This report covers:
- Droopers
- Shimming
- Adjustable mounts
- Scope rings with fixed droop
- Important to know!
- Summary
Today’s report will be a reminder of a few of the little things we need to know about scope mounts/rings. It’s a subject that affects many shooters.
Droopers
I’ll talk about rifles that droop. The word “droop” is not as clear as it could be. The bores inside the rifled barrels don’t actually bend downward. They simply point down in relation to the rest of the rifle.
This is most commonly seen on breakbarrel spring-piston rifles, which gives rise to the belief that only breakbarrels droop. Nothing could be farther from the truth! Most rifles with fixed barrels also droop.
The AR-15 is one of the most common droopers among firearms, though that might be because there are many more of them than any other model of firearm rifle. I have a Remington bolt action model 721 in .222 Remington caliber and it’s a huge drooper.
In the past 20 years I have assisted several AR-15 shooters at the range whose scopes ran out of elevation adjustment before the bullet was hitting the point of aim at 100 yards! They thought the scope was broken. In one case where the shooter allowed me to shim his scope in the mounts at the range, everything was corrected.
Shimming
A shim is a thin piece of material that raises the scope tube it’s placed under. Shimming the rear scope ring makes the scope point downward, which corrects the downward angle of the barrel to some extent.
A shim cut from an aluminum soda can has been laid in the bottom scope ring.
Shims must be thin or the scope rings will damage the scope tube when the top straps are tightened. I find the material cut from an expired credit card is about the right thickness. But all credit cards are not the same. Many I have measured are 0.030-inches/0.762mm thick, but I have some that are as thin as 0.023-inches/0.5842mm. The aluminum from soft drink cans is thinner and also works well.
Shims should be considered a fallback solution, as they take the scope tube out of alignment with the holes through the scope rings. A small bit of misalignment is okay as long as the scope top strap screws are not over-tightened, but you do have to use reasonable caution when shimming. A much better solution is an adjustable scope mount.
Adjustable mounts
Years ago the B-Square adjustable scope mounts were the most common adjustable mounts on the market. They worked but were extremely fiddly. Unless they were properly installed they could come loose, causing the scope to lose zero.
A better solution is the Burris XTR Signature ring set. These are two-piece rings with inserts that change the angle of the scope tube without putting pressure on the tube like shims do.
The inserts for these Burris rings can be moved all around the inside of the rings to point the scope tube in any direction you want. This view shows how the inserts fit inside the ring cap and saddle. By rotating the inserts you also get left-right adjustment.
Sportsmatch also makes two-piece scope rings that adjust for both windage and elevation. I have a set mounted in my Air Arms S510XS rifle and I have vowed never to remove them — though the temptation has been great. The temptation is great because in my opinion, these are the best adjustable scope mounts on the market. I wish I had more of them.
Sportsmatch adjustable mounts allow for both vertical and horizontal correction. Each ring also tilts forward and back to take all strain off the scope tube.
Scope rings with fixed droop
Another way to get the scope to droop is with a set of scope rings that have a fixed angle of droop. I showed you three UTG ring sets that were shown at the 2025 SHOT Show.
Three drooper rings for 30mm scopes were shown at this year’s SHOT Show. They have a 20, 30 and 40 MOA droop.
These rings will work on airguns of course but they were also made for firearm rifles—specifically the AR-15 platform. But shooters who only shoot firearms aren’t as aware of the droop issue as airgunners. These resonated with me the moment I saw them.
The droop angle on these is fixed and can’t be changed, but now hear the most important lesson in today’s report.
Important to know!
If a mount that can’t be adjusted has you hitting your point of aim close up (10 meters for an air rifle), who cares if the elevation of your scope is almost dialed as low as it will go? What you don’t want is the elevation dialed up as high as it goes because that allows the return spring for the scopes’ erector tube to relax. The erector tube is where the scope’s reticle lives. If the return spring gets too weak the scope may flop around and not hold zero.
Summary
Today we have considered a few important facts about scope mounts/rings. More can be said but this report covers the most important things.
“A shim cut from an aluminum soda can has been laid in the bottom scope ring.” — Amen!
BB,
I’m with you on that; I’ve got a bunch of soda can shims in the upper right drawer of my desk.
So far, I’ve used them to get 4 scopes where they let the air rifle hit point-of-aim with spring pressure to spare.
On the first one, I did have a ‘floating zero’ till I read some of your previous reports, thank you! 😉
Blessings to you,
dave
BB,
I have a set of the Sportsmatch rings. They reside on my BSA R10 SE and I vow they shall stay there. They are indeed the best type rings that are available.
https://www.pyramydair.com/product/sportsmatch-30mm-rings-fully-adjustable-high-11mm-dovetail?a=4353
Do not under any circumstances remove them from your Air Arms S510XS. Your will be sorry. Just buy another set. Yes, they are expensive, but they are worth it.
Okay everybody,
I didn’t say it. RidgeRunner did.
