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

PNWdude67

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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.
After seeing how much is spent on a receiver and separate base, then another base for that receiver and bedding 4 rings .... ugh. Why not just get a receiver with integral base like the Lone Peak Fuzion and ARC rings or a Spuhr mount and be done with it? Also, funny how Murphy’s law works and the only time your scope shifted in the rings was the two shots you took on game not during load development or range time. 🤷🏻‍♂️ Sure is cool it stayed put perfectly for a measurable follow up both times ...rather be lucky than good any day.
 

codyadams

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After seeing how much is spent on a receiver and separate base, then another base for that receiver and bedding 4 rings .... ugh. Why not just get a receiver with integral base like the Lone Peak Fuzion and ARC rings or a Spuhr mount and be done with it? Also, funny how Murphy’s law works and the only time your scope shifted in the rings was the two shots you took on game not during load development or range time. 🤷🏻‍♂️ Sure is cool it stayed put perfectly for a measurable follow up both times ...rather be lucky than good any day.
If I would have known that the original mount wasn't going to work, I obviously wouldn't have went with it, so factoring in the cost of that mount, as well as the next mount system I purchased, doesn't really make sense. In the future however this experience will certainly affect my choices for a mounting system, any custom action I get from here on out will have integral rails for sure. And I'm pretty sure the optic shifted at other times as well, but during the load developement stage, a shift of half to 1 MOA can often be attributed to the changes in seating depth, powder charge, or other variables in a load, so it simply wasn't noticed. I would bet that is was slowly shifting a little every shot as time went on, but at shots under 300 yards, a 1-1.5 MOA, maybe even 2 MOA change might not even be noticed when shooting game, a little forward or back but still in the general center of the heart/lungs area would be acceptable. But when I had to take my longer shots, it showed itself. That is my theory anyway, from how it acted.
 

LeddSlinger

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There’s nothing wrong with that mount. It’s how you mounted it and the compound you used.

You DO need to lap the rings first to make room for the bedding and attempt to keep the layer of bedding the same thickness (even shrinkage). If you don’t lap first then you might as well not even bed the rings at all. You’ll end up with excessive stress on the scope tube, bad contact when the bedding shrinks with the same weak pressure points. If you, or Ryan Pierce, or anyone else thinks lapping the rings prior to bedding is “counter intuitive” or not required then you are absolutely wrong.
 
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codyadams

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There’s nothing wrong with that mount. It’s how you mounted it and the compound you used.

You DO need to lap the rings first to make room for the bedding and attempt to keep the layer of bedding the same thickness (even shrinkage). If you don’t lap first then you might as well not even bed the rings at all. You’ll end up with bad contact when the bedding shrinks and the same weak pressure points. If you or Ryan Pierce think lapping the rings prior to bedding is “counter intuitive” or not required then you are both absolutely wrong.
They were lapped prior to bedding. When I said lapping is counterintuitive, that was referred to as after doing the bed job. But thanks for your opinion. Also, people like Kirby Allen also think that the mount I used is a problem.
 

LeddSlinger

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They were lapped prior to bedding. But thanks for your opinion. Also, people like Kirby Allen also think that the mount I used is a problem.
Don’t know Kirby Allen and don’t care. All I know is what “I” know from experience.
Granted that mount is not what I would choose to spend any money on, but if done properly with JB weld then I’m sure it would easily hold up to the recoil and muzzle blast of any 338 Norma.
 

sp6x6

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Same light 338 NM,pinned rail,oversized screws,NF tit rings,11 years no issues
 

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codyadams

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Don’t know Kirby Allen and don’t care. All I know is what “I” know from experience.
Granted that mount is not what I would choose to spend any money on, but if done properly with JB weld then I’m sure it would easily hold up to the recoil and muzzle blast of any 338 Norma.
One of the top custom magnum rifle builders in the country, owner of Allen precision and designer of the Allen Magnum and other cartridges. Knows more about stuff like this then most men could hope to learn in their life.
 

Wedgy

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Don’t know Kirby Allen and don’t care. All I know is what “I” know from experience.
If you aren't willing to learn from the experience one of the best in the business that is your choice but I keep an open mind especially to those who are at the front our sports development.
The photo is the same mount and March scope as Cody's on a 6.5x284, it is pinned & bedded to the receiver and uses #8 screws. Rings were lapped, bedded and no release agent used. It has not moved and I am confident in it. The photo is to show how much surface area the 4 screw DNZ has and yet it still moved on the 338NM.

Happy D Day everyone.
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WiscGunner

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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.
One thing to keep in mind is the use of Loctite and its purpose. Loctite is simple a glue to fill the space in the threads to great more surface area to reduce movement caused by vibration. Loctite becomes less useful in high torque locations than in low torque situations. Small screws with light torque benefit greatly from Loctite while “larger” screws with higher torque benefit less.

The mist important thing to remember about Loctite is it a LIQUID. This means normal metal/metal torque limits are not the same as hydrolic torque limits. A torque wrench gives a reading not knowing what materials are being measured.
Metal on metal torque provides resistance to loosening through the spring tension of deforming the metal if the threads, body and head of the screw.

Liquid “torque” readings are simply pressure levels of the hydrolic fluid. This, by its very nature, gives false readings of functional torque as you are really (mainly, mostly or completely depending on the exact application) reading the pressure PUSHING on the liquid and nor PULLING on the threads. This will, to varying degrees, apply all or some of the “torque” in the wrong direction. An incorrect but easy way to thing of it is the loctite being a shim under the tip of the screw causing the screw to bottom out with out tightening at the head. This can “feel” tight in the hand but parts being connected can still be separated by feet.

If you choose to use Loctite, it cannot be stressed enough that less is more.

Long story short, 20in/lb of “torque” on screws with loctite was not in fact 20in/lbs of clamping force on the scope.
 

LeddSlinger

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If you aren't willing to learn from the experience one of the best in the business that is your choice but I keep an open mind especially to those who are at the front our sports development...


Happy D Day everyone.
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Learn and keep an open mind? There’s is no new information being shared here. Nothing new to me about bedding scope rings or how to pin a base or drill and tap for bigger screws. Even using 2 sets of rings is an old practice by those who actually think it helps. This is all ancient knowledge in large magnum rifle world.

I just picked up a BAT HR Lapua action for my next build. Takes a lot of variables out of the equation with an integral rail. Had Defiance Deviant Tactical Lapua as well and is a pretty good action with integral rail. Not as nice as the BAT tho. Have a Kelby Atlas Lapua action with screwed and pinned base that also works perfectly fine. It’s all in the procedure. I always tell people you can have the best rings and bases money can buy but they won’t do their job very well if not installed correctly.

Ive seen the Allen magnums and no offense to Mr. Allen but there’s nothing cutting edge there. Just more wildcats in the pile. It’s all fun but nothing special. I have wildcatted many of my own original designs as have tons of other people over the last 70 years.
 
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