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Thread: Rifle canting, crosshairs not well aligned,

  1. #21
    Join Date
    Nov 2012
    Posts
    107

    Default Re: Rifle canting, crosshairs not well aligned,

    The thing that started me bending my HW barrels years ago was a fall my brother took while squirrel hunting with his R9.

    He was in the WV woods stalking a squirrel when he stepped on a slippery moss covered sloping rock and with the fall he tossed his R9 "muzzle first" onto another rock. My brother was undamaged, however the added Beeman muzzle break was dinged up saving the barrel crown and his old Japanese 3-12x40 AO Bushnell scope had a scuffed up AO. He tested the poi that was previously "spot on" at his 30 yard zero distance and found that the POI had shifted 3" from the fall. The scope still functioned properly so all he did was to re-zero the scope to compensate for the bent barrel and the R9 functioned perfectly after that.

    Years ago I messed with a couple brands of adjustable mounts and both times I was frustrated with the set-up time (a couple hours) and then having the adjustment shift after shooting for a while. After that I simply used my scope turrets to "dial out" any barrel droop or snoop and lived with an off-center reticle in the scope. That got me to thinking that if a fall could shift the poi 3" at only 30 yards and all still function to at least "minute of squirrel head" accuracy then it would be no big deal if the barrel were bent so the poi was close to the aim point of an optically centered scope.

    Since that time I've always bent my HW barrels to keep the poi close to the aim point at my 30 yard zero distance and it works well for me. The whole purpose of the "barrel bending" or adjustable scope mounts for me was to provide similar spring tension all around the erector assembly so it doesn't "float around" with the two way recoil of my piston guns. Keeping the erector assembly near center also minimizes "thrashing around" which is damaging to scopes in general.
    These sketches may be of interest........


  2. #22
    Join Date
    Nov 2012
    Location
    Cuyahoga Falls, OH
    Posts
    352

    Default Re: Rifle canting, crosshairs not well aligned,

    I understand the concepts and ideas your work supports. I have two old external adjustment scopes both with parallax adjustment that I use on my old Winchester 52C and Remington 40X .22lr target rifles. One is a Fecker 16x made in the 1940's and tho other a Unertl 20x made in the 1960's. Both have spring systems to allow recoil control for big rifles too that isn't needed in the 22. These are old enough that the crosshairs may actually be spider silk. I don't know for sure. Zeroing one at 200yds in a 22lr does move them off center a ways.

    If I had the experience that you do I might try barrel bending but really haven't seen the need as neither of my air rifles appear to have too much droop. Since I don't like or shoot break barrels I haven't tripped over that problem too much. Although I have dropped rifles, and myself in the dirt more than once over the years.

    Where did you find the drawings that you show here? I would like to get a copy of the reference from which they were taken for my library. Source?

    Dave
    Dave Thomas

    Shoot safe. shoot straight, have fun
    Teach a kid to shoot

    RWS54, 4.5mm, RWS 4-12x50CI
    FWB300SU, 4.5mm, Clearidge Ultra RM 3-9x32

  3. #23
    Join Date
    Nov 2012
    Posts
    107

    Default Re: Rifle canting, crosshairs not well aligned,

    "Where did you find the drawings that you show here? I would like to get a copy of the reference from which they were taken for my library. Source?"
    Upper sketch found here............
    https://www.bing.com/images/search?q...pics&FORM=IGRE

    The lower sketch from this page.............
    https://www.bing.com/images/search?q...=0-0&sp=-1&sk=

    To save an image I right click on the image I want, then select "save image as", then select folder to save to (I usually select "desktop"), I also rename the image but not really necessary, then I click the "save button" at the bottom. The next thing I do is to open the image in GIMP which I've downloaded to my computer and crop the image as desired (also not a necessity) for uploading to my PhotoBucket or Snapagogo software for posting on the forums.

    As far as droop is concerned, droop isn't the only consideration since windage may also be "off" due to scope dovetails not milled exactly parallel to the receiver and other mechanical reasons related to manufacturing tolerances. Matter of fact, I can move the poi laterally with my break barrel R9 or HW95 simply by adjusting the pivot bolt tension. Every HW break barrel I've owned have had excessively tight pivot bolt tension straight from the box and after adjusting the tension for my preferred tightness the scope windage needed to be readjusted.

  4. #24

    Default Re: Rifle canting, crosshairs not well aligned,

    Dave,

    I'm going to throw this out to you and fade back into the woodwork.

    There are two issues. Cant and barrel indexing.

    You can talk to powder burners or some airgun benchrest guys about indexing. Most airgunners don't even know what it is. It does matter IF you're after maximum repreatable accuracy in all wind conditions.

    Turning to cant, there is a simple method that any airgunner can use to get the reticle to track straight up and down over the bore. No fancy tools or rests are required, although a vice rest will make the process faster.

