Scope rings on rifles

[schoolcop]

Hey Guys, I'm pretty new and inexperienced when it comes to rifle shooting but, I would like to get more involved. I have a Savage FP10 in .223 that I just put on a Leupold Mk4 4-14X40 (?). I used Warne brand rings but it looks like I bought the wrong height. How do you know what size rings to use when mounting a scope on a bolt action? Is there a size ratio type rule to go by with the scopes front diameter? I think I'm using high size rings and I'm not getting a good fit with my cheek on the stock and trying to see through the scope. Thanks for any help.

[Randy]

The lower the scope is mounted the better.

Measure the outside diameter of your scope's objective, then divide by that by two.
Example Mark 4 4.5-14x40mm LR/T Target  an O.D. of 50mm.  50/2=25mm (.98")

This will be the dimension above which the ring and bases combined will need to raise the scope's center-line to clear a barrel that is the same diameter as the action..

Once you have that key dimension, all you need to do is select a base and ring combination that equals that dimension plus
3mm-5mm to accommodate lens covers.
25mm+3mm=28mm (1.10")

Figure out how thick the base is.  IE: Badger Ordnance Remington 700 base is 7mm thick.
28mm-7mm=21mm (.82")

You will need rings which will take up the rest of the dimension. Pay attention because this is where most of the confusion and inconsistencies come from. Manufacturer's ring heights are not uniform from brand to brand, IE: Burris' low is not the same as Leupold's low.  Ignore their descriptions and go by the actual measurement of the ring.  The actual measurement of "ring height" is determined two different ways.  Some measure from the top of the base (where the ring contacts it) to the center-line of the ring (Fig. A).  Others measure from the top of the base to where the ring first contacts the scope (Fig. B).  If the brand you are considering measures their ring height like Fig. B, you will need to add 12.7mm for one inch scope and 15mm for 30mm scopes to get to the center-line of the ring which is also the center line of the scope.

The below diagram will help more than words.



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[schoolcop]

Thanks Randy. I ended up going with Leupold  low, rings and they fit great. The bottom of the front objective is just a few mm above the barrel. Now the fun part, sighting it in. I may stop by a local gun shop and ask them to bore sight it just to get it in the neighborhood.

[Randy]

schoolcop, I would not pay anyone to bore sight the scope.

Many shooters still prefer the old-fashioned way of bore-sighting -- remove the bolt, arrange the rifle in a steady rest, then aim through the bore at a target. Now adjust the scope's reticle to coincide with the target. This method is very simple and fairly accurate.

[JimP]

I'll second Randy's suggestion...... unless you have more money than you need.  There are folks here that would be glad to help you out with that for nothing.... just ask.

[iiranger]

#1).  How? The catalogues used to contain many, many tables by manufacturers giving the correct combinations. Real simple, there are low scopes with no bell in front or small bell. 4x or less. They could be mounted with "low rings." Then came the early 3-9x with larger front bells. And "medium" height rings. Then the huge front bells that supposedly let you shoot after twilight... and some "high rings" were not high enough. You start mixing makers and you are on your own...

#2). Jack O'Connor did a magazine article that Weaver (of Tx, then) used to include with scopes. Real brief, you have three "lines" to consider.

1). "Line of bore." You look through the barrel. Straight line for all practical purposes.

2). Since you cannot fire the gun while looking thru the bore (surprise) you put reference points outside the gun, usually on the barrel and called "sights." This gives you "line of sight." Again, straight line for all practical purposes.

3). "Bullet path." Aka "trajectory." This is a curve, a parbolic curve. (accelerates as it progresses [down because the bullet is slowing in forward motion but falling as fast]) Once the bullet has left the barrel, it starts to fall. It never, NEVER rises above the "line of bore" BUT ... /THEREFORE you have to lower the rear of the barrel to point the bullet above the point you want to hit so the bullet "falls" into your target/point of aim.

Lowering the rear of the barrel causes the "line of bore" to cross the "line of sight."

And you can "sight in" for crude beginning using this first "cross." Rimfires, 12.5 yards. Centerfires, 25 yards.

The story that sticks in my head... You survey 100 yards, approx. completely level. You hang a target at say 48 inches. You return to the bench, place gun 48 inches off ground. Bore sight on bull. Exactly level. .22 Long Rifle. Load. Close action. Fire. You will find the bullet has struck 12 inches below the point of aim.

Move back to 125 yards. The bullet will strike 36 inches below point of aim. [BORE SIGHTED!]

Little crude but this is also true for .45/70 factory loads. 10x bullet weight but about the same velocity/ballistic efficiency.

SO with a .22 long rifle, you sight in to cross the first time at 12.5 yards. At 50 yards you will be about 2.5 inches high. You will hit point of aim at approx. 77 yards. And at 100 yards you will be about 3 inches low. If I remember, 15 inches low at 125 yards.

O.K. This is what the tables in the backs of reloading manuals are for. The ballistic efficiency of bullets varies with shape and velocity. You pick a bullet and "look it up." Hopefully you will have approx. velocity. [Now if you have an 18 inch barrel carbine and the data is for a 26 inch barrel... you need to do a lot of interpretation.] As I recall 150 grain pointed .30 in, say, '06... [approx. 3,000 feet per second...] hits point of aim at 25 yards. 2.5 inch high 100. 3.5 inch high  at 175 yards. Hits point of aim again at 225 yards. 8 inch low at 300.

But don't take my old memory, use the tables. Bore sight in your home at 25 yards or close... then you shoot and see how far off you are. At 25 you should be on the paper. LUCK.