Bore Sighter...

88Mustang

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I got a green laser Boresighter a couple weeks ago (https://www.amazon.com/gp/product/B007WQJCWC/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1 )

I followed instructions, hung the reflective target on the back of a wheelbarrow, measured out 75 feet and lined up the reticle to the laser dot. According to the doc sighting in should have put the POI at around within three or four inches from the POA @ 100 yds.

So I went to ENC to zero 2 rifles (the suppressed spikes and a Colt Competition that I last shot was at a half day carbine class with @JBoyette in 2017)

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I launched a few shots at 100yds but was not hitting the target that I could see. So I went to a target at 50 yds, the POI was way off, but I was able to see the hits on paper. I zero'ed at fifty then moved back to the 100 yard target, zero'ed to 100 yds and did lower group than the upper group then the center group.

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I am not a MOA shooter, more like a 3 or 4 MOA on a good day with barricade.
I was using the range's lead sled which are a little beat up. I did get a card with the rifle that had a sub moa group on it.
 
Maybe I’ve bought junk boresighters in the past, but I’ve never had good luck with them.

I’ve started removing the BCG, clamping the upper to a vise and just looking through the bore to a 25 yard target. Adjust the reticle to be in paper and take a couple shots. 25yd Zero from there within a couple shots and easily on
paper for a final zero at 100 or 200.
 
Just start with a big piece of blank paper at about 25 yards, put a mark to aim at and shoot one bullet. Measure and adjust.

Now if i was buying new rifles as frequently as I wanted and mounting scope all the time, I could see trying to find a little shortcut.
 
I have a few bore sights and really have not had any luck with any except the 45/70. As others have said. I start between 25 and 35 yards with a couple of shots to see where I am hitting, then out to 50 to may any adjustments. Looking for groupings below bullseye an inch or 2. Then out to 100 to finish zeroing the scope. I just bought a roll of brown paper so I would have a clean target that is bigger than a 18 x 12.
 
Run a small test.

Install the boresighter laser and turn on. Take a marker and place a dot on paper and at 15yds have the laser impact your dot. Go back to the firearm and without moving the gun rotate "twist" the boresighter 180degs. Go back to the paper and mark the new location of the laser.

This is why these things suck ass.

John
 
I eyeball it, too.

I've got lucky and had it super close at 200. Couple clicks off.
 
After reviewing the documentation again, I realized I did not follow the procedure outlined (SMDH). I am going to try again later this week. I would like to be able to skip the 25 yd get on paper and just get on 50 yd target. I can't shoot on my property (no backstops) and not having to get on 25 yd and 50 yd would be a time saver. I zero at 50 yd with the all but the rifle at top of post. The scope requires 100 yd zero for the BDC (Primary Arms GenIII ACSS 1-6 x 24).
 
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So with a bdc reticle i have a procedure to guarantee the bdc matches the bullet drop.

When you get it zeroed let me know
 
Fyi For everyone reading this topic.

When you see pictures of a bullets trajectory its curved. Now the first 1/10th of that curve is set by sight height over bore. The other 9/10ths is baby rocket science.

The height of the sights over bore is known as mechanical offset.

How tall or short the mechanical offset sets the zero "0" line of departure for the firearm.

We must understand that a bullet never rises in flight, a bullet is no loft capable, but some designs are more aerodynamic then others. But even the best BC never gains altitude.

The up angle of a bullets flight is 100% based on the angle of departure. Also the angle of pitch the barrel is pointed in in relation to the line of sight.

In measurement, we have 60 MOA to a single degree "1". A typical centerfire rifle from .223 to 300wm can impact a target at 1000yds with less then 1/2 a degree of angle of departure off the line of sight index.

The index point i am speaking of is known as a zero. Pick a caliber, pick a distance, make point of aim and point of impact meet and we have a zero.

The issue with bore sight tools is not the tool but the understanding of the whole process. A good understanding is this rule.

5yds = 500yd zero
10yds = 400yd zero
20yds = 350yd zero
40yds= 300yd zero
50yds = 200yd zero
100yds = why do you have a bore sight tool?

The bore sight tool only does a fixed point in space where the line of bore and when adjusted, the line of sight meet.

If i do a 5yd bore sight i get my line of sight to meet the laser, then take off 15moa of elevation.
 
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Fyi For everyone reading this topic.

When you see pictures of a bullets trajectory its curved. Now the first 1/10th of that curve is set by sight height over bore. The other 9/10ths is baby rocket science.

The height of the sights over bore is known as mechanical offset.

How tall or short the mechanical offset sets the zero "0" line of departure for the firearm.

We must understand that a bullet never rises in flight, a bullet is no loft capable, but some designs are more aerodynamic then others. But even the best BC never gains altitude.

The up angle of a bullets flight is 100% based on the angle of departure. Also the angle of pitch the barrel is pointed in in relation to the line of sight.

In measurement, we have 60 MOA to a single degree "1". A typical centerfire rifle from .223 to 300wm can impact a target at 1000yds with less then 1/2 a degree of angle of departure off the line of sight index.

The index point i am speaking of is known as a zero. Pick a caliber, pick a distance, make point of aim and point of impact meet and we have a zero.

The issue with bore sight tools is not the tool but the understanding of the whole process. A good understanding is