Author Topic: mounting scopes  (Read 4160 times)

Offline ribbonstone

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mounting scopes
« on: October 14, 2006, 04:38:04 AM »
Most airguns are simple to get a scope attached to, but there are problem children out there that don't make it easy.

The easy ones are generally full sized spring-air rifles of low power/vibration and the almost recoiless rifles (CO2, single stroke pneumatic, pre-charged pneumatics).   A good set of rings seems to do the trick for these.  Cheap rings generally will strip the threads if you crank on the clamp-action too much, so often the little thin cheap rings that come as a "freebie" with the gun scope combinations aren't trustworthy. Good ones (at a good price) are the AGE "Rocktite" two piece...mostly becasue of the large size dual screws that clamp the ring to the gooves.   Am sure there are others, but the pair of AGE's run about $20.  Can look at others, what is needed seems to be good large headed screws..big threads are harder to strip out than small ones..and a wider sized ring ('cause clamping area counts).

 Common multi-stroke pneumatics have some issues.  The typical mounts for Sheridan, Benjamin, Corsman rifles clamp onto the barrel and reciever. Have seen barrels on Benjamins and Sheridans that have come seperated from their tubes from the mount.  The scope mounts pretty high...leverage being greater with that kind of distance, side pressure applied to the scope can detach the barrel.  The old Benjamins were better abut this; they had a lug about 4" down the barrel for the rear sight base. This lug had a lot of base area, so it's bond with the pump tube was greater, and fitting the mount on that short well supported 4" of barrel seemed to cause a lot less trouble. Current Benjamins and sheridans  are clean-lined, no lug for sight mounting...looks good, but isn't as strong.

Are mounts that were designed to take advanatge of the two tapped holes in the reciever's right side (for mounting a reciever sight).   I'e not used these (yet) and will let someone else comment on them.

(personally, I gave up mounting scopes on multi-pump pneumatics and just go with the Williams 5D sight.  If you "just gotta" I'd look into having that long reciever on modern Benjamin/Sheridans cut for grooves.)

Are some problem children in the low power or recoiless catagory, mostly centered on the length and placement of the scope grooves.  Short scope grooves won't be a real problem, just use the two piece rights/mounts and be happy...but they are often in the WORNG PLACE to make this easy.  The "cure" is the cantlliever mount.  Think of a picture of an aircraft carrier...that deck jutting off the front..that's pretty much the idea of  cantilliver mounts.  Most are reversalbe, so you can jut that unsuported flight deck forward or aft.

Hard recoiling spring airs can be troublesome. The only good ways to make the mount stay fixed in the gooves are:
1. Use a one piece mount. This greatly incleases the amount of clamping area in the gooves, and the more area clamping, the less likely it is to shift.
2. Use a mount with a built in recoil stop.  This can be a simple pin that will let you lock into a recess in the reciver or it can be a threaded pin. Either way, it needs a recess in the reciever.
3. Scope stops.  These work like the bottom part of a ring, made flat, with a pin that will lock into a recess.  

Pesonally, the best way is a one piece mount with a recoil pin.  It gives more area for clamping, the pin acts on the whole mount (not just one ring), and the mount does not realy on the scope's tube for alignemnet or strength.  For the money, it's hard to bear the Accushot mounts, currently selling for about $15.

Got to admit, I really rely on these inexpensive mounts. Can usually cut them into two-part mounts, shorten the middle section, or flip one end aroung, and get a scope mounted on nearly antyhing with scope gooves reguardless of where those grooves are or how long they are.  Guess you could do that with other mounts, but these are $15 a pop and the last I looked, Beeman was asking somthing like $65 for theirs.
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The bent and missaligned:

Some pepole will realign the barrel (rebend it) while other's will look to a specailized mount to cure the problem. Some people will shim mounts and even file on bases to get them closer to alignement...and that can work fine, if you know what you are doing.  I've bent them, and proably will again, but as more and more alloy and plastic parts find their way into airguns, it's not something to even consider due to some gun's construction.

Barrels can be bent horizonatally or vertically (or both).  Barrel can be dead straight, but the reciever/barrel juntion missaligned from the factory. Can have the scope gooves cut out of line (usually on cheaper guns) or have the scope goove/rail mounted off line for those that use that system rather than cutting grooves in the tube itself.

Are mounts made to give windage and elevation adjustments seperate from the scope.  The only two I've used so far have been one from B-Square and one from Gamo. Bothe worked, but neither wer on hard recoiling guns, so I can't swear first hand how they'll hold up to a pounding.  Price is in teh $40-$45 range, and they do cure the alignemnt problem pretty well.  Be ready with your mounting tools to spend some time fiddling to get the scope on target; can be fustrating, but it will eventaully get you were you are going on everything but the seriously damaged rifles. HINT: you'll be happiest if you set the scope to it's middle posisions and use the mount to get roups as close as possible to center...keeping your scope close to the middle range of adjustments uses the optically best part of the lens system.

