Help needed for reticle adjustment

[Crysknife1013]

I'm new to the red dot game. So I am looking for advice and guidance on the results I got the other day.

I'm sighting in a Sig Romeo-X Pro on a Sig P320-M18. I started my sight-in with the pistol supported on a sandbag on a bench. The target was 7 yards away. To my surprise, 4 out of my first 5 shots were right on top of each other as you can see below (group #1)

IMG_4601 Recircled by dalipiojr, on Flickr

I adjusted the reticle and shot another 5 rounds (group #2). As you can see above, the point-of-impact (POI) was almost perfect. To say the least, I was pretty happy with those results.

I moved the target to 15 yards so I could fine tune the aim. But as you'll see below, the groups opened up a lot.

Target B String 3 by dalipiojr, on Flickr	Target B String 4 by dalipiojr, on Flickr
Target B String 5 by dalipiojr, on Flickr	Target B String 6 by dalipiojr, on Flickr

I was still shooting from the same rest on the same bench. I was mindful of my breathing, keeping the dot steady, and my trigger pull. I did not rush anything. I was not slapping the trigger. I was shooting the pistol at 15 yards exactly the same as I was shooting it at 7 yards. But as you can see, those groups aren't as tight as they were at 7 yards.

Ignoring the size of the groups, each group does seem to be to the right of my point-of-aim (POA). So I am inclined to making an adjustment to move the POI to the left. Would you concur?

As for elevation, the groups are also low. But I hesitate to make an elevation adjustment because at 7 yards, the elevation was almost perfect. Should I make the adjustment?

Thanks in advance for your thoughts and opinions.

[Crysknife1013]

Update with additional question and TTT...

Doesn't ballistics science say that the bullet should still be arcing upwards at 15 yards? How are the shots hitting low? At 15 yards, the shots should be landing higher than at 7 yards, right? This is another reason I hesitated to adjust the elevation at 15 yards.

[foothillman]

In my opinion.....

Using a rest puts the handgun and the shooter in a awkward position.
Most likely belly high with shooter on his knee or bent over.
If bent over you head is looking up compared to your body.
The target usually at a upward angle to the handgun.
Getting good results @ 7yds and changing to 15yds most likely caused a change in your grip/stance/target angle/head position.

Rest Vs. No Rest


Whether or not you use a rest while zeroing your red dot is about preference.

When you shoot using a rest, you have a more relaxed posture which is different from the actual shooting scenario.

But, those who can’t shoot good groups without support should use a rest to avoid human error.

My second opinion.....

Good groups first......zero second.....no rest.

P.S. Think you got zero.

[foothillman]

M2C on this

All shots the same, distance to target has changed.



Using 9mm, 115g, red dot 1" above barrel, zero 15yds.
You have 2 zero 15yds and 52yds
@ 5yds 1/2" low, 10yds 1/4" low see table.

You are correct that the holes should be high after first zero up to 1/2" high @ 35yds until you get to the second zero.





If you ZERO @ 25YDS the arc is much flatter out to 50yds, second zero @ 33yds and will shoot low @ 15yds 1/4" @ 10yds 1/2"
My opinion...better to shoot low and hit then shoot high and miss.

Using the chart if you consistently hit 1/2" low @ 7yds your zero is about 25yds.

Bullet drop "hold over" is not a factor for handguns in a defensive situation.

[Crysknife1013]

Thanks foothillman for all the info and data! Those target illustrations were eye opening. And that Black Basin Outdoors ballistics calculator is really helpful.

I never imagined that groups could open up that much from 5 to 50 yds! So based on those illustrations, my group sizes at 15 yards make a little more sense.

But I'm still flummoxed on how my shots are landing low at 15yds when compared to 7yds. According to the Black Basin Outdoors ballistic calculator you show above, the groups at 15yds should have been ~0.5in high compared to those at 7yds. (BTW, I forgot to note that I was using Aguila 124gr FMJ that day. Out of all the bullets available in the list, did you pick Aguila FMJ 115 arbitrarily? Or are you partly psychic? You were really close! lol)

Black Basin Outdoors Ballistics Calculator Aguila 9mm 124gr Chart by dalipiojr, on Flickr

Black Basin Outdoors Ballistics Calculator Aguila 9mm 124gr Table by dalipiojr, on Flickr

But I think you're on to something with "target angle/head position". I'm going to have to go back and be more conscious and aware of those aspects.

[Scotty]

One technique I use with red dots is not to zero using the center of the dot. Instead, use the top of the dot at 12 o'clock position. There's too much wiggle room if you use the center of the dot. Also recommend using higher round count so you get a better idea of where the rounds are going. Your group stairs aren't consistent enough.