iron sight elevation adjustment formula???

Donny Fenn1

Donny Fenn1

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an acquaintance has a 577 nitro express double rifle that he is currently playing with, iirc there is a formula for the amount of front sight to be filed off or added to to get a certain amount of travel on paper.....anybody know it?
 
Donny Fenn1 said:
an acquaintance has a 577 nitro express double rifle that he is currently playing with, iirc there is a formula for the amount of front sight to be filed off or added to to get a certain amount of travel on paper.....anybody know it?
Click to expand...
A .577 Nitro Express....KA - WHUMP!!!

There is some information on Brownell's website at www.brownells.com/aspx/NS/GunTech/sight.aspx that you might find useful.

ps- this information is provided on the agreement that you post pics of that rifle for the rest of us GN to see!:p

Stuart
 
I wouldn't start filing a .577 express double, if you screw it up, your really screwed (ain't a lot of spare parts). Most double express rifles are regulated so that both barrels fire to the same point of aim at a certain distance ( I am not sure what that distance is on your particular double) but try it at 50 yards, 75 yards, 100 yards, 150 yards. I don't believe they would go as far as 200 yards, but you never know. If it is regulated so both barrels hit the same place at 100 yards, at 50 yards they would be off and at 150 or 200 yards they would have crossed and be off.
 
A very good point, Bearman. Might be advisable to acquire a spare front sight to experiment with, although I would be inclined to experiment with the loads first and adjust them to suit the sights.

Getting a front sight would likely necessitate bubba-ing an old military sight or something as it is highly unlikely (!) that the .577 has a now-standard 3/8" dovetail on the front.

Donny Fenn, you might also check out the "Sporting Rifles and Other Old Guns" part of the British Military forum as well:

http://p223.ezboard.com/fbritishmilitariaforumsfrm4

If my experience with the Martini-Enfield forum is any indication, there should be a good number of folks there who will be able to help.

:) Stuart
 
I found this a long time ago and memorized it (I've tried it and it seems pretty good):

Sight Radius (Inches) X Desired Correction (Inches) / Distance (Inches) = Adjustment (Inches)
*Make sure you are making the adjustment in the correct direction.

e.g. 6.5" X 3" off target / 2000" inches away = 0.009" adjustment

As you can see, it doesn't take much :)
I will not be held responsible for any damages done to any firearms with this formula :D
 
I had put this up on another site some time last year. I'll add it here for you.

-----------------------

If you prefer to file down your existing sights, the following may be of interest to you.

POI - POA

M = S x D ÷ ( R x 12 )

Where:

M = amount of movement or change in sight height needed (in INCHES)
D = distance needed to move the bullet's strike to hit point of aim
R = range to target (in FEET)
S = distance between front edge of rear sight and rear edge of front sight blade (sight radius in INCHES)

Example:

Your sight radius is 5.7 inches and you need to move the bullet's strike 3 inches lower at 25 yards (75 feet):

M = 5.7 x 3 ÷ ( 75 x 12 ) = .019

Thus you need to raise the front sight (or lower rear sight) by .019 inches.

Regards.
 
There's a .577 NE double rifle listed here for $47,500US. ###.thadscott.com(change the x's to w's.) Still think it's a good idea to be filing the sight?
Midway lists RCBS .577 3" dies at $400.99US with a minimum 90 day wait. Bertram brass is listed at $98.99US per 20, no wait though. Barnes XLC 750 grain bullets at $27.99US per 20. Woodleigh 750 grain FMJ's are only $49.49US per 25. Ammo-one wants $34.75US per shot for Kynoch 750 grain loaded ammo. Although most sites say about $20US a shot. Just over 7,000 ft/lbs. with a 750 grain bullet though.
 
thanks boys, i had the pleasure of firing this beasty on the weekend and after two shots i said "thanks, i'll stick to my 22 centerfires...."

i should have known that you guys would want a pic, this rifle has a lever under the trigger guard that you push to the right(after half cocking the hammers) to break it, at fifty yards one barrel shoots 6" high and 2"right and the other is about 8" high and 3" left, right now they are working on loads of about 1500 fps iirc over 58g powder, i don't remember the bullet weight, the literature on it says the faster you shoot the closer the shots will become....
 
"Cartridges Of the world" states a 750 grs bullet at 2050 fps for 7010 fpe as
factory number. So your gun should be regulated to shoot this load well
(in fact the amount of recoil makes an express shoot both barrels at same
point of impact). Then the height of the shoots should be ok too as sights
have been regulated for this load at factory as well.

Shortly said I wouldn't play with the sight but try to have the good load
to make my gun shoot right. If you have acces to a chrono it will be easier...

Jocelyn.
 
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