Light rifles, big cartridges, and scope mounts - learned my lesson, now it's time to pass it on.

[freddiej]

Cody Adams, thanks for sharing your experience. I do not normally deal with super boomers like yours. I have dealt with the RUM's, the Win Mags, and the Weatherby magnums. I try to tell the people not to use the Leupold standard, Redfield Junior, or other dovetail front/double screw rear setup. but there are always people that insist on having them put on harder kicking magnums. I remember one vividly. a guy came in with a full Leupold setup and scope and asked me to mount the scope. The rifle was a featherweight 300 Win Mag. I asked him if he really wanted this scope and this mounting setup combination. He said, "yes". I did not even say another word but, "I will have it done in 3 days." I still have that whole setup in my shop to show what one round of 180 grain of factory 300 Win Mag will do to these setups. BTW, the scope had to be sent to Oregon/Leupold for a new scope tube. the double screw assembly and the mating surfaces were blown out, the scope tube was bent, and the front ring was slightly loosened. the good news was all 3 of the 6-48 screws held. I have yet to find anything good about the Leupold standard bases and rings. but that is just me.

 

[Northkill]

Fortunately, he was experienced and calm enough to spot his misses and adjust in the heat of the moment. Most everyday hunters would have emptied the rifle and not been calm and cool enough to do what he did.

^^^^^ This.

 

[jimbo300]

I never had an issue with rings allowing the scope to slip, I usually use NF or Badger Ordnance steel rings. I have however, had issues with keeping picatinny rails mounted on heavier recoiling hunting weight rifles. With the weight of some of today's top optics, the problem can be compounded. That led me to the idea of using the recoil lug for a dual purpose. Myself and a shooting buddy, who is also a great gunsmith came up with the system linked to below. It takes the shear force off the base screws, they simply hold the base in place...works like a charm.

Manufacturer of SARS, Recoil lug, Scope rail,1913 rail

Accuracy assured, competition recoil lug,scope Rail, patent pending

www.accuracyassured.com

SARS Patent

Recoil Lug, Scope Base,

www.sars20x.com

 

[Arkansasdad]

I did clean all the shoe polish off the tube and got it down to the factory finish prior to reassembly, as well as cleaned up any remaining polish from the devcon itself, however your concept makes sense. But people like Ryan Pierce and other very smart rifle builders bed their rings religiously, and never have issues, so I figured that bedding the rings would be the ticket. I may reach out to him about his ring bedding process, if he would be willing to share. Bottom line, there wasn't enough grip. Something as simple as going 25 in-lbs vs 20 may have been enough to keep the scope in place, or roughing up the surface slightly, but on such an expensive optic, I didn't want to take the chance of possibly damaging it by over torquing, I do not know where the max is as it isn't openly stated in the manual, so I wanted to stay safe. If 20 in-lbs on that much surface area doesn't hold it, then I will simply increase the surface area.

I will also say that even though the devcon was slick, the grip it gave on the tube was outstanding. When I initially tightened it down, just using an Allen key and rolling it in my fingers to tighten the screws for all 8 screws, not even grabbing the short end and adding any torque, was enough to prevent me from being able to turn or push the optic forward or back. The screws had to nearly be loose to move the scope, the grip was so good. That is why I was so shocked it moved! I have used the Burris signature rings and their smooth poly inserts have almost as much grip, but like I said, I could push the scope down into the bases and nearly lift the rifle up without the ring top caps being installed, the fit was that good. I'm still blown away it wasn't enough, so my solution is maximum possible grip.

Try Near Mfg. out of Canada. You will be happy. Happy shooting.

 

[Triple BB]

Easiest way I've found to eliminate scope movement is take some 3M adhesive spray. Spray it close on some plastic or something you can throw away. Take a Q Tip and smooth it out on your top rings only. Tighten everything to specs and let it set for a couple days before shooting. The scope will never move again. I've also had good luck with rosin, but spray adhesive is stronger...

 

[Wedgy]

Look at Near Manufacturing and their Alpha Mount rings. I had the same issue on my braked 300 WSM and his rings and base solved my issue. Put the same on my 338 LM and no issues.
Richard Near explained to me the snapping back and forth movement caused by braked rifles during recoil can be very violent in a microscopic way. It beats up scopes and mounts.

The Near mount looks very close to the 4 screw DNZ setup that Cody used.

