Using my 'furry calculator' to zero a scope w/1/4" clicks

Discussion in 'Large-Bore/Small-Bore Rifle/Shotgun' started by jim brady, Nov 6, 2015.

  1. jim brady

    jim brady Well-Known Member

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    A short time ago, I mounted an old 3X9 scope on my Marlin 336 in order to work up a 'best load' for my .30-30 that I'd never reloaded for before. I've had many standard hunting scopes over the years, and I usually bore sight the scope before going to the range to fine-tune it for my typical 100 yard zero. What I found, while trying to get the scope/rifle on paper at 25 yards was something I'd never really thought about before: the exact number of clicks to move a bullet impact one inch at various distances. Knowing that my impact will change 1/4" at 100 yards for each click, here's what I re-discovered:

    For 25 yards - to move the impact 1 full inch took 16 clicks
    For 50 yards - to move the impact 1 full inch took 8 clicks
    For 100 yards - of course the scope needs 4 clicks to move 1 full inch.

    The scope was off about 3 full inches both windage and elevation, so it took 48 clicks to move the impact to the center of the bullseye on a target set at 25 yards. I used to just fire a group, and guestimate how many clicks to adjust the scope, fire again and repeat the same thing. Using the formula about should save a bunch of ammo to zero. You still need to know the trajectory at different ranges for your caliber/rifle, but this should help. At least I hope so.
     
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  2. langenc

    langenc Active Member

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    For some reason many scopes don't have the click value noted on them.

    I occasionally run across someone having trouble w/ getting on paper. When I told the fellow that he needed to go down 88 CLICKS he said "NO-the gunshop bore sighted it" and he would only move about 10 click at a time and only windage or elevation separately.

    Oh well. It was his $45 worth of slugs that he wasted.

    Another friend was shooting a lever w/ scope and not doing well. Finally I hollered --CEASE FIRE....when I noted the turrets were on the top and LEFT of the mounted scope. That scope was mounted by a gunshop. I told him to take it back and get his money refunded. He said "they are out of business" and I said "No wonder..."
     

  3. tuckerd1

    tuckerd1 Moderator Supporting Member

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    I tried to explain that to a friend a week ago when we were testing new scopes at 25 yds. He was hard headed. He shot a lot of bullets before he got the desired result.

    I then set down with a rifle with a new scope. Shot my first round which was on paper. I went to cranking on the dials without counting. He just looked at me kind of funny. It only took about 6 shots to get me high and center on the paper.
     
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  4. flintlock

    flintlock Well-Known Member Supporting Member

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    It's good to know the click value. I just use a bore sight to roughly zero the crosshairs. The with the rifle well rested and the turret covers off, I'll shot the target, usully at 25 yards. Saves walking. Then I'll have my shooting buddy adjust the scope while I hold on the target until the cross hairs are centered on the first shot. The second shot will be pretty close to the point of aim. Then I'll move it back and fine tune it. Saves a lot of ammo, give me good results.
     
  5. jim brady

    jim brady Well-Known Member

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    I've seen a lot of "experts":rolleyes: working in Gun Shops. I know someone will come back and say 'Brady's Furry Calculator needs batteries' - but what I wrote is a general hint for figuring out how many clicks to move most scope's.

    I've found that the best thing (for me) was to get the rifle shooting at 50 yards for windage and elevation for a newly mounted scope, then, after your windage is set and your elevation is close to the bullseye, THEN to move out to 100 yards. For the first 50 yard shots, you can get a really steady hold - carefully squeeze - and look where the bullet impacts. I walk in my targets like that, and I've found it saves a lot of ammo. No need to fire a group - you are just walking in your zero. As long as you shoot carefully ONE shot at a time is all it takes.

    When you get out to 100 yards to set your zero, you want to fire slowly so as not to heat up the barrel - that will change your point of impact. Some guys shoot 3 round groups - others like a 5 round group. As far as I'm concerned, 3 rounds tells me where my sights are as long as I'm doing my part.

    I like Flintlocks suggestion of moving the crosshairs to the point of impact. Works great as long as you have a very steady rest.
     
  6. Don Fischer

    Don Fischer Well-Known Member

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    After bore sighting I always fire a shot at 25yds and then with the same hold on the target move the cross wires to the bullet hole. That will get you on paper at 100yds. Then after the first shot at 100yds I do the same thing if I'm using a strong enough scope to see the holes. One small diff here, some times I take the original POA and move the bullet to where I want POI to be. Two shots and you are pretty much there.
     
  7. Jeff Brown

    Jeff Brown Well-Known Member

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    I generally at 25 yds with new scope. shoot 3 for print. then while holding on target my exact hold for previous shots.

    I have a friend move turrets until cross hairs line up to impacts. then move to 100yds and repeat.

    Takes a little practice to hold then gun and let the crosshairs move. but after a couple attempts it gets pretty easy.

    6 to 9 rounds to get on at 100 and only because I shoot 3 for print