GTA
Airguns by Make and Model => Diana Airguns => Topic started by: del on February 21, 2014, 12:26:37 AM
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I have a RWS 34 and am considering shiming under the scope mounting rail to compensate for barrel droop. I think I can build a ramp the length of the rail using sucessively shorter strips of soda can material in layers (4-6) to gradually raise the rear if the rail. Brass would be another option.
Sloping the entire rail would allow the scope rings to remain perpendicular to both the mounting rail and the scope tube. The scope would remain parallet to the rail, and point slightly downward from its original position. Has anyone tried this?
Yes, I know about the droop compensating mount and ring combinations.
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Sounds like a jolly good idea. Why don't you do it and see how it turns out. The overlying condition is that you report back on your success.
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Here's how I've made a "few" drop compensator mounts...
(http://farm2.staticflickr.com/1122/5140830142_e61dba8d27_z.jpg)
1st - The original mount with a thin enough plastic wafer - this one was 1mm thick - perfect...
(http://farm2.staticflickr.com/1388/5140227433_e53c4beb06_z.jpg)
2nd - Mix some resin glue thoroughly...
(http://farm2.staticflickr.com/1365/5140830296_6e6d3e386b_z.jpg)
3rd - Cut a small square of the plastic wafer and place in the rear clamp...
(http://farm5.staticflickr.com/4011/5140830468_565e0451c9_z.jpg)
4th - Put ample resin glue in both clamps, making sure that spacer/wafer is on the rear of the rear clamp...
(http://farm5.staticflickr.com/4147/5140227583_2c312554f8_z.jpg)
5th - get a alloy tube (or any tubing) 1" dia and wrap some cling film around it and clamp it down and leave to cure overnight...
(http://farm5.staticflickr.com/4050/5140227683_763a347dee_z.jpg)
6th - Undo next day and pull tube away...
(http://farm2.staticflickr.com/1134/5140830740_b9fdbca4f5_z.jpg)
7th - Sharp cutter, cut away excess...
(http://farm5.staticflickr.com/4010/5140830958_6221b6901a_z.jpg)
8th - Voila. One sloping mount...
It works and is so easy to do...
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Or this..............
https://www.pyramydair.com/product/utg-drooper-scope-rail-11mm-to-weaver-adapter-compensates-for-droop?a=4191 (https://www.pyramydair.com/product/utg-drooper-scope-rail-11mm-to-weaver-adapter-compensates-for-droop?a=4191)
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I just used a water bottle and cut shims to tip the scope parallel with the barrel
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I just used a water bottle and cut shims to tip the scope parallel with the barrel
I used to do this and maybe still will but this method actually wants to bend the scope tube by lifting the back end upwards (presumably you are lifting the back end to compensate for droop) and might break or dislodge something inside without your knowledge. It may not show immediately though. Even just a small shim might be enough to make this happen. I know that many do this, including me at times but I don't make it a practise nowadays, unless the scope only needs the smallest lift. The top halves of those clamps, when done up tight, will both be on two different angles and that's where/how the bending "might" result or at the turret where they both meet. That and sometimes the rings cut into the scope tube because of this "angle". I've had it happen on one of my own and seen it on others scopes too...
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Here's how I've made a "few" drop compensator mounts...
It works and is so easy to do...
Thanks for the idea. When I do this I'll use two part epoxy putty. Comes in a stick. Cut off enough for the job, knead until it's an even color and apply. It's less messy to work with and great for filling gaps.
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I have a RWS 34 and am considering shiming under the scope mounting rail to compensate for barrel droop. I think I can build a ramp the length of the rail using sucessively shorter strips of soda can material in layers (4-6) to gradually raise the rear if the rail. Brass would be another option.
Sloping the entire rail would allow the scope rings to remain perpendicular to both the mounting rail and the scope tube. The scope would remain parallet to the rail, and point slightly downward from its original position. Has anyone tried this?
Yes, I know about the droop compensating mount and ring combinations.
DON'T do it. That seems plausible till you figure out the screws have been bucked like rivets and they are not coming out. You bend the barrel, shim or droop like the guys shows or you do it with a 1" ball end mill and machine it with the needed angle. Taking the rail off the tube will be opening up a can of worms for no gain.
