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Author Topic: Scope trouble  (Read 1097 times)

Offline Barebuck

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Re: Scope trouble
« Reply #15 on: September 06, 2020, 10:05:04 AM »
I just had the same issue with a new scope mounted on a new magnum rifle. I wonít mention manufacturer name.

But here goes it:

First of all a little history. I just happen to be a Tool and Die Maker by trade and working to .0001Ē is a daily occurrence. Iíve been in the trade for close to 26 years and I might have a good idea how to measure things.

Ok. New rifle and Iím breaking in the barrel according to manufacturerís procedure which requires a 50 shot process with lots of cleaning, so Iím not worried about having the scope dialed in instantly. As Iím reaching 35ish shots I notice my sub MOA gun is not repeating. Iím doing three shot group. Id make elevation and windage corrections before the next group of shots. Proceed to shoot my three rounds. The first shot would be close but no where near sub MOA. By the third shot its way the hell off.

Now Iím getting pissed thinking itís my rifle. Iím three weeks from hunting season and donít want to deal with warranty issue. So I take the gun to work. First thing I do is take the gun apart, I mean every down to the roll pins in the bolt. Iím measuring and inspecting everything. Itís all good actually very good to the point Iím impressed with the craftsmanship, very impressed. Which is tough to do with a toolmaker. I clean everything (like medical room clean), and put the gun together. On the way, I do some polishing, edge softening and edge breaking to improve the cycling of a short action magnum, but thatís a different story.

Next up, the scope. First thing I do is clean the scope with denatured alcohol and a soft cloth. Low and behold as I rotate the scope around I see scratch marks the width the rings and itís only on the bottom half (the reason why I didnít  see it earlier). Houston we have a problem. I measure the 30mm scope itís right on the ding dong at 1.1811Ē (30Mm). Next I visually inspect the rings, look fine. On the inspection table I put a ring on the scope and torque it to 16 in/lbs. I grab the 1-2Ē micrometer and measure parallel with the parting line on the scope, it measure 1.1836Ē. This tells me the scope is belled out .0025Ē. Next I measure 90 degrees to the previous measurement. I get 1.1789Ē, this way the scope is smashed .0022Ē. Not good. I take the scope rings off. Clean them up and head back the 5-axis CNC. I use it as a CMM (coordinate measuring machine). The rings end up measuring .0023Ē big. Yep, the companies (rings and scope same manufacturer) top shelf rings measure .0018Ē larger then the spec which was .0005Ē.  A total of .0023í above nominal ..... (suggestion buy scope and rings from same manufacturer. If they are not and thereís a problem theyíll point the finger at the other guy when addressing it). So, mechanically whatís happening is thereís two point loads on the scope, the top and bottom.

Now that I know the problem I call the manufacturer tech support. I attempt to explain to him what is happening, why and how I know. Iím not sure he understands. I ask him how we are going to resolve this. He tells me to try torquing it down to 20-21 inch/lbs. and put a piece of tape next to the scope ring which would be an indicator the the scope is moving.

Hunting season is near and now I donít want to deal with warranty issues, again. So, I mount the scope, torque to the new suggest in/lbs and go one step further. I put loctite on the ring surface. This Significantly increases the coefficient of friction. I head to the range, shoot five times, and have the gun dialed into 1.5 MOA (which realistically is about my accuracy). I havenít had the problem since.

In December, Iíll be contacting the manufacturer about some quality control issue and hopefully trying out their warranty. Itíll be a fun process which will start with tech support. They wonít be able to address it so Iíll have to work up the chain of people. Fun, fun, fun..

 






Offline wadu1

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Re: Scope trouble
« Reply #16 on: September 06, 2020, 10:08:24 AM »
Get one of these,  https://www.amazon.com/Wheeler-Firearms-Accurizing-Torque-Wrench/dp/B07YXCX5JT

Remount the scope, make sure everything is clean and free of oil and dirt and when the cap of the mount is installed the gap on either side of the scope has to be equal.  Cross torque in an X pattern after snugging each screw evenly first making sure the gap on either side is equal.  You are correct in that the scope has definitely moved.  Good luck
Like Mag-Willy said good advise. I can loan you my Snap-On torque driver, Iím at evergreen sportsmanís once or twice a month.
"a fronte praecipitium a tergo lupi"

Offline hunterofelk

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Re: Scope trouble
« Reply #17 on: September 18, 2020, 11:48:17 AM »
Looks like the ring diameter and scope diameter are equal. When the screws are all turned down there is not enough surface pressure to keep the scope from following Newton's first law.  That scope is a 30 mm isn't it? Burris has some rings that have inserts to replicate lapping the scope rings.  If you don't know about lapping go to Brownell's, look up scope ring lapping kit and there is a video.  A cheap fix is to remove the scope from the rings, clean all oil from the rings inner surface, and then put a layer of electrian's tape on the inside of the ring.  Tighten or torque the screws as Caseknife suggested.

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Re: Scope trouble
« Reply #18 on: September 18, 2020, 03:13:33 PM »
Looks like the ring diameter and scope diameter are equal. When the screws are all turned down there is not enough surface pressure to keep the scope from following Newton's first law.  That scope is a 30 mm isn't it? Burris has some rings that have inserts to replicate lapping the scope rings.  If you don't know about lapping go to Brownell's, look up scope ring lapping kit and there is a video.  A cheap fix is to remove the scope from the rings, clean all oil from the rings inner surface, and then put a layer of electrian's tape on the inside of the ring.  Tighten or torque the screws as Caseknife suggested.

I 2nd this diagnosis of ring diameter and scope diameter seem the same.  You should have some air gap between the two halves to torque down on.  :tup:

 


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