Shoots high... Front sight replacement?

[mysticbear]

I recently bought a Winchester Model 88 in 308 cal with a Williams Peep sight. After a couple of months storage it finally went to the range. I found out that it is shooting good groups, but all are high by about eight inches at 100 yards.

I do not believe that the installed Williams sight is the correct one for this model as I have already maxed out the adjustment. I can not find a model or series number on the peep sight to confirm my theory.

Replacement is not a good alternative as some wood was removed by the previous owner. He did a half decent job and the stock does not look chopped up, however if a different sight were installed I think the inletting would be very noticeable.

I'm thinking about replacing the front sight.

The factory front sight is .312 inches high and the replacements increase in height in steps of approx .031 of an inch.

Does anyone have a graph or experience that can tell me how much the point of aim would be lowered at 100 yards by increasing the height of the front sight by 3/100's of an inch.

Tnx for your help
MB

 

[josquin]

There is information on selecting the right front sight height
in the Williams Catalogue, pg.36 http://www.williamsgunsight.com/.
(The catalogue is a 9mB .pdf file, so hopefully you are on high-speed)

Here's the text, but w/o the illustration:

Step by step procedure for
selecting open sights for
tapered rifle barrels.

STEP ONE: Measure diameter of barrel at
Point “A” where front sight is to be installed.
(Example: .660 Dia.). Then divide this diameter
in half to determine height from center of
bore to top of barrel.
(Example: .660 ÷2 = .330).

STEP TWO: Measure diameter of barrel at
Point “B” where rear sight is to be installed.
(Example: .820 Dia.). Then divide this diameter
in half to determine height from center of
bore to top of barrel.
(Example: .820 ÷2 = .410).

STEP THREE:Select rear sight to be used
and add its height to the height determined
in Step Two. (In this case we have selected
the WGOS with 3/8” blade rear sight which
is .560 high at its center of elevation adjust-
ment). This gives you the total height of the
rear open sight from the center of the bore.
(Example: .410 + .560 = .970).

STEP FOUR:You now subtract the height
from the center of the bore to the top of the
barrel determined in Step One (.330) from
the total height of the rear sight determined
in Step Three. (Example: .970 - .330 = .640).
This tells you that you need a front sight
ramp and bead combination approximately
.640 high to accommodate the rear sight.

STEP FIVE: Using the Williams Sight
Combination Chart you select a ramp and
bead coming closest to your height needed
as determined in Step Four (.640) which in
this case would be the 7/16” ramp with
.290N bead giving a height of .6375 as
shown on the Chart.

By following these procedures, sight
combinations can quickly and easily be
determined. When selecting ramp and
bead combinations from the Chart, the
height need not be exact as there is ample
elevation adjustment in the WGOS open
sight to compensate for slight variances.
Point “C” in the above drawing shows the
proper line of sight parallel to the center
of the bore when the proper combination
is used. When ordering sights and you are
still in doubt as to the proper combination
please include the dimensions of your barrel
at points “A” and “B” so we may assist you
in the proper selection.

The Brownell's website also has a front sight calculator:
http://www.brownells.com/aspx/NS/GunTech/sight.aspx

Stuart

 

[mysticbear]

William's Data on sights

Thanks for the help "JOSQUIN"

I had a look at this information prior to my post. The problem is that the peep sight is side mounted at the rear of the receiver. It is difficult to get an accurate measurement from the centerline of the bore. It may not be impossible but is beyond my expertise.

Sometimes quick and dirty works.

The Brownells site gave me the info I needed..... tnx.

I have copied it to this thread for the use of others.

.................................................................................
Formula

Amount of Error X Sight Radius divided by the Distance to the Target = Sight Correction Needed


If you are shooting low, you would replace your front sight with a lower sight, and conversely, if you were shooting high, then you would replace your front sight with a higher sight. Add or subtract the number of thousandths needed to the actual height of your sight and you will have the correct height of the replacement sight.

Example
At 100 yards (3600 inches), your shot is 6" low and the distance between your front and rear sight is 19.5".

6 X 19.5 divided by 3600 = .0325


Since you are shooting low, you would need to lower your front sight by .032".


MB

 

[bisonhd]

Had the exact same problem on a 88. I had to put a higher front site on. No great expense. Sorry but I sold the gun and can't give you a measurement.

 

[Why not?]

Mysticbear,

Often the front sight blade needs to be repalced with a higher one when receiver sights are installed on bolt action rifles. It is not difficult to calculate how much higher you need, and you need not worry about barrel daimeter at all.

Here's the math:

1) Measure the distance between the receiver sight and the front sight in inches. (Lets say it is 30 inches for the purpose of this illustration.)

2) Now, the distance to the target is 100 yds = 300 feet = 3600 inches. So, the ratio between the sight radius and the target distance is simple to calculate, just divide the samller number into the larger one.

(In our illustration, the ratio is 30" to 3600", or 1 to 120. That means that for every one thousandth of an inch the front sight is moved, the aiming point will be moved 120 thousandths.)

3) Your current setup is shooting 8.000 inches high with the sight at its lowest setting. You need the point of impact to be moved down that much, so the front sight has to be changed to one that will move the POI that much.

4) Since one thousandths will move the point of impact 0.120 of an inch, the the amount needed to move it eight inches is 8.000 divided by 0.120 = 0.06667 inches.

5) Therefore, a front sight that is .067 inches higher will just get you what you need.

6) Finally, you should get a sight blade that is slightly higher than the calculations indicate. (For the purpose of our illustration, .075 inch higher would be about right.) You will have plenty of adjustment in the receiver sight to compensate for it shooting lower than you need right now, and still be in the range if you get some loads that shoot even higher than the one you are using at the moment.

Let us know how you make out.

Ted

 

[mysticbear]

Thanks to all

Thanks for the information I'm going to order a new sight on Monday.

Now!

Any tips on removing the front sight?

I was thinking of trying that new product that freezes warts to super cool the sight. The idea is that it will shrink/contract which will loosen it in the dovetail and pop right out with a gentle tap with a plastic hammer.

Has anyone tried anything similar? I will let you know how I make out.

MB

 

[cosmic]

I dont think the wart remover idea will fly - its a caustic, not a cooling agent. ..

BTW - If you want to confirm your correction, build up the front sight with silly putty, or aluminum foil, with the receiver sight at mid point. I've often found that the above geometric correction tends to overcompensate - I usually end up with about half that estimated by calculation.
More food for thought - give consideration to installing a firesight...

 

[senior]

I have 2 -100s with peeps, neither with a Williams thou. The Lyman side mounted peep required a front site .550" high Seems like a lot but peeps on these style wins require it! I bought a little block from Williams that doves into the existing one & provides another dovetail on top to mount the front site, works pretty good & keeps the site post from becoming TO HIGH & fragile!

It's called a --Front Sight Riser Block-- & comes in two heights---.250" & .340" Go for the .340 you'll need it. they are quit resonably priced too.

After you get the block installed go to a dealer & select a good solid (read heavily constructed) front site about .210" or higher & have it bore sited with it installed, that way you'll know before you leave the stove if it's gonna be high enough.

Hope this helps.