TimmyMac1
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+1 for the droop compensator mount. One came with my 34 T06 Striker combo purchased 8/2013 and no scope mount issues what so ever.
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Here's how I've made a "few" drop compensator mounts...
It works and is so easy to do...
Thanks for the idea. When I do this I'll use two part epoxy putty. Comes in a stick. Cut off enough for the job, knead until it's an even color and apply. It's less messy to work with and great for filling gaps.
Yeah, I've used that stuff too. I first saw it about 20 or more years ago. I don't know much about its stability or shrinkage factor but it cures pretty darned hard alright. The stuff I used came in a stick too, like a stick of candy with an outer and an inner part, each different coloured. Looked so good it was tempting to take a bite, but that wouldn't go down too well in your guts, I'm sure. Like you said, you cut off as much as you needed and worked it together 'til it was all one colour then put it where you wanted it to be, and it was done... Over here it was made by CRC...
Actually I still have a stick ot two - good thought..!!
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Yeah, I've used that stuff too. I first saw it about 20 or more years ago. I don't know much about its stability or shrinkage factor but it cures pretty darned hard alright. The stuff I used came in a stick too, like a stick of candy with an outer and an inner part, each different coloured. Looked so good it was tempting to take a bite, but that wouldn't go down too well in your guts, I'm sure. Like you said, you cut off as much as you needed and worked it together 'til it was all one colour then put it where you wanted it to be, and it was done... Over here it was made by CRC... Actually I still have a stick or two - good thought..!!
That's the stuff. The last one I used up was sold as fuel tank repair. It's bonding qualities are not as good as liquid epoxy, it'll stick to whatever you put it on, but it's great for filling gaps. I used it once to fill a rock hole in a motorcycle crank case. I filed it to match the surrounding aluminum and it blended in perfectly. There was no shrinkage and it never leaked a drop of oil. Another time I got tired of replacing rubber engine mounts. The engine torque kept tearing up the rubber part of the mounts on my turbo Eclipse GST. I mixed up a big batch of epoxy putty and filled in the holes in the mounts making them a solid mount. That was almost ten years ago and the epoxy putty filler is still in there doing what was intended without cracking.
I used some last night to fill in a gap on a homemade piston seal dovetail. They claim it's as strong as steel when cured. I doubt that but it's pretty close to the truth. Very handy stuff to have around when used in the right applications. JB Weld makes it too.
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Why is it called barrel “droop”?
In theory, if the bore center line is exactly parallel to the scope centerline the POI will always be low by at least the same amount, and then comes gravity.
My (select barrel angle) 124 shot way high after a cocking accident (my careless son), but I was able to bend it back its original POI. That was easier than repairing the broken stock. After 35 years it is still as accurate as ever spitting out 8.18grs at 865fps with the original spring.
8)
(http://i865.photobucket.com/albums/ab218/Sunchaser01/AGs/DSCN1629a_zpsd8b197cd.jpg) (http://s865.photobucket.com/user/Sunchaser01/media/AGs/DSCN1629a_zpsd8b197cd.jpg.html)
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Gravity conspiring with subsonic speed and time over distance results in a POI lower than the POA. We call that drop and if the barrel is not parallel to the scope groove that would be droop or squat depending on the direction. We must take into consideration scope range of adjustment, mount height, velocity, caliber, projectal weight and ballistic coefficient as well as distance to Target to determine the need for corrected(drooped mounts).
In a nut shell it is real nice to have a scope on target with centered turrets so the adjustments are to compensate for distance and windage issues related to the pellet being fired rather than using the available adjustment range to get on Target with little left to reach further out.
Droop mounts let the scope look where the gun hits without being wound out to the Max to do so. From calling the mounts droopers we came to the point where the consumer says the gun has droop but what they normally mean is it shoots low and you want mounts that look where it hits.
I always build guns with the compensation built into the scope rails or groove cut. Guns with parallel grooves to the scope as well as guns with barrels pointing slightly downward can all benefit from mounts cut to compensate for all the things that conspire to use your adjustment range up.
