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

My buddy hunts in Africa at night with a 5 pound 375 h&h ackley. 56mm schmidt and bender.

His smith puts talley lightweight on it. The base broke, not the screw but the base broke. He had too little space between scope and barrel. Scope was hitting barrel during recoil and transferred that energy to the scope base.

Scope is still good and after giving it more space [could see space, could barely get a piece of paper through] and talley rings have held up since.

Talley lightweight and hawkins hybrids have all been good to me. Clean rings and scope tube with alcohol. Loc tite all screws. 375, Rum, prc, nothing has moved with larger scopes.
 
codyadams said:
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.
Click to expand...
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
 
I've had scope movement issues in the past from a couple of popular name brand rings and a picatinny rail screw loosening issues on 2 rifles.

Since then:
I switched to Seekins or Nightforce bases WITH RECOIL LUG topped with Seekins or Nightforce HD rings on all of my scopes from lighter hunting scopes on Creedmoor, 308, 6.5-284, 280AI and 300 Win Mag hunting rifles... to really heavy NXS and ATACR scopes on Long Range rifles from Creedmoor on up to 300 Win Mag and have NOT had one move yet.
This also allows me to switch scopes from one rifle to another (if needed) without the fear of recoil moving the scope in the rings.
It was costly but it solved my problems and kept my zero's!
 
codyadams said:
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.
Click to expand...
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.
 
OP, Mr. Adams,
My sincere thanks for educating me on muzzle breaks. Before your thread I never thought to or bothered to consider the affects of re-directed recoil of a rifle with a muzzle break.
I own two rifles with MB's a 338wm and 7mmstw and their MB's were not my choice but factory installed and these were at that time my only option if I wanted that rifle in that caliber.

I bought a Tikka T3 in 300wsm 6-7 years ago and and since rarely shoot my other magnum boomers.
 
I'll admit that I am an optics nut job. Not only do I look at optics by looking through them, but I try to learn about the company and exactly what goes into the process from design to build. Boring research for the most part but well justified in my opinion.
If I'm gonna spend money (usually quite a bit) on all the many categories related to hunting, I wanna know that my optics were designed and built with the utmost care and attention to detail. The small things that some companies either do or don't require in the assembly/quality control process can be the culprit for failure in the field.
Yes, it's difficult to afford some of the optics that come with assurances. But consider the cost difference (alpha glass VS budget) into the big picture. Even a do-it-yourself hunting trip can run into some serious cash. Hiring an outfitter takes things to a new level of financial sacrifice. Some more exotic trips can run into the 10's of thousands$. There are hunting leases, tree stands, blinds, food plots, trail cams, etc etc. The average hunter spends far more than most non-hunters would guess.
The real telling part of the equation is that many items on the list of expenditures reoccur every single year. If we are lucky they will do so until we are able to enjoy the sport with our kids and grandkids. The purchase of a scope is a one time cost. The difference between A+ glass and a B- option is a drop in the bucket of dollars that you'll spend on other things, year after year on the reoccurring costs. That's one variable I can control and it might boil down to an extra 30-40 bucks a year in total if I can manage to live an average life span.
Optics, especially your rifle scope, is the one component where, if it fails, can totally change the outcome of that day's hunting, at a minimum. For some it could mean a catastrophic end to the one chance at a certain animal that finally happens after yrs of pursuit, patience, hard work, and, yes, money.

All of my rambling relates to the original post, and I am really glad he shared his story. It was interesting to read, but also adds another item on the checklist that should get serious attention. 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.
I've used Nightforce rings on all my rifles for some time, and right now the biggest banger I own is a .280ai. So the recoil is nowhere near a .338. But If I do acquire another big magnum, I'll remember this story
rammac said:
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.
Click to expand...
Well that certainly makes sense. In a microscopic kinda way, the two surfaces need a little traction to adhere to one another.
 
Varmint Hunter said:
I'm a no-frills scope mounter and have gotten to appreciate the Burris Signature rings on most of my big game rifles. Loaded with maximum charges and heavy bullets, I have not had a scope move on my 300RUM or 338RUM. Both are standard weight rifles with Kirby's PK side discharge brake. Even my 500 S&W shorty rifle wears Signature rings w/o issue.

There are unquestionably stronger mounting set-ups available but I haven't had the need for one yet.
Click to expand...
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
 

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