Scope Base Question

[striker]

Heres an interesting question.  Do any of you do anything with your scope bases for extra stability or strength?  The reason for this question is because I have noticed that between 1/4 to 1/3 of the scope base is unsupported by the barrel.  Has this caused any problems on your Handi, and if so how did you correct it?  Thanks again for all of your input

[quickdtoo]

I prefer the shorter standard base over the inch longer ultra base for that reason. Some shooters bed the unsupported end, I prefer to mount my scopes on the supported part if I can. The only issue I see with that is as the barrel warms, it's going to lift the end of the scope base and if the front ring is mounted there, it's going to change POI even more than just what's caused by the barrel heat without a change in mounting.

To make the base to barrel mounting more solid, I lap the base on the barrel where it does touch to make more contact with the barrel, there are high spots on the base around the holes and on the edges. Lapping instructions are in the FAQ in Perko's bedding post. After lapping I bed it in blue loctite, once it fits the barrel better, it doesn't take much media between the base and barrel to make it real solid. Clean the factory thread sealant out of the mounting holes first, make sure the bottoms of the holes and shiny bright before remounting.

[Fred M]

Tim

The only issue I see with that is as the barrel warms, it's going to lift the end of the scope base and if the front ring is mounted there, it's going to change POI even more than just what's caused by the barrel heat without a change in mounting

If that statement had any validity then all dual base mounting system on SS rifles like the Ruger Varmint, Merkel, Blaser, Ferlach and my own would be totally inaccurate. Barrels just don't heat up in one spot only.
If you were measuring group sizes by 0.0001" like in Bench Rest then you would have a point.

Neither thermal nor scientific reasons could validate the above, any expansion caused by temperature generated in a rifle barrel at the mounting rail even very hot would require very sophisticated optical comparators. A crooket barrel will warp with heat but not at the breech.

Point of impact changes caused by thermal expansion in a hunting rifle such as a Handi could not be measured with any amount of certainty.

The set screw on the overhang can be used to change elevation impact by torqing this screw. Raising the overhang by one thou would generate a change of about 1.25" at 100 yrds. The exact change in impact can be calculated if the thread size of the set screw is known together with the distance between the two rings.

[Mac11700]

Fred:

I've tried what you saying...with the Ultra Scope rali and ran the screw down to make contact...and the point of impact shifts as the barrel heats up...and this is with a totally free floated barrel with no wood contact...say what you want...but it really does change...this is the reason NEF C/S will tell you NOT to run the forward screw down and contact the barrel...they advise .001" or .002" of clearance...call Gordon at NEF and ask him...

Mac

[quickdtoo]

Fred, my thoughts are since the barrel is much smaller there, it will expand quicker with heat, since that is true for bull barrels vs standard barrels...... And I remembered the 1" change in POI per .001" change figure. And since H&R's instructions for setting the screw on the Ultra rails to be .0015" off the barrel, it supports my thinking.

[Fred M]

Mac and Tim.
To start with I said to torque the screw so you can get the scope x-hairs in the optical center if need be. Setting the screw to just make contact does not make any sense to significantly change point of impact. But having it just touching could set up unwanted vibrations??

Look at it this way the expansion ratio for steel per 100F is 0.00067 per foot or 0.0000558 per inch and since a barrel can be considered a tube expansion takes place in a radial fashion and the change in diameter will be expansion/3.14. To make a long story short the increase in diameter at the scope rail is 0.0000195" and just a little bit less at the set screw that is if you run up the temperature from 70F to 170F.

You do the math and tell me how much a barrel needs to expand and how hot it need to get to make a measurable change at 100 yrds.

The smaller part of the barrel will expand less than the thicker part at the same temperature because there is less metal to expand if that makes any sense. Whether the part of the barrel at the set screw get gets hotter faster than the rest of the barrel seams conjecture but it could be.

I have said this before that I did bent down the rail overhang and then adjusted with the screw to get to the optical center. This setting has never changed with temperature that I could see. Same as my front mounting base never changes the impact that I can measure, since I have trouble measuring groups in 10/0000.

If you believe that the screw, 2 thou above the barrel, will give you the best mounting system, then so be it, but that was not the idea to put the screw there in the first place. As you know the screw also has a set screw to make sure the main screw stays in place when it is torqued up since horizontal vibrations could rattle it loose.

I have made good use of this screw to achieve the best optical x-hair center. It is the same as using shims under the bases to get the best optical center. I don't suppose I need to explain how to put the x-hair in the optical center of the scope. But I will if some body want to know. It is an important part of proper scope mounting.

[quickdtoo]

Since the Ultra rail set screw adjustment instruction that Mac and I pointed out came direct from H&R, I guess we'll just have to agree to disagree, Fred. :wink:

Here's the method I use to center the reticle, quoted right from Leupold's web site..

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.

 

If the reticle is off much when I bore sight it, I use the Burris Signature offset inserts to optically center the reticle in the mounted position. This offers lateral as well as vertical adjustment without touching the turret adjustments and they prevent damage to the scope, unlike other rings that offer lateral only adjustment.

[Fred M]

Tim.

Here is something that too came direct to me from H&R,

Handi rifle do not need a heavier latch springs. nor stronger ejector springs.  There is nothing wrong with your barrel if it shoots 2-1/2" groups. I don't matter if the bore is 0.0015" oversize.

I would not hang my hat on much coming from H&R. I have a lot more confidence in my own observations and math rarely fails when properly applied.

I always use a collimator to set up my scopes and bases. The Burris Signature system is good but in Canada very expensive. They are not worth my while besides the offset plastic rings inserts are an outrages extra.

The mirror centering system sounds like a good way to do it. Never heard of it. With the mirror flat against the objective lens how do get light into the scope?

Here is an old proverb translated and used with disgression.

Believe nothing that you hear and only halve of what you see.

[quickdtoo]

The light has to come from an angle, I place a mirror on a table or my bench and stand the scope on its objective end, since the reflective part of the mirror is the thickness of the glass below the surface of the mirror, light has to enter thru that thickness, some mirrors that are thinner don't work, needs to be one with thicker glass to allow more light in. Experiment a little with the light source angle and you'll find out what works best. It doesn't work on all scopes, but about 90-95% of all those I've tried it on, it works great. It's real cool when you can see 2 sets of reticles, one is the reflection, the other is the actual reticle and you can see it move towards the other one when you adjust the turrets, line em up until you can see only one set, and the scope is optically centered. :wink:

I have a lot more confidence in my own observations.....

Me too!! Whatever works for ya, but on the same note, I'll do what works for me. :wink: