Fitting and Mounting Scopes
Many people will spend many hundreds of $ on airguns and scopes, only to ruin accuracy by failing to properly mate the scope to the gun. Failure to align the mounting rings can put the scope under stress, misaligning its internals. This is most harmful to the variable scopes which have sliding lenses that must remain in perfect alignment when zooming, or changes in the scopes zero will occur. Even the best variables have some impact shift when changing powers under perfect conditions. Applying pressure to the tube with misaligned mounts can cause larger impact shifts.
An additional factor affecting spring airguns is their two way recoil. This recoil effect does not occur in firearms or in other types of airguns. Spring airguns produce a soft rearward recoil, then a sharp jerk forward as the spring slams forward. Heavy or light pellets can also be a recoil factor. This can cause internal problems in conventional scopes, most of which are not constructed with this type of shock in mind. (Airgun scopes themselves are not entirely immune to this problem, especially the cheaper ones.) It can also cause the scope to slip rearward in the rings, and/or the mounts to slip on the gun. Some spring guns are worse offenders than others, but it is something you must consider in all spring air rifles. Avoid cheap aluminum two piece mounting rings such as Tasco. They are more likely to slip than steel rings.
Scope stops are built into many airgun mounting rails, and clamp on after market stops are also available. Both of these to address the potential slippage of the feet of the mounts on the rail or groove of the gun. It is best to use mounts designed specifically for spring airguns.
Proper alignment not only aids in keeping the scope internals working smoothly, but also provides more surface area contact between the scope and the mounts. Some gun/scope combos may require a third mount to obtain enough contact area to stop scope slippage in the mounts, even after alignment, and friction enhancing products are applied between the mount and scope.
As you can see, scope mounting on spring airguns is not a trivial matter.
Spring airgun certified scopes are available, and should ALWAYS be used. Even then, scope problems can occur. Some just refuse to believe that a lowly pellet gun can distroy a rifle scope. "I used one on my.458 thunderbluss for years and it still works just fine. Do you really expect me to believe an AIR RIFLE will tear it up? Fit that guy for a strait jacket."
They will just have to learn the hard way.
Another factor affecting break barrel guns is obtaining the proper angle of the scope in relation to the barrel. If you have one of these guns, and have problems sighting in you will definitely need to get a set of drooper mounts from MAC1 Airguns
. They are expensive, but I advise spending some money here, if you have to save somewhere else. Trying to use standard mounts with shims would likely result in misalignment, and adjustable mounts on spring guns will not hold zero.
If the gun has a built in scope stop, it should be utilized. Clamp on scope stops may have to be employed.
Aligning the scope within the rings can be addressed in several ways, all of which are likely to be needed. Rings can be swapped front to back, and they can be turned around. Since there will always be slight dimensional discrepancies, one particular combination is sure to yield a better fit than all others. Fit can be checked by laying the scope in the bottom rings and determining when it fits the best. It is time consuming, since the rings must be tightened down in all possible combinations, but worthwhile.
Note: If you use a one piece airgun mount, you may not need to do the next steps. I have never used a one piece mount, and do not know if they are likely to line up correctly without extra work. Two piece mounts will almost always need some fine tuning done to them to get proper alignment.
The next step is more involved, requiring the purchase or making of some specialized tools. Brownell's
sells them. One is a set of pointed one inch diameter steel rods. They are used by clamping into the rings and mounting on the rail or groove. If perfect alignment is achieved, the points will touch, if not, they will be skewed. Chances are they will not touch perfectly. I have never used these myself, preferring to move on to the next step. A one inch steel bar with a handle on it, and a container of abrasive. Assuming you have lined the parts up the best way, it shouldn't take too long grinding the mounts, to make a fitted channel with a large contact area to resist scope slippage. You should also keep track of which tops go to which mounts, as well as well as their orientation. If you loose track of which one goes where, you can try all the combinations, one way will probably fit better than the others.
Put it all together very carefully with gel Superglue on the base of the mounts. Some clamp the rings directly on the scope, some use thin paper or labels on the top part of the rings, some use dried contact cement or Goop (Wal-Mart and hardware stores often have Goop) on the bottom of the rings. (Do not put it on the scope body and glue the scope into the rings, it is used as a friction enhancer, not a glue. Let dry for 48 hours.) You will likely have as good or better results on the screws in the top of the rings, by very lightly oiling the screws, rather than using them dry or with LocTite. So far, I have had good results clamping directly to the scope and using oil on the screws.
I have used a BSA 4x32 on an XS-B18
with no problems. The B21 B22 SM1000
is not going to be so easy, or allow the use of inexpensive components. I am researching this now, and will advise some specific parts soon. I have mounted TF90's
on these guns, and so far so good. These are very tough red dot sights and should be considered as an alternative to a scope. They are capable of outstanding accuracy and will withstand springer recoil.