Of the two, the B-Square does the job and has a cleaner look to it...would still be my preference.






Robert

Offline DanoInTx

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Re: mounting scopes
« Reply #1 on: October 14, 2006, 04:11:41 PM »
This is a great how-to, or whatever you want to call it.  I wish I had some of this advice when I was shopping around for stuff.  Hey Wonder if Gene could combine this with some scope selection posts and put it in the library?  Gene, what do you think?

Dan
Dan

Current shooters: Beeman HW97K .177 with Hawke Eclipse 4x16x50SFAO and Steve C. stock, Beeman R9 .177 with Hawke Airmax 4-12x40AO and Gene\'s Midas touch, Air Arms S200 with Bushnell Banner 6x24x40AO Rowan brass bling and Steve C. custom stock, BAM B25, BAM B40 .177 with BSA 3x12x44AO, Benjamin Marauder .22, Benjamin 397 pumper.

\"repeat this mantra:
Air gunzzzzzz, air gunzzzzzz, air gunzzzzzzz!!!  ...You will feel better\" T.E.C.2008

Offline ribbonstone

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Re: mounting scopes
« Reply #2 on: October 14, 2006, 05:26:14 PM »
Decided to try mounting a scope on a Benjamin one more time but I'd have to try something to lessen the chance of seperating the barrel and main tube.

Decided to try a modern Benjamin 392.  Did decide to keep the cost of the experiment down by using an old Sheridan one-piece mount that was rattling around the shop for the last decade and a cheap 1" 4X scope that was on sale locally.

Coated the barrel and pump tube with release agent and bedded each 1/2 of the mount with AccuraGlass...was trying to even out the stress and asssue full even contact. Once cured, demounted, trimmed the flashing of excess 'glass, and mounted that 4X (yep..even with release agent, still peeled some of the paint that modern Benjamins come with as a finish).

(Am reminded by a friend, the very first scope mounts for Sheridans were one piece but were made to clamp over the RECIEVER...they had a cut-out for loading pellets...and might have been a pretty good idea as the reciever has a lot more area connected to the pump tube.)

With the new models reciver being alnost 2" longer than the old Benjamins, the scope need about 6" sticking back from the rear ring...that's a lot of scope, most modern scopes don't have that much distance behind the turrets. Compact scoped doen't have that much sapce no matter how you try to mount them; better to stick with longer "full sized" scopes.  Ended up having to put both rings ahead of the sope's turret, which reduced ring spacing a bit, but got eye relief right.  IF I were to buy a scope just for this, would be one with a straight tube without an enlarged occular...am thinking about it.

The modern Benjamin's stock has a lot less drop and a higher cheek piece, with is a help with a scope. Also means I have to kind of crunch my face down hard to line up with open sights.

So far so good...shot it for an hour or so before dark, getting it sighted in and playing around with different pellets.  Time will tell if this one stays zeroed or not and if the 'glass bedding keeps stress more even and keeps the barrel and pump tube from seperating once it takes a knock.
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So long as I'm mentioning things: "Perfect Rounds" may be perfectly round, but they certainly aren't all the same diameter.

While working with the Benjamin 392 scope-mount job today, played around with an old Benjamin 310 smooth bore "BB".  One shot, the gun wouldn't fire the ball out of the barrel. Needed a rod to knock the ball out; was stuck in the very start of the barrel.  Spent a good amount of time wondering what was wrong with the rifle and cheking things when it turned out that the ball knocked out ran .182". Who'd have thought that a rifle that can shoot a round lead ball to 706fps wouldn't have the force need to swaged down a ball .003"?

Sorting through a can of 500 balls would take a long long time.  By setting the caliber to .178", locking it, laying it on it's side, and taping a short paper funnel over the "slit", can use it as a fast-pass gauge.  The ones that fall though are .177" or less...the ones that won't pass are over .177" (you just dump the one that doesn't pass  out of the paper funnel and into a differnt container).  Of a can of 500 (with about 490 still unfired), were 47 larger than .178".

Running the ones that passed the .178" test thorugh a seond test to sort out the ones smaller than .176" neted 21 balls.

So I have 422 that are between .176 and .178, with 68 that are out of bounds.  The too-small ones won't jam the rifle, but they won't shoot for sour-snail-s### either. Did find that a smooth bore can do pretty good work out to 12 yards or so once you feed it consistant sized ball.

Robert

Offline Gene_SC

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Re: mounting scopes
« Reply #3 on: October 14, 2006, 10:42:59 PM »
Excellent Review Ribbonstone. Thankyou for this fantastic contribution..

Gene
THE ONES I SLEEP WITH: BSA Lightning XL, AA TX-200, AA ProSport, BSA Ultra, HW-97K, Crosman NPSS .177, FX Cyclone, HW-30 Nicle Plated, AA-S200, Crosman Marauder, CZ-634, R-9 DG, Webley/Scott UK Tomahawk, Benji Kantana, Benji Marauder, Benji Discovery.....
....

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