Zero Ranges Benefits/Drawbacks Specific for 6.5 Grendel

[Klem]

Ulmapache,

For a Point Blank Zero you need to know what bullet you will be shooting, its muzzle velocity, and vertical diameter of the kill zone on the target. Then use a ballistics calculator to work out the zero range for the most amount of distance to target a bullet aimed at the target, will land within the kill zone.

JBM Ballistics is a free online resource that can do this. Enter your bullet and its velocity. Set the range increments to 1 (yards or metres) and click Point Blank Range. Watch how the bullet is already in the kill zone, climbs and passes the POA, climbs above it to apogee which is the top of the kill zone, then drops past the POA again, back down to the bottom edge of the kill zone.

For example, a 120NBT at 2340fps with a kill zone/'vital-diameter' of 15-inches crosses the line of sight at 16yds, climbs to 7.5" at 226yds, falls past the POA again at 382yds, then drops to the bottom edge of the kill zone at 448yds. This is with a sight system 2.5" above the barrel axis like on an AR. I believe 15" is the vital zone the USMC uses, but don't quote me on that.

Obviously if only part of the target is showing you will then have to aim slightly below or above, depending on how far away it is. So you still need to be able to judge distances. For fully exposed targets out to 448 yds just point and shoot.

For hunting game with a PBR your kill zone needs to shrink to match the size of the intended target, and to be humane. Not the size of the animal, the diameter of its vital organs.

If you choose the closest bullet/POA intersection to zero the gun (16yds using the above example) your distance to target and zero needs to be absolutely precise. This is because any error will be magnified downrange. You could use the farthest intersection to zero but then that's a bit of an effort to check targets at 226yds (above example). Target structures normally sit at 100yd intervals on rifle ranges so you may as well use that to zero. Check JBM's prediction of where the bullet will be at 100yds. Using the above example it will be 10" high at 100yds. Zero the gun to be 10" high at 100 and you're good to go.

[Bonas]

I zero everything at 100. That way, with insignificant exceptions, all my DOPE is up. No matter what rifle I grab, if I'm significantly inside 100, hold up. If I'm signficantly outside 100, hold up. In terms of practical accuracy, I think this is as good as a MPBR zero, and it reduces the risk of blowing your hold if you have to shoot outside of your MPBR zero. If the shot is so long that I can't easily estimate the hold well enough to hit, for my shooting, I'll have enough time to check the hold before I have to shoot. I used to zero rifles differently based on their intended uses and finally just simplified it.

[Stinky Coyote]

Ulmapache,

For a Point Blank Zero you need to know what bullet you will be shooting, its muzzle velocity, and vertical diameter of the kill zone on the target. Then use a ballistics calculator to work out the zero range for the most amount of distance to target a bullet aimed at the target, will land within the kill zone.

JBM Ballistics is a free online resource that can do this. Enter your bullet and its velocity. Set the range increments to 1 (yards or metres) and click Point Blank Range. Watch how the bullet is already in the kill zone, climbs and passes the POA, climbs above it to apogee which is the top of the kill zone, then drops past the POA again, back down to the bottom edge of the kill zone.

For example, a 120NBT at 2340fps with a kill zone/'vital-diameter' of 15-inches crosses the line of sight at 16yds, climbs to 7.5" at 226yds, falls past the POA again at 382yds, then drops to the bottom edge of the kill zone at 448yds. This is with a sight system 2.5" above the barrel axis like on an AR. I believe 15" is the vital zone the USMC uses, but don't quote me on that.

Obviously if only part of the target is showing you will then have to aim slightly below or above, depending on how far away it is. So you still need to be able to judge distances. For fully exposed targets out to 448 yds just point and shoot.

For hunting game with a PBR your kill zone needs to shrink to match the size of the intended target, and to be humane. Not the size of the animal, the diameter of its vital organs.

If you choose the closest bullet/POA intersection to zero the gun (16yds using the above example) your distance to target and zero needs to be absolutely precise. This is because any error will be magnified downrange. You could use the farthest intersection to zero but then that's a bit of an effort to check targets at 226yds (above example). Target structures normally sit at 100yd intervals on rifle ranges so you may as well use that to zero. Check JBM's prediction of where the bullet will be at 100yds. Using the above example it will be 10" high at 100yds. Zero the gun to be 10" high at 100 and you're good to go.

That's huge vital zone, for coyotes you want to be closer to 4", the Mississippi guy above has a 3" for 0-200 yard fast offhand and that's a great choice, for combined coyotes and big game I aim for around 4-5", the grendel made me squeeze up to around 5.3" as 200 is the round number for that in my short barrel rigs with hornady black, I don't do as much coyote work as I used to so it's ok, a strictly big game hunter will often choose 6-8". The the points have been made by choosing the nearest round closest to that. Ie; 200 or 250. For most slower cartridges 200 works best, easy to remember for zero checks etc. Multiple rifles, you know the baseline zero is 200...like the guy above trying to simplify things for all his rigs, he's handicapping himself by at least 100 to 150 yards in order to do this so a negative trade off for one who prioritizes hunting over all others things though. There are only so many windows considering the bulk of the cartridge choices to game sizes we use. We're talking 2400-3200 fps and 4-10" verticals to land inside, when you play with those calculators you'll see where the rounds land for the game sizes you want to have a point shoot window and the round numbers that land to them. Did all that ages ago so it's institutionalized 200 for bulk of average speed cartridges and 250 for the faster cartridges. 100 will always remain a target or a mental only convenience and an easy 100-150 yard handicap zero for hunting. It's not really a discussion, you can't really argue with the velocity numbers vs the kill zone sizes, those are set in stone, and you can't really argue where 98% of all game is killed inside either, and you can't really argue that inside that window is when game most likely to sense you and reduce your time available is at it's peak, and so you can match them all up with the maximum odds or you can play a lottery with mr. Murphy and run some other logic that will still likely work much of the time but it's not the best for task at hand and it will catch you out...typically on animal of a lifetime, it will slow you down. The killers know how to set up for 'hunting'. Everything else is 'fack around and find out' territory.