I'm having a devil of a time working out what ring height to use with my scope.  The scope is a Sun Optics Shorty Forty compact scope 3-9x40AO with a 1" tube.  I will be mounting it to a cantilever Leupold Mk 1 IMS mount, which will then be mounted to my flattop.  The height of the Leupold mount is .764 inches.

 

I'll be using Weaver Tactical four hole skeleton rings with the following options for height.

• 1" Medium: .280"
• 1" High: .400"
• 1" Extra-High: .520"
• 1" Ultra-High: .640

Ideally the overall height would be on par with the Burris PEPR mount, which btw was my first choice but the scope is too compact to fit on that mount.  There is only 3.25 inches from bell to bell on the Shorty which really complicated matters.

 

Thanks for your input.

I had the same problem with my scar 17.  I went with seekins matched rings on my vortex viper 2.5-10x44.  Extra high 1.4" or AR high 1.6" rings on flat top.

A couple questions:

 

1. Does you flat top rail extend from the receiver to over the barrel in the same plane?
2. Different ring manufacturers measure their height differently. Looking at the picture below, are the dimensions you state dimension A or dimension B?
3. What is the outside diameter of the objective bell

 

Adios,

 

Pizza Bob

According to Leupold, the Riser mount is .764" high and 5.52" long.  It is cantilevered and extends beyond the receiver.  As you can see it can extend over the barrel by about four slots and a bit.

 

 

Unfortunately Weaver does not provide a detailed diagram with dimensional specs.  I can only assume that the measurements on the Midway site are for the base to the saddle, i.e. measurement B as depicted in your image.

 

The objective bell is 50mm with an additional 2 or 3 mm for the AO adjustment ring.

 

Are there low rings offered? I always like to get the centerline of the scope as close to the centerline of the bore as possible to lessen parallax. If your top rail extends, in the same plane, out over the barrel, even with the lowest rings listed (medium - .280") the objective end of the scope will be .500" above that rail.

 

If you have BUIS on the gun, you may need to consider clearance between the ocular lens/housing and the rear sight. On my set-up below, I needed to clear both the front & rear BUIS, which is what really dictated mounted scope height. Not too critical as the cheek piece is adjustable.

 

 

Adios,

 

Pizza Bob

Are there low rings offered? I always like to get the centerline of the scope as close to the centerline of the bore as possible to lessen parallax. If your top rail extends, in the same plane, out over the barrel, even with the lowest rings listed (medium - .280") the objective end of the scope will be .500" above that rail.

 

If you have BUIS on the gun, you may need to consider clearance between the ocular lens/housing and the rear sight. On my set-up below, I needed to clear both the front & rear BUIS, which is what really dictated mounted scope height. Not too critical as the cheek piece is adjustable.

 

 

Adios,

 

Pizza Bob

 

This has nothing to do with parallax.  The reason your scope should be as close as possible to center line of bore is two fold your head/eye position, but additionally so when you zero your scope it is as close to mechanical center as possible.

I have a Redfield mounted with a crappy Truglo one piece on the rifle at the moment.  The Truglo mount was supposed to be for the Shorty.  I took it off and measured it from the bottom of the mount where it meets the rail to the tube.  It's just under 1 inch.  With the Leupold riser and medium Weaver rings the combined height should be just about 1.044 inches.  Just a hair more than the Redfield/Trugol set up. The Shorty forty has long eye relief so it wont get in the way of the CH and should have plenty of clearance when I get around to adding a BUIS.  heh, I just realized something.  I have a great scope with a crappy mount on it now and I'm putting on a great mount with a crappy scope in a few days.  My .243 rifle wants it's Redfield back.

 

So, that's what I settled on.  We'll see how it works out when all the parts come in next week.

Frank is right. I was confusing the optical aberration of parallax, which is whether the image falls ahead of, on or behind an interior lens after passing through the objective lens, with bullet trajectory vs. line of sight. Sorry. Otherwise, the dimensions are correct as is the desire to have the centerlines as close as practical.

 

Adios,

 

Pizza Bob

The parts came in......

 

I should have gone one ring height higher.  I rec'd the riser and rings yesterday, mounted the scope last night.  The scope clears the mount, but just barely, but not really.  The ocular tube ever so slightly touches the mount but I can still turn the magnification and focus rings.  Also, I had to position the scope more forward on the mount than I'd like.  This means I had to mount the riser farther back so now I'm not sure I'll be able to fit a folding rear sight when I get around to doing that.  I'll try it out the way it is but will have to order a set of taller rings so I can mount a BUIS when I get around to that.

 

FYI.  The Leupold riser looks really good and seems very solid.  It's also very light.  Makes my rifle look all hoytie toytie.  The Weaver Skeleton rings are okay but not nearly as "quick" as one would expect.  They have a tendency to fall apart at the clamp when mounting or removing and require some fiddling to get them to go on right..  But once they are on they are pretty solid.