Sight height ratios?

[OI phones in...]

Is there a way to calculate the optimal height for a front sight from the height of the rear sight? I'm thinking there should be some calculation that would work kind of like how any M16/AR can be "mechanically zeroed" with a specific post/adjustment based on the rear sight mounted...

[Pete44ru]

[Is there a way to calculate the optimal height for a front sight from the height of the rear sight?

The front sight height =
The total height measurement of the rear sight (in the middle of it's elevation adjustment range) from:
the top of the rear sight blade to the bottom of the barrel, minus:
one-half the barrel OD @ the rear sight blade, minus;
one-half the barrel OD @ the front sight bead, plus/minus:
any barrel dovetail cut or front sight ramp, as YMMV.

.

[OI phones in...]

Thanks. Just what I was looking for, though I will have to adapt a bit for a reciever peep... but that's just math.

[Pete44ru]

For calculating the front sight height, with a receiver peep sight, simply extend the bore's C/L to the rear of the bolt (firing pin), and measure the distance from the C/L to the center of the aperture, with the peep in the middle of it's elevation adjustment range - then move to the muzzle measurements, as above.

.

[Old Ironsights]

OK... so here goes...

Existing front sight is 1/2" from top of bead to bottom of dovetail.

It's 1-1/4" from Firing Pin to CL of Aperature.
BBL OD at front sight is 9/16
Top of Ramp is 3/16 to OD of bbl.

So: Front Sight should be:

1-8/32" - (9/32-6/32) = 1-5/32"... that doesn't seem right... ...

1-8/32" - (9/32+6/32) = 25/32"... Better??? It's more than the 16/32" that's up there now but not as redical as adding over 7/8"...

Gaaah....

[bcp]

Brownells will do the math for you:

http://www.brownells.com/.aspx/lid=1318 ... Calculator

Bruce

[Pete44ru]

Existing front sight is 1/2" from top of bead to bottom of dovetail. - Useless measurement, fahgettaboutit - you're firguring for a replacement sight blade, and this measurement will only serve to confuse.

It's 1-1/4" from Firing Pin to CL of Aperature. - This measurement is what the total front height figure MUST equal, PROVIDED the aperture is midway up/down in it's adjustment range.

BBL OD at front sight is 9/16 - Good, now take half of this 9/16 muzzle diameter (9/32") as the first third of your front sight height calc.
The second part of the calc will be the ramp height (see below first, though).

Top of Ramp is 3/16 to OD of bbl. - This is another useless measurement - what is needed is (*) the height of the front ramp from the top of the barrel to the bottom of the front sight insert's female dovetail slot.

SO -

YOUR front sight blade height will equal:

1-1/4"
MINUS
9/32"
MINUS
The front ramp measurement as above (*)

(note: it's OK, to add the 9/32" half bbl diameter to the ramp measurement, also in 32ths, THEN subtract that figure from 1-1/4", or 1-8/32" or 40/32", samey-samo)

.

[adirondakjack]

I may be just an ignorant redneck but I never knew there were such tables. I do it this way.

Shoot at target at say 20 yards (that happens to be 720 inches). If say the rear sight at lowest step still shoots high, measure how much, figure out yer sight radius (front sight to back sight in inches), figure out HOW MANY sight radii you are from target (divide 720 by yer sight radius), then take that number and divide the distance yer bullet strike was from POA by it. Yer gonna end up with some measure that is .XXX inches. Ya need that much MORE front sight than what ya have.....

Hint, if ya ever cut a rifle barrel shorter, and try and use the existing front sight on the shorter pipe, yer gonna run into this. Been there, done that, got the new, taller sight, all happy happy.

[Old Ironsights]

Try again.

If I am understanding correctly, the center of the aperature & the top of the front sight should form a paralell plane roughly 1-1/3" from the center of the bore. True?

