Reticle question

[usherj]

I have a question about using the duplex reticle for holdover at longer ranges. I have a Sightron S11 3-9x42 with std duplex. The mfg states that the distance between the ends of the heavy reticle is 13.2". I am assuming that this is at 100y, although it wasn't noted. This would make the distance btween the cross hair and heavy post 6.6" at 100y. Now my question:

Assuming the data given was correct (I will field verify after hunting season), would the following dimensions be logical to assume for the distance between the cross hair and the start of the heavy reticle?:

200y 13.2" (6.6 x 2)
300y 19.8" (6.6 x 3)
400y 26.4" (6.6 x 4)

I'm really only worried about 400y, since I would zero at 200 and hold the crosshair on the back for a whitetail (9" drop) at 300. If this is true I should be in good shape, since the estimated drop at 400 would be 26".

6.5x55 with 140g partition (.490 BC) at 2600fps

I have been considering a numbe rof options and this would be a way to just use the existing scope and a rangefinder. Thanks for any advice

[charles p]

I don't have that brand of scope, but at 400+ yards I show a little daylight (just a very little) above the deer's shoulder.  Seems to drop in just fine.  I wouldn't take a shot at 500+ yds.  Took two whitetail doe last year at 450 yds with this holdover.  Thought I was shooting the same doe but my dog and I found two in the soybeans.  Yardage measured 450.  Rifle was a 270 with 140 grain Sierra.

[yooper77]

Don't be a arm chair ballistic technician.  Don’t attempt to use ballistic charts and hope your bullet finds its home.

You are already stretching the distance, so please make absolutely certain you and your firearms can routinely shoot at those ranges.  Practice, practice and practice, or pass on the shot.

I sight in my rifles to approx 3 to 4 inches high at 100 yards, so I hold on hair for long range.  I don’t shoot over 300 yards anyway, I can always stalk closer or I pass on the shot.

yooper77

[diggler1833]

Good advice there.  Either practice at that range or don't take the shot at all.

[sscoyote]

"I have been considering a numbe rof options and this would be a way to just use the existing scope and a rangefinder. "

That's exactly right! The plex reticle is the simplest ballistic and rangefinding reticle made. I also use my plex-reticled optic in 1 of my handguns for the longer ranges on coyotes (XP 17 MIV). Here's how i do it. I have a 4-12x Burris Mini on top that measures (subtends) 2.7 inch PER hundred yds. @ 12x. Your calcs. r exactly right for what the stadia points will subtend at longer ranges--it is proportional (rangefinding is NOT tho!). All downrange zeroing and stadiametric rangefinding (rangefinding with reticle stadia) is based on the most basic form of the mil-dot mil-ranging formula. Here it is--

tgt. size x range of reticle subtension measurement / reticle subtension / quantity of "gap" tgt. occupies = range

Looks complicated--super simple to apply. Let's say u're shooting at an antelope doe that measures 14" back to brisket, and the laser's not cooperating. U know that the subtension of that optic is 6.6 inch per 100 yds. (IPHY). U bracket the doe and u see that it occupies about 6 tenths the distance between x and plex post tip (PPT).  Now just plug in all the varaibles to calc. range--

14 x 100 / 6.6 / 0.6 = 350 yds. See how that part works?

Now use the same basic formula with a ballistics program for your load, this time tgt. size is bullet drop and the gap part is where to hold for your plex reticle. Ie. suppose u see that the bullet drops 15" @ 350 yds. from the ballistics profile. Here's the same calc--

15 x 100/6.6 / x = 350
 x = .6 the distance between x and PPT. See how that part works? Now do the same for 10 mph windage for that range (using your PPT's for windage reference)

heres what that entry looks like on your range sticker that's attached to the inside of your Butler Creek ocular cover (assuming .3 hold for windage--whatever it is)--

350-0.6-0.3

Now finish the chart in 25 or 50-yd. increments for your trajectory/reticle profile.

Of course these guys are right, with one minor change-- CALCULATE, verify, troubleshoot (if the profile isn't on the nose), then practice (x3...or whatever).

[sscoyote]

Here's how to practice--call the local brickyard and see if they have any cinder block molds they're getting rid of. These are 1/2 inch plate that'll take a bullet strike just as good as any steel out there (lbs. per $, that is). They'll usually give it to you. Burn holes in it for suspending (drills won't touch it). Get 3 pieces of steel rod (rebar's great), 2 copper or galvanized plumbing T's and couple steel S-hooks (from rubber bungee cords, that folks always lose off their vehicles. In other words they're found free on the road. The heavier ones that r closed on 1 end used on cargo tie-downs r even better--again free on the road). Now pound 2 of the rebar into the ground se the T's on top and slide the 3rd thru parallel to the ground. Get the el cheapo Wal-Mart paint @ 1$/can (white's what i use). and your set--Mom loves to hear the impact of bullet striking steel (just like everybody does)--



And another closer pic--

[usherj]

Thanks, sscoyote. Your info was exaclty what I was looking for. Plus you can read, as shown by your notice of my mentioning "field verify" in my post, which some failed to. I plan to use a 4'x4' target backer with alternating black and white 12" bars on the side so I can judge the relative dimensions compared to the reticle at varying ranges. I'll let you know how it turns out. Thanks again

[sscoyote]

Just ran your #'s thru JBM ballistics (sea level) and looks like your 400 yd. zero is right at the lower post tip (6.3 MOA). Be kinda cool to see just how well the system works. The 500-yd. zero is 10 MOA, which should be 5.7X using the lower PPT. Can u try it out that far where u're shooting? Be interesting to see if those calcs. r correct...or at least close.

[usherj]

Thanks again. Lots of info that I didn't know existed. I will try it out in a couple weeks. There is a 1,000yd range adjacent to my club, but use is limited because it crosses our access road. Of course elevation is entry level, reading and compensating for wind will take lots and lots of study and practice.