a little help with bullet drops and turrets

N

nwvh longhair

New member
I was wanting some help converting bullet drops at given ranges to minutes of angle.

I have been prairie dog/ varmint shooting for a few years and generally use guestimation and the balistic plex reticle on my Burris scope. This year I would like to get a little more sophisticated with it and use the turrets and a drop chart.

I am shooting a savage 10fp in .223, with a 26" bbl. I will be shooting federal jhp 50 grn. I found stats for the rounds on the federal web sight, including velocity and drops at various ranges. I would like to be able to convert those bullet drops into minutes of angle so as to be able to look at a card on my stock and directly dial the turrets for the appropriate yardage.

Will this be a sufficient way to go, or am I trying too much of a shortcut?

thanks
 
I have used that method for many years.

A Leica range finder is helpful.

A muzzle break is critical to have so that you can see your hits and adjust the point of impact. Depending on a shooting buddy as a spotter does not work much of the time due to the fact that he have a 7x, 8x, or a 10x pair of binoculars which is just not strong enough power to spot exact bullet hits. Spotters often blink at the gun shot and they don't see exact bullet impacts very well.

I put pen striping material on my target knobs and mark them at various yardages that I can shoot actual targets at. I use the bullet chart and known click value to mark the target knobs to the distances that I want to shoot.

On your scope, you will have either a 1/4" clicks or 1/8" clicks. You sould spend some time establishing exactly what the "click value" is for your scope.

Next, convert the drop chart into clicks.

For example:

100 yards each click = 1/4"
200 yards 1/2"
300 yards 3/4
400 yards 1
500 yards 1 1/4

You may want to establish a click value for ranges beyond 200 yards and mark your scope accordingly.


Realize that any system of establishing a "zero" at a particular range whether it be a mil dot or a turrent knob that is marked for a particular distance will change because altitude, temp., humidity and most of all, wind direction and speed. The Marked distances on the scope become a good place to start.

I used this system on chucks, ground squirrels, and p. dogs which was very effective on a scope of high quailty that had repeatable knobs. I screwed my scopes up and down all day long, day after day, after day.

Now that you have learned to dial up and down for elevation, you might as well mark your scope for windage:

4 clicks = 1
8 clicks = 2
12 clicks = 3
16 clicks = 4

Watch the wind direction and dial in clicks for holding off for the wind. You will develop a feel for how many clicks is needed.

As you adjust your scope to get "dialed" in at a particular range, you may develop the need to place your shot in a particular place on the animal instead of just aiming for center of mass.

When you see a "Party" of p. dogs at a certain distance, start working on the outside edges of the group (Party) and work your way in. When you see a dog sitting on a hole, try and put enough "English" on the dog to dump him off in the hole to clog it up, sometimes it takes 2 dogs to get'r done. As you work your way through the party of dogs, aim for specific spots on the dogs and adjust your dial accordingly. Eventually, you will end up with one of those sneaky buggers with only the top of his head showing. If you can catch him right under the chin, it may lift him out of the hole 6 feet! As you learn to place your shots with precision, it give you the ability to take shots that give spectacular launches such as the Texas heart shot.

If you plan on shooting past 250 yards, this system beats the heck out of a "hold over" system.

Don't forget the muzzle break so that you will be able to see your hits.

I am able to get some unreal velocity with accuracy out of my 223 when loaded with N-133 with the 50's and N-135 with the 55's. Accuracy with the Vit N powders is unreal, to say the least. Use thick cup primers such as the Rem 7 1/2, CCIbr-4, or the CCI450. I shoot the 50's at 3600 and the 55's at 3500 in my 223 with bug hole accuracy but tough brass is required such as Lapua or IMI, my barrel is 26" long.

Don't let your ammo sit out in the sun and get hot or else your day may be full of all kinds of surprises like hard extraction, high pressures and shots that fly off accordingly. Lots of powder types get blamed for being "temp sensitive" because a guy lets his ammo get warm or hot to the touch.

Good luck!
 
so by what you are saying a 12 inch drop at 300 yards would be: 12 / .75 = 16 clicks or 4 minutes

correct?


So on my range chart I would have 300 yards = 4 moa

(made up numbers for example only)
 
I live and breathe MOA, and yes to about 500 yards you can just go with the rounded
100-1/4
200-1/2
300-3/4
shooting a 50 gr from a 223 you'll max out around 500 yards,

you'll be only as accurate as your drop chart, I tweak mine to my rifle, factory specs will usually differ from your actual results.

the definition of moa is: a unit of angular measurement, actualy equal to 1/60th of 1 degree or 1.047 per 100 yards

to accurately convert drop by MOA its done like this, just an example here
6.5 gibbs, sighted in at 300 yards
range 775 yards, drop 86.7",

86.7 (actual drop)/1.047 (true MOA)=82.8/7.75 (range in hundreds of yards)=10.75moa actual drops
RR
 
Thanks guys, good info

The reason I said 4 moa rather than the 16 clicks is because the turrets are marked with whole numbers (minutes) every 4 clicks and its easier to crank up 4 marked numbers, than to count clicks.

