Height adjustment change for peep sight

[mrd]

Posted this in the flint lock section but thought I'll try here too. I have a Thompson center peep and sighting in at 85yds. Anyone have a ballpark idea on how much height change a one full turn or even down to 1/4 turn would give me?

 

[pacanis]

There's a formula for figuring out how much to move irons to get a certain amount of correction and at what distance. You also need to know your sight radius.
Then it would come down to you measuring how much your peep sight moves when you adjust it for elevation. And of course having a starting point where you are hitting now.
I don't have the formula with me at the moment

 

[64Springer]

Posted this in the flint lock section but thought I'll try here too. I have a Thompson center peep and sighting in at 85yds. Anyone have a ballpark idea on how much height change a one full turn or even down to 1/4 turn would give me?

Put up a large target.

Fire one shot.

Turn the knob one full turn and fire another shot.

Measure the distance between the two holes and you'll have your 1 full turn answer.

Divide that distance by four and you'll have your 1/4 turn answer.

The answers to these questions are solved by getting behind the rifle and burning powder and ball.

 

[pacanis]

Here ya go. This will get you pretty close.

Everything is in inches. So:

Inches to move X sight radius /Divided by inches to target

So if you are 8" low at 85yds and your sight radius is 28"
8(28)=224/3060=0.0732 means you need to raise the rear sight a hair over 1/16"

So once you determine where it's hitting now, and how much one turn of your adjustment moves the rear sight...

Bob's your uncle

 

[mrd]

Here ya go. This will get you pretty close.

Everything is in inches. So:

Inches to move X sight radius /Divided by inches to target

So if you are 8" low at 85yds and your sight radius is 28"
8(28)=224/3060=0.0732 means you need to raise the rear sight a hair over 1/16"

So once you determine where it's hitting now, and how much one turn of your adjustment moves the rear sight...

Bob's your uncle

So let's see if I've got this right. My radius is 31" and saying the same 8" low , my adjustment per inch is about 1/64"

 

[pacanis]

So let's see if I've got this right. My radius is 31" and saying the same 8" low , my adjustment per inch is about 1/64"

I'm not sure what you did there, but throwing a 31" sight r into the formula comes to 0.0810"
So that also means a touch over 1/16" total adjustment of either the raising the rear sight or lowering the front sight.
Not per inch.

 

[pacanis]

Or you could also load it with a heavier charge

 

[mrd]

Okay thanks. My bad math had me at .123

 

[pacanis]

That would have meant almost 1/8" total adjustment.
But you need something to accurately measure with to use this formula. Or at least to determine how much your peep sight adjusts per turn.
With a peep sight that can screw up or down I'd just turn it, lock it in place, and see how much the group moves.

 

[mrd]

Thanks! I do have calipers and a 6" ruler

 

[64Springer]

Scale...

 

[mrd]

Now that I know how small an adjustment can change P.O.I. I'll just tweak it . What do you mean scale?

 

[Rebel bull]

ruler=scale (high tech machinist term)

 

[leadhoarder]

Knowing the threads per inch of the adjustment screw can be helpful here.

 

[45man]

I'm not sure what you did there, but throwing a 31" sight r into the formula comes to 0.0810"
So that also means a touch over 1/16" total adjustment of either the raising the rear sight or lowering the front sight.
Not per inch.

,0810 is correct but that is a tad over 5/64", that being .0781. Using a good caliper can set the sight but so can just shooting the rifle.

 

[pacanis]

,0810 is correct but that is a tad over 5/64", that being .0781. Using a good caliper can set the sight but so can just shooting the rifle.

Yes.
And 5/64 is a tad over 4/64
He's adjusting an adjustable sight. Not cutting a dovetail. I'm just getting him in the ballpark.