Length of Case - Useful for Zeroing

Heym SR20

Well-Known Member
I had a session on the range the other day - not overly successful as very hot, barrels hot, heat haze and thought scope had crapped out as it was shooting a bit too high. Cool of the day its all fine.

But key thing was I wasn't quite how high it was shooting and of course didn't have a tape measure with me.

In the cold light of two days later just sitting at my desk with the target in front of me and its much better than I thought. All rounds into an 1 1/2" group. And have discovered and will patent a very useful measuring stick.

A Cartridge Case.

Now a 243, 7-08 or 308 case is 1 1/2" (give or take a nats testicle) from the base to the shoulder and 2" or 50mm long

So at 100 yds, go to your target, base of cartridge in middle of target, shoulder of case middle of group. Thats a 200 yd zero for most rifles.

For those with longer cartridges

7x57 - shoulder is at 1 3/4" and case length 2 1/4" or 57mm

And the 7x65R (long 30-06 length) is 2" to the shoulder and 75mm long overall (a bit over 2 1/2").

So there in solves the problem.
 
except i have a thin thumb and its less than 1" wide its not 1" from nuckle to tip either. this is where i went wrong - convinced myself i was shooting 3" high.

Just measure the width of your thumb, or a finger. It doesn't matter what the actual measure is: it just gives you a reference value.

So my thumb is 2cm wide, and I go from there.
 
never have subscribed to this so much high at 100 is a 200 yd zero , just zero properly at the range you want then adjust accordingly with your turrets or aim off.
 
I'm inclined to agree with tackb. However if you want to zero high why not just use one of the print off targets that have a 1" squared background?
 
never have subscribed to this so much high at 100 is a 200 yd zero , just zero properly at the range you want then adjust accordingly with your turrets or aim off.

Tend to agree with Tackb. While I usually "zero" 1 1/2" high at 100 yards I always wonder what it actually is at 150/175/200 yards. I know what the ballistic charts say but? Next time I zero I will try some shots at more distant targets to get a better feel for the "actual" bullet drop at distance. I suppose it's all about confidence.

Willie
 
I used to zero an inch high at 100yd. Now I zero bang on at 100 and aim off at longer ranges- much more straightforward I think. 1" is quite a lot if neck shooting. I forgot about the 1" high and 'creased' an 80yd neck shot hind last year. Dropped on the spot but up and off a minute later. The experience changed my mind- bang on 100 yd zero keeps it simple, I think.
 
Over here the accepted rule of thumb regarding drop with normal deer cartridges ie 6,5x55 308. 30-06 with a muzzle velocity of around 800m/s is 15cm low at 200m and 50cm low at 300m if zeroed dead on at 100m.
 
Over here the accepted rule of thumb regarding drop with normal deer cartridges ie 6,5x55 308. 30-06 with a muzzle velocity of around 800m/s is 15cm low at 200m and 50cm low at 300m if zeroed dead on at 100m.

many use the 209 system here , 200 yd zero , 2" high at 100yds and 9" low at 300yds , it works near enough for killing shots on uk deer out to 300yds
 
I use rule of thumb literally. My thumb joint to tip is 1.25" and across the joint measures 1". My rifles shoot approx. a thumb high at 100 and a thumb low at 200.
 
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