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Scope ring series: Part 5

Part 1
Part 2
Part 3
Part 4

This report covers:

  • Why adjustable rings?
  • Barrel boring — yes and no
  • Hammer-forged?
  • Adjust by remounting the rings
  • B-Square
  • The AA adjustable ring
  • B-Square AA rings are no more
  • Summary

Today’s report is about adjustable scope rings. How could I forget them? Yet forget them I did until you readers reminded me.

Why adjustable rings?

You guys always tell me that you don’t like to shim a scope because of the danger of bending a scope tube if the top saddle screws are tightened too much. I have done that and I’m sure anyone whoever shims scopes has done it at least once. It looks bad and doesn’t do the scope any good, either.

But there must be a reason for wanting rings that adjust. I will leave the issue of barrel droop alone because we have covered it several times in recent weeks. What about side-to-side corrections? Why would we need them? Aren’t barrels bored straight? Yes and no.

Barrel boring — yes and no

Yes, the holes that go through rifle barrels are very straight. But they don’t always align with the outside of the barrel. In other words, the barrel may look like it’s pointed straight, but the rifled tube inside may be angled off to one side. I don’t mean that it’s bored on one side of the barrel; I mean the axis of the tube isn’t in line with the outside of the barrel. This is so much of an issue that custom barrelmakers will turn the outside of the barrels they rifle true to the axis of the bore, once it is rifled — sometimes for an optional fee!

I once had the stub of an inexpensive Crosman barrel that had been cut off. As I recall, Dennis Quackenbush gave it to me. It showed the axis of the bore off the centerline of the barrel by as much as 0.125-inches (that’s one-eighth inch for Americans)! I don’t know where that piece of barrel is, but I doubt I threw it away. If I ever come across it I’ll show you.

Hammer-forged?

What about hammer-forged barrels? Well, they still have a hole drilled through them, but they don’t start out as long as the finished barrel, so the deep drilling process can leave less of a runout. The cold forging process makes the steel flow to the barrel’s desired length. It also work-hardens the steel, inside and out. The hole that is drilled through the barrel is slightly larger than the rifling mandrel that will impress the rifling so the mandrel can slide through. Any offset tendency will mostly be ironed out in the forging process. I believe this makes hammer-forged barrels less likely to shoot left or right. But I don’t know that.

Adjust by remounting the rings

The point is, barrels do shoot left and right as well as down and very rarely up, and something has to be done. Before adjustable scope rings there was shimming, plus turning the rings around. With one-piece rings you have two possibilities. With two-piece rings you have six possibilities. Yep, count them:

1 – Both rings forward
2 – Front ring forward rear reversed
3 – Front and rear reversed
4 – Rings swapped, front for rear. Call them both forward now
5 – New front ring forward new rear ring reversed
6 – Front and rear rings reversed

This is another reason I like two-piece rings. But sometimes no solution is found with any of these possibilities. I HAVE shimmed a ring on one side, but only because I was too poor to buy an adjustable set. But when B-Square hit the market with their AA adjustable scope rings, things changed forever.

Build a Custom Airgun

B-Square

For reasons I don’t exactly remember I became friends with Dan Bechtel, the founder and owner of B-Square. He was interested in expanding his line of firearm scope rings to the airgun market and came to me for advice. This was back in the Airgun Letter days.

The first thing he and I did was measure the width of as many different 11mm dovetails as we could find. We discovered that not only were the groove widths different, the angle of the grooves was also different and that made a huge difference in how deep the scope ring base jaws went into the grooves. Some were cut on a 45 degree angle and others on a 60 degree angle.  We found “11mm” airgun dovetails that varied from 9.4mm to greater than 13.5mm wide. In all honesty Bechtel’s people did most of the work, but he came to me to see whether I knew of anything else that he hadn’t tried. I guess that is how we met.

We discovered that BSA and CZ had the widest dovetails. I forget who was the smallest, but it could have been some older Dianas like the 25/27/35. In fact I think it was. My point is, people don’t think about things like this when they buy scope rings. They ought to fit — right? On the other side of the coin the folks at BSA probably said, “Let the rest of the world do it our way,” and the folks at Diana said the same, only in German. So you end up with forty-leven different dovetail widths that scope ring manufacturers have to deal with and the folks at the Pyramyd Air call center get yelled at because they didn’t correct your order when you bought a rifle, scope and rings from them last week. What is the matter with them? Don’t they KNOW?

