Dialing Scope Turrets – “The Bolt Trick”

One of the techniques we teach at our long range shooting school and day clinics…

The Blind Bag Test

A common theme in the threads in the Handloading section is “Will this (fill in the blank) help my accuracy?” Whether it be neck turning, weighing cases, deburring flash holes, getting Redding comp dies, etc., many of us wonder “Is it worth it?”

And the truth will generally be difficult to pin down. Mainly because in some instances __________ will help one’s accuracy, and in others–it won’t.

Being human, we can fall for the “magic mitt” effect with regard to whether or not something makes a difference. A children’s story tells of a little boy who was having trouble catching the baseball during his Little League games until…  until his father loaned him his “magic mitt.” The child then believes that the mitt has magic, and he then–through his belief that it will work–performs better himself.

In another scenario, it is easy to get drawn into the belief that you must do A, B, C, etc., in order to get even a modicum of accuracy. By skipping any of these “benchrest proven” steps we spoil our chances (so we are taught) to an acceptable outcome with our field rifles. Thumb through the latest flyer from any reloading supply retailer. It’s easy enough to see that the industry feeds into and profits from the proliferation of such ideas.

Now.  Getting back to what I mentioned earlier about truths. Many presumed truths will not be absolute because they will not apply to every situation. In an extreme example, if one were to neck turn a batch of .223 cases for a Ruger Mini 14, and compare the difference in accuracy to non-neck turned cases in that blunder-buss of a rifle  he would almost certainly see no difference in the accuracy level. I don’t think any thinking man would dispute this.

But somewhere along the continuum that runs between Ruger Mini 14 accuracy and the bug-hole accuracy of the winning benchrest rifle, neck turning–assuming the brass cases do not have evenly made necks–begins to make a difference. Flash hole deburring will begin to make a difference (assuming the particular lot of brass shows obstructions here, and the rifle firing the shots is accurate enough to display the difference). Reducing runout to .002″ or less may begin to make a difference, again, depending on the abilities of the particular rifle–and this will also be a bullet dependent measurement, so .004″ of runout with one bullet might make it misbehave in an extremely accurate rifle, but .006″ of runout on another bullet may go unnoticed in that same rifle. Here is where one guy says “Four thousandths of runout makes a difference.” And the other guy says “No it doesn’t, I tested that theory.” Only thing is, they were talking about different bullets in different rifles.

But where (again, on this continuum) do these things actually begin to matter? If, for instance, it could be scientifically proven that a particular rifle could realize an improvement in 600 yard accuracy when the runout amount was reduced from .004″ to .002″ with a particular bullet, how much difference might this actually make? Almost certainly very little. Maybe–and realistically–so little difference that any accuracy advantage would get “lost in the noise” of other factors like wind, shooter limitations, etc. 

In the end, there is only one way to know whether a particular step of match prepping will help you or not. You’ve got to test the idea–and you have to test the idea correctly.

You cannot simply take two rows of assembled cartridges to the range or field and fire the “improved” group at one target and the “unimproved” group at another. Your own psychology–the placebo effect–will call “advantage improved” before the first shot is fired, and your subtle, unconscious behavior will quite possibly force the outcome that you already suspect, and perhaps want to believe. We’re all human, and this effect is alive and well at all times. Scientists know this, which is why they take measures to conceal–often even from themselves–which group is which. A third party will hold the information as to which group of subjects got the medicine, and which got the sugar pills. And only after the test results are in do the scientists ask the third party to reveal which group was which. These scientists realize that their own body language and other behaviors might induce certain outcomes in the study groups, so they do not want to know which group is which as the test is under way. 

And this is also how we should conduct tests to decide whether or not performing “presumed improvement A” (on sale from MidwayUSA this month~!) really helps or not.

So. Let’s say we want to check the effects of neck turning in a particular rifle with a particular lot of brass. (And remember, we must realize that the final results of any such test will only be applicable to the test rifle, and the test batch of brass. Different rifles and different lots of brass will almost certainly realize different results). 

We assemble forty or so cartridges, identical in all respects save the one that we’re testing. This means that group A will have the necks turned, and group B will not have, or vice versa.

Once you have completed the forty or so cartridges, the next step would be to examine them all to see if it is obvious by looking at them which is which. If you can tell the difference with the Mark 1 eyeball then you’ll have to enlist the help of an assistant when you get to the range. He/she will load the rifle for each shot while you look away. You should also look away as you eject the shell casing, and allow your assistant to pick it up and put it back into the bag.

