Sunday, July 20, 2008

New Scope - Sightron SI HHR 3-9x40

My new scope is on its way, a Sightron S1 with their new Hunter Holdover Reticle (HHR). I picked the scope because for the price, reviews said Sightron's optics were very comparable with many more expensive scopes. I looked at one at a local shooting store before ordering it (for $40 less, not counting tax...) online. You can't beat free shipping.

One of the things I was really excited about was the ballistic holdover reticle, which allows you to determine where to hold the Point of Aim (POA) for different ranges. Of course, it's set for the ballistics of a particular factory ammo, but with a little tinkering and handloading with my Savage 11GL in 308 Winchester, I should be able to determine the appropriate ranges for each of the hash marks.

Another reason for choosing the ballistic reticle was that it can be used for determining the range to target for objects of known size. The military uses the mil-dot system, which uses equally spaced dots of a specific size across the vertical and horizontal axes to determine windage and elevation as well as distance to target. The problem with it is that you either have to have a spotter to do the math for you, or you have to carry ballistics cards to simplify the process. I wanted something a little easier. Since hunting is a little more forgiving than target shooting (especially at the ranges I'm capable of actually hitting anything!), I figured that it would be possible to use the HHR reticle to get a good approximation of the range to my target - a deer or an elk.

Sightron's website has the dimensions for the reticle at both 3x and 9x power at 100 yards, so a little simple algebra in Excel, and a little graphics wizardry in PowerPoint, and I came up with the following chart (click to see it full size). (I also have one for Elk). According to Chuck Hawks, the average size of a deer from back to chest is 18 inches. (An elk averages 24 inches.) The resulting chart lets me set the scope at either 3x or 9x, then based on the measured size of the animal, tell approximately the range of the deer. I added in the Point of Aim (relative to the scope reticle, not the deer in the image!) to help me remember the amount of holdover for that range. A little practice, and memorizing my charts, and hopefully I'll be able to get a good working estimate for range and holdover very quickly when I'm in the field. The little X's on the diagram are to show that those are outside the view of the scope, out of range for my level of skill, or beyond the responsible killing ability of the ammunition.

For those who are wondering, I based the holdover on the averages of ballistics data from available over the counter loads from Winchester and Remington. Once I work up my handloads, I'll adjust the diagram accordingly.

1 comment:

Keith Walker said...

Truly, you have a dizzying intellect. lol