Quick — what’s the castor angle of your vehicle’s front wheels? No, they don’t KNOW. They also don’t know whether you are buying the rifle for yourself, the scope for your son and the rings for a friend. Get it?

The AA adjustable ring

Once the 11mm base issue was resolved (thank the Lord for Picatinny bases!) B-Square set about to design and manufacture their AA scope ring. It centers around a gimbal that can be adjusted both up and down and left and right.

B-Square gimbal
This split ring gimbal was the basis of the B-Square AA adjustable scope ring. You are looking at the bottom of a scope ring flipped upside-down. This steel split ring is a gimbal that threads onto a stud that sticks up from the mount base. There are two holes on opposite sides of the split ring/gimbal that the noses of two small adjusting screws enter, allowing this split ring/gimbal and the scope ring attached to it, to be pushed side-to-side and also to rock forward and back. This is why the scope ring will tilt when the rings make the scope tube change its elevation and angle.

B-Square ring
And here is the entire assembly, right side up. The oversized hole at the base of the ring allows it to be adjusted in all directions. Now that you see the gimbal in the scope ring you understand how this system works.

B-Square AA rings are no more

B-Square AA rings were difficult to mount correctly and many people had problems with them coming loose. I did all I could for folks, but the blog wasn’t as well-known at the time so many folks didn’t know where to turn. I even edited and rewrote the installation instructions that came packaged with the rings, but as I said, it was just too difficult for a lot of people. If you read that three-part blog report I linked to above and here you will see that Paul Capello used to be an active blog reader and that was where the inspiration for the television show American Airgunner came from.

Sadly B-Square AA rings are no longer available new because B-Square is no longer in business. When Dan Bechtel became too old, he no longer managed his company day to day and no path of succession had been established. The company went on for a short time but eventually ceased doing business.

Dan passed away several years ago and the AA rings are history. But they did establish an important thing. The gimbal principal allowed for the scope rings to tip forward and back, as well as swiveling side-to-side, without putting a strain on the scope tube. Later manufacturers did this in different ways but they all learned from the genius of Bechtel.

Summary

Wow! Shoot fire, and cowabunga! I had no idea there was so much to tell when I started this series — especially on adjustable rings! I forgot that I was there for a lot of the beginning. We ain’t done with adjustable rings yet!

45 thoughts on “Scope ring series: Part 5”

          • hihihi: It’s been a long time since I finished the second year of Mandarin Chinese in 1968. But, I can answer your query: “Yes, it is equally difficult to abide the linguistic conventions of a ‘foreign’ language.” That is particularly true for Chinese in that there is no alphabet but individual characters in the written form. New terms are devised by sequencing characters together, whereas in alphabetic written languages another language term can be “transliterated” (sounded out) in the first. In a sense, a ‘foreign term’ can be ‘adopted into’ the person’s native tongue as needed. It takes a very skilled translator to move between the disparate languages; exacerbated by those that are more different than similar. Indeed, human history is replete with friction caused by or worsened by our inability to communicate fully.

  1. It would be nice if some manufacturers of airguns simply stated on the box, “Adding a scope to this airgun will only increase its appearance.”
    Then again, it may be misinterpreted for a Chinese statement that adding a scope will make things look bigger.

    • That is truly funny and also a reflection of a really possible reality! I took two years of Mandarin at Miami University (Ohio) with my last Chinese language involvement in ’68. The potential for such “unique” consequences comes from linguistic dissimilarities. We have grammar in English, Mandarin as word order. Put things slightly askew in the order and unexpected things can happen quickly enough.

      • lFranke
        Ran into it a lot growing up in a Brooklyn NY melting pot. My apartment landlord had a very well designed and nicely painted sign at the bottom of his whitewashed basement stair that we found very entertaining. “PLEASE CLOSE LIGHT WHEN YOU LEAVE” He was from Poland. I could make fun of him because I am part Polish. I told people it was the part of me I sit on, my brain was German, and the rest was English.

  2. Can’t sleep. But this is fascinating. A challenging engineering problem to align a scope to a bore that is not aligned with the outside of a barrel. Not a big problem for target shooting at a set distance, But seems like a real problem when the distance to target is variable.

    More please. I have at least one air rifle begging me to scope it. I have a Walther Terrus .22 with a dovetail scope rail. The safety is located so as to make mounting the AirForce peep sight too far forward. The open sights are not precise enough to do justice to the accuracy potential of the rifle. I’m thinking a Bug user is the way to go. I am open to any other advice.

