This is the third installment in our tech article that outlines everything you wanted to know about telescopic sights and the mounts that hold them but were afraid to ask. In this third and final part, I am going to cover - overcoming drop, the lowdown on mounts, installation hints, the B-Square, Beeman, and RWS mounts.
As misunderstood as airguns are, the scope mounts that fit them are even more so. As I sat down to finish this portion of this article, I thought back to my first experience with installing a scope on an air rifle. It was a FWB 124 Deluxe, and after having spent what I considered a small fortune on an overpriced BB gun, I sure wasn't going to spend all that money on those silly, odd-looking scope mounts that Robert Beeman was telling me I needed to do the job right. In fact, I had the perfect scope, too. I probably don't need to tell you what a miserable experience that turned out to be. I stopped just short of ruining that rifle, called up Beeman and ordered the correct mount and an air specific scope to boot. I can't tell you how many great shooting experiences that I had with that rifle over the next several years, but I used it for darn near everything and it remains today one of the yardsticks by which I measure other field-grade sportier rifles. The reason that little FWB was such fun to shoot was because it was so trouble-free and it was amazingly accurate. All that was in part due to the correct combination of scope and mount.
If you have any experience shooting air-powered rifles or pistols, then you know that the lowly pellet is far more subject to the detrimental effects of gravity than a speeding bullet. Compared to even the smallest, lightest bullets like the .22LR or .22 Short, air gun pellets are much lighter in weight and are propelled by a much lower-powered energy plant. Even though some air rifles attain the same velocity as some rimfire rounds, the striking energy is still much lower due to the lower weight projectile. Most rimfire rounds are 30 to 40 grains in weight and travel from 950 to 1124 fps, with some of the new "hypervelocity" rounds traveling 1600 fps. The average .177 caliber rifle pellet is 8 to 10 grains and travels 850 to 1100 fps.
The best field shooters that I know are the individuals that can accurately estimate range and know their rifle's velocity at those given ranges. Here's a clue. An 8.6-grain, round head .177 caliber pellet, shot from a field rifle with a muzzle exit velocity of 850 fps will still be traveling 750 fps at 10 yards, 688 fps at 30 yards, and 600 fps at 50 yards. If you sight in this air rifle to strike point of aim at 10 yards, then the pellet will be approximately 1 - 3/4" above the line of sight and drop to be very close to right on target again at 30 yards. Continuing down range, that pellet will be 1 - 3/4" low at 50 yards. I've never conducted any tests to see how much elevation adjustment is required to overcome initial pellet drop, but remember that gravity begins to degrade the flight of any projectile the moment it exits the barrel. Manufacturers of air rifles and pistols have come up with an ingenious way to help us shooters keep their products on target and make them far more easy to use. If you closely examine any break-barrel air rifle, you will see that the barrel looks as though it drops away slightly from the receiver at the pivot point or the breech. Some models exhibit this trait more than others, but all break-barrel rifles will show it to some degree. What you are seeing is barrel angle. If you are a converted firearm shooter, this can be disturbing at first. The standing opinion concerning firearms is that the barrel of a rifle must be rigid, straight and true to achieve the pinnacle of accuracy. This is fine for conventional firearms, but just the opposite is true for an air rifle. Because a break-barrel design pivots at the point of the breech, the barrel must be adjusted to "register" to align with the potential flight of the pellet and not the receiver. Some manufacturers register the barrel to strike at point of aim at different ranges. Some manufacturers register the barrel to be used most effectively with a scope. The degree of barrel registration depends on the intended us of the air rifle.
Most, but not all Beeman "R" series rifles have the barrels registered for use with a scope. This is why the Beeman 5030 and 5040 Series Scope Mounts do not require any external adjustments but are compensated to help you strike point of aim at ranges less than 30 meters. A compensated scope mount has a small degree of taper built in to accomplish this.
Most, but not all RWS rifles come with the barrels registered for use with the open sights included with the rifle. RWS uses 40 yards as their intended range to strike point of aim. That way the sights have plenty of adjustment for both windage and elevation at the closer ranges. If you have a RWS rifle, you will need to use an adjustable mounting system like the RWS "C" Mount. The added windage and elevation adjustment in the mount allows you to approximately zero the scope without using the scope's internal adjustment for changes in windage and elevation due to the changes in pellet weight or estimated range.
The vast majority of scope mounts made for air guns are attached by some sort of clamping system. The ring or mount simply clamps to the top of the receiver that is machined with a dovetail cut along both sides that accepts a matching dovetail piece on the side of the mount. Most air guns made in Europe feature a nominal 11mm dovetail. I say nominal because this dovetail can measure from a little less than 10mm all the way up to 11.5mm wide. Manufacturing tolerances between different brands of air guns are not identical. The BSA line of air guns uses a 13mm dovetail. This means that mounts or bases made for similar, nominal 3/8" dovetails found on many rimfire rifles will not fit BSA air guns. There are some model specific mounts for air rifles that have other means of attaching scopes but these are the exception and not found very often.
One very important feature to remember when selecting a mount for your air gun is to make sure it includes an integral recoil stop or a separate recoil stop can be installed in conjunction with the mount. Recoil stops help alleviate the effects of push-pull recoil that's inherent to all spring piston air guns. Most recoil stops attach to the dovetail and include a pin or screw that, once tightened against the receiver, increases the strength of the mount it's placed behind. If installed properly, a recoil stop will completely eliminate scope slippage. And remember, the larger the scope, the greater the effects of recoil. Long scopes with large diameter objective lenses are a dream to look through but they are heavier and will respond to the effects of air gun recoil to a much greater degree than a smaller, lighter scope. If you use a large scope, don't forget the recoil stop and sometimes even dual recoil stops are necessary.
