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Large Mag Scope question


killer_pigeon
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Technical question please

 

I have a 5-30x50 scope and normally shoot 100-300 yards, went out on sunday and tried to zero it at 600 yards and it wouldnt click round enough, ie it ran out of clicks on the elevation.

 

is this normal for a large mag scope to have limited bullet drop range ? or is it just the scope limiting me?

 

Its on high rings and could possibly go on medium rings at a push but Im not sure it would help, would i be better on with lower mag

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I have a similar problem with a Nikon 8-32 x 50, the adjustment is quite limited.

 

When setting the scope up in the first place the vertical adjustment needs to be centred (wind from on end to the other counting clicks and then half way back again) and then use shims to pack the mount.

 

In your case, decide whether you need to add a shim to either the front mount or the back mount, loosen things off a bit and slide in a thin shim (old negative or cut from coke can). That should enable you to wind things back and get you within the range of turret adjustment once more.

 

Using shims is a completely standard technique even though purists may suggest otherwise.

 

600 yards...... blimey!

Edited by dadioles
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What might "make do" on a low end scope is a lot different to the "purist" approach when considering high end optics on serious rifles generating recoil. It is without doubt that when you deliberately distort a scope tube you are inviting problems with both consistent zero and permanent tube damage.

 

I think the original post was a good question to ask when in doubt and if it is a Z6, im sure he will want to make sure he does not damage the scope and will use the correct mounts or bases to solve his problem, not a coke can.

 

Don't be so disparaging about a coke can - drinks cans are an excellent source of high quality thin sheet aluminium or steel.

Shimming a scope is standard practice and it is easy to cut a small square of metal from a coke can which is only a few thousandths of an inch thick in order to fractionally raise the scope tube within a mount. You are not distorting the tube but obviously need to intelligently apply the correction.

I take your point about the cost of the scope which suggests that the op should be able to afford a new set of rings which can cost as much as a half decent scope and still need tweaking.

 

Ideally, the turret adjustment should be more or less centred when the rifle is shooting at zero. That leaves plenty of adjustment and ensures that the lenses in the scope are lined up optimally. This is achieved by shimming. Too often I have seen guns with the scope turrets adjusted almost to the end of their travel and all that serves to do is misalign the optics and increase glare from stray light.

 

Scope manufacturers approve of shimming - presumably they know what they are talking about - you can even buy shims, but it is easier to cut your own from thin sheet aluminium or steel (back to the coke can). A drinks can has a wall thickness around 0.003" which should be more than enough to get your scope back nearer the centre.

 

Bushnell produced this guide:

 

SHIMMING FOR MAJOR ELEVATION ADJUSTMENTS:

 

• Shim Front Base For Additional Down Movement

• Shim Rear Base For Additional Up Movement

• For Major Windage Adjustments We Suggest Using A Windage Adjustable Mount

• For Best Results Use The Lowest Profile Mounts Possible

 

 

SHIM TABLE

 

DISTANCE (Yards) _ SHIM THICKNESS (Inches) _ POINT OF IMPACT (Inches)

25 ---------------------- .001 ---------------------- 0.25

50 ---------------------- .001 ---------------------- 0.50

100 --------------------- .001 ---------------------- 1.0

200 --------------------- .001 ---------------------- 2.0

25 ---------------------- .002 ---------------------- 0.50

50 ---------------------- .002 ---------------------- 1.0

100 --------------------- .002 ---------------------- 2.0

200 --------------------- .002 ---------------------- 4.0

25 ---------------------- .003 ---------------------- 0.75

50 ---------------------- .003 ---------------------- 1.5

100 --------------------- .003 ---------------------- 3.0

200 --------------------- .003 ---------------------- 6.0

25 ---------------------- .004 ---------------------- 1.0

50 ---------------------- .004 ---------------------- 2.0

100 --------------------- .004 ---------------------- 4.0

200 --------------------- .004 ---------------------- 8.0

25 ---------------------- .005 ---------------------- 1.25

50 ---------------------- .005 ---------------------- 2.5

100 --------------------- .005 ---------------------- 5.0

200 --------------------- .005 --------------------- 10.0

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I'm still confused as to why you would want to zero @ 600yds. If you are setting up a ballistic turret then I fear you are pushing the bounds of functionality and morality with this... will you honestly be shooting at a live target as far out as 600yds? if the answer is yes (and this isn't a critical response, each to their own) then quite frankly, you are using the wrong scope for the job, you need something designed to give you the flexibility out to that kind of range... PMII or similar tactical scope, not only will that give you the elevation but also will give you the markings you need for holdovers, something the Z6i doesn't do... (I do have one btw!)

 

If you are using the Z6i for log range target use then again, the above stands... it isn't designed for it and doesn't have the features you need for it.

 

As for shimming and ring elevation, the general rule of thumb is to have a base (or rings) that gives half again the total elevation range of your scope, so, for example, if your scope have a total of 40 MOA of travel, you should ideally use a base or rings that have 20 MOA of elevation built in, that will give you the optimum range for your scope.

 

I also don't care what any one says (even the manufacturers! I doubt you would find Zeiss, Swaro or S&B saying it's ok to shim!) shimming WILL put unwanted stress on the scope tube, mechanically, it has to! Inagine your rings as paralel lines. If you shim one up then the paralel lines won't match, they will be offset. Not a problem if you can change the angle of the rings to compensat, but you cant, therefore you are going to risk damage to your scope.... I certainly wouldn't do it on my 2K + scopes!!! buy a base or rings with the correct elevation built in.

 

Bodge a £200 scope :yes: not a £2,000 scope :no:

 

My PMII on my TRG has 90MOA (ninety) of elevation adjustment, I still have a 20MOA base on there though (S&B suggest it should be 40MOA but I have no desire or opportunity to shoot out to 2,000 yards! :lol: ). This ensures that even when shooting out to the extremes.. 1,100, 1,200 yards, I am not putting any undue pressure on the internal mechanics.

Edited by Vipa
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