  3. I have some “standard” one-piece and two-piece rings. Most of these are slowly being replaced with adjustable rings. I also have adjustable 11mm to Picatinny rail adapters. Some of these adapters will not only tilt but allow a little side to side adjustment. They often have stop pins to allow mounting securely on sproingers.

    I do not know if they still do such, but I had a one-piece scope set that would not tightly grip my Gamo CFX and PA machined it to grip tightly.

  4. Love this topic. Being an incurable optic switcher and owner of many adaptors, risers, one piece, two piece and at least one three piece set of rings, this report contains a wealth of useful information.. I too am gradually switching over to adjustable rings but still have lots of scopes mounted that are shimmed. Many of my scopes are the popular priced variety that work very well at my maximum 25 yards.. But I want lots of turret spring tension to preserve POA/POI so adjustable rings make this much easier to do.

    PS: Anyone out there using the disallowed in competition optic tubes? I am curious enough to want one.

    Deck

  5. On barrels, Hammer forging has come a long way and if done properly is hard to beat, little pun for y’all. I like the Krieger method of barrel making best, bore the barrel, turn the O.D, do all outside machine work on the barrel then rifle it. Krieger famously makes their M1 Garand barrel this way, quite a bit of machine work, lathe and mill on the outside of the Garand barrel and I believe this is why Krieger Garand barrels are by far the best. On the “11”mm dovetails , older Anschutz and Suhl rifles have a big radius on the top of the receivers and these days the only rings I find to work are B&M. Years ago B&M became my standard when the only choice is to mount to the “11” mm dovetail. On shims, Hawk makes plastic 20 MOA shims that I have had some success with,
    Back in 2001 when I lived in Benbrook , TX I worked as a set up and programming man in a CNC shop in FT Worth and almost took a job with ‘B” Square. God had other plans and I still have a steady job.

  6. B.B.

    “All gun barrels droop. AR-15 barrels droop more than most.”
    Yes, you have mentioned it many times. However, to channel my inner 5 year old, WHY?
    That has never been explained.

    Thanks,

    -Yogi

    • Yogi,

      I think air rifle barrels point down mostly because they are bent when pressed into their base block. As for AR-15s I don’t know. I just know that there are special drooper mounts made just for them. As far as firearm rifles go, the drooping issue is far less than with AR-15s and air rifles. They might only shoot 12 inches low at 100 yards. Scopes correct for that without an issue, so nobody cares.

      BB

      • Tom Gaylord (B.B. Pelletier) how interesting! That would never have occurred to me.

        I wonder if there is a manufacturer who would care to confirm, maybe even elaborate on that? 🙂

          • Tom: Wow! Talk about a rapid turnaround from a request! Tinkerbel and Fairy Godmothers have nothing on you! Are there ANY adjustable mounts made today? Apparently, the one you wrote about is no longer available?

            I have rued the lack of adjustable mounts every time I mount up a scope on another springer. I would love to be able to get in the black BEFORE even touching a turrent (assuming that the scope is a “Zero” W/E from production – something that can be easily checked by rotating the scope in a set of fixed rings to see if the cross is staitionary).

            I would gladly get rid of the assortment of plastic shim pieces I have accumulated in the gun cabinet over the years and pay more for such a set of rings! Not have to take all the acetaminophen would pay for the difference in ring cost!

            Thanks, again for pursuing this issue that is a serious one, particularly for us archaic springer types who think that compressed air is at the end of a piston stroke.

  7. hihihi,

    Wrote: “I wonder if there is a manufacturer who would care to confirm, maybe even elaborate on that?” Do Not hold your breath!
    On the AR-15 (Stoner Rifle family) the upper, the scope/sight rail, the barrel, the barrel nut, the gas tube, the gas block, the gas rings, etc, etc, are all typically sourced from individual suppliers and assembled by the Name on the Rifle company, MAYBE! You might have a “real” gunsmith involved somewhere in all that but even that is doubtful. The tolerances that cause the apparent difference in POA and POI is caused by WHAT? Your guess is as good as B.B.’s, mine, or any reader of this Blog! Gravity is probably enough to take all those loose spots and make the rifle shoot DOWN more often then some other way.
    How big of an angle does it really take to be off by an inch or a few cm at 100?
    Hang a weight on the end of a benched rifles barrel and see how much the POI shifts when you take it off
    https://www.1728.org/angsize.htm

    shootski

    • Thanks shootski, I was beginning to feel dizzy, holding my breath in anticipation of an actual manufacturer’s honest disclosure of why we get bent barrels with random boreholes that are then fitted into the action at some downward angle and scope rails that are probably aligned in yet another direction… I’m just happy that they look like guns! 🙂

      Joking aside, all my airguns are capable of more accuracy than I am.

