I've got a SA M1A with a "NM .72" front sight.  I see that GI NM sights are .62.  I've also seen something to the effect of using the blade width for rangefinding - 20" target with 22" barrel with .72blade = target is width of blade at ~200m.  Right?

What are advantages to .62 over .72, and how would the rangefinding calculation differ with a Smith GLFS (i.e. shortening the sight radius).

Thanks,

BC

Quoted: I've got a SA M1A with a "NM .72" front sight.  I see that GI NM sights are .62.  I've also seen something to the effect of using the blade width for rangefinding - 20" target with 22" barrel with .72blade = target is width of blade at ~200m.  Right? What are advantages to .62 over .72, and how would the rangefinding calculation differ with a Smith GLFS (i.e. shortening the sight radius). Thanks, BC

Hey, let us know how those  almost five-eighths and three-quarters of an inch wide front sights work for ya. I'm thinkin' they would probably equal target width at around ten yards?

Seriously, I can't remember what the formula is for ranging with the .062" or .072" sight is. (Truth be told, probably never knew it in thefirst place)There's so many combinations of barrell length and front sight width today, the best bet would be to take your personal setup and using different sized targets, determine how many MOA the front sight covers at the range.Once you know that and the size of your target, you can get pretty close with estimation.

This doesn't answer the question for the GLFS or 18.5 " barrels but only for the front sight on a USGI style flash suppressor on a 22 " barrel.  From M14 Rifle History and Development by Lee Emerson:

"Front Sight - The front sights are classified by the blade width.  The standard or USGI front sight is 0.084 " wide.  The military National Match front sight is 0.062 " wide.  The USGI and NM M14 front sights can be used as a range finding device by the shooter.  Assuming a 22 " barrel length, a 20 " wide target (frontal view of a deer) will appear to be the same width of the front sight post at the following distances: 0.062 " USGI NM sight - 230 meters (251 yards), 0.072 " Commercial NM sight - 198 meters (216 yards), and 0.084 " USGI sight - 169 meters (185 yards).  NM sights will be marked NM 062 or NM 072 as appropriate."

Also, the NM 072 is from the commercial Springfield Armory, Inc.

What's a decimal place between friedns?