which is making sure the bullet lands exactly where I point the crosshairs and then will true the data. This means shooting 300m, 600m and 800m and recording the exact amount of elevation required in the scope to hit the steel target. That information gets entered into my ballistics App in MRAD and it true's all my data up and gives an exact muzzle velocity.
Above you can see the elevation turret on my Kahles 624i scope. Each click (little line) is 1/10th of an MRAD. So the 1 you see is 10 clicks, 1 Mil (Milradian). The scope gives me 25.7 Mil in elevation in total.
So, what all that means is when I range a target at say, 487m with my laser rangefinder, I can input that into the ballistics calculator and it will spit out an elevation to dial into the scope, in MRAD, so that the bullet lands at the crosshairs, where I am aiming. There are other ways to do it, like holdover but that's more technical and besides, the field firing solution (FFS) is still required to hold over.
Anyway...That's it.
Design and create your ideal life, don't live it by default -
