Rifle Scopes i need help scope wont zero 20 moa base bushnell

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bbhank

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    • Aug 9, 2009
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    #1
    Hey guys I have a question:

    A freind is working with a 98 mauser that has been converted to a 308. We put a 20 moa ken farrell base on it and the glass is a bushnell 6500 series with 50 minutes of adjustment. There is a little over 3/8"s inch between the bottom of the objective and the barrell.

    So here's the problem with the scope all the way bottomed out is still shooting 4' to high.....

    Please help
     
    #2
    Re: i need help scope wont zero 20 moa base bushnell

    it appears that you have to much cant in your base. if you switch to a 15moa base you might just might make it on target with the scope bottomed out. or maybe taller rings. its a geometry problem.
     
    #4
    Re: i need help scope wont zero 20 moa base bushnell

    Id say this sounds like you have some other issue besides the scope or mounting. IE rifle issues. Even 20moa is only going to give you 20" of adjustment at 100yds, and even less if you are zeroing closer.

    My guess would be when the barrel was installed to the action it is not true. Just a guess.
     
    #5
    Re: i need help scope wont zero 20 moa base bushnell

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jonaddis84</div><div class="ubbcode-body">Id say this sounds like you have some other issue besides the scope or mounting. IE rifle issues. Even 20moa is only going to give you 20" of adjustment at 100yds, and even less if you are zeroing closer.

    My guess would be when the barrel was installed to the action it is not true. Just a guess. </div></div>


    I would entertain this idea however the rifle was zero with a different base and scope combo. the rifle has shot 3/8" groups at 100 all day long previously. I am sure its in the
     
    #6
    Re: i need help scope wont zero 20 moa base bushnell

    Interesting, your problem is backwards of what you normally run into, especially since the bell is still 3/8" off the barrel (quite high).

    Have you tried removing everything (scope,rings, base) cleaning the mating surfaces, and going through the whole procedure again?

    If you have another scope with the same tube diameter, put the gun in a vise with the 6500 on it, pay attention to where the crosshairs are at, remove the scope and just set another one in there and see if its in the same general area.

    Possibly you got a bad scope, but thats such a huge error if you are bottomed on elevation and still 4' high. At least if you get it zeroed youll never run out of elevation!
     
    #7
    Re: i need help scope wont zero 20 moa base bushnell

    im thing the issue is in the height of the rings and base, my thing is the center line of the scope and teh center line of the bore are two far apart. does anyone know how the measurement between the two centerline effect zero?
     
    #8
    Re: i need help scope wont zero 20 moa base bushnell

    First off, at what yardage is it shooting 4ft high?

    Just to confirm, when you say it is shooting 4ft high, you mean the bullet is impacting 4ft ABOVE the crosshair correct?

    If that is the case, having the scope mounted high above the bore-line would cause the reverse of your problem (bullet impacting BELOW the crosshair). Unless you are shooting at 25-50yds where the bullet is climbing above the scope centerline, but 4ft is still very extreme for this. With my scope mounted 1-7/8" above the bore centerline, my bullet path is 1.1" above the scope centerline at 25 yards, not 4ft.
     
    #11
    Re: i need help scope wont zero 20 moa base bushnell

    remove scope remove 20moa rail turn rail 180 degrees and reinstall replace scope and try again.
    the thinner end of a rail goes at the barrel end the fat end goes toward the shooter.

    before you do the above try below.

    pull the bolt and sand bag the gun so you can see the target in the center of the bore. look through the scope and see where the cross hairs are pointed. can you dial the hairs on to the target?. recheck through the bore that the target is still centered. doing this will at least show you if the knobs are moving the crosshairs in the hoped for direction.
     
    #12
    Re: i need help scope wont zero 20 moa base bushnell

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BadBot</div><div class="ubbcode-body">remove scope remove 20moa rail turn rail 180 degrees and reinstall replace scope and try again.
    the thinner end of a rail goes at the barrel end the fat end goes toward the shooter.</div></div>

    I was going to suggest this, but gave him the benefit of the doubt.
     
