whenever I have a new rifle, I try and remember the ballistics chart for use in the field. As memory slides, and too many rifles jumble the brain, I came on something I call "Jameisters Rule of Threes". Not sure its original. but then Jameister is not my real name!

While loading for a few medium bore rifles, I found the following.

For a 7mm rifle, (may work as well for a 270 or a 300 with right bullet weights) shooting 150 or 160 grain bullets, (maybe also for 140,have not checked) at 3000 fps with .475 to .525 ballistic coefficient, a simple rule of threes can work out to shootable distances:

Within the tolerance of an inherent error of a MOA, the rifle sighted in at 3 inches high at 100, will be 3 inches high at 200, just less than 3 inches low at 300 yards. Then its 13 inches at 400 and 30 inches at 500. No one I know needs to know about 600 yards, but said round will be almost 60 inches at 600 and almost exactly 90 inches at 700 yards.

3,3,-3, -13, -30, -60, -90. I can remember that.

Especially the first five hundred yards, 3,3,3,13,30.

A similar mnemonic for windage at 12 miles per hour sidewind keeps you within a few inches as well.

For the first 400 yards, each 12 miles of wind drifts within a few inches of the following: 3,6,9,12, and fudge a bit more at 500 yards. I know it exagerrates the 100 yard effect, but that is the exception that proves the rule!.

If somneong has a better simpler way let me know!

This is the way I remember ballistics

If you zero for 200 yards, look at the drop for 500 yards, divide by 2 for 400 yard drop, divide that by 3 for 300 yard drop. Works for every cartridge

Example:

If a 30-06 load drops 42" at 500 yards, divide by 2 and the drop at 400 yards will be 21", divide that by 3 and the drop at 300 yards will be 7", zeroed at 200 yards, 1.7" high at 100 yards.

270 load drops 36" at 500 yards, 18" at 400, 6" at 300 yards.

It is always very close. That way I only have to remember 500 yard drops and I have a definite yardage (200) that the rifle is zeroed.

Well I must admit that is easier, plus you can have a 200 yard zero.

thanks for the 500 by 2 equals 400 by 3 equals 300 and dead on at 200 rule.

Lets see: 5by2by3equals 200.

Jameister

I prefer a computer generated drop chart, whicj after real world checks, is adjusted to reflect the results. Usually it is the BC that needs changing in the chart.

I zero at 200 and note the ranges at which the bullet drops 4" and 8" below line of sight. That covers just about anything I'd ever do with a rifle, but I don't hunt very open country.


Okie John

I switched to a Burris scope with Ballistic Plex reticle that has additional aim points for 200, 300, 400 & 500 Yds. (Leupold offers the Boon&Crocket reticle) You don't have to memorize trajectories, just sight in at 100 Yds and then use the appropiate aim point for the different distances. Works just like using sight pins on a bow.

For my 7mm-08 shooting 145 Speer SP HotCors @ 2,825 FPS, here is how the actual trajectory stacks up to the Ballistic Plex reticle espected trajectory. The "Difference" column shows how high or low the actual impact would be for that yardage using the appropriate aim point.

Range_____Actual_____Bplex______Difference
100Yds____0.00"_______0.00"_______0.00"
200Yds____-3.6"_______-3.1"_______-0.46"
300Yds____-13.0"______-13.5"______+0.46"
400Yds____-29.5"______-30.1"______+0.60"
500YDs____-54.2"______-55.3"______+1.06"

The longest burm @ our gun range is 200Yds and I have verified the 200Yd impact of -1/2" using the 200Yds aim point. I haven't been able to verify the 300Yd impact yet but will definitely do so before attempting a shot at that range. I don't see myself ever taking a shot over 300 Yds. My longest shot to date on game was 225 YDs.

In my opinion, these bullet drop compensating reticles are great and anyone that hunts areas where long range shots are the norm should take a serious look at this type reticle.

firstshot
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Make your first shot count!

Hey FS

That's damn close and a good application. I have the same scope reticle on my 270. Have to have a real flat shooting caliber for that reticle since it is made for the 22-250 shooting a 55 gr bullet.

The TDS reticle in the Kahles or Swarovski work better for medium droppers like the 30-06 or 338. I have a Kahles with a TDS reticle on my 30-06 shooting a 200 gr Accubond and it works good up to 400 yards.

Don't know about the Boone & Crockett.

I have a mildot reticle scope going on my 6.5/284 and I'm just going shoot it at all the different ranges and see the actual point of impact for each dot and then build a referance card for it.
Zero the first shot at 100 yards and shoot for all the rest of the dots.

quote:

Originally posted by woods:
Hey FS

Have to have a real flat shooting caliber for that reticle since it is made for the 22-250 shooting a 55 gr bullet.

Woods

Just curious where you heard the Balistic Plex reticle was made for the 22-250? I don't understand the statement as I first used the BPlex reticle on my BAR 30-06 and now for my 7mm-08 and the Bplex worked great for both. Now the Burris Ballistic Mil-Dot reticle was in fact created for flat shooting varmit loads. (Check out link below)

With the "standard" caliber trajectories like the 30-06, .270, 7mm-08, etc., you sight in dead on at 100Yds and the additional aim points are for 200, 300, 400 & 500 Yds (Or you can make up your own). For "Magnum" trajectories, you can sight in dead on at 200 Yds and then the additional aim points are for 300, 400, 500 & 600 Yds.

Here is a link to Burris Ballistic Plex Tech Notes that explains the whole BPlex process.

It could actually be used for virtually any caliber/bullet/velocity combination. Basically your "zero" distance as well as the other aim point distances can vary depending on what caliber/bullet/velocity combination you are using.

My scope came with 30 different caliber/bullet/velocity caliberations from .223 Rem to .300 WSM / SAUM. There is even one for 22LR & the 36grn CCI hollow point. For this one the "zero" is 50Yds with the other aim points being 75, 100, 125 & 150 Yds.

Or, as I mentioned earlier, you can make up your own caliberation chart by choosing your "zero" sight in distance and then actually shooting your rifle to determine the "0" impact distance for the other aim points.

Like you, I don't know much about the Boon & Crocket reticle other than it is similar in function to the BPlex.

firstshot
---------------------------
Make your first shot count!

First Shot

You are right. I was thinking of the Ballistic Mil Dot, my mistake