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 Post subject: Diana 24 mount T05
PostPosted: Sun Aug 28, 2016 3:31 pm 
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Joined: Sun Jul 24, 2016 8:57 am
Posts: 52
Looking for a scope mount for a new to me Diana 24. Is this one (I'll source in Canada) a good match? RWS 86315502 Lock Down Scope Mount - 1 in.

https://www.amazon.ca/86315502-Lock-Dow ... B003TKR7BS


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 Post subject: Re: Diana 24 mount T05
PostPosted: Sun Aug 28, 2016 3:59 pm 
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Joined: Sat Jan 25, 2014 9:16 pm
Posts: 1271
Location: United States
Too spendy imo, I'd get one of these:
http://tinyurl.com/gppbjbx
http://tinyurl.com/hyr85qn
I have both and they're very strong and very nice looking. Plus they're lower than that RWS, which I prefer to have the lowest mount that will fit for accuracy, but some prefer them higher if needed for comfort. The UTG one-piece can be drilled/tapped to make it a 5 screw clamp if needed, but I seriously doubt you'd need to with that gun.


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 Post subject: Re: Diana 24 mount T05
PostPosted: Sun Aug 28, 2016 4:22 pm 
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Joined: Sun Jul 24, 2016 8:57 am
Posts: 52
Forgot to mention would like to compensate for barrel droop. So far $45 at DL


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 Post subject: Re: Diana 24 mount T05
PostPosted: Sun Aug 28, 2016 4:30 pm 
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Joined: Sat Jan 25, 2014 9:16 pm
Posts: 1271
Location: United States
Most people including myself just shim the scope at the aft end. Easy, free and adjustable to perfection.


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 Post subject: Re: Diana 24 mount T05
PostPosted: Sun Aug 28, 2016 5:06 pm 
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Joined: Sun Jul 24, 2016 8:57 am
Posts: 52
What material would work for shimming - don't have any film/negative stuff. Would clear heat seal laminate that you use for documents/business cards work?


