Is it "really" 100 yards?

[miningshawn]

For years I have done work ups and groups from the same benches and shooting to the same target boards at my local range. I was making adjustments to my ballistic tables for the upcoming season when I had a passing thought - "I wonder if it really is 100 yards?".

I measured a few mornings ago and lo-and-behold, 103 yards using the Vortex Razor HD 4000. Being a surveyor by trade I brought out a Trimble S9 and a prism and verified at 309.138 feet.

For the average Joe sighting in a hunting rifle, a rando plate banger, or a non-competitive shooter the distance wouldn't be as critical. When shooting past 600 or so yards it really shows up in the drop number!

 

[Big Mc]

For years I have done work ups and groups from the same benches and shooting to the same target boards at my local range. I was making adjustments to my ballistic tables for the upcoming season when I had a passing thought - "I wonder if it really is 100 yards?".

I measured a few mornings ago and lo-and-behold, 103 yards using the Vortex Razor HD 4000. Being a surveyor by trade I brought out a Trimble S9 and a prism and verified at 309.138 feet.

For the average Joe sighting in a hunting rifle, a rando plate banger, or a non-competitive shooter the distance wouldn't be as critical. When shooting past 600 or so yards it really shows up in the drop number!

I am a RPLS here in Texas, and have found my local range has the same problem. I hope you can come up with a fix. Tommy Mc

 

[Ned Ludd]

At my range, the distances are neither in yards, nor meters. I've lasered all the ones I regularly use and recorded the values, so it's not a big deal to me. However to anyone that doesn't know, their predicted drops may not always match up very well.

 

[Rocketvapor]

Using your favorite ballistics calculator what is the difference in a 100 vs 103 yard zero?
@ 600 or 1000 yards? That's drop from 100 to 103 yards built in error.
3 yard error @ 600 (really 597 or 603) is bigger when the bullet is falling out of the sky

 

[drop_point]

If I plug 100 vs 103 on most my rifles, it doesn't make a lick of difference and is within the click values of my scopes.

 

[Rocketvapor]

Try 595 to 605 yards with a 600 yard zero and 1 yard steps in your calculator.
3 yards is a little more than 0.1 MOA
+/- 3 yards at 1000 yards is about 0.2 MOA

 

[JFrank]

For years I have done work ups and groups from the same benches and shooting to the same target boards at my local range. I was making adjustments to my ballistic tables for the upcoming season when I had a passing thought - "I wonder if it really is 100 yards?".

I measured a few mornings ago and lo-and-behold, 103 yards using the Vortex Razor HD 4000. Being a surveyor by trade I brought out a Trimble S9 and a prism and verified at 309.138 feet.

For the average Joe sighting in a hunting rifle, a rando plate banger, or a non-competitive shooter the distance wouldn't be as critical. When shooting past 600 or so yards it really shows up in the drop number!

Makes a huge difference at a 1000 yards

 

[Rocketvapor]

How huge?
100 yard zero @ 1000,
100 yard zero @ 1003,
103 yard zero @ 1000,
103 yard zero @ 1003 yards?

I guess it has something to do with drop per yard.

 

[Mikemontminy]

How huge?
100 yard zero @ 1000,
100 yard zero @ 1003,
103 yard zero @ 1000,
103 yard zero @ 1003 yards?

I guess it has something to do with drop per yard.

.22 LR real huge.

 

[Rocketvapor]

what's your drop per yard @ 100 vs drop per yard @ 1000


Some ranges with a slab might be set up for prone from the grass in front of the slab for prone competition..

 

[6MMsteve]

I use google earth it says 317 ft

 

[Rocketvapor]

My local range, Honey Island Shooting Range measures 302 ft from front of slab to target stands using Google .
My range finder says 301 ft.
Using a 28" barrel sticking out past the slab several inches and I'm pretty close

 

[alf]

So do you measure from the scope or the muzzle.......

 

[dellet]

Sue them for false advertising.

Actually its probably not all that uncommon to have the "100 yard target" actually be 100 meters. I know of at least two.

 

[Rocketvapor]

100 meters is 328 ft.
That's not fair for those that use MOA.

 

[dellet]

100 meters is 328 ft.
That's not fair for those that use MOA.

Really sucks when you go to a 22 shoot and know one tells the new guy.

 

[miningshawn]

Wow, can of worms opened...

So 3 yards at 100 yards is a 0.03 difference. That would mean a 3% difference at any other given range. Using a .308 RPR shooting a 185gr Juggernaut at 2630fps (my training rifle, coincidentally) lets see what happens at 1000 yards - WITHOUT CORRECTION.

(0.03%)*(1000) = 30
1000+30=1030
The drop at 1000 yards using Strelok Pro (my primary shooting app) is 30.71 MOA
The drop at 1030 yards using Strelok Pro at 1030 is 32.25
32.25-30.71=0.54 MOA.
(0.54)*(1.047)*(10)=5.654 inches

Let's discuss an all-too-probable scenario. I show up at the range early in the morning of the day I want to shoot. I know that today's weather is forecasted at 92 degrees, but I did my work-up at 44 degrees. I stop by the sight-in board to do a quick check and I group slightly higher than usual, so I either hold bottom-of-plate on long shots, or do an actual zero adjustment. (Not wanting to change my zero stop, you can guess which one I choose). The first course-of-fire is a 12" diamond at 1020 yards. I plug in 1020 to Strelok and it tells me 31.73 MOA. Using the same math above I would have seen 30.15 MOA If I had calculated for a 103 yard zero. The bullet sails over the top of the target, most likely off-center because my wind holds aren't tuned in yet.

This actually happened. I went back to the range and found out exactly how it happened.

Now it's 7 months later and I am not in a hurry. If I would have known then what I know now, I may have had better results on that very important first course-of-fire and been much more confident on the following.

Lesson learned... Check your zero distance!

 

[6ShotsOr5?]

There is a well known LGS with pistol and rifle ranges, and trap and skeet fields, in north Houston area, address is on Treaschwig Road. Their rifle range had gotten shorter over the years due to real estate development behind the range. The longest range now is supposed to be 100 yds, but I measured it with a laser and it measured 88 yds. If you zero there and tell your ballistic engine that you zeroed at 100, you will be way off at long range.

 

[Fuj]

Old school..... I used my 100 ft. Lufkin tape. From the front
of our benches, Our target frames are 10 inches too long.
Considering how much barrel is hanging over the bench,
close enough.

 

[jdh47]

Well now that you know you can compensate right?