Reticle Perpendicularity by Darrell Holland

[foreign]

ok i think i see where mkollman74 is getting messed up. lets say we take a rifle and level it with a level on the action somewhere. then we mount a scope on it and set the normally horizontal xhair as verticle. so now we have a scope that is at 90 degrees to the rifle. lets say the scope is 1.5 inchs above the center of the bore. then we cant the gun to the right 90 degrees so the x hairs in the gun ( the usual verticle one) is verticle. assuming that the bullet path is straignt for the moment and the line of sight is parallel. then the bullet will hit 1.5inchs left of line of sight at any range.
now we all know that bullets dont travel in straight lines other wise id be shooting bunnies at 1km. if the bullet path was horizontal with the line of sight at 100m then the impact point would be 1.5inch left and 0 up and down. then go to 200m and the impact point would be 1,5 left and lets say 2 inchs down. then at 300m impact would be 1.5 left and lets say 6inchs down. and so on. the up and down could be corrected for, but the bullet path would always be 1.5 left. this is where the issue lies. no one wants there bullet to always be 1.5 left.
so with the same scope rifle set up and sighting in at 100m we would dia the scope across 1.5 inchs so that at 100 the line of sight on bullet path would cross.. so this would be making a triangle with the shortest side beind 1.5 inchs(distance between sight and bore) the other side of the triangle 100m and the last side slowly slopping into the point. then at 200 the impact point would be 1.5 right and x low. at 300 would be 3 right and x low, at 400 would be 4.5 right and x low at 500 would be 6 right and x low and so on. this is because the bullet was sent on its way crossing the sight path on a left to right course. sighting in at 300 for example would greatly reduce the effect.
i think that is the confusing part explained. well unless i confused myself while writing this.
so the key is to just have the scope level and the bore axis verticly under the x hairs and ensure that the scope is level when shooting. cheers

 

[bigmo101]

All I have to say is great article. I tried it out and it worked absolutely awesome.

 

[glockman55]

I had basically this same question. One further question: Am I reading this wrong or is the suggestion to mount the scope perpendicular to the bore of the rifle? I have never understood how you can position anything in a relationship perpendicular to a round object. Since it is round, it really has no X or Y axis does it? Level is level, and plumb is plumb, right? If a cylinder is rotatated, up and down don't rotate with it, they are fixed in space. The bullet still exits the barrel, and gravity still pulls straight down on it. Any wind still deflects it to the same degree.

I do not mean to appear argumentative, I just don't understand, and wish to. I want to be better at this long range game. So, if the barrel is round, and I naturally cant the rifle, why shouldn't I mount my scope so that it appears perpendicular the horizon to my eye using my natural hold? The canting only rotates the barrel along its longitudinal axis, the bullet still travels the same path, right?

If I need extra elevation, and I dial it in or hold over, the impact will still travel in line with the vertical wire of my reticle because I am moving the canted rifle up to adjust to the new point of aim. The center of the barrel still moves in the same direction - up. Rotating the barrel by canting doesn't change the direction by which gravity pulls the bullet straight down, it doesn't alter the ballistic arc. So, I am still confused as to why a naturally canted hold on the rifle would produce an off shot unless the rifle itself were held perfectly perpendicular to the horizon for that shot. If I cant the rifle but have mounted my scope so that even with that cant its vertical wire is parallel to a plumbline, shouldn't that be OK? I can see where dialing elevation into a scope mounted at an angle to a rifle held perfectly plumb would produce a horizontal dispersion.

But holding a rifle at a slight cant and mounting the scope so that its reticle is parallel to a plumb line even given that cant should have the same effect as an offset type of scope mount such as was used on some M1s during WW2 by military snipers. In effect you are holding the rifle with the scope slightly to one side. Am I wrong? I barely passed high school geometry... Again, no flames, just curiosity and respect for the expertise on this forum.

I use a Bore Level, all my rifles have a one piece weaver style mount and this works good to level your bore while mounting and leveling your scope to the bore. I can leave this mounted to my rifle while shooting if I need to keep it level for long range shooting. MidwayUSA - B-Square Bubble Bore Level Weaver-Style

 

[hosboss2002]

Wow, thanks for the Great article. I just purchased my second long range gun, this one a remington 700 sps varmit in .308 calibler. I ditched the stock and went with a Bell and Carlson, adjusted the trigger, installed Badger Ordinance Rings and Mount, Harris Ultra-light 6-9" swivel bipod, and a 16x42 Super Sniper scope. I have yet to fire a round down range still waiting for a couple parts to arrive. But after reading this article I will definately try this I think it is very important to have scope perpendicular.
Thanks,

 

[fj40mojo]

My method for mounting a scope and aligning the reticle is as follows. First I assume that the bottom of the action is perpendicular to the bore. That being said I remove the barreled action from the stock and place it on a level surface with the action supported on a pair of precision ground 1-2-3 blocks and I use a machinist jack set to support the muzzle end of the assembly. With the scope loose in the rings and as close as possible to the location I want it to be for proper eye relief I can rotate the scope within the rings and use a machinist set up square indexed of the same level surface as a verticle reference line. Line the verticle crosshair up with the verticle edge of the square and you are plumb. I've tried putting spirit bubbles on the tops of the reticle caps and on the reticle itself and it's never worked out, at least not to the level of precision that I'm after. I prefer to use machined surfaces to reference off of when trying to maintain parallelism and perpendicularity. All these tools can be purchased from MSC or Enco for less than what you 'd spend on most of the scope leveling gadgets that are on the market.

