It’s nice to have all of these remedies available but I’ve got the Talley lightweight rings holding my Zeiss HD5 on an old Vanguard 300 Weatherby going on 7 years a few hundred miles of NW Colorado oak brush, trees & rocks still holding zero. Two shots - one elk 1 deer about 40 miles of brush trees & crap taking the finish off scope & rifle - maximum loads of IMR 4350 pushing 180 grain Barnes about 3200 FPS. This & 3 other 300 rifle varieties with different scopes no issues.
My Dual dovetail mounts held when my son dropped my favorite 7 mag directly on the Leupold 4.5-14x50 bell from about 5’. Unfortunately the scope didn’t fare as well. I’ll check in next week but likely going back for repair. Shot 1 ragged hole before the drop.
I have bedded bases for years and lapped rings but never bedded the scope. Something new to look at.
Early on, I'd bed the scope I was going to use in the rings. As things evolved, I began mic'ing scope tubes and found that 1" tubes ran the gamut from .995 to 1.003. I've since settled on bedding the lapping bar. If you do this and use a bedding compound that isn't too 'hard' (relative term), the scopes rings become universal for any scopes in that family of tube size. That's why AcraGlas Gel is my go-to for bedding rings.
The late Norman E. Johnson put me on to checking tube diameters. At first I was skeptical but after checking a couple dozen I found out he was correct. Norm was one of the first guys doing this and writing about it. His work on this and also on properly bedding the action was very, very helpful to a young guy like me looking for guidance.
Good shootin'. -Al
Al. Thanks for all the advice and demonstration in this thread. I was following your instructions to the letter on a SS M70 .270 WSM that I was swapping the mounts for Leupold Backcountry. The bases looked like they were a good fit, but I bedded them per your instructions, and it turned out they were really not in good contact at all, only touching at a couple of "strips" on each base. From now on I will plan to bed them all. I lapped the lower rings, as I knew they were both tilted towards the center of the receiver from previous measurements of the receiver and shimming previous bases. I was about to bed the rings using the Wheeler lapping bar, as you advised, but decided to measure it first. Though my scope was spot on 30mm at 1.181", the lapping bar was .006" under this, and I was afraid it would make too tight of a fit. I throw this out as advice that everyone ought to measure the scope and the bar in making their decision. Given my disparity, with a bit of trepidation, I spread some release agent on my scope and pushed it into the Acraglas Gel. Since it lacked the weight of the lapping bar, I added a couple rubber bands to keep just a little pressure on it while the glass cured. It turned out fine, with the rear base just perfect, but I suppose I did not press the forward one down hard enough as I had thicker cured gel here, and a little bit of a void. I went ahead and cleaned everything up and mounted the scope. Do you think this'll be OK? Take a look at the last attached picture. Looked pretty well supported overall so I let it be.
There's few things more "HORRIFYING!" than a "dreaded" "mark" upon one's scope tube. Give or fhuqking take. Hint.
Over a decade ago, you posted [aka NOBODY] about ring lapping and lap dancing.
I believe no one changes their mind through facts or analogies. But fear or being laughed at CAN move the needle.
To make fun of them, enter their frame of reference and embrace it in a ridiculous way. You have done that.
All I can offer is my calculation about 30-06 recoil force on scope mass meets the low coefficient of friction when oil gets between the receiver and scope base.
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. -Ernest Hemingway The man who makes no mistakes does not usually make anything.-- Edward John Phelps
The line up bars with the sharp little points will show you more than the lap dancer.
