Drifting Iron Sights - Question - How To Mark

[jjohnson]

Hi, guys!

I have a couple of firearms that have 'drift adjustable' (I spit) sights on them that need drifting. I have my brass rod, ball pein hammer, and wooden shims in my vise.... I know this will hurt me more than it will you....

Question is, I KNOW when I whack the sight to move it, I'm either (a) not going to budge it or (b) move it TOO far. Right? So I am sure you guys do something to mark a sight or the dovetail before moving it so you can see where you've been - but that's my guess. Do you use a pencil mark, chalk, what? Could one of you kind folks give me a clue on what's the best way to do this? I'd prefer to use something like a sight pusher, but I have different firearms that need a sight drifted, so I'm going to wind up doing this without a special tool. Thanks in advance for your help.

 

[tac5mh8]

Heres my 2 cents worth, I use a digital cailiber, Find a fixed point on the weapon to hold one end, and the other on sight, Note the starting reading, then in thousands you can determine how far you move it, There is a formula for this. I dont it off hand, But Brownells has it somewhere in there site, Hope that helps.

 

[JoeHatley]

2 pieces of masking tape. Draw a witness mark accross them prior to moving the sight.

Joe

 

[ArmedBear]

At auto parts stores, you can get fine tape meant for pinstriping. That should work. So does masking tape, if you have enough room.

After the gun is sighted in, take the tape off and you can make a little scratch that goes over the barrel and the sight. Then you can tell if it gets knocked out. Unless you really care about the finish.

 

[WayneConrad]

The formula is easy, because it's based on ratios. No sines, cosines, or other fancy stuff needed. If it gets tricky, it's just from unit conversions.

You need to know: Distance from front sight to target (A), distance from back sight to front (B), and the distance between point-of-impact and point-of-aim (C).

What you want to know: Distance to drift rear sight (D) to move your POI onto your POA.

Let's say that:

A (front sight to target) is 50 yards, or 1800 inches.
B (back sight to front sight) is 18 inches
C (POI to POA) is 4 inches

And now the math, which is super easy. The triangle formed by the front sight, POI, and POA is similar (shares the same angles) with the triangle formed by the front sight, the back sight when set at POI, and the back sight were it set for POA. Don't worry if that didn't make sense. It's harder to explain than it is to understand, so it's my fault if it's not clear.

Being similar trianges, the ratio C/A must be equal to the ratio D/B. Therefore:

D (distance to drift rear sight) = B * C / A

Let's try it for our made up numbers:

D = B * C / A
= 18" * 4" / 1800"
= 0.04"

There you go. Drift the rear sight 4 hundredths of an inch in the appropriate direction and you ought to be spot on.

 

[Firehand]

For front sights, what sometimes works and is more delicate an adjuster is one of the SKS/AK front sight tools. If the sight blade sticks out to either side a bit, you can often put the side with the hole over the base on the side you're moving toward, and use the screw to push the other side. Can make very small adjustments with this if it fits.

When that won't fit, I like the caliper as noted by tac5 to read how far I've moved it.

For front sights, what I'd REALLY like is one of the old British army tools for the purpose; VERY precise adjustment available.