By Caliper this time:

Center Aperature to Firing pin = 1.300

Bottom of Front Dovetail to bottom of bbl = .655

BBL OD = .578

1/2 .578 = .289

1.300 - (.655-.289) = .934

So the new front blade should be more than twice the height of the original (.443)?
Why doesn't that make sense...

[bcp]

It should be not quite parallel, as the barrel has to point above the target.


Parallel diagram

[Lefty Dude]

I have used the Williams & Brownells calculations on several Rifles to purchase & install both rear & front sights. It works well and is the proper way to go. You must use .001" of an inch conversions from fractional, example: 1/8" = .125", 1/4" = .250", etc.
You work off the center line of the bore at the location of the sights.

[Pete44ru]

[Bottom of Front Dovetail to bottom of bbl = .655]
[BBL OD = .578]

Someting's fishy here.......................... According to your "measurements", if one subtracts the .578" BBL OD from the .655" measurement of the bottom of the dovetail to the bottom of the same barrel - the ramp ends up only .077" tall ? I don't believe so - I can't think of any ramps less than .250" high, from the barrel top surface to the bottom of the female dovetail slot.

Is there a typo or a transcription error, from the measurement to the writing pad ?

Think about this:
The peep height above bore=1.30".
The TOTAL front sight height - ramp & blade MUST equal 1.30 less i/2 muzzle OD (.300"), or 1.0"

If, in fact, your rifle has a miniscule-height front sight ramp, the fact remains that the peep aperture is 1.30" above the bore C/L, and the top of the front sight needs to be almost as high - whatever it takes.

A rilfe would look dis-proportionate, with a low ramp and an overly-tall sight blade, so the best solution is to combine a new/higher ramp with a sight blade in proportion height-wise (70/30) with a new sight blade in a combination 1.0" high, total ( 1.30" peep sight height minus 1/2 muzzle OD of .300").
That combo CAN be a 1/2" high ramp and a .500" sight blade, but a higher ramp/shorter blade would look more proportionate.

.

[Old Ironsights]

[Bottom of Front Dovetail to bottom of bbl = .655]
[BBL OD = .578]

Someting's fishy here.......................... According to your "measurements", if one subtracts the .578" BBL OD from the .655" measurement of the bottom of the dovetail to the bottom of the same barrel - the ramp ends up only .077" tall ? I don't believe so - I can't think of any ramps less than .250" high, from the barrel top surface to the bottom of the female dovetail slot.

Is there a typo or a transcription error, from the measurement to the writing pad ?

Not that I can find - which is why I'm so confused:
Ramp

Barrel (sorry for the wobble - which also opened up the caliper to .581)

Barrel + Ramp .655

Think about this:
The peep height above bore=1.30".
The TOTAL front sight height - ramp & blade MUST equal 1.30 less i/2 muzzle OD (.300"), or 1.0"

If, in fact, your rifle has a miniscule-height front sight ramp, the fact remains that the peep aperture is 1.30" above the bore C/L, and the top of the front sight needs to be almost as high - whatever it takes.

A rilfe would look dis-proportionate, with a low ramp and an overly-tall sight blade, so the best solution is to combine a new/higher ramp with a sight blade in proportion height-wise (70/30) with a new sight blade in a combination 1.0" high, total ( 1.30" peep sight height minus 1/2 muzzle OD of .300").
That combo CAN be a 1/2" high ramp and a .500" sight blade, but a higher ramp/shorter blade would look more proportionate.

.

Which is why I'm even more confused by your "RANGE REPORT: 1956 Savage 99-EG" thread. You could bring your group up by going from a .475 to a .530 using the OEM ramp. Using MY OEM ramp, none of my calcs will allow that. I don't think my Lyman peep sits any higher than your Williams, (bottomed out in this pic, now set Up to 50%):


How high is C/L of your Williams?

[Pete44ru]

OK, a couple of things first.

1) I installed a new front sight blade, higher than issue, to LOWER (not raise) the point of impact - as it was shooting 12" too high with the peep all the way down using the issue height front sight blade.