    #13
    Re: i need help scope wont zero 20 moa base bushnell

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BadBot</div><div class="ubbcode-body">remove scope remove 20moa rail turn rail 180 degrees and reinstall replace scope and try again.
    the thinner end of a rail goes at the barrel end the fat end goes toward the shooter.

    before you do the above try below.

    pull the bolt and sand bag the gun so you can see the target in the center of the bore. look through the scope and see where the cross hairs are pointed. can you dial the hairs on to the target?. recheck through the bore that the target is still centered. doing this will at least show you if the knobs are moving the crosshairs in the hoped for direction.

    </div></div>

    For real.Old school bore sighting does work and it does sound like the base is canted wrong.

    ~Reagan
     
    #14
    Re: i need help scope wont zero 20 moa base bushnell

    The point of a 20 MOA rail is to give you more elevation to crank out to longer ranges. If the rail was backward it would be hitting low.

    It sounds like for whatever reason you are getting more than 20MOA of cant in the scope, a lot more. I'm going to assume that the rail is in the right configurations, high end back, if it's not you have real trouble. Four feet is HUGE! At ~1moa per inch you are 48MOA high! If you assume that the scope should have zeroed at about the center of its travel on a flat base then you should be about 5moa off the bottom with the base, so based on that you're about 53MOA higher than you should be.



    First check that everything is tight and there is nothing under the base, next make sure you got a 20MOA base and not a 50 or 60MOA base. Looking at Farrells website they sell bases to 60MOA. That's my first guess.

    Next I'd first try reversing the rings. If that fixes it you somehow have rings with cant built in.

    Other than that go to another scope and see what that tells you. If it will zero then it's your scope, if it wont then it's something in your mounting.
     
    #15
    Re: i need help scope wont zero 20 moa base bushnell

    another option is to shim the front ring so the scope is pointing more inline with where your barrel is. I had the same problem on a range rifle, was shooting a foot and a half too high for a 300 yard zero, put a bit of brass shim stock under the front ring and tightened it down, this raised the scope just enough so that I had 4 minutes of down left once I got my zero.

    the way it was explained to me is, the barrel was pointing higher than my point of aim (with the scope bottomed out), so by shimming the ring, it raised the scope up just enough to bring these two inline.

    and before someone asks, it was a 20MOA base and WAS on the right way.
     
    #17
    Re: i need help scope wont zero 20 moa base bushnell

    maybe im confused but if its shooting 4 feet ABOVE the crosshairs at 100 yards then you went too far... adjust up... with the way you have it now the POA will meet the POI at a much further range. the crosshairs being 4 feet low at 100 yards at 1000 yards would equal 40 feet low if the bullet impact stayed level but since it dosent and at 1000 yards drops maybe around 400 inches or so in a .308 then that equals around 33ft of bullet drop...

    so you have a little down adjustment to go beyond 1000 yards. so if your crosshairs are below the POI now and your bottomed out then go UP with the elevation... your adjusting the reticle when you turn the turrets not the barrels angle vern.

    4 ft in MOA means you need 48 MOA up or 192 clicks if its a 1/4 inch click scope. if its in mills thats 13.3 mills or 133 clicks on a .1 mill adjustment scope. UP UP AND AWAYYYYY!!!!

    if the scope was maxed out up then you would be screwd but its maxed out down as i understand it.

    am i the only one who really got this or am i missing something? keep in mind im new to this stuff but looking at the data it looks right on the money with the 20MOA base... or do i have my up and down confused?...or do you guys?...
    shocked.gif


    EDIT: ..but thinking now i have it confused aswell...but it still sounds right if by chance OP had up and down backwards
     
    #18
    Re: i need help scope wont zero 20 moa base bushnell

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kentactic</div><div class="ubbcode-body">maybe im confused but if its shooting 4 feet ABOVE the crosshairs at 100 yards then you went too far... adjust up... with the way you have it now the POA will meet the POI at a much further range. the crosshairs being 4 feet low at 100 yards at 1000 yards would equal 40 feet low if the bullet impact stayed level but since it dosent and at 1000 yards drops maybe around 400 inches or so in a .308 then that equals around 33ft of bullet drop...

    so you have a little down adjustment to go beyond 1000 yards. so if your crosshairs are below the POI now and your bottomed out then go UP with the elevation... your adjusting the reticle when you turn the turrets not the barrels angle vern.

