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Nikon scope problem

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Nikon scope problem

Postby ramsco on Tue Aug 22, 2006 11:45 am

HELP!!!!! I am mounting a new Nikon Omega scope - 3-9 with nikoplex on my TC Encore muzzle loader. First I used the one piece TC mount and could not get the scope to adjust high enough to hit the bullseye at 100 yards with two "777" pellets and saboted 240 gr bullets of TC make.
So, I purchased new two piece Maxima bases and weaver rings and tried again - same thing - can only get groups 4" low at 100 yards. I run out of scope adjustmant.
The bases mount flush and tight with the barrel and the rings are also tight. I get great 100 yard groups - 1.5" but can't adjust the scope high enough to get into the bullseye. I had a Leupold 1-4 and was able to adjust it with the one piece mounts.

Something is wrong and I think I have eliminated all possibilities except the scope...could it be at fault?
Should I just get on with it and shim it? (front or back?)
Thanks in advance for the help.
ramsco
 
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Postby Steven_L on Tue Aug 22, 2006 5:13 pm

Hi,

I'm very disappointed as well. Tell me, how much elevation adjustment did your Leupold have left? The catalog shows 67 MOA total, where the Nikon shows 60. If the Leupold was nearly out of adjustment, the problem is not your scope, it's your Encore barrel. You did right by eliminating any ring/base problem. The T/C Duo rings are superb. Pick out a 100 yard target and see if you can get 60 inches of elevation from your Omega scope.
I tried to call Nikon and ask them about any potential problems with this new offering, but I got older and greyer waiting on hold like normal. I perused the internet and forums, but the scope hasn't been out long enough for reports from the field.
That you're not using the 150 grain charge the scope is calibrated for should have nothing to do with it.
Many of us are interested in this new Omega, and it even crossed my mind that I might need one. I'd sure appreciate you keeping me informed. I first need to know the answer to the elevation questions so we can eliminate scope problems if possible.
Aim Hard!

Steve at OpticsPlanet
http://www.opticsplanet.net

Phone: (800) 504-5897
Fax: (847) 919-3003
Steven_L
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Scope out of useable adjustment range?

Postby MrGman on Tue Aug 22, 2006 9:07 pm

The short answer is, if your bullets are hitting low and you cannot raise your point of aim with the scope any further than you need to raise the rear mount. Either by shimming the mount on the barrel or shimming up the inside the ring on the bottom so the scope sits higher in the rear ring. My estimation is that you want no less than 10 mils (0.010 inch) increase and no more than 20 mils. If you raise the back end of the scope by that much and not raise the front end then the scope will point downward moreso at a slight angle and therefore to bring it to the point of aim on the target will raise the barrel and thus give you back some adjustment range. If this presents problems you can try milling out the front ring to lower it and not adjust the rear ring. I would not go past 10 mils for the first attempt. I have done this in the past and it works quite well.

You could first boresight the scope to the barrel as is. A laser boresighter at 50 yards minimum would be very good. If the scope cross hairs appear to be well below the red dot of the laser than the scope mounts and the scope are not your problem, it is you load. If the scope cross hairs are above your red dot and cannot come down any further your mounts are either not of the same thickness, your barrel or receiver outer dimensions are such that they are not parallel to the bore path of the barrel, or you scope isn't right (which I most seriously doubt).

If you have an optical boresighter you could do the same thing, its accuracy will be somewhat less but they do put you in the ballpark. And inthis case would still show you in which direction the error really lies.

I don't shoot muzzle loaders. I am guessing that two "777" pellets actually refers to two present loads of powder that are pelletized and is a certain total grain weight of some value that is less in energy than 150 grains of the type of powder normally used to launch a 240 grain slug to have the expected ballistic path. If its significantly less than the normal powder charge for a 240 grain slug, have you tried using more powder to see if the bullet path will reach above the point of aim that the scope is limited to? Or is 3 pellets considered too much charge for that particular slug and barrel? Can you simply try another loose powder that you can get closer to the "150 grain charge" that is expected?

I suspect that your new scope does have just 7 MOA less than the old one per the vendors published data just as Steve has determined and that the old one was already near or at the limits of adjustment but because it accomplished the task you never questioned the load.

