Centering/leveling scopes and barrel whip. Jack Roberts??

B

Bofire

New member
Jack, Or anyone who knows more than me please respond.

Could you tell me a little about sight in. referencing the practice of centering the crosshairs first, and leveling the cross hairs and how that works considering "barrel whip".

As the barrel whips, is the scope still centered? I know one centers based on a still/cold barrel however when you actually shoot the bore is not in the same spot when the bullet exits. Or is that difference not relevent?

Reading this I am not sure I understand my question, LOL
hope ya'll do.

thanks
Carl
 
Alot has been done to get the crosshairs centered in the scope I think it was Lee Six who first made mounts to do just that but they were expensive and I see someone else is making some now and it is more of a scope thing than barrel.
 
The answer to centering the reticle can be found at Leupold. Once the reticle is centered, a laser bore sighter will tell you if the mounts have the scope centered, if it's off very much, you can use Burris Signature rings with the offset insert kit to literally zero the scope without touching the turret adjustments.

Tim

http://burrisoptics.com/rings.html

Quote:
The Leupold Answer Guide

Centering of a scope's adjustment dials

The elevation and windage adjustments of a scope are easily centered. Place a small mirror against the objective end of the scope. That would be the end farthest from your eye as you look through the scope. Make certain that the mirror is large enough to cover the entire objective. It must also be flat against the objective. With the scope's power selector ring set at the lowest magnification, look through the eyepiece as you would while aiming at a target. If the scope's windage and elevation adjustments are off center, you will see two images of the reticle (cross-hair). To reach the center of the adjustment range, simply turn the elevation and windage dials until you see only one image of the reticle.



http://www.leupold.com/resources/MyInfo81/Answerbook/findanswers.aspx
 
Wow, wrong target, great info.
So if I use a bore sighter, I understand that it aligns the scope cross hairs and bore, but when you fire the bore is not in the same place, due to whip.
Is this just something one must live with? as there is no way to Predict the point the barrel will be at while "it whips".
sorry I am making this so complicated.
Carl
 
Bofire, I am not Jack Roberts nor do I have his credentials, but , let me see if I can help. I am not very good with wording either but here goes. Lets start with the scope. We want to install it on the rifle with as little need for adjustment as possible. This will keep the cross hairs in the center. In the old days as you moved the cross hairs you could actually see them out of center in the scopes. Now the optical illusion that is built into the scopes makes them allways look to be in the center when they may not be. if they are way out of center in the erector tube it will cause fine adjustment problems. Dan Newberry can explain this better than I can.

Now assuming we have a scope that is optically centered, we mount it to the rifle using adjustable base rings such as the Leupold type. The rear base is adjusted using some sort of bore sighting technique. This gets the first shot on paper. fine adjustments are made till we have the rifle hitting where we want it to.

Barrel whip. Yes the barrel will whip much like a garden hose does when we turn the volume up to full blast. But being steel it does it microscopically(is that a real word?)
If the barrel is floated it wil come back to rest at the same point after every shot.Therefor when the next shot is fired it is starts its travel from the same barrel position. If the barrel is making contact or the action is not glass bedded and is moving in the stock, you can not expect consistent shot placement.Now , will the whip throw the shots. Yes. That is why bull barrels will shoot better than a sporter weight barrel. less whip. also why custom loaded ammo will shoot better in either. We want the bullet leaving the barrel as consistently as possible during the harmonics of the whip. Ideally it will leave during the same point of whip on every shot.

Scope leveling. not even going there. been there done that in the last week. lol. Suffice it to say. a level scope directly over the bore of the rifle is the best way to set the rifle up.

Hope I haven't confused you more than when I started. Randy
 
Carl, I intentionally didn't address the second half of your question cuz I don't know that much about the technical aspects of barrel harmonics, other than I know it exists and can affect performance a lot....I was leaving that part to Jack and those that are more knowledgable about it.

On the reticle centering, some scopes are real hard to see the reticle reflection in the mirror, working with differing light source angles will usually allow you to see what your supposed to, although I have found one scope that I was unable to see anything regardless of light angles....out of about 50 that I have used the technique on.

Tim
 
Wrong target, I have a way that I have used for years, allthough I will try the mirror tonight. I think that may be a better way. I have a cigar box. On each side I have a vee cut into the edges. lid has been cut off. I sit it on the bench and lay the scope in the vee pointed at peg board wall. turning the scope in the vee notches while looking through it at a reference point will show the cross hairs moving. i adjust the windage and elevation screws till it no longer moves on my reference point. Crude yes, but it works.
 
Thanks to both of you. Maybe this is not something solvable,it is just one of the variables one must deal with.

I have been off work for two weeks and my brain is searching for something to do. Maybe there is no way to calculate barrel whip due to the number of variables.
Not my area of expertise in Engineering, now if ya'll want run utilities or build a structure, I'm yer guy.

Anyway it is a fun brain stretcher, I will await Jack response, if he does.. The guy really seems to know his rifles.
thank you again
Carl
 
Carl. A rifle barrel vibrates the same with each firing so you want space your firings the same you want to catch the vibration on either it's highest or lowest extreme. Bill Calfree has wrtitten alot of articles for Precision Shooting Magazine in regarts to barrel vibration and the use of barrel tuners. You work your loads for the barrel and not the scope. From everything I've ever read the barrel vibration is vertical it moves up the back down and flattens out then back up and the tunrer allow the barrel to open up then flatten so you elimate that extra vibration. I'm no expert or gunsmith just interesting to follow Bill's thinking.
 
Last edited:
I just got back in town. I was in Reno 3 days.

The advise you got about centering reticles etc. is good but I don't think that is what you were asking about. I think you were asking how barrel vibrations affect sighting in? They do, of course change point of impact. Hopefully in a consistant manner so you get a small group.

You are already taking this into account when you center your scope because you center the scope to the point of impact. The scope is not centered with respect to the bore but to where the rifle impacts. It can be significantly different from where the barrel points at rest.

Jack
 
Back
Top