 

[Varmint Hunter]

I shoot a fully custom 338 RUM as well, any pet loads you might want to share that have worked well for you? With bullets, primers and powders getting harder to come by, always looking to improve/change with different powders that are currently available until shortages get better!
Thanks,
Mark in Texas

My preference is 89.0gr RE26 in a Nosler case lit by a Fed 215M primer under a 250 Accubond or 250 Berger Elite Hunter. Both shoot under .5 moa at 400yds. I dropped two bull moose with the Accubond and performance was perfect. One bull was shot straight through both shoulders and the bullet was caught in the opposite side hide. After passing through all that heavy bone the bullet still hung in there with a remaining weight of 140gr. The bull flipped over backwards and twitched. DRT

The other bull was hit broadside in the center of his vitals. He began to walk and I rushed off a second shot which hit low in the chest behind the front leg. The bull walked out of sight but was piled up dead about 40yds away.

 

[Chas1]

On my 338 AX the stainless mount is pinned and I used 4 Nightforce Rings and it has stayed rock solid. I agree with others and wouldn't polish rings and scope.

 

[Sanford338]

My preference is 89.0gr RE26 in a Nosler case lit by a Fed 215M primer under a 250 Accubond or 250 Berger Elite Hunter. Both shoot under .5 moa at 400yds. I dropped two bull moose with the Accubond and performance was perfect. One bull was shot straight through both shoulders and the bullet was caught in the opposite side hide. After passing through all that heavy bone the bullet still hung in there with a remaining weight of 140gr. The bull flipped over backwards and twitched. DRT

The other bull was hit broadside in the center of his vitals. He began to walk and I rushed off a second shot which hit low in the chest behind the front leg. The bull walked out of sight but was piled up dead about 40yds away.

I too have had good results with the accubonds and the berger elites. I've got to add some barnes TSX and TTSX 225's & 250's to the list..my 338 loves most anything in the 225 & 250 range...pretty easy to find a sweet spot... call it my elk thumper..got a new Wby 30-378 MK5 RC been playing with...it's a shooter but heavy for an elk gun. Thanks for the info!
Good Shooting & Good Hunting to ya!

 

[Philward]

I suspect that your problem was the frictionless fit between the scope and rings. Bedding the rings and polishing the scope tube reduced the friction between the two.

Most rifle chambers are finished to 16 line per inch smoothness so that cartridge case will stick to the chamber, any smoother and the bolt lugs will take a beating because the case will slip and put up to twice the amount of pressure on the lugs.

Before you make all of those changes try roughing the bedding a little and test a few rounds after reinstalling the scope. You won't need much roughness, make a slightly crosshatch pattern using a 600 grit wet dry Emory cloth.

This is what I was thinking when reading the original post.

For all my years hunting and shooting I've never torqued scope mounts, just tightened to feel. Never had any slip or come loose, more and trouble with adjustments. Never left and marks on scope tubes. Not shooting a 338 Norma either so there is that. Recently I bought some EGW rings and base for a Remington 700LR 7mmRM. Decided to do it right and torque them as the directions say. I couldn't believe how light the torque felt, except for the ring to base torque.

I assume when you bed the rings to scope that the torque is spread over a larger and more consistent area, so a little more torque wouldn't hurt it at all.

I wouldn't call 9.6lb a light rifle either.

 

[gabell727]

I did clean all the shoe polish off the tube and got it down to the factory finish prior to reassembly, as well as cleaned up any remaining polish from the devcon itself, however your concept makes sense. But people like Ryan Pierce and other very smart rifle builders bed their rings religiously, and never have issues, so I figured that bedding the rings would be the ticket. I may reach out to him about his ring bedding process, if he would be willing to share. Bottom line, there wasn't enough grip. Something as simple as going 25 in-lbs vs 20 may have been enough to keep the scope in place, or roughing up the surface slightly, but on such an expensive optic, I didn't want to take the chance of possibly damaging it by over torquing, I do not know where the max is as it isn't openly stated in the manual, so I wanted to stay safe. If 20 in-lbs on that much surface area doesn't hold it, then I will simply increase the surface area.

I will also say that even though the devcon was slick, the grip it gave on the tube was outstanding. When I initially tightened it down, just using an Allen key and rolling it in my fingers to tighten the screws for all 8 screws, not even grabbing the short end and adding any torque, was enough to prevent me from being able to turn or push the optic forward or back. The screws had to nearly be loose to move the scope, the grip was so good. That is why I was so shocked it moved! I have used the Burris signature rings and their smooth poly inserts have almost as much grip, but like I said, I could push the scope down into the bases and nearly lift the rifle up without the ring top caps being installed, the fit was that good. I'm still blown away it wasn't enough, so my solution is maximum possible grip.