 

[trebark]

My method for mounting a scope and aligning the reticle is as follows. First I assume that the bottom of the action is perpendicular to the bore. That being said I remove the barreled action from the stock and place it on a level surface with the action supported on a pair of precision ground 1-2-3 blocks and I use a machinist jack set to support the muzzle end of the assembly. With the scope loose in the rings and as close as possible to the location I want it to be for proper eye relief I can rotate the scope within the rings and use a machinist set up square indexed of the same level surface as a verticle reference line. Line the verticle crosshair up with the verticle edge of the square and you are plumb. I've tried putting spirit bubbles on the tops of the reticle caps and on the reticle itself and it's never worked out, at least not to the level of precision that I'm after. I prefer to use machined surfaces to reference off of when trying to maintain parallelism and perpendicularity. All these tools can be purchased from MSC or Enco for less than what you 'd spend on most of the scope leveling gadgets that are on the market.

wow - that sounds complicated.

Try the easy way.... Wheeler Engineering Level-Level-Level Scope Crosshair Leveling Tool - MidwayUSA

 

[glockman55]

I Agree!!

 

[fj40mojo]

From the linked site:

The simplest, most accurate scope leveling system ever devised to level your scope as you mount it on your rifle. The magnetic base in the rifle level bridges the bolt raceway, allowing you to position your rifle almost perfectly level. Then level the scope, tighten the rings and the job is done. Works with practically any bolt-action rifle. Set includes two levels.

It may sound complicated but it is undoubtedly more accurate than this gizmo. With my method I'm using precision ground tools (1-2-3 blocks) to support the barrelled action parallel to a reference surface and using the same surface to reference my vertical crosshair again with a precision ground tool (machinist square). If I wanted to get really anal about it I'd use a surface plate as the support surface, but I think this might be overkill. The goal here is to elliminate as many variables as possible and make your initial set up as accurate as possible. The only variable left in my set up is how well I can visually align that vertical crosshair with the edge of the square. The only way I can figure to do it more accurately would be to set it up on an optical comparitor which isn't an uncommon tool in a tool and die shop, but not something I have in my machinist box.


Enco - Guaranteed Lowest Prices on Machinery, Tools and Shop Supplies

Enco - Guaranteed Lowest Prices on Machinery, Tools and Shop Supplies

Enco - Guaranteed Lowest Prices on Machinery, Tools and Shop Supplies

 

[Darrell Holland]

Gentlemen,

Greetings, using parallel blocks or any other widget to level the rifle is fine. Just be sure the bases are in the same plane and are parallel. The base screws must be on C/L with the action as well. When we drill our 6-48 screws to 8-40's we machine a mandrel that screws into the action which is held in a vise and the bottom of the action is supported/squared to our parallel ( 123 block) We next center the spindle to the receiver mandrel and drill and tap new holes to that centerline.

Using our Perfect Picatinny Rail one machines the front and rear base into PERFECT alignment and then mount the rail ensuring a PERFECT STRESS FREE mounting to that particular action. Ring lapping takes just a few seconds and you've done the customer/yourself and stellar job of mounting yoru scope to the rifle. For more information on our mounting system , we've added the instructions to our web page at hollandguns.com. Feel free to take a look, I'm sure you'll grasp what we'vbe done and understand the importance of our system.

With huntng season upon us, I wish everyone a successful and rewarding time in the field.

Respectfully,


Darrell Holland

P.S. We will have our NEW line of scope levels out in the next 3-4 weeks, 1.00 inch 30 mm and 34 MM Models a s well as our Picatinny rail version. These are AWESOME scope levels and are sure to please. I'll post a few photos as soon as I get them back from anodizing.

 

[Len Backus]

Darrell, Ernie was telling me about the new scope levels. Knowing your attitude about perfection I am eager to learn more.

 

[Darrell Holland]

Dear Len,

Yes, we are completeing our NEW line of scope levels that will compliment the customers rifle. These are beautiful scuplted rings with an off-set, I use a 3/8 bubble level that is easy to see and read, even if you have aging eyes....

I think I've designed the off-set so as to provide a binocular view in the scopes field of view. The shooter never has to pick his head up from the stock to see if the rifle is plumb.

They will come in three sizes; 1.00 inch 30 mm and 34 mm all designed with the same off-set allowing viewing with windage and parallax knobs. All Holland Signature Series scope levels are hard black anodized for maximum durability and outdoor use.

You may want to give some thought to offering them in the GEAR SHOP????

I'll send photos for your review when I get them.

Thanks for the interest, I'm confident you'll appreciate our efforts!

Respectfully,


Darrell Holland

 

[nice one]

they do look the bizz can you post me one 30mm to england please [email protected]

 

[hddm3]

Thanks for the tips. Awesome.

 

[SBruce]

If this thread isn't dead, I've got a question for Mr. Holland.

It makes perfect sense to me (your article) but I've got a couple of questions. Probably stupid ones, but nonetheless.

If after we dial up 10 or 20 moa and shoot again, lets say we're 1/2" off the plumb line to the left. This tells me that we need to rotate the scope clockwise (viewing from the rear) in relation to the rings/rifle. Is this correct??

It seems easy enough to do when we've got an ACD on the rifle or ring half, but what about when the ACD or level is mounted on the scope tube? Seems that we'd now need to remove the level and then rotate the scope clockwise. Then, after doing so, we'd re-mount the level when the crosshairs are parallel with the plumb line and our impact is finally on the line?? Am I correct in this assumption? Seems harder to do and possibly takes more steps when the ACD mounted on the scope tube??

Thanks in advance.