Buy a set of Sportsmatch adjustable scope rings!
BB
RR, BB and everyone else
Don’t forget the Dampa mount of the same company if you want a scope to survive a powerful springer. Quality scopes cost…
Bill,
All of the sproingers I have here will not allow mounting scopes.
RR no doubt about you. I was just trying to be helpful to the readership like yourself and BB by enabling for something really useful.
Bill,
I apologize to you then. I did see such, but since I have no use for it, I did not look at it. Yes, Sportmatch does make a considerable variety of mounts.
BB,
LOL! What can I say? I like ’em!
For the unwashed, FX, Westhunter, Monstrum, et cetera, make height adjustable mounts. I seem to recall seeing another company that made fully adjustable mounts but cannot find them at this time. These Sportsmatch rings are very well made and will allow you to almost zero your scope without using your scope adjustments.
Another error which BB does not mention in this blog and these mounts can correct are windage errors that the bore can induce or the scope mounting slots do not properly align with the bore. This last is far more common than you may believe in even the best made air rifles. My pre AirForce HM1000X had this issue. This air rifle was why I purchased these rings. Hey, if you are gonna pull out the bucks, pull out the bucks. 😉
These days it is more of a pull out the Grants and Benjamins; perhaps eggs will become a suitable form of currency. Faberge eggs definitely would be suitable.
A lot of good tips and suggestions to be found here; time to spring for a set of Sportsmatch rings; could be the solution to zeroing in that Pentax scope on FM’s 10/22 which has become sorta tilt-at-the-windmills contest, not helped by FM’s innate stubborn determination to zero it in again.
FM,
I have seen quite a few Faceplant pictures of some stupid sod proposing to a dame with a carton of eggs. She is commenting “He went to Kroger!”
For a time, large eggs were $9.59 a dozen here. No one bought them.
I usually cut some pieces off of old 35mm film negatives to use for shims. The adjustable rings do seem to be a better solution. Thanks for the report.
A side note, the Carcano rifle that was used in the JFK assassination needed scope shims on the front ring because the scope “drooped” (the points of impact were higher than the scope aim point could be adjusted for a zero at 100-yards).
35mm film negatives, records, pay telephones, dinosaurs…. *sigh*
Something else to consider is bending the scope tube.
As BB points out, when shimming it is important to not tighten the ring screws all the way as this may induce bending or crushing the scope tube. It is important to loosen the front ring when making any shimming or adjustments at the rear ring as this may induce a bending effect to your scope tube.
Many of you will spend a considerable amount of money on your air rifle and/or its scope. Why go cheap with the rings?
Commenter signing in as RidgeRunner,
What have you done with our RidgeRunner? We want him back! 😉
BB
BB,
Are you sure?
I use Sportsmatch and Monstrum adjustable mounts but often use shims as described here. Shimming is a quicker fix. Being a habitual optics switcher quick fixes are useful as long as it works. So far I have not crushed a scope tube. I have learned from BB over the years that it is best to have close to maximum turret spring tension to hold zero. I’m told many scopes have only one turret tension spring but I strive for strong tension on both elevation and windage knobs.
Deck
In my opinion the easiest way to determine good turret spring tension is:
1- Count the number of complete turns the scope knobs adjust between stops.
2- After sighting in both turrets should be somewhere between 2/3 and maximum tension.
Deck
Here’s a fundamental question, perhaps a dumb one, but here goes: I know that some sighting mechanisms turn right to move the sights up, but others turn left. I assume this is true with different scopes as well. However, when adjusting a scope, are all scope turrets universally threaded to tighten the erector springs when the turrent screws are turned clockwise (“righty, tighty”)? Or, are some scopes threaded to tighten those springs when turned left? I have only limited experience with scopes and really don’t know if the springs inside are tightening or loosening as the adjustment knobs are turned this way or that. Thanks.
RG
For what is worth I have seen both. Please don’t ask me if I remember what was the scope with counter clockwise down movement. It must have been an older German scope.
I also have used shims cut from plastic milk cartons or distiled water bottles. Works well.
Mike
Two more items/ideas not mentioned in the article here. One solution is drooper mounts (https://www.pyramydair.com/search-results-ext?keyword=drooper mounts) I’ve used these on a few of my Dianas/RWS air rifles. The other thing I’ve had some success with is swapping the mounts (rear to front or if one piece, just turn it around). Sometimes this will introduce or negate the drooping effect as the rings may not be perfectly concentrically bored.
Fred formerly of the Demokratik Peeples Republik of NJ now happily in GA
Fred
Ditto to your comments. The hinging Picatinny to Dovetail rail type are handy for Diana springers that have no scope stop holes. This drooper mount has a robust stop that goes against the forward end of rail.
The stationary type works well with any rifle that has Dovetail rails with scope stop holes.
They are heavy and can add weight to the rifle which for me often enhances accuracy.
PS: The optics choices are almost as much fun for me as the airguns.
Deck