I used to think this too, then I learned that the two line-up bars with their sharp points can be out of alignment in angle and the points will still line up. This is especially important when using them for their original purpose, "turning in" the front ring on Redfield Jr style bases (or both rings on Dual Dovetail bases). Think about it - if the rear ring (the one with the windage adjustments on a JR/SR-type base) is not perfectly aligned with the bore, and you mount the one bar in it, then turn in the front ring until the second bar's points line up, that doesn't do anything to insure the two bars are parallel and aligned. In fact, if the rear ring is centered over the bore but misaligned off bore axis, the front ring has to be equally misaligned in the opposite direction for the two tips to line up. If the rear ring is aligned with the bore in angle but offset to the left or right because the windage screws are not perfectly centered, the front ring has to be misaligned in angle to the opposite side of the rear ring's offset. I think it was Mule Deer who pointed out in one of the GG chapters that it's really better to use the flat ends of the bars for aligning turn-in rings, as at least then you can see that the flats are parallel, meaning the two bars are also parallel. Having set that, then the rear base can be adjusted left or right until the two bars are aligned. But regardless, I don't think anything will indicate misalignment better than a single known-straight bar of the right diameter laid into both rings. Take a look at the attached: If I had clamped two pointy alignment bars into these Leupold Backcountry bases after they were bedded and torqued down, the points would have lined up fine, even though both bars were misaligned by a small bit in angle - in this case, both sloping slightly "downward" towards a point between the two bases. But two strokes of the lapping bar showed (as I already knew from having to shim the previous bases) that both ends of this receiver have a slight slope towards the middle. The pointy tips of line-up bars would not have shown that.
One note - after you bed Correctly, the screws should abruptly come to a stop vs tensioning up over 10-30 degrees of turn. This occurs because you have taken the “crush” or compression factor out of the contact points.
One note - after you bed Correctly, the screws should abruptly come to a stop vs tensioning up over 10-30 degrees of turn. This occurs because you have taken the “crush” or compression factor out of the contact points.
I noticed that. Thanks for the point-out. If I had not measured its depth, it would have been easy to misinterpret this as the front-most screw bottoming on the barrel threads. Rex
Thanks for all the advice and demonstration in this thread. I was following your instructions to the letter on a SS M70 .270 WSM that I was swapping the mounts for Leupold Backcountry. The bases looked like they were a good fit, but I bedded them per your instructions, and it turned out they were really not in good contact at all, only touching at a couple of "strips" on each base. From now on I will plan to bed them all. I lapped the lower rings, as I knew they were both tilted towards the center of the receiver from previous measurements of the receiver and shimming previous bases. I was about to bed the rings using the Wheeler lapping bar, as you advised, but decided to measure it first. Though my scope was spot on 30mm at 1.181", the lapping bar was .006" under this, and I was afraid it would make too tight of a fit. I throw this out as advice that everyone ought to measure the scope and the bar in making their decision. Given my disparity, with a bit of trepidation, I spread some release agent on my scope and pushed it into the Acraglas Gel. Since it lacked the weight of the lapping bar, I added a couple rubber bands to keep just a little pressure on it while the glass cured. It turned out fine, with the rear base just perfect, but I suppose I did not press the forward one down hard enough as I had thicker cured gel here, and a little bit of a void. I went ahead and cleaned everything up and mounted the scope. Do you think this'll be OK? Take a look at the last attached picture. Looked pretty well supported overall so I let it be.
Thanks again, Rex
Rex, it looks like you've done a fine job.
You pic of the base bottoms show just how precious little contact there was between the base and receiver.
A little bit of a void isn't something I'd worry about. Even with a bit of a void, you'll have a better quality contact area than if you hadn't bedded. If you feel the urge to make it perfect, don't try to fill in the void as you'll end up with high spots. Best to take it out completely and redo it, if you want to go that way.
For some reason (likely ease of material availability) most commercially available 30MM lapping bars measure smaller than 1.181 . I made my 30mm bar from 1.187 stainless round stock and it's stayed at 1.181 after many lapping jobs. If yours is a bit small, just wrap a piece of high quality painters tape around it before setting it in the epoxy...that tape measures about .005 thick. Wax the tape to seal it and the wax will also act as the release agent. Measuring scope tubes can be revealing!