I posted this same question up on another board, and one of the guys there said that without chrony readings of actual muzzle velocity I was just wasting my time. Will there be enough variation from the Federal websites velocities and bullet drops to make that data useless?
 
I just went out a couple days ago PD'ing with my new Nikon Buckmasters 6-18X mil-dot. I used turret for elevation and reticle (dots) for windage with this reticle and tgt. size. The system works about as good as anything else would considering it was on a 17 Fireball XP-100, and the wind was blowing 10-15 avg. My buddy was shooting i was spotting and i called windage correction to him as close as possible. He made a couple hits between 400 and 500 yds.

I chronographed the load and calcd everything. The turret was very close even to 500+/-, and wind was quite close most every shot.

At 18X the subtension between dots is 2.3 MOA, and we just calcd. holdoff by dividing each 50 yd. 10 mph windage value by the dot to dot subtension of 2.3 MOA. For example if the 400 yd. windage was say 3.4 MOA then just divide that value by 2.3 = 1.5 "mil"-dots.
 
This program help me and you can print your results on a blank card. You can set it up for your situation as you like. I have used this on shoots at 4300' and 300' elevation and the program calculates very well for environmental changes like wind, elevation, temp, humidity, and pressure. The best thing is you can adjust results to reflect MOA, inches, and any variation of fractions. Also the program has data for all the different ie BC and SD if you pick from the manufacture list it makes it much easier.

Just take your elevation, barometric, and temp readings from a gps and enter it into your laptop at the range and your good. I carry a small printer and print a card on location when needed.

http://www.eskimo.com/~jbm/ballistics/traj/traj.html
 
Last edited:
longhair,
ammo companies like to exagerate they're loads, just like anyone else, they wanna be the best. but at what cost?
you can dial in make POI hit POA to within 2" at your range of choosing but not with the specs you get from the factory.


You must have a solid number to start with, I use muzzle velocity, with that I can shoot a little and figure alot and be able to dial my scope to POA out to 1000 yards. It seems complicated but its not that hard.
RR
 
Having a reference card on the side of the stock seems like a good idea, which it is for target shooters. When shooting live animals, at a relative close distance under 450 yards, you need to cut your reaction time, that is why I taped the target turrents with 200,250,300,350,400,450, yard increments for my 223 shooting 50g bullets.
 
I use the trajectory calculator that yotekyller posted and shot a rockchuck at 350 yards on the first shot. It works really well for me.
 
Quote:
I was wanting some help converting bullet drops at given ranges to minutes of angle.

I have been prairie dog/ varmint shooting for a few years and generally use guestimation and the balistic plex reticle on my Burris scope. This year I would like to get a little more sophisticated with it and use the turrets and a drop chart.

I am shooting a savage 10fp in .223, with a 26" bbl. I will be shooting federal jhp 50 grn. I found stats for the rounds on the federal web sight, including velocity and drops at various ranges. I would like to be able to convert those bullet drops into minutes of angle so as to be able to look at a card on my stock and directly dial the turrets for the appropriate yardage.

Will this be a sufficient way to go, or am I trying too much of a shortcut?

thanks



I did a similar thing, but transferred the data to a stick on label, covered with clear tape, on my scope. Now, I just dial up the range I want to shoot, rather than looking at a table, then counting the clicks on the turret. It works well enough out to about 600 yards, which is as far as I will shoot with my .220 Swift. On the Swift, I start from a 200 yard zero. On my .223, I start from a 100 yard zero.

Here's a pic with part of the label visible on the elevation turret on the left side.

Be aware than often the bullet drop tables are in error, sometimes significantly at the longer ranges. One, I used, was off 1 1/2 MOA at 500 yards.

IMG_0265.jpg
 
I have a drop chart with me while hunting, which has been tweaked to my rifle, shooting under my actual conditions.
I use this to around 700 yards, beyond this I have a PDA running exbal which has my load data preloaded, I add in the current conditions, wind speed and such, I use this for shooting out to 1K or more.
RR
 
To followup with RR, a PDA with Exbal or the like will give much in the way of info. I've been messing around with one and it comes in handy for in-the-field number crunching...

Given you have accurate atmospheric conditions to input and a known b.c of your bullet, you can prove your actual muzzle velocity based on your bullet's real time drops at known distance.

From there, your drops at longer ranges from the PDA should be very very close, given the same conditions of course...

As far as counting clicks goes, you are MUCH better off learning to use the numbers already marked on your turret OR making a label for them as shown above. Trying to count off "20 or 50 something clicks" or more in the field will only lead to confusion.

If your scope has an MOA reticle, think in MOA. If it has a MIL reticle, hopefully your turrets are also in MILS. Matching the two makes doing all this stuff MUCH easier.

With matching reticle & turret values AND if recoil allows, you can spots you own misses in the scope. Then just measure the distance of your miss to the intended target with the reticle, and send another round down by holding off via that distance. OR, or dial your turrets to that measured distance and let one fly...
 
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