Posting here vs laser forum as I find this one more knowledge-saturated to my question.

I found the stock mount on my DBAL i2 was slightly loose and every 3rd hunting trip slowly losing zero. I ended up getting a Larue mount and want to try and recalibrate. I do not have a bore laser device.

I need thoughts on my logic and efficacy of this method.  I want my laser offset parallel to my RDS.

My RDS is zeroed at 100y. It’s dead on. My sight is a T2 LT660 lower 1/3 mount.  What I did: I know the LT660 T2 is 1.64 inches from dot to top rail. I then measured the offset of the IR laser (left) from center of the rail and the exact distance below the T2. I plotted all points on a target. Putting the rifle on a rest, and the plot-target on the wall 6 feet away (same height as rifle in the rest), I put the RDS aligned with the appropriate mark on the target. Turning on the IR laser, I used my NODs to adjust the projection to its appropriate target point.  My anticipation is I should be close in real life POA and POI until l can verify through actual shooting.

Holes in the logic? Too short of a distance with this method?  Better way given tools I have? My backyard is about 40 yards wide so gives me more room to test but more concerned about leveling and ground unevenness (yep, don’t have my leveler).

Sounds fine to me.

Everything I have is co-witnessed to the same POI at 100 yards. Day scope,  visible pointer, IR pointer, night vision scope.   The cross check is the fact that the red laser pointer is
visible in both the day scope and the night vision scope.   Everything is on throw lever mounts and repeatability has been proven.

Red laser and IR are not slaved so independent exercise. Aapreciate your input on my logic though

At the farthest distance possible during the night, look through your RDS over lap it with your IR laser. Now your holds are exactly as your RDS without firing a shot.

Similar concept but I am going for offset vs overlap. That way at a longer distance I won’t get the laser crossing over the bore line.

Is the short distance I initially attempted invalid at longer distances? I swear the logic was sound to me.

I think the parallax variable at 6 ft is a problem. Further out is less of it

If you overlap the 2 at the furthest distance you can see in theory the 2 will never cross over, but since lasers and RDS are not meant for precision aiming and the adjustments are 1/2" moa at 100 it's all about getting as close as possible. At 50 yards looking through your RDS it's hard tell if it's a constant or intersecting zero. As far CQB shots offsets you just have to know what your rig will do at those distances. For me if possible I'd rather use a passive RDS under nods vs an IR laser which is one of the reasons I choose a PVS 14 mono tube vs  running duals. It's faster, more precise, and I don't have to change settings if all of a sudden the lighting changes from dark to light. I also use the standard 1/3 co-witness RDS mount mainly due to having back up irons if needed. By canting your head slightly forward and laying your ear lobe on the stock acquiring a sight picture through my RDS has not been a problem. I've tried the KAC Skyscraper and all sorts of risers but the weight, loosing your backup irons, possible parallax shift, unstable chin weld and shear weight was enough to go back to a standard 1/3 mount.

thanks, munny.  Played around at 30 yards in the backyard, the lasers were off on visible and IR.  Not terribly, but it seems the parallax at such a short distance indoors was the issue.  the weak point

Dont forget about preloading your adjustments so they hold zero properly amd that goes for Steiner as well as L3

Yes counterclockwise 8 times to bring back clockwise if that’s the necessary adjustment route

I typed up a long winded post with data about "constant vs converging" laser zeroes in another thread, but didn't post. This was one of my points of contention.

When you zero according to the offset method, especially at close range, you're one click away (or sometimes zero) from having a diverging zero that never crosses the vertical sight plane. Then the whole "I never have to hold windage with my laser" theory goes out the window.

Edit to add re: your original question, 6 ft is not enough for any kind of zero, unless you're just trying to get on paper. A better way to get on paper is to overlap your NV compatible red dot on a distant object, just take the upper in the backyard & shine it on some trees. It's idiot proof, I would even take a 200 yd laser/rds overlap over a 25 yd live fire zero. This is also one of the reasons NV compatible red dots rule for night guns in my opinion, super quick & easy to confirm.

I’ll be verifying at 50 and then 100y the goal was to find a method to be close as I’ll likely be hunting before the live fire verification

Overlap at 100-200 yds is the best option in this situation.

I don't know that you're missing anything so much as you may be overthinking it...

A variable frequently left out of the offset/coaligned discussions is the laser's beam divergence, the laser is not a single stream of projected photons, it's more of a "cone" emitting from the device.

Shorter range zeros with calculated offsets can be effective--if they're done right, but basically require charts and graphs and slide rules and probably a lengthy PowerPoint presentation to get right, not to mention you need to adjust them based on specific pieces of equipment. The Telluric targets make it easier if you match everything to the stated specs for the target, but as with any fixed BDC, it is still a general approximation.

Moreover, small errors at shorter ranges compound at actual engagement distances (something learned by many a Soldier moving form the zero range to the qualification range ).

The long and the short of it is that despite whatever intellectual capital you may devote to producing a "perfect" short range, offset zero, will still not be a precision target engagement tool--this is not to say that IR lasers are not capable of practical precision by an experienced user, they most certainly are, but when you combine all the variables, to include beam divergence and the laser's adjustments, you really won't be getting a much (if at all) more precise zero than you would by simply coaligning the laser to your day sight POA at the furthest possible distance.

The best advice I usually have is to make sure to get a good, solid, confident day zero and learn your offsets--coalign your laser, and then shoot.

~Augee

Good points, Augee.  The challenge is the laser bloom with a 2MOA dot...and what accurate convergence actually would be.  I suspect, even with an IR light reducing bloom, the MOA is roughly 4-6 MOA.  This makes co-alignment a challenge

Still overthinking it. I use a 3/4" circular road reflector at 200m on a checkered panel, when the reflector blooms, the laser is on, you can try and adjust and see how many "clicks" you get if you really want to try to "center" the beam on the reflector, but it won't be many, if at all, I think the most I've gotten is two clicks on the reflector, at which point you can't even split the difference, you just need to flip a coin and roll with it. Mostly, I just lay the weapon on the center of the panel, the reflector is invisibly small at that distance--if my dot is in the center, and the reflector blooms, it's zeroed.

My boresighting panel:



~Augee

I think this is probably the best method you are going to find.

Obviously the solution is we need to go shooting soon.  I want to hear pings on steel at 500 under NODs.

Like Augee said, it's difficult to get it exactly on and has a 1-2 click variable and because of the bloom I always overlap the red dot and laser at the furthest distance I can see. With my pvs14 mounted on a GI mount I will turn the laser vertical adjuster 10 clicks up to see if the laser is truly overlapping the red dot, then I click 10 to the right and 10 down to check the horizontal alignment, then finally I click 10 left to re center both the IR laser and red dot. With this method I've rang steel at 450 yards. Just keep in mind to preload your vertical/horizontal adjusters as recommended by both Steiner and L3.

All good points, and this may be my best answer

Match your optic point of aim with your laser point of impact at somewhere between 100 and 200 yards and you'll be fine.

Bloom, target identification, skill, external ballistics, and conditions make anything else a waste of time.

This.
I try to match the zero on my RDS, which is 50 yards typically. Shorter distances, I expect to see 2 dots, with the lazer dot just below the RDS, with the two intersecting around 50 yds. I do not expect to be shooting much longer range, especially standing free-hand shooting.