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 Post subject: Re: Diana 24 mount T05
PostPosted: Mon Aug 29, 2016 4:43 pm 
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Joined: Sat Jan 25, 2014 9:16 pm
Posts: 1271
Location: United States
I've used brass shim stock and plastic of .0075" and .010", but only because I have it on hand. People use a variety of plastics like from soda/water bottles or retail pkgs, and alum from cans. Just don't use something that'll change over time, like steel that may rust and expand, or paper/cardboard that will decay. You can even use rubber which is probably ideal since it's grippy, conforms better and shock absorbing. Like from a bike inner tube. Yet another option would/could be silicone sealant if you wanted to try.
Excluding rubber, I'd sand both sides of the shim material with at least 320, but closer to 180 is probably better, that way the material can stick better to the scope, mount and other shims. Using a yard/meter stick lined up with the barrel you can see the angle difference at the scope and estimate the shim needed. Shim to that height and give it a try. Now the simple version which I bet most people do is just use that estimated shim height and call it good. For more detailed info, the why's and risks to the scope, read on:
To get the correct shim height for your gun and range you need to center the inner (erector) tube in the scope as close to center as possible. This will give you the best optical alignment, and good spring tension. Start by eyeballin the inner tube thru the front lens with a flashlight and use the W/E screws to center it. Or estimating center by cycling the W/E screws all the way in/out then setting each half way, which isn't as accurate as eyeballing imo, plus there's a risk that cranking the screws all the way down "may" weaken the leaf return spring opposite the W/E screws which can also be seen thru the lens. Once the tube inside is centered you can use your estimated shim(s) and shoot at the range you plan on sighting it in at and adj shims if needed to dial in the elevation within reason. For guns used at various ranges, like most of us do, it's best (imo) to sight the gun in based on it's power level/trajectory. Ideally if you know your velocity with your fav pellet you can plug that data into the free program "Chairgun" and it'll tell you your zenith, then from there you can make your elevation choice. Should make sense when you see the graph of your pellets trajectory, and how a setting just below zenith, say 1/8th to 1/4", will give you a nice stretch of distance that the pellet will hit +- that distance from the reticle. My preference is to have the scope mounted as low as possible to take the best advantage of that, but mostly I do it for looks b/c I hate a scope on stilts. Once you're close to on target you can use the W/E screws to fine tune it. This way the scope is as close to center as possible for optical alignment, and more importantly imo, good spring pressure from that leaf spring. The reason is when unshimmed you have to adj the elevation screw out (unscrew) to compensate for droop which reduces spring tension on the inner tube. Springers have a very harsh reverse recoil (kinda a double negative so should it be "coil"? :p ) when the piston impacts the breech and that shock is what breaks scopes, but it can also upset the setting because the inner tube can jump around. If it jumps and lands back in the exact same place no biggie, but apparently scopes aren't that precision. I'm guessing the more friction/stiction at the pivot joint, screw contact patch, and less spring tension are the problem(s). If they all worked perfectly it would never happen, but it does and all you can really change is spring tension. If people still have an issue after centering then they have the option of cranking the W/E screws in say 1 turn further from center which leans on the spring more. Then you simply have to shim accordingly, which may involve offsetting the shim to the side a bit to compensate for that windage change, which may also need to be done if the gun simply shoots too far to one side. With a D24 I can't imagine you'd need to crank your W/E screws in further but fyi to better understand the whole ordeal.
When adding shim you add to the lower side of the rear mount, obviously, but you can only add so much before the scope will no longer fit in the saddle, so lay one shim down but rather than all the way across 9-3 O'clock lay it say 8-4. If you need another shim 8-4 may still work, but better to either make it a bit shorter or taper the ends so it fits better. Make sense? So ideally when the scope is pressed into the saddle it'll be as well and evenly supported as possible. And yes people have dented their scope by using too wide a shim which pinches the scope, or a too short which dents it. The scope tube is made from very strong heat treated alum alloy, but it's very thin. It's hard enough that it cracks as it bends, so keep this in mind when tightening the cap screws down on an imperfectly shaped shim. Another concern is the scope and mount will no longer be parallel so the front bottom edge of the front mount may dent the scope tube a bit. Possibly the fwd edge of the shim at the rear as well, but you can also set each shim a bit back relative to the previous, and/or taper them. This is all dependent on how much shim/angle there is, how tight you go with the screws, how weak your scope is, and how sharp the mounts edge is. The ones I linked you have that traction tape in them which means it helps with this problem since the scope rests on that tape so it can handle a bit of angle before touching the alum, plus the tape holds much better so less tightening needed. Something to think about if you have an expensive scope, and how deep the dent combined with that harsh reverse recoil can break a scope at that crack. Not trying to scare you, but I want you to be aware since it does happen to people, usually by accident because they hear about scopes not staying put so they crank the piss out of those cap screws, but almost always it's the gun to mount that slips, not the scope in the mount. Plus with that new traction tape I doubt anyone has had a scope slip. Having that tape on the rear saddle is up to you since the shims won't exactly match it. So you you can just leave it and not worry about it, remove it, or maybe put the tape on the scope instead which will no doubt help prevent denting. Also be a bit wary of torque pattern for the caps, so torque the 4 screws like a cars head, meaning working around so they're more even as you go and even when done.
Optionally to help avoid possible denting you can shave the edge of the mount a bit, kinda like how some people align-hone mounts on firearms, which seems kinda hard core anal, even for me.
Again, not trying to scare you, just inform so you/anyone is aware of possible issues. If all tightened within reason it shouldn't dent, and small dents are just cosmetic anyway. If anything I wrote doesn't make sense just let me know and I can explain it better.


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 Post subject: Re: Diana 24 mount T05
PostPosted: Mon Aug 29, 2016 5:46 pm 
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Joined: Sun Jul 24, 2016 8:57 am
Posts: 52
Wow thank you very much for the informative info!


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