As you've discovered, a well done bedding job on the bases and rings acts just like a well done pillar bedding job on a stock. The screws come up to 'tight' right now. Nothing stretching or twisting and trying to conform...it's 'there' right away.
For some reason (likely ease of material availability) most commercially available 30MM lapping bars measure smaller than 1.181 .
First, great info. Thanks Al and others.
Let me throw this out there. How much does the thickness of the lapping compound add to the circumference of the bar? Could the reason they are slightly undersized be because they are taking the addition of lapping compound into consideration?
Let me throw this out there. How much does the thickness of the lapping compound add to the circumference of the bar? Could the reason they are slightly undersized be because they are taking the addition of lapping compound into consideration?
Possibly. I'm sure that the 1" bars measure closer simply because of material availability in that size. Either way, it's not a biggie when it comes to lapping because, as you correctly point out, the compound adds thickness anyway. The only issue is if you want to use the lapping bar as the 'slave' scope tube for bedding. But that's no deal breaker and there are multiple end runs around that small issue. That's where a compound like AcraGlas Gel works so well for tube bedding (having a small amount of conformity) rather than a hard compound like JB Weld, etc.
Let me throw this out there. How much does the thickness of the lapping compound add to the circumference of the bar? Could the reason they are slightly undersized be because they are taking the addition of lapping compound into consideration?
Possibly. I'm sure that the 1" bars measure closer simply because of material availability in that size. Either way, it's not a biggie when it comes to lapping because, as you correctly point out, the compound adds thickness anyway. The only issue is if you want to use the lapping bar as the 'slave' scope tube for bedding. But that's no deal breaker and there are multiple end runs around that small issue. That's where a compound like AcraGlas Gel works so well for tube bedding (having a small amount of conformity) rather than a hard compound like JB Weld, etc.
Good shootin' -Al
If using the actual scope instead of the bar for bedding in the rings, is there any issue with using those harder compounds like JB Weld or Devcon?
Am I reading it correct that you oil the mount screws before turning them into the action?
Torque values are calculated with lubed threads.
No, I just mounted a Vortex scope last week and the manual said that the specs were for dry screws and that you would need to reduce the torque if using lubricant.
Originally Posted by shrapnel
I probably hit more elk with a pickup than you have with a rifle.
Originally Posted by JohnBurns
I have yet to see anyone claim Leupold has never had to fix an optic. I know I have sent a few back. 2 MK 6s, a VX-6, and 3 VX-111s.
If using the actual scope instead of the bar for bedding in the rings, is there any issue with using those harder compounds like JB Weld or Devcon?
In general, they seem to be a bit harder on the scope finish, with the quality/thickness of the finish being the biggest variable.
I'm a 'functional' type of guy so a few character marks doesn't bother me. One of my test scopes looks like a family of those Duluth Trading angry beavers gnawed on it. -Al
Thanks for your reply, Al. I had an epiphany after doing the job that I should have just wrapped a single layer of that wide clear packing tape around my lapping bar, and it would have been perfect. Clear tape versus masking tape due to the smooth finish on the clear tape versus the bumpy texture of the masking tape. I'm going to shoot the rifle tomorrow and see If things improved. Because the rear base ended up being nothing but a skim coat of AG Gel, and the front base had a thicker layer since it didn't get squeezed out as well, I calculate I lost 6-8 MOA of vertical range due to the minor tilt up of the scope in the rings now. If I had been using the lapping bar to bed the rings, I think I would have been more willing to press harder to get good squeeze out. So maybe I will redo it, but not until shooting tomorrow.
. I made my 30mm bar from 1.187 stainless round stock and it's stayed at 1.181 after many lapping jobs. If yours is a bit small, just wrap a piece of high quality painters tape around it before setting it in the epoxy...that tape measures about .005 thick. Wax the tape to seal it and the wax will also act as the release agent. Measuring scope tubes can be revealing!