Oh yeah. The bags.  What you’re going to do with the group A and group B cartridges–before you head to the range–is you’re going to place each group into its own paper bag. Obviously you’ll need to use identical bags (or boxes or whatever). Write “group A, turned” inside one bag, and put those shells in there. Write “group B, un-turned” inside the other bag, and put those shells into it.

Somewhere before leaving for the range, you’ll deliberately mix these bags up. If you have to, have someone switch them around and give them back to you. The main thing, and the most important thing is that you do not know which bag is which. The human mind is amazing, and can even unconsciously discern little subtleties about one bag, and unconsciously realize which one it is (assuming you put the cartriges into the bags yourself, that is). So be thourough and careful with this “blind bag” test. If possible, have someone else fill and label the bags.

Set up two identical targets at the range. Two bullseyes on the same square of paper should be fine. Shoot two fouling shots from a clean barrel, and make sure those fouling shots are put together with the same powder as you’re using in the test. Bullets with the same jacket material should also be used (i.e. moly, naked, etc.)

Next step. Most folks will not have ever considered this, but it is of vital importance to the validity of the test. Fire one shot from the first bag (remember, you don’t know which is bag A or B at this time) at the first bullseye, then fire one shot from the second bag at the second bullseye. Keep alternating back and forth in this manner. This will spread the barrel fouling and heating effect evenly across both groups. This will also spread the “damn I’m getting tired and bleary eyed and I gotta take a whizz effect” evenly across both groups.  If you’ve shot comparisons in the past without doing them in this alternating manner, I would respectfully question your results.

Once you’ve fired all forty (or so) shots onto the paper, then–and only then–do you reveal to yourself which bag was which.

And of course you’ll know–more surely than the average guy doing the average test will know–whether the “improvement” actually helps or not.;)

Dan

www.BANGSTEEL.com
Practical Long Range Rifle Training… OCW handload consulting…

Marking Non-Resettable Scope Turrets for Long Range

This video will show you how to label and mark your scope turrets for long range elevation dialing–particular to scopes which do not allow turrets to be reset to “0”…

Canted Scope vs Canted Rifle

This picture represents a canted rifle underneath a level scope. You’re looking at the buttstock of the rifle, and on through the scope. The orange circle is the approximate location of the bore of the rifle. The blue dots represent the fall of the shots as they go downrange; they fall with gravity along a line which is represented by the vertical crosshair in the scope.What we must concern ourselves with to understand this issue is the scope and the bullet path. When you dial the scope’s erector to zero for windage, you are essentially aligning it with the bullet path–not the barrel!

So if a scope is mounted slightly canted, but held level, the bore of the canted rifle would only be off to the side a fraction of an inch (perhaps 1/16 to 1/8 inch) underneath. It would look something like this:

Is it important that the bore isn’t 100 percent underneath the scope’s vertical crosshair? Actually, no.

Think about it this way:

If you have the scope dialed to a perfect 100 yard zero with one particular load, and then you switch to another load, you’ll likely note that your windage zero will change. Has the scope moved? No. Has the barrel changed? No. Only the direction that the barrel is throwing the shots has changed. Barrels, by their very nature, throw shots here, there, and yonder.  So you must dial the scope’s erector to follow the general path of the new load to get your zero. This may take the scope’s centerline well away from the boreline–but that’s not what’s important. Bullet path and boreline are two different things.

You see, the scope’s erector is never actually aligned with the bore of the rifle to begin with–it is aligned with the path of whatever bullets you are setting the zero for.

What I’m saying is that you can have a slightly canted scope, with the barrel underneath at, say, 5:30 and so long as the scope is held level, the shots will still fall parallelwith the vertical crosshair.

In the top image, there is the ideal situation where the scope’s vertical crosshair perfectly disects the fall of the shots.

In the second image, the scope is mounted with a slight cant, but since the scope is being held level, this means that the rifle bore is off by a bit underneath it. It’s at 5:30 rather than 6 o’clock. Note how the shots fall just slightly to the right of the vertical crosshair. Groups forming downrange would probably never indicate that the 5:30 rifle cant even existed, as these shots would only be off to the right of the vertical crosshair a tiny fraction of an inch.

What if you layed the rifle on its side?