    1.) Set the gun up on a rest(or pillow) and use you mark 1 eyeball to intsall the scope with the reticle and rifle plumb. It doesn't have to be perfect.

    2.)Place a large paper target at 10 yards, or the max that you can get indoors. It also works outdoors on a very calm day.

    3.) Scribe a plumbline on the center of the paper, then turn it into a crosshair by scribing another line at 90 degrees to the plumbline.

    4.) Turn you scope reticle full up. Line up the reticle with the crosshair on the target and take a few shots.

    5.) Turn the scope reticle full down and repeat.

    6.) Draw a line through the center of both groups. It likely be canted to the plumb reticle.

    7.) Put the gun in a rest ( You can even use a pillow or sandbag). Line up the reticle with the crosshair.

    8.) Carefully loosen the scope mount screws WITHOUT ROTATING THE RIFLE.

    9.) Now rotate the scope until the vertical crosshair is lined up parallel to the line you drew through canted line drawn through the two groups. Tighten down scope mount screws.

    10.) Shoot the two groups again, lining up the reticle with your target crosshair. If you used a rest, my bet is your groups will be exactly up and down on the crosshair on the target. If you used a pillow or sandbag rest, you may need to repeat the process until all error is eliminated.

    11.) Once you've got the reticle tracking plumb to the bore, place the rifle back in the rest and line up the reticle with the target crosshair.

    12.) Set the scope level to indicate level with the vertical reticle line in your scope parallel to the original plumbline on the target.

    You now have a scope reticle that tracks perfectly up and down over the bore when your level reads level. It can be done on any airgun out there. You don't need a flat spot on the rifle on which to set a level, which often is inaccurate anyway.

    The method is most useful for people who use the elevation turret. It is still useful for holdover shooters to eliminate shooting cant, which does matter.

    Don't be surprised if you find a scope that that will only track straight up and down over the bore with a rotated reticle. The scope is broke.

    If anyone that's read all the way to this point and thinks it's way too anal, noodle through the process. Once you figure it out it's really fast and extremely accurate. It's just tough to explain in print.

    It doesn't resolve issues caused by barrels that are not indexed properly. That's the anal part that only FT shooters get into.

    Knobs

  5. #25
    Join Date
    Nov 2012
    Location
    Cuyahoga Falls, OH
    Posts
    352

    Default Re: Rifle canting, crosshairs not well aligned,

    Thanks for the input. I have tried numerous methods but not the one you describe. I will give it a try sometime soon. I am sure I will learn something from it.

    The devices i used in my tinkering are designed to put the center of the barrel under then center of the scope body. That doesn't mean that the reticle inside the scope is in alignment with that plane. Your method might take care of that problem. I'll see.

    This issue is most important in shooting at variable distances and at pretty long ranges. Fixed distance shooting off a rest allows one to zero it without having to compensate for the reticle imperfections.

    A few years ago, someone told me about a mirror method to optically center the scope. It seems that the mirror technique might serve to do what we are talking about here too.

    NOW ALL I HAVE TO DO IS FIND THE REFERENCE AND DO IT.

    (A PAIR OF NEW EYES MIGHT ALSO BE HELPFUL.) Mine are pretty much a mess after 6 cornea transplants and a raft of other surgeries. I have to rest mine ONE useful eye so I can shoot at all.

    Cheers and Thanks for the input.
    Dave Thomas

    Shoot safe. shoot straight, have fun
    Teach a kid to shoot

    RWS54, 4.5mm, RWS 4-12x50CI
    FWB300SU, 4.5mm, Clearidge Ultra RM 3-9x32

  6. #26
    Join Date
    Aug 2013
    Location
    Lebanon, CT
    Posts
    246

    Default Re: Rifle canting, crosshairs not well aligned,

    Dave, if you stand the scope on a mirror with the front end down, you'll see the crosshairs when looking through the scope. Adjusting the turrets, then turning the scope in a circle until the reticle stays centered will do what you're looking to do. Problem is, the scope is centered, but doesn't take into account how accurate to the barrel it is. RC

  7. #27
    Join Date
    Nov 2012
    Location
    Cuyahoga Falls, OH
    Posts
    352

    Default Re: Rifle canting, crosshairs not well aligned,

    yes, I thought that to be the case. They are two different things. Optical centering and centering above the bore.

    I suppose that the truly picky would use adjustable mounts to allow the two centerings to get together.. Hmmm! The only fully adjustable rings I tried didn't work that well. I have two sets - one in 30mm and one in 1" in the box in my workshop. KISS is my motto.


    Dave
    Dave Thomas

    Shoot safe. shoot straight, have fun
    Teach a kid to shoot

    RWS54, 4.5mm, RWS 4-12x50CI
    FWB300SU, 4.5mm, Clearidge Ultra RM 3-9x32

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