    4 ft in MOA means you need 48 MOA up or 192 clicks if its a 1/4 inch click scope. if its in mills thats 13.3 mills or 133 clicks on a .1 mill adjustment scope. UP UP AND AWAYYYYY!!!!

    if the scope was maxed out up then you would be screwd but its maxed out down as i understand it.

    am i the only one who really got this or am i missing something? keep in mind im new to this stuff but looking at the data it looks right on the money with the 20MOA base... or do i have my up and down confused?...or do you guys?...
    shocked.gif


    EDIT: ..but thinking now i have it confused aswell...but it still sounds right if by chance OP had up and down backwards </div></div>

    I guess he could be turning the knob the wrong way. The up --> on the knob means the impact goes up, not the cross hairs. That would actually explain it, if he's going the wrong way it will have 2 MOA left. I guess they could be going the wrong way.
     
    #19
    Re: i need help scope wont zero 20 moa base bushnell

    yeah i slapped myself... but as i was confused so perhaps he may be aswell... because like i said it makes sense if he has them backwards. it would all add up... :p
     
    #20
    Re: i need help scope wont zero 20 moa base bushnell

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kentactic</div><div class="ubbcode-body">yeah i slapped myself... but as i was confused so perhaps he may be aswell... because like i said it makes sense if he has them backwards. it would all add up... :p </div></div>

    You make perfect sense.Thats how I see it.If you install a 20moa rail on the correct way,the scope is zeroed(equal moa up/down)then don't you turn the POI up?I install my -20 moa rails and then add +20 moa to my scope to be back at zero.Doesn't this make sense??Also,1 moa is 1" at 100yards.You guys do the math for 4ft high...hmm

    ~Reagan
     
    #21
    Re: i need help scope wont zero 20 moa base bushnell

    Not going to read all of this crap... but if the problem is that you installed the base and you're out of down travel to get you zero'd at 100, just skim bed the base with the front a hair higher than the rear.
     
    #22
    Re: i need help scope wont zero 20 moa base bushnell

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: brasscow</div><div class="ubbcode-body">Not going to read all of this crap... but if the problem is that you installed the base and you're out of down travel to get you zero'd at 100, just skim bed the base with the front a hair higher than the rear. </div></div>

    I think he has bigger problems than that, the initial post said he was out of travel and 4 feet high at 100 yds, that's ~48MOA too high. Either something is broken or the elevation knob was being turned the wrong way.
     
    #24
    Re: i need help scope wont zero 20 moa base bushnell

    Sorry Guys,

    I should have updated every one, turns out there was a manufacturing flaw in the base. I will gladly tell you the base was made by Ken Farrell and before anybody flames him I will have you know that we are more than satisfied with the solution. Some how the rear of the base left the shop way outta of spec. So not only is Ken going to replace it he is going to redesign the base so it matches one of his low profile bases. Not only that but he insisted in getting all the specs regarding the action and barrel so he set up my buddy with the right rings as well. Nobody is perfect and everyone makes mistakes, however Ken's customer service philosophy is perfect. I recommend that all of you buy his products, he is truly a great guy.

    SCL
     
    #25
    Re: i need help scope wont zero 20 moa base bushnell

    Ah well good to hear its just the base and not the scope.

    Problem will be solved in no time and before you know it, enjoying the pleasures of shooting.

    Still going with a 20MOA base?
     
    #26
    Re: i need help scope wont zero 20 moa base bushnell

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: send it 77</div><div class="ubbcode-body">Sorry Guys,

    I should have updated every one, turns out there was a manufacturing flaw in the base. I will gladly tell you the base was made by Ken Farrell and before anybody flames him I will have you know that we are more than satisfied with the solution. Some how the rear of the base left the shop way outta of spec. So not only is Ken going to replace it he is going to redesign the base so it matches one of his low profile bases. Not only that but he insisted in getting all the specs regarding the action and barrel so he set up my buddy with the right rings as well. Nobody is perfect and everyone makes mistakes, however Ken's customer service philosophy is perfect. I recommend that all of you buy his products, he is truly a great guy.

    SCL </div></div>

    That makes sense.I hope all works out.Goodshootin'

    ~Reagan
     
    #27
    Re: i need help scope wont zero 20 moa base bushnell

    In these days and times it is hard to find something that is made good and when you do seems like their customer service is bad.But is good to hear that he is going above and beyond to make it right.People like that in the economic times we are in are far and few between so I think the outcome is very good.
     
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