2) The higher front sight blade that I installed, is disproportionatly taller than the Savage 99 ramp it's mounted in, because I had no choice.
The front sight ramp on my Savage 99 is integral with the barrel, and not easily removeable/replaceable, as a screw-on or sweat-on ramp.

3) The main point, as I posted above, is that the top of the front sight MUST be approx the same height above the bore C/L as the center of the peep aperture.

A sight installer does whatever needs to be done, to make that happen.

FWIW, I just measured the distance from the bore C/L of my Savage 99 to both the top of the new (higher) front sight blade, and the center of the (now zeroed) peep aperture.

Both measured exactly 1.0"............................... So, the peep aperture on my Savage 99 is closer to my bore C/L than the aperture on your rifle is to it's.

Your front ramp DOES look inordinately low, and IMHO looks like it needs to be switched out to a higher ramp - which in combination with a proportionatly shorter sight blade - would both look good and allow you to zero the rifle.

Since you need a total ramp & sight blade height of 1" above YOUR barrel top to make your 1.30" peep height measurement, I would recommend a new ramp, 9/16" high, like this Williams Streamlined Ramp:

http://www.brownells.com/.aspx/sid=3622 ... __Screw_on

topped with a front sight blade about .435" high (7/16"), like this Lyman .440" Gold bead:

http://www.midwayusa.com/viewproduct/?p ... ber=365876

That 9/16" ramp + the 7/16" sight blade equals the 1" height above the bbl top you need ( 16/16") - but the same height can be put together with other combinations of ramp/sight heights, although most ramps are lower, like 3/8" or 5/16" high or less.
Just keep in mind that a ramp lower than 9/16" will need a sight blade taller than .435" to make the height of 1" you need.


BUT - B 4 you do any of that, please simply install a .530" or .570" front sight blade in place of that old .500" (1/2") blade on your Savage 99 (plastic/cardboard or a paper clip will do), and shoot it @ 100yds (zero).
It worked on mine, so it should be pretty close for yours.


.

[Ben_Rumson]

Measuring my Savage 99 E w/20" barrel....Muzzle measures .577", pretty close to yours.. The front sight is marked 31. The book tells me this is a Lyman number... The book shows that number is the one to use with their receiver sight.. No. 57SA. Averaging 5 measurements of my front sight front sight height (can’t really get on it square & plumb) tells me it's .410" tall and this corresponds with their chart... sights available in the book on either side of ..410 measure .390” and .445”.. The width of the sight is 7/16ths inch... From bottom of barrel to top of bead.. 1.070" Hope this helps...

[Pete44ru]

The Savage 99 measurements differ, due to different barrel contours, and different peep sights having different heights above the bore, ergo needing different height front sights.

In any event, the peep measurements, from aperture center to bore C/L, are hard to guestimate.

I found that, on my 99-EG, the firing pin (bore C/L) is even with the bottom edge of the extraxtor on the side of the bolt, making it easier to use a straightedge to extend the bore C/L backward under the peep to measure the drop more accurately.

I'm surprised that the Lyman on OI's Savage is .300" more above the bore C/L than the Williams on mine - but there ya go.


.

[Old Ironsights]

OK, a couple of things first.

1) I installed a new front sight blade, higher than issue, to LOWER (not raise) the point of impact - as it was shooting 12" too high with the peep all the way down using the issue height front sight blade.

Yep. That's what I need to do too.

2) The higher front sight blade that I installed, is disproportionatly taller than the Savage 99 ramp it's mounted in, because I had no choice.
The front sight ramp on my Savage 99 is integral with the barrel, and not easily removeable/replaceable, as a screw-on or sweat-on ramp.

Ditto. Mine's a 99C...

3) The main point, as I posted above, is that the top of the front sight MUST be approx the same height above the bore C/L as the center of the peep aperture

A sight installer does whatever needs to be done, to make that happen.

FWIW, I just measured the distance from the bore C/L of my Savage 99 to both the top of the new (higher) front sight blade, and the center of the (now zeroed) peep aperture.

