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Iron sight adjustment questions

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April 02, 2021, 09:38 AM
gpbst3
Iron sight adjustment questions
My iron sights are hitting about 1.5in left at 25. These are suppressor height and I have a RMR.

Do I move the rear sight to the right? Is it worth moving for and inch?

I was playing around with a sight pusher and it very difficult to tell if I even moved the sight. Is there a way tell?


April 02, 2021, 09:46 AM
12131
If POI is left, move rear sight to right.
If POI is right, move rear sight to left.

In other words, move rear sight in the direction you want the POI to move to.


Q






April 02, 2021, 10:19 AM
sigfreund
quote:
Originally posted by 12131:
In other words, move rear sight in the direction you want the POI to move to.


Yes, that.

Depending upon the gun and sight, it may be possible to draw a fine pencil line along the base of the sight to serve as a witness mark to show how much the sight is moving (if at all). What gun and sight(s) do you have?

There are some mathematical calculation methods using trigonometry that can be used to determine how much a sight must be moved to achieve the desired point of impact, but they require some exact and difficult-to-impossible measurements, so I’ve never been successful except with trial and test. The pencil line can be used as a guide, though: move the sight enough to cover the line then test fire to see how much that changed the point of impact. Repeat with a new line if/as necessary.




6.4/93.6

“Wise men talk because they have something to say; fools, because they have to say something.”
— Plato
April 02, 2021, 10:50 AM
photohause
Just this one gun? If not, check your grip.


Don't. drink & drive, don't even putt.


April 02, 2021, 10:57 AM
PHC
I take it you are shooting from a GOOD rest and not moving or jerking at all, if this is the case I would adjust my sights.


Retired PHC USN
April 02, 2021, 01:09 PM
gpbst3
Glock 17 with ameriglo sights.

I did not have the best rest. Mag resting on a railroad tie and the frame on a rolled bath towel lol.

When I align my iron sights my red dot is slightly left.

I will have to try pencil mark. Too bad I don’t have any more HD ammo to shoot. My ball ammo hits about an inch low compared to HD.


April 02, 2021, 02:49 PM
konata88
1.5” left at 25 yards? Dang, what kind of groups are you getting that you can discern 1.5” at 25 yards?




"Wrong does not cease to be wrong because the majority share in it." L.Tolstoy
"A government is just a body of people, usually, notably, ungoverned." Shepherd Book
April 02, 2021, 03:06 PM
dehughes
quote:
Originally posted by konata88:
1.5” left at 25 yards? Dang, what kind of groups are you getting that you can discern 1.5” at 25 yards?


That’s not hard to determine. You take the average center of a group and measure its distance from the center of your aiming point on the target, and there you are.

Even better than a pencil mark is the edge of a brass rod or punch used to mark the inside of the dovetail as a reference point for how much you move the rear sight. I have done this before with great success, as it gives you a nice clear point of reference.


________________
tempus edax rerum
April 02, 2021, 04:19 PM
sigfreund
quote:
Originally posted by dehughes:
Even better than a pencil mark is the edge of a brass rod or punch ....


Thanks for that tip.




6.4/93.6

“Wise men talk because they have something to say; fools, because they have to say something.”
— Plato
April 02, 2021, 07:51 PM
Genorogers
quote:
Originally posted by konata88:
1.5” left at 25 yards? Dang, what kind of groups are you getting that you can discern 1.5” at 25 yards?


I'm with Konata88 in asking the question....plus I'd leave the sights right where they are and hold right 1.5".
April 02, 2021, 08:40 PM
DaBigBR
As stated by another member, you take the center of whatever group you have to determine for far. 1.5" would be fairly easily identifiable at 25 yards with the gun benched.

Rear sight movements are always the same as the direction desired, fronts are opposite. The acronym FORS (front opposite, rear same) is easy to remember.
April 02, 2021, 10:17 PM
357p239
Almost every gun I pick up shoots to the left in my hand. It may be trigger manipulation or grip but I find it simpler to adjust the sight. Having done that, if I shoot the gun left handed the variance is lessened but the gun shoots to the right. The guns seem to shoot away from my gripping palm.
April 02, 2021, 10:55 PM
konata88
Depending on the sight radius, how much are we talking about moving the sight? 0.5mm?

Are the groups repeatable day in day out?

Pretty awesome if one can consistently shoot tight enough groups at 25 yards where one inch matters.




"Wrong does not cease to be wrong because the majority share in it." L.Tolstoy
"A government is just a body of people, usually, notably, ungoverned." Shepherd Book
April 03, 2021, 02:01 AM
kkina
The formula for sight adjustment is: (Error ÷ Distance) x Sight radius = Correction amount.

So with a 6.5" sight radius: (1.5" ÷ 900") x 6.5" = .011", or about 0.28 mm.

You would move your rear sight about eleven-thousandths of an inch to the right. This is like 3 or 4 hairs' width.



ACCU-STRUT FOR MINI-14
"First, Eyes."
April 03, 2021, 06:33 AM
Blume9mm
I would do two things first.... have someone else shoot the pistol and see where their groups land and also try centering your finger on the trigger. personally I would not try to 'correct' 1.5" at 25ft.

The reason I say this is the Romeo sight on my P320 showed me that the sight picture would move to the left just about that much if my finger was not centered exactly on the trigger.


My Native American Name:
"Runs with Scissors"
April 03, 2021, 12:14 PM
Jim Watson
25 yards? Kkina has it, .011".
25 FEET? move sight .032".

What does it matter what somebody else does?
How much practice are you willing to do to learn a new grip and finger?
April 03, 2021, 02:30 PM
kkina
If I'm reading your second post correctly, your RDS is correctly sighted to POI, which does suggest your iron sights are a hair off. It's up to you whether you want to adjust it. Since you already have a sight pusher, I would probably go for it, but then I tend to be pretty OC. Big Grin

Of course, if your optical sight is correct, adjusting your irons is easy- just shift your rear sight until it lines up with the red dot. Co-witness is your friend.



ACCU-STRUT FOR MINI-14
"First, Eyes."
April 04, 2021, 11:53 AM
gpbst3
quote:
Originally posted by konata88:
1.5” left at 25 yards? Dang, what kind of groups are you getting that you can discern 1.5” at 25 yards?


Let me clarify I’m in no way shooting 1” groups. The average of my shots could benefit by moving an inch and a half.


April 04, 2021, 01:58 PM
OTD
quote:
Originally posted by konata88:
Depending on the sight radius, how much are we talking about moving the sight? 0.5mm?

Are the groups repeatable day in day out?

Pretty awesome if one can consistently shoot tight enough groups at 25 yards where one inch matters.


sight adjustment and group size don`t relate to each other. you can calculate the personal off / deviation form the center of target with any group size.

A 1.5" adjustmet at 25yds with a conventional M3 rearsight spindle would be 2 to 3 clicks. It´s pretty common in target shooting to adjust such errors during an exercise of competition.

Using a sight adjstment tool with an M3 spindle would take approixiately have a revolution to get the front in line again.
April 06, 2021, 02:29 PM
ironrider
First thing I'd do is move the target in to 10 yards and get a good rest. A tight group is an absolute necessity to begin sighting in.