Much has been written about aluminum mounts versus steel mounts. My opinion is that I've never seen an airgun mount fail because it was made from a specific material. A mount will fail because it is not designed and made correctly. If total weight is a concern, then choose aluminum. You can cut the total weight of your air gun by a few ounces. If you appreciate the durability of steel, then choose steel.
We get constant questions about which is better, a two-piece mount or a one-piece mount. Actually, it is a matter of application. A two-piece will provide greater flexibility of mounting position if you are using a very long or very short tube scope. A one-piece mount has greater surface area to grip the receiver, so if you are using a large scope that is more likely to move due to recoil, a one-piece mount may be the best choice. If you want to get right down to it, a one-piece mount by design is stronger, but again, I've never seen a two-piece mount fail because it was made two pieces. Air gun scope mounts fail because of poor design or poor construction. Match the correct mount to your specific air gun and scope combination and you won't have any problems.
If you are installing your own scope, here are a few things you will want to do to help ensure an effective installation.
1.Use denatured alcohol to completely degrease the mount, receiver, rings and scope tube. 2.Use low-strength Loctite #222 or medium-strength #242 on all mount and ring screws. The inherent vibration of air guns will cause even correctly tightened screws to loosen over time. Make it a part of your normal maintenance to check all your scope mount screws on a regular basis. 3.Use only mounts and rings specifically designed for air guns. I don't care what anyone else tells you, they are not the same and will only cause your problems.
B-Square, Beeman and RWS Mounts
Here is an alphabetical listing of the different air gun scope mounts that we carry and a brief description of their individual features. While this list is by no means exhaustive, we have found that with the following mounts we can accurately install a scope on all of the different rifles that we carry as well as many brands we don't. There are other mounts made by other manufacturers, but I've never found the need to sell them. This is in no way a judgement on the quality or effectiveness of the mounts we don't carry, it's just that we try to keep things simple here and tend to go with what works.
B-Square - The B-Square Company has been around for many years and has manufactured mounts for conventional firearms of all types. About a year ago, they came up with their "AA" design of adjustable scope mounts specifically for air guns. I believe the "AA" designation stands for adjustable air gun. The entire line of B-Square mounts is machined from high-strength aluminum and finished in a black hard-coat anodizing that very closely matches the polished, blue finish found on many air rifles. They are available in one-piece and two-piece designs. The mounts are unique because they pivot on the center axis of the ring, which allows for precise alignment of the rings with the scope tube. This pivoting feature is also the basis for the elevation adjustment as well. The ring caps are a "saddle" type that snap over the scope tube and attach with two screws on both sides of the ring. When all four screws are tightened down, the scope is held very securely in the ring. A threaded shaft in the center of the ring base accomplishes elevation adjustment. Opposing set screws, which also serve as windage adjustment screws, are tightened down when the ring is raised to the required height. An integral scope stop is included on all models. If you are using a scope with a large diameter objective lens, then you may need a 5mm and 10mm riser screw that is available to help provide the necessary clearance between the objective bell and the receiver or barrel.
Beeman - Beeman has provided mounts for their rifles for about as long as they have been in business. Robert Beeman was one of the first endorsers of scope use for air guns because he discovered how optical sighting even further enhanced their inherent accuracy.
Beeman scope mounts are made from aluminum and feature a matte, blue finish. The rings are horizontal, 50/50-split designs that include four cap screws on each ring. Each ring measures 7/8" in length so there is plenty of surface area to securely hold the scope. The base of the ring is an integral part of the base itself, again adding to the overall strength of the design. The #201-05-5032 and #201-05-5033 mounts include a built-in 0.75mm of taper to help overcome barrels that are registered with a slight droop such as the "R" Series Beeman Rifles. Beeman makes eight different variations of their mount. It is available to fit 1" and 30mm scopes and in both one- and two-piece models to match Beeman rifles as well as air guns from many other manufacturers. They also have "high" versions to accommodate scopes with objectives bells up to 56mm in diameter. Their newest additions include extended versions of their two-piece mounts for greater flexibility of ring placement when mounting full-length scopes. All models feature an integral recoil pin that can be removed if your air gun does not require it.
To put all three parts of this article into perspective, I need to go back to last year in the November newsletter when I first laid out the ideas and goals that I hoped to accomplish. As I started writing this article, it became clear to me that I really needed to put the first part last and last part first, so that's why I switched around the parts from the original plan. I deliberately left out the section I had written on the best use for the many different types of scopes that are available today. Instead, I chose to interweave through the entire article the constant thread that the best scope for your air gun is the scope that you like to use. To some that may seem like a cop-out, but here is why I chose that path instead.
Over the years, I've softened my hard-and-fast views that used to dictate a target scope must be used for target shooting and a hunting scope must be used in the field. Today's telescopic sights contain so many great features that the line between absolute usage has become blurred at best. Target specific scopes might not be the best choice for a dedicated field hunter, but if that's what they enjoy using, who I am to disagree? Actually, as my quest for smaller and smaller targets at longer ranges become an obsession, my choice in field scopes has changed drastically from what I would have chosen just a few years ago. As I look back, many of my choices in scopes were dictated by availability. Today's shooters have a lot more scopes with far more features to choose from, so why limit or predicate your selection on what I find best. My advice is to buy a scope that you think will fit your needs and don't be afraid to change if you think another one will do it better.