If you laid the rifle on its side (and mounted the scope upright, with the elevation turret up top),

…this would of course put the scope about 1.5 inches to the left of the bore. If you zeroed the scope for the shots to fall dead on at 100 yards then yes, you would have an angular relationship with bullet path and line of sight. You’d only be zeroed for 100 yards. From the rifle to the target, you’d begin with almost 1.5 inches of error, slowly correcting until you got to 100 yards, then beyond 100 yards your shots would deviate farther and farther from the windage zero you had at 100 yards.

However, if, as is shown in the drawing immediately above, you were to take into account that 1.5 inch difference with the “sideways rifle,” and you dialed the scope so that the shots fell 1.5 inches to the right of the crosshair intersection at 100 yards, these shots would stay only 1.5 inches right of the line of sight all the way downrange (wind factors and such notwithstanding).

In another possible scenario, you could simply take this sideways rifle and dial the windage zero to be correct at 1000 yards. Then, you’d be off a little less than 1.5 inches at 100 yards, and the bullet would begin “closing in” on the windage–and the closer the bullet got to 1000 yards, the more it would close the 1.5 inch gap. At 1000 yards, the bullet would cross the line of sight, then begin deviating in the opposite direction, and by 2000 yards, it would be about 1.5 inches to the other side. Obviously, this 1.5 inches would not be much of a factor at the longer ranges. 

So, with the slightly cant-mounted (but held level) scope, you’re not going to be off anywhere near 1.5 inches all the way downrange. It’ll be more like 1/8″ or so–and wouldn’t even be noticed in a 1 MOA group size.

So remember: It’s bullet path, bullet path, bullet path—not the barrel that you’re aligning the scope with.

The above is a top view, looking down at the rifle and scope, and bullet path(s). The blue area would represent the scope’s range of WINDAGE alignment; in other words it can be dialed to windage zero anywhere in that blue zone. The orange lines represent the various paths different load recipes might cause the bullets to fly. You can dial the scope to align with any of these paths.

All that really matters is that the bullets be released relatively close to the vertical crosshair and all will be well.

When the barrel releases the bullet, the bullet goes up, then it comes down. It does this regardless of where the barrel is in relation to the scope. All you are doing with the scope windage adjustments is aligning the erector to be closely parallel with that bullet’s path. The key words here are CLOSELY PARALLEL, and once the scope’s windage is set to be parallel with the bullet’s path, you will not have to change windage for various ranges–it’ll stay the same–even if the barrel is at 5:30 or 6:30, or even 5 o’clock or 7 o’clock underneath the scope. You might get lucky and have your bullet fall perfectly along the vertical crosshair of your scope, but that’ll be the exception; not the rule. Chances are, if you could somehow determine the “perfect bullet” path, it would be 1/8″ or even more, to one side or the other of the vertical crosshair. Big deal, though–such a small amount of error won’t be noticed on the targets.

The problem that some of us may have in understanding this is we are assuming that bullets eminate in a straight line from the bore of the barrel–which they do not. Some bores are not even drilled straight through the barrel, so you could have a scope centered “perfectly” over the barrel and still have a “canted bore.” But relax. Hold yourscope level for each shot and you’ll still shoot just fine.

I have a ScopLevel on a Bushnell Elite scope. The level is mounted to the tube of the scope, and I move that scope from rifle to rifle as I test different guns and different loads. It’s currently on my recently rebarreled Remington 788, and it is not perfectly straight with the receiver. I noticed this when I put the rifle on a bench at our rifle range. However, since I began testing that rifle, I have hit varmints at 200 yards, 540 yards, and 755 yards by making elevation changes only. I did not make windage changes for these shots because the wind wasn’t at issue. A couple weeks ago, again, without touching the windage turret, I dialed in my elevation for 1050 yards and shot at this target:

While the group has moved a tiny bit to the right, that is to be expected at such long ranges as the bullet’s spin causes it to move slightly aside.

Paralleling the scope’s line of sight with the bullet’s path is really no big deal.

Keep the scope level, and don’t worry so much about whether it’s perfectly straight up and down over the bore. It’s nice, yes, to have a straight scope. But if your scope is slightly canted in the mount, just level the crosshairs as you normally would, and you’ll have no trouble at any range.

One last illustration, which I hope will bring it all together… 

Dan Newberry

www.BANGSTEEL.com
Practical Long Range Rifle Training… OCW handload consulting…