Long Range Front Sight Subtension System 1377

[sscoyote]

Been awhile since I've posted here, but I thought some might like to see some of the stuff I've been doing lately. Always thought Elmer Keith was a fascinating character of long-range open-sight shooting lore. After researching his system and the math behind it I thought it'd be interesting to try it with my 1377, especially since the sight radius is relatively long, the front sight is basically vertical, and the rear notch sight fits the system well. Turns out that an MOA system can be established with the front sight height relative to the sight radius such that it can be matched to a ballistics program and applied for longer ranges. So I painted a rectangular section along the front sight, and took measurements of all 3 "units" (see pic). The 1st unit from top of sight to top of white is .103", total white unit is .151, and bottom unit is .042". Sight radius is 12.625", so each MOA is
1) .103 x 3440 (3600" = 100 yds. / 1.047 for MOA = 3440) / 12.625" = 28'
2) .151 x 3440 / 12.625 = 41'
3) .042 x 3440 / 12.625 = 11'

My stats in Chairgun are 400 fps mv, .03 BC for 10.5 gr. domed pellets (corrected for true drop). .3" sight height above bore, 20-yd. zero

Thought to test it at 80 yds. several months ago, and was able to hit a 12" serving tray about 50% of the time in some wind using a 3.0 "unit" hold all the way to the bottom of front sight (about 81 MOA). Thought that was pretty cool.

Last week I went to R&L Airgun Fun Shoot he has every year, and pulled it out with mom spotting and was able to hit one of the 3.5X10" steel silhouettes he had set up at 50 yds. 5 out of 8 shots using a reference of 1.2 "units" down with a 1st shot connection. That was so rewarding I can't tell you guys how much. Thought I'd post this if there's any interest in it. Love the math (especially when it actually works)!