      • Yogi,

        Some few do!
        But there is way more to the story.
        But the problem is what reference you start with and which you are comparing it to; especially on an AR or other component/platform rifle. So yes the bore axis is a good place to start and then move to the sighting device line of sight. That sounds great until you need to get to the target.
        The external ballistics of the cartridge determine some amount of variance of/between the POA and POI. With a scope it also begs the question of click centered scope Reticle or optically centered scope. Next is the sighting system line of sight collimated to the bore axis line extended? And, finally how do you determine/eliminate the degree of Cant? Gravitational? Geoposition? Some other 3D reference system?
        Talk about a can of worms!
        I know I can’t put them all back in the can!

        shootski

  8. Not sure if I mentioned this before but I found there can be a significant side to side offset when mounting a scope with dovetail rings that have one half of the mounting blade machined into the ring base with the opposite side having the screwed down tightening clamp. The fixed blade will position the scope more left or right depending on which side you have the mounting screws on.
    The width of the dovetail and its cut dimensions may not be the same as the engaging blades of the scope mount. In which case the intended centering point of the dovetail may not match the intended centering point of the scope ring forcing it to position more to one side. And of course, positioning the rings mount screws on the opposite side will change its centering position in the opposite direction.

    Dovetail mounts that come with two flip blades to engage 11/32 or 3/8 dovetails may have a better chance of centering but then you have mounts that are designed for one size or the other and you must determine which blade edge goes into the ring and which goes into the dovetail? Not always so obvious.
    Best to just leave those as they came from the manufacturer if you can or at least pay attention if you must remove the blade to install the mount.

    Never really looked into any differences between picatinny and weaver mounts that may affect centering and I’m not sure if it’s of any significance if there is. For all types actually. One or two clicks may be enough to compensate for the offset but it’s nice to know info if you are at the edge of adjustments.

  9. BB-

    The B-Square rings mentioned are now Sun Optics USA brand. The 1” low rings are model number SM0101. It (and other sizes) are available at Adorama and elsewhere.

    • Paco,

      Yes, I see that. Well, Sun Optics was started by two former B-Square employees, so it doesn’t surprise me. One of them passed away a few years ago and I don’t know if the other guy still owns the company, but the mojnts are still available.

      Thank you!

      BB

  10. A novel solution to this problem is on my most recent purchase of a Reximex Regime (Apex anywhere outside of the UK). The picatinny rail is actually adjustable for height and elevation. It’s one of those simple ideas which makes you wonder why it’s not a standard feature on all rifles.

  11. All FM can add to the conversation is that there is so much to be considered when mounting and centering a scope that he is amazed he’s been able to hit anything at any respectable distance with any of the scopes he’s ever used. 😛

    • FawltyManual,

      NOT just scopes! It really is true for any sighting system.

      When you throw a stone, a knife, a dart, an axe, or use a sling to hurl a smooth round river pebble and bring down the Big Philistine with nothing but your eyes…NOW that is what truly amazes me!

      shootski

  12. Hello everyone, I am kinda late to the game, but I have been so busy I can’t see the light of day…

    Sun optics did carry on the adjustable mounts for a while, I bought the last 3 sets of them Optics planet had in stock.I joke that I bought the last 3 on the planet (optics planet).

    I have them on my avengers. Sadly, the rings are discontinued by the manufacturer, but they are still on their webpage.

    They do pop up on FleaBay occasionally if you are into that sort of buying experience.

    https://sunopticsusa.com/airgun-scope-mounts-1-weaver-base-sm0201/

  13. It’s a shame that the 12mm dovetails were never standardized.
    Now we put huge, ugly looking picatizraiks on slim airgun and .22 rifles, because the picatinny rail works perfectly. But a small dovetail would do the trick and be much more elegant and unobtrusive.

    • Mel83,

      “Now we put huge, ugly looking picatizraiks on slim airgun and .22 rifles…”
      I guess you don’t like their looks! But as you said they do work perfectly and even stop scope creep on Magnum Springers!
      There are covers available that can be easily cut to size to cover the unused parts of the rail.

      shootski

      • I also use them, but would prefer a smaller 12mm rail with recoil lug cutouts as a second standard for civilian arms
        Some European manufacturers (Contessa, ERA Recknagel) actually have precise hardened 12mm rails which allow you to mount QD mounts that hold perfect zero.

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