If you are bound to this particular load for whatever reason, then tilting the scope downward (in front) or up (rear) mechnically is the way to go. I use 10 mil thick aluminum sheet stock to raise the rear mount or scope in the mount when I have to. Its no big deal. Good luck
MrGman
 

Thanks for the help

Postby ramsco on Wed Aug 23, 2006 8:11 am

Wow! what great replies. Thanks for taking the time.
Steve, I really like this scope. I opted for the nikoplex (standard) cross hairs instead of the range finding gimmick. That's made for 150 grains and I believe in the advice I got about accuracy vs big loads. The old buffalo gun (45-70) used only 70 grains of black powder and was accurate and had enough power to drop buffalo. So I am satisfied with 100 grains of the 777 AND it is more accurate from the bench than I can shoot the gun in the field. The scope is great with a long eye relief so settting it up in the summer and then shooting with a few layers of clothing in the winter it will still be right there! I'd buy another one if I had another Encore!
MrG, thanks for the great technical information. It always confuses me trying to figure which end is UP! I usually like to find the root cause for a problem rather than treating the symptoms but in this case becasue the gun shoots so accurately shimming the back mount is the way to go. We'll see this weekend how it works. The 777 is a newer pyrodex product that seems to be a bit more powerful than regular pyrodex and it is much cleaner, allowing for a somewhat "easy" second load in the field. With the plastic sabot, sometimes a local tree is needed to hold the "ram" end of the ram rod to seat the bullet. I did try what is described by some as the most accurate load of 93 grains of loose pyrodex but the 777 shoots as well and is so much easier in pellet form and as I said, it fouls less than regualr pyrodex. With the #209 shotgun primer as the cap, ignition is not a problem.
What I should do is get out the old TC Hawken I built and used to kill many deer. Open sights. blackpowder, patched ball - so much simplier!
Thanks again for all your help.
ramsco
 
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Postby Steven_L on Wed Aug 23, 2006 4:12 pm

Hi,

Ya didn't answer the questions! How much adjustment was left in your Leupold and how much total elevation do you have in your Nikon?
You bought top quality equipment and shims should not enter the picture, nor should any scope be at max adjustment. You have eliminated a mount problem. You have a mechanical problem with your barrel or your scope. Eliminate the possibilities and get whatever is left over fixed or replaced. Do it now while you have time before the season.
Aim Hard!

Steve at OpticsPlanet
http://www.opticsplanet.net

Phone: (800) 504-5897
Fax: (847) 919-3003
Steven_L
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Scope problems unanswered questions

Postby MrGman on Wed Aug 23, 2006 8:21 pm

Thanks for the kind words. For the sake of knowing the real source of the problem to solve the mystery it would be good to answer Steve's original question as to how much adjustment room in the vertical axis was there in the original Leupold scope. We both want to know if that scope was already at or within a few clicks of the end of its adjustment range to work on that particular rifle with that particular load.

Also if you can borrow a boresighter, (you should get one to keep for just these type of issues as they are good tools and so cheap to buy nowadays) and tell us if the cross hairs of the scope is already well below the centerline on the bore scope or above it. That will also help to answer whether its mounting issues or ballistic issues. It is possible that the mounts are offset or that the bore of the barrel is not concentric to the outer wall. One quick check I always do is to reverse the mounts if they are the type were that can be done, and see if the point of aim changes. May be that one mount was taller than the other.

I am sure we can solve the puzzle and fix the problem together. So please check the older Leupold scope and tell us if it was already at or near the end of its vertical range.

Thanks for explaining about the 777 pellet type powder. Have you chronographed this load to see what its velocity is? I am always curious about these things.
MrGman
 

I'm trying

Postby ramsco on Tue Aug 29, 2006 4:07 pm

Hey Steve, chill out! I'm trying my best. Had to go to Florida for a funeral so could not devote my time to the scope. The Leupold was not any where near fully adjusted. Looking at it now reminds me that with the one piece TC mount I could not get the scope close enough to my eye so I drilled and tapped two new holes so I could use two of the holes that came in the barrel and two new ones and move the scope back far enough to see out of it! So, the new rings are positioned back in the original holes and perhaps the barrel is causing this "tilt" Ballistics is NOT the problem as this load is the one I used previously and is recomended by TC.
I shot it this weekend after shimming the back of the base and it has mucho adjustment up and down. Shoots fine. HOWEVER I will invest in a laser bore sighter so I can play with the possibilities -switch the mounts and be able to get it back on paper easily.
Thanks again for your help!
ramsco
 
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Location: NJ

Postby Steven_L on Wed Aug 30, 2006 5:17 pm

I'm chilled and truly sorry for your loss. Glad you have an idea what happened and I anxiously await the results from your latest experiments. Good luck!
Aim Hard!

Steve at OpticsPlanet
http://www.opticsplanet.net

Phone: (800) 504-5897
Fax: (847) 919-3003
Steven_L
Site Admin
 
Posts: 2244
Joined: Fri May 19, 2006 10:35 am

Scope problems resolved

Postby MrGman on Fri Sep 01, 2006 8:24 pm

Also my condolences for your loss.

Can you tell us how thick a shim you used to bring it into useable range? Also look forward to hearing more of the experimentation results.
MrGman