Question from a noob

[barryrod]

I have been shooting for a while but just now getting the bug regarding longer range shooting. I went to a range the other day and shot out to 500yrds.

I shot a 300BO with a 16in barrel and P-300 2-7 scope using Magtech 123gr rounds

My question has to do with Zeroing at 100 yards. I zeroed the the scope at 100 yards getting decent groupings. later hit the 200-500 yd range. I figured to try 200yrd using the BDC and dropped 1 dot on the reticle. I was shooting high so I used center dot and hit after hit followed. I dropped 1 dot for 300 and was dead on, same for 400 and 500.

Why did the zero at 100yrds hit center at 200 as well? Is it due to the arc maybe hitting peak about 150yds or so?

I am trying to wrap my head around the reasoning for this

Thanks in advance

Barry

 

[SubOptimal]

It is all about the angle of your barrel with reference to the ground. If your target is higher than the barrel you will be pointing it up which will effect the POI, it is entirely possible that your bullet was still heading up at the 100 yard line and had begun dropping at some distance between that and the 200.
BDC reticles assume a level barrel.

 

[tcole75]

I attempted to shoot to 500 for about a year with a bdc reticle. I quickly learned that it doesn’t really work. I would recommend getting a scope that you can dial with figure out your velocity. Then hopefully find someone that has done some long range shooting to show you the ropes.

 

[SubOptimal]

The issue with a BDC reticle has nothing to do with the reticle, it is really a user issue.
The reticle is designed around a specific load. That means bullet, for BC, powder charge for velocity and even primer.
It is on the shooter to calibrate the reticle to his equipment and specific range and weather conditions.
That is why shooters use data books specific to their gun and load, even atmospherics might require a separate page, not really might, will is more like it.
The numbers on the reticle mean nothing until you find out what they mean under actual field conditions with your gun and at your location using your selected load.

 

[tcole75]

I tried using velocity and entering everything in to get the correct drop but it doesn’t matter what so ever when there’s no call for wind you can hold over all day with bdc reticle but if there’s a 15 mph cross wind you won’t hit the target that’s why I would recommend getting a scope you can dial with.

 

[SubOptimal]

Most of the shooters I know dial elevation and hold wind. Be it estimated wind or measured wind, you still have to observe the effects of wind at long distance using clues available to you. It is actually pretty rare to have wind at the shooter and wind at the target to be the same. Now even a simple duplex reticle will give you a primitive yardstick to work with, assuming you have read the manual that comes with the scope.

 

[tcole75]

I agree I shoot with a few guys that hold their wind for me. It’s easier to dial than to attempt to hold but with a bdc you can’t hold wind it just accounts for the bullet drop.

 

[SubOptimal]

You have a vertical crosshair and a target that is something wide, right?
Use that information for your hold.
10 mph wind at 9 o'clock, 300 yards out, hold the left edge of a 10" wide target, if you miss right, increase your hold by the amount of the miss.
Can't spot you miss? You have other problems than wind hold.