Some scopes have so little adjustment range it is amazing they can ever get sighted in on guns without Droopers. Earlier Elites From bushnell come to mind as a scope with about 20 minutes up and 20 minutes down and that is all the adjustment they have.
An airgunner needs around 10 minutes of adjustment range normally and that needs to be close to the middle of the total range for the scope to be useful. On Elites you really need to Nail the droop it needs.
TimmyMac1
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Pretty slick idea!
The epoxy would also give a sort of "lapped straight" type scope support if a straight mandrel were used! No need for lapping compound and the tedious "setting in" of the ring seats! I have a decades old Beeman one piece mount that I may subjugate to this treatment!
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I like the apoxy idea. But isnt it much easier and better ton just bend the barrel? High end gun manufacturers do it, field target people do it, I tried it twice and it worked perfectly. POI is exactly where I want it with the scope zeroed and not one detectable negative side effect. I wish I would have known this before I spent money on 2 droop compensating mounts that I d.id not need. Maybe for some reason a barrel cant be aligned to the rail but I cant imagine why
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I appreciate all the responses and helpful advise. I finally decided to bend the barrel. I found it much easier to set up than I expected. The force needed was much less than I expected. All the doubts I had about doing this were completely unfounded.
With the rear sight removed, I used a piece of sewing thread looped over the safety and stretched (just touching the front of the scope rail) all the way to the front sight. The gap between this scope rail line and the end of the barrel was my benchmark for bending. When looped over the front sight and stretched to the back of the receiver, the thread slightly missed the center of the rear sight holes, so I bent the barrel laterally and was able to move the rear sight setting to a neutral position. I also tried a metal yard stick to determine these adjustments, but found the thread worked best for me.
My D34 had enough droop that you could see it all the way across the room, and the rear sight being set 1/16" to the side didn't suit my eye either. It may not shoot any better, but having the scope, the rear sight, and the barrel all line up sure boosts my confidence in the rifle.
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I like the apoxy idea. But isnt it much easier and better ton just bend the barrel? High end gun manufacturers do it, field target people do it, I tried it twice and it worked perfectly. POI is exactly where I want it with the scope zeroed and not one detectable negative side effect. I wish I would have known this before I spent money on 2 droop compensating mounts that I d.id not need. Maybe for some reason a barrel cant be aligned to the rail but I cant imagine why
Yep.....been bendin' R9 my barrels after centering the reticle in the scope for years! I simply bend the barrel till the poi is within 1/2" at 30 yards and then use the scope turrets to "fine tune" the poi. Here's my "barrel bendin' tree" at my practice range that's used for "lateral and upward" barrel tweakin'..........
(http://img.photobucket.com/albums/v734/wved/Field%20Target/BarrelBendTree.jpg) (http://smg.photobucket.com/user/wved/media/Field%20Target/BarrelBendTree.jpg.html)
(http://img.photobucket.com/albums/v734/wved/Field%20Target/BarrelBendCrotch.jpg) (http://smg.photobucket.com/user/wved/media/Field%20Target/BarrelBendCrotch.jpg.html)
If I need to add "droop" to the barrel I use this.......
(http://img.photobucket.com/albums/v734/wved/Airgun%20Mods/R9BarrelBend.jpg) (http://smg.photobucket.com/user/wved/media/Airgun%20Mods/R9BarrelBend.jpg.html)
Then the final tweakin' is done at the "barrel bendin' tree". :o
As you've mentioned, very little actual bending is needed (not enough to actually see) to shift the poi a couple inches at 30 yards so it's a matter of goin' "slow and easy" till the poi agrees with the centered reticle!
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(http://img.photobucket.com/albums/v734/wved/Airgun%20Mods/R9BarrelBend.jpg)
I really like this idea..
When I first saw your pic above the the "bending fork in the tree", quite some time ago, I used to get shivers up my spine, not because of the idea itself,, more for the fact that I'm more likely to mess it all up if I tried it. I'd probably end up with a vertically shooting barrel (well bent upwards),, but this idea has merit,, just easy as she goes I guess. Yeah, I like that...