Jump to content
SASS Wire Forum

formula to calculate front sight height


Bugler

Recommended Posts

I have a copy of a '73 Colt SAA that I lost the front sight on during a match last summer.

My local gunsmith put a replacement on that is too short as it's POA and POI are 6" high at ten yards over a solid rest.

The barrel is a 7 1/2 inch barrel and I am firing .38 Spl with 158 SWC and 4 gr. of Unique, so it is NOT a hot rod round by any means.....

How much needs to be added to the existing front sight to get POA to center?

 

Bugler

Link to comment
Share on other sites

So, are these calculations correct?

 

6" high x 7.5 sight radius divided by 360 (10 Yards) = .125 additional height required?

 

Bugler

Link to comment
Share on other sites

Sounds right.   6" high at 10 yards is WAY off point of aim.

 

You need a taller sight by 1/8 of an inch.

 

But often a feller will shoot to a different spot in unsupported position compared to a revolver off a rest.   Before you make a final choice of sights, try offhand as you would shoot in a match.  Yes, it's work to get to a tight group that lets you really see the POI.  But hey, as a target shooter AND a musician, you know hard work pays off.   :P

 

good luck, GJ

Link to comment
Share on other sites

I mis-measured the sight radius of my 7 1/2 '73 colt clone.....it is a 10" sight radius from the top of the cocked hammer to the front sight.....So that would be a total height of .392 right?

 

Bugler

Link to comment
Share on other sites

No ... no ... nooooooooo ...no ... nope ... naw ... 

The sight radius is from the portion of the rear sight that you are looking at .... to ... the highest part of the front sight that you are looking at (when aiming).

 

I don't have a 7 1/2 SAA around here but I have a boatload of 4 3/4 ... AND ... the sight radius for the first 4 3/4 I captured is 5 1/2 inches  ... sooooooooo ...

Your 7 1/2 should be in the vicinity of 8 1/4 inches .. 

 

nope.gif.9ac03dfe7009bce94409dd71529625ff.gif

Link to comment
Share on other sites

8 hours ago, Larsen E. Pettifogger, SASS #32933 said:

 

Ummm, nope.  That one is for putting a brand new sight on a new rifle barrel.

 

 

OP needs this one:

https://www.brownells.com/aspx/learn/learndetail.aspx?lid=13093

 

And plugging in the revised distance between sights of about 8.25", you would get a taller front sight addition of 0.138"   So, measure existing front sight body and add 0.138" inches or slightly more.   If the front sight on most single action revolvers looks way too tall, you probably are about right to start sighting in the gun.

 

good luck, GJ

Link to comment
Share on other sites

5 hours ago, Patagonia Pete said:

No ... no ... nooooooooo ...no ... nope ... naw ... 

The sight radius is from the portion of the rear sight that you are looking at .... to ... the highest part of the front sight that you are looking at (when aiming).

 

I don't have a 7 1/2 SAA around here but I have a boatload of 4 3/4 ... AND ... the sight radius for the first 4 3/4 I captured is 5 1/2 inches  ... sooooooooo ...

Your 7 1/2 should be in the vicinity of 8 1/4 inches .. 

 

nope.gif.9ac03dfe7009bce94409dd71529625ff.gif

I guess my tape measure must be metric then......it actually measures 10' from top of cocked hammer and top of front sight.

Link to comment
Share on other sites

1 hour ago, Bugler said:

I guess my tape measure must be metric then......it actually measures 10' from top of cocked hammer and top of front sight.

OK .. I guess I am missing something. 

Why are you measuring from the top of the cocked hammer??

Some black powder revolvers notch the hammers and that "is" the rear sight .. but not SAAs ... 

Sight radius is the distance from the rear sight to the front sight. ???

Link to comment
Share on other sites

OK ... if you "really do/did" have one of these Cimmaron Richards-Mason or something like it ... where the top of the hammer "IS" the rear sight ...

... that is very cool ... 

... AND ...

You would indeed measure from the top of the (cocked) hammer to determine your sight radius ..

... AND ... (even better) ...

You wouldn't have to put a taller front sight on ... all you would have to do is trim a bit off the top of the hammer (to bring POI down).

 

richardmason.jpg.f26b8571aeabdadfa5a1a91756aac117.jpg

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.