Why It Can Be Important to Lap Even High End Perfectly Aligned Rings

BigDave · 03-30-2015, 05:24 AM

The rings were perfect. The rail was perfect. The 30mm scope tube was oversixed enough that it created issues. These were easily corrected by extensive lapping..fittig the rings to the scope!

Read on if this sounds dangerous. Far from it. The end result was perfect. Photos coming. I promise.

Hardware:
1) Seekins Low rings..alloy. crossbolt is PROPER size and has a tight fit with only.008" clearance in the rail lugs. Two flush side screws for clamping instead of an ungainly nut. Torque: caps screws t-20's I think. They take 20 inch lbs. The same size side clamping screws are 55 inch lbs

Bushnell Tactial Elite ERS G2 reticle 6-24X50mm 30mm tube. Side focus mil/mil..no other features. comes with 3 inch sunshade only.

Holland anti cant bubble similar to the Vortex which is too chunky to fit under my low rings. Holland is sweet but pricey.

Wheeler Scope mounting kit..106usd..has everything..220 grit compound, bubbles, loctite, lapping bars, drill attachment for bars. Alignment bars. Fat Wrench and bits. Calibration certificate too.

Old fashioned DIAL metal slide micrometer. Not digital.

Tipton Best Gun Vise...just dandy for my needs. I could use more storage is all for tools and parts. It did hold the gun well, but you must fiddle with the adjustments to get things just right.

SAFTEY GLASSES

Vitiman E oil for your destroyed hands after all those chemicals.

Nitrile Gloves which I look at but rarely use. :)

Gun oil

400 grit/2000 grit sandpaper

Dremel, rouge and a polishing kit. Cut off wheels too.

Heat gun for heating up locktite for removal. Its just a habit.

Two drills...one battery and a 1/2 inch cord version

Two cans non chlorinated brake clean( I get a case at a time)

Dykem High Spot Dye(blue)

Once Quart Laquer thinner. Only thing that removes the blue Dykem dye

roll of paper towels

Q tips

Aluma Black

Micro Fiber towels to temp raise cheek weld until the additional comb kits come from Triad.

Triad Stock Pack Larger Modular

Triad rear Wedge bag for stock. Nice.

Whia German magnetic torx driver (useful!)

A few more small tools...to many to list.

""Secret sauce." metal protectant. Do not need oil. Better look and feel with out all that gun oil I may share this find I made on my own. We'll see.

My Seekins rings, EGW rail were 100% straight and aligned. The receiver was flat so the rail needed no bedding.
I used Dykem Hi-Spot Blue machinists dye on the EGW rail mounting surfaces. There was a 30% amount of non contact(voids) even though it LOOKED perfect. The dye dont lie.

I LAPPED the rail. How? I figured it out. I found a very thin piece of 600 grit and covered the receiver. I smeared oil as a lube for cutting and lapped and lapped that rail until I could see it conform to my receiver. Was that perfect? No. Was the end result a LOT better? You betcha. I removed almost no anodizing, but I took some high spots off the mounting surface to give it much better fit.

Some gun oil on the blued receiver mount areas to keep rust from forming. Purple loctite and 20 inch lbs on the T-10 6-48 screws for the scope rail.

Seekins Rings mounted. Bushnell 6-24x50mm mounted. Hollland anti cant bubble mounted.. The Vortex bubble is too chunky for my low mount clearance. The Holland is much slimmer. I got all three bubbles to match up perfectly. Only the Holland buble was permanant.

Just saying..i finally got a stable platform for the Bushy. Oh, my. Even in twilight at 24 power it was just great. I love this scope so far. The side focus is very precise, but you can get a very crisp image with careful focusing.

The Seekins rings needed extensive lapping because the Bushnell tube was quite a bit larger than 30mm (in machinist terms) I dont know if the lapping had much to do with accuracy. Maybe. The rings were 100% true. I just did not want huge scope "bite marks" in my Bushnell scope. Now the fit is so much better...a LOT better.

The Wheeler lapping bar was so perfect. It mike'd at precisely 30mm. The Bushnell was 30.08mm which is quite a bit too large if you dont want ring "bite" marks. The scope would not even slide in the bottom ring shells with out marring the sides of the scope.

I eventually had to use the drill attachment on the lapping bar. I finally (checked 4 times) achieved a contour that allowed the scope to slide in the bottom ring shells with out catching/marring. Even after the healthy lapping, the Seekins rings showed a good sized even gap on both sides when torqued to 20 inch lbs.

I was able to dial in 3 inch lbs ( on the Fat wrench)to maintain a precise even torque on all eight cap screws whilst lapping. Yes, the Fat Wrench is infinitely adjustable. You have to feel the gradations in between the 5 inch lb increment hash marks.

The lapping was a huge success. The Bushnell might mar a bit but it will not be gouged by the rings at this point. A precise 30mm tube is plenty big to get clamped super tight by my rings. Why does Bushnell make its tubes out of spec like that? On purpose? I took plenty photos. Will post later. No bad things about Bushnell. The image is stunning, even in twilight. I needed it on a steady rest like my rifle to be able to see out if it properly. I have to say I am extremely pleased. I am hard to please when it comes to optics...so.

This just goes to show you...no matter how much confidence you have in your rings, there might be something else out of spec. So always lap. I started with a test lap to see what was what. You can tell what is going on by observation, "feel" and a Micrometer. I could feel the Bushnell scope being gouged when I slid it. I could see the marks. Mike'ing the scope tube told me it was the scope that was out of spec, not the rings.

So I fit the rings to the scope. The job was long but turned out particularly well. There is 100% EVEN surface clamping now. The scope is like a rock in those rings now.

Did you mount your scope in rings with no lapping and no scope bite? Congarularions and condolances too. You missed out on a very Zen Medatative process that is part of the Art of Gun Light Gun Smithing and maintance. I never get frustrated. If I have an issue I step back and take a break and then look at it again and solve it. That to me is part of the big picture and quite rewarding. I realize we are all differtn. I am not saying you will get the same thing out of puttering that I do. I do putter with precision tools, mind you! :)

I did take plenty pix. I am exhausted. Too tired to transfer and publish. Will do later.

FTW!

BigDave

**Russmerle** · 03-30-2015, 03:10 PM

Hey Dave,

I just wanted to give you a heads up that the side focus isn't exactly just a focus. It is used for reducing parallax. If you cradle the rifle or set it up on bipod and rear bag and, without touching the rifle, look through the scope and move your head side to side slightly without allowing the rifle to move, you will notice that the crosshairs seem to move about the target. The "side focus parallax adjustment", as Bushnell calls it, can be adjusted until that movement goes away. You will have to adjust the side focus parallax adjustment when moving between different shooting distances.

When you set up at 100 yards, you should adjust your parallax knob to remove the shiftiness and then not mess with it unless you are changing your shooting distance. Some scopes have numerical values etched on the side parallax knob; ie 50, 100, 300, etc... That will get you in the ball park but you should still check it out to ensure you're reducing your parallax.

If you already knew this I really do apologize for the post. I looked up the scope just to make sure I wasn't spitting BS because I think some scopes really do have a side "focus only" knob. Yours, however, is definitely for reducing parallax.

I didn't know this until I was hanging out with a regular F-T/R shooter and he explained it to me. It really did tighten up my groups too... I guess it won't matter that much if you just want to plink, but if you're really pushing your skills and your rifle, it will make a big difference. Especially with your set-up. She's going to be a real shooter.