Both measured exactly 1.0"............................... So, the peep aperture on my Savage 99 is closer to my bore C/L than the aperture on your rifle is to it's.
.

I used both a tape & the calipers to measure from firing pin to center of aperature. I used a nipple-pick from my caplock pinched in my Meirit Iris to get the center of the aperature. The tape measure read 1-1/3" +/- a frog hair. The caliper read a dead 1.300". Dunno how different that should be between an '80s 99C in .308 and a '50s 99E in .300, but there it is

Your front ramp DOES look inordinately low, and IMHO looks like it needs to be switched out to a higher ramp - which in combination with a proportionatly shorter sight blade - would both look good and allow you to zero the rifle.

As with yours, I don't think it's removable...

Since you need a total ramp & sight blade height of 1" above YOUR barrel top to make your 1.30" peep height measurement, I would recommend a new ramp, 9/16" high, like this Williams Streamlined Ramp:

http://www.brownells.com/.aspx/sid=3622 ... __Screw_on

topped with a front sight blade about .435" high (7/16"), like this Lyman .440" Gold bead:

http://www.midwayusa.com/viewproduct/?p ... ber=365876

That 9/16" ramp + the 7/16" sight blade equals the 1" height above the bbl top you need ( 16/16") - but the same height can be put together with other combinations of ramp/sight heights, although most ramps are lower, like 3/8" or 5/16" high or less.
Just keep in mind that a ramp lower than 9/16" will need a sight blade taller than .435" to make the height of 1" you need.


BUT - B 4 you do any of that, please simply install a .530" or .570" front sight blade in place of that old .500" (1/2") blade on your Savage 99 (plastic/cardboard or a paper clip will do), and shoot it @ 100yds (zero).
It worked on mine, so it should be pretty close for yours.
.

I'll see what happens...

[Old Ironsights]

Measuring my Savage 99 E w/20" barrel....Muzzle measures .577", pretty close to yours.. The front sight is marked 31. The book tells me this is a Lyman number... The book shows that number is the one to use with their receiver sight.. No. 57SA. Averaging 5 measurements of my front sight front sight height (can’t really get on it square & plumb) tells me it's .410" tall and this corresponds with their chart... sights available in the book on either side of ..410 measure .390” and .445”.. The width of the sight is 7/16ths inch... From bottom of barrel to top of bead.. 1.070" Hope this helps...

The white bead front sight I drifted out measures .443 - or close enough to your .445 above as to make no odds... yet I'm shooting waaaay high (dead on zero @ 200yds with 145gr MilSurp .308 and aperature bottomed out...) which is why I'm trying to figure out the "correct" new sight to buy & drift in... especially as I want to shoot 180gr for hunting...

[Old Ironsights]

GAAAAH!

This shows exactly why I failed the "mechanical aptitude" part of the ASVAB (and was told I could be anything but a mechanic...)

The 99 bolt shifts DOWN .300 when opened... and of course that minor detail escaped me when measuring...

So...

1.000 - (.655-.289) = .634

Still taller than yours Pete, but not nearly as bad...

[Pete44ru]

Un-huh.

Please - just buy ($11 @ MidwayUSA) & install this .570" tall front sight blade, and be done with it.

http://www.midwayusa.com/viewproduct/?p ... ber=472823

I'll guarantee that, if it won't zero @ 100yds with that combo, I'll buy the .570" sight blade from you.

Whaddaya got to lose, except maybe 3-5 rounds ammo ?

.

[bcp]

Rifles sometimes don't behave by the numbers, so precise calculations may not always allow you to select the right sight height. One size higher or lower may work better.

Get a flat head screw that will fit inverted in the front dovetail (with a bit of filing or some tape or shim on the bottom.) Adjust your rear site near the middle. Cut the screw a little long and shoot-trim until shots are where you want them. Remove and measure. A good hardware store will have a nylon screw, making it easier to shorten.

Bruce