I have learned that for anything over a 270, I need 35 in lb of torque. The ring manufactures give torque values that aren't enough to hold a 308, much less a 300 win mag. For decently made scopes, including Nikon, nightforce, you can go up to 50 lb with not problem, but you have to go up to at least 35. Any scope or rings that can't handle over 40 in-lbs is junk.

 

[dougduey]

The Near mount looks very close to the 4 screw DNZ setup that Cody used.

I don't think you looked at the Alpha Mount. It's not even close to what Cody used.

 

[codyadams]

Man. Hmmmm. I don't think you should be able to lift your rifle after pressing it into your rings, to me it sounds like they needed lapping. If I cant set the scope in the lower rings till its completely flush, it gets lapped. Because its binding. And by lapping you will get more contact surface. Ive never had to bed the rings themselves, just bases. As a matter of fact I learned how to bed with jb weld and kiwi as the release agent on a DNZ mount like yours. It wouldn't sit flush to the receiver. So after bedding that set up was ok. I then got smart and went to a 20 base and Warne rings and its .5 moa now. Am not a fan of DNZ, but thats me. Other people like em good for them. And I would never bed a scope to the rings permanently, or semi-permanently. I think you should've ditched the DNZ and tried the new base and rings first. IMO. But I hope it works for you. And the spec from the scope manufacturer is made not knowing the width of the rings. I would just go with the ring spec. And blue loctite all mounting screws

If you talk to Ryan Pierce of Piercision Rifles, he beds every scope in the rings, and he says the same thing, that the fit is tight enough that he can lift or nearly lift the rifle after lightly pressing the optic into the ring bases. It has nothing to do with needing lapping, there is no binding, lapping would be counter intuitive, a good bedding job gives 100% contact of the rings to the scope, not 95% or 98% like a really good lap job might do. And as far as what I did first, was exactly what you just said....I am switching from DNZ one piece base to a rail base and set of 4 rings. The base will be pinned with either 2 or 4 pins.

 

[LeddSlinger]

I'll start this thread by saying that I am in no way bashing on the manufactured of the scope mount I used, it is in no way the mounts fault, but instead my fault for not choosing the appropriate mounting solution for the extreme situation I put it in. The mount I used is a quality piece of kit, and I have used it on other rifles with good results.

I just discovered this yesterday, and I am frustrated it took me this long, and I should have known better, but now I do.

I have a relatively light .338 Norma Magnum, all in with 3 rounds ready to hunt, it weighs 9.6 lbs. It has a MBM titanium 5 port Beast brake, which does a fantastic job of managing the rifle, I spotted every impact last year during hunting, from 180 yards to 883. I would put the felt recoil to about that of a heavy .308 winchester, shooting side by side with my fathers 10.5 lb AR-10 in .308, it is very similar. However, when building this rifle, I knew that the entire amount of recoil would be felt by my optic mounting solution, as that is initiated prior to the muzzle brake doing it's thing and slowing down the recoil. That recoil comes out to just shy of 50 ft-lbs and about 18 fps with my loads, so pretty significant.

Because of that, I upgraded my base screws from 6-48 to 8-40. When choosing a mount, I wanted to keep weight down, but also keep a solid mount. This is where I messed up. I chose to go with a DNZ 1 piece base/4 screw ring combo, as seen in the photos. I bedded the mount to the receiver with devcon for added strength and to keep everything perfectly strait. Next, I bedded the March 2.5-25x52 into the rings, again with devcon. I polished kiwi shoe polish into the scope tube until it was a high polish, an extremely thin layer to ensure the best bedding possible. The bed job came out great, I could push the scope down into the lower rings and nearly lift the rifle up with only the fit, not even having the ring caps on, so I was very confident that after proper torqueing of the bedded ring caps, the scope wasn't going anywhere. In checking the March scope manual, it only stated that usual torque for ring caps is 15-20 in-lbs, but will vary based on manufacturer. The DNZ rings stated a max of 25 in-lbs, so I torqued to 20 in-lbs as that was the top end listed in the scope manual.

During load development, the rifle would shoot very good, but have an occasional flyer, never bad, usually within .75 MOA of my group, but nevertheless, it would happen. I chalked it up to my shooting, groups were still always under 1 MOA, most of them falling well under half MOA. During my hunting season last year, all was going well, the rifle was used for several pronghorn out to just under 700 yards with stellar performance, that is until my mule deer.

I hiked in to one of my honey holes at first light, and like they were on que, I spotted a group of bucks out in a field about 570 yards off. There was one nice buck in the group that was a 160 class buck, so I decided to take him. It was first light, sun wasn't up and there was nearly no wind, so since I was shooting across a canyon, I doped for a 2 mph L to R wind, going up the canyon. I settled in behind the rifle, lined up on the buck, and took a perfect shot. As I was waiting for impact, I knew that was a dead buck for sure, until I saw the impact high right, over his back and back by his flank. I knew this wasn't right, so I adjusted to my impact quickly. The buck ran about 60 yards and stopped, pretty close to the same range. I lined up again, took another shot and placed a perfect quartering to shoulder hit, and dumped him in his tracks. However, I had to adjust 2 MOA to the left and down almost the same for the hit. This was a verified load, and I was confused. After I got the buck off the mountain, I went to the range and shot it. Sure enough, I was hitting around 1.5 MOA high, and 2 MOA right. I re-zeroed, shot a confirmation group, and shot some steel at range, and everything seemed good. I was confused why it happened in the first place, but everything seemed good again.

Then, I went on my elk hunt. We got on to a large herd, and I picked out a 320ish bull. Range was 883, so I knew I needed to take my time, but thankfully I had plenty. There was a pretty stout ground wind, but the wind out in the canyon was consistent, around 5 mph left to right, and between mirage and debris floating in the air, it was relatively easy to read the wind. I lined up my shot, and fired. Again, I saw the impact high right, almost the same place, over his back and back near the flank. I dialed to my impact, he moved a short distance laterally and stopped. I lined up a second shot, and on impact dumped him, the bullet hit right at the neck shoulder junction. Then, my season was over.

In the off season I began doing load development on a different bullet. The other day, I took a picture of my rifle in a new tripod I got. I was looking at the photo, adoring my beautiful rifle, when I noticed something off. The proportions of the scope/mount didn't look right, and there seemed to be more room between the barrel and scope bell than there previously was. I dug up a photo of my rifle from right before my 2020 season, and saw the difference in the photos below.

Before season, 2020 -
View attachment 277949

Just a few days ago -
View attachment 277950

Notice the difference where the scope level is in relation to the turret body, as well as where the rear ring is in relation to the eye piece. The scope had scooted forward nearly a quarter of an inch in around 100 rounds. While I can't say 100% that is what caused my issues during hunting season this year, I wouldn't be surprised if that was the cause. So, to remedy this, here are my plans -

I ordered a 20MOA rail. I am going to bed and pin it to the receiver. While the pinning may not be necessary, it will be added insurance on that aspect of the mount system. The rail has an integrated level, making room so that the entire scope tube can be used for....

2 sets (4 rings) of Seekins precision rings. I will put 2 of the rings pushing forward, 2 of them pushing rearward, to counteract the thrust created by the muzzle brake. I believe this is what Kirby Allen does on his rifles. I will bed the scope into the rings again, but this time I will not use release. The scope will still come out if needed, at most some heat can be used to help them release.

This is the strongest most secure method I can think of to keep the scope in place. I also plan on marking the scope tube with a marker in an inconspicuous location, so that I can monitor for any movement of the tube in these rings, though if it does, I'm not really sure what more I can do to prevent it, but at least I will know.

I will update this thread as time progresses, but I figured that since I had to learn the hard way, I would admit my faults and hopefully help the next fella to prevent this issue. Just go overkill from the start with big boomers like this, just like the professionals do (there is a reason they do it) and you will not have the problems.

Thanks all, and good shooting.

I wouldn't use Devcon to bed the scope in the rings. One, it shrinks quite a bit in cold weather at a different rate than your aluminum scope tube. Two, it does not have very good grip on the cured surface.

I only bed scope tubes with JB Weld. Very grippy surface when cured and can be made to have even better grip by coating the surface with black permanent Sharpie marker ink then rubbing it briskly with your finger. Super solid hold even on the hardest hitting calibers. Try it and if you do it correctly, I guarantee that scope won't move.

Going to a set of 6 screw rings would help for sure, but using two sets of rings is a little ridiculous, no offense intended. If the mounting job is done correctly, there is no reason a single good set of rings won't work perfectly. Seekins is an excellent choice for a brand. They are top notch quality and strength for a two piece mount design. If you are fully concerned about strength and rigidity, just buy a Spuhr one piece mount and be done with it.

On another note, that particular model of March scope has been proven to move under recoil and change point of aim on different magnification levels. The couple March 2.5-25 scopes I know of that were tested against a frozen optic on a scope checker mount did not pass the test very well. And that was only tested with the light recoil of a small 6mm round. So obviously your scope moved in the rings under recoil, but I bet that scope reticle is moving internally from time to time as well. Especially when subjected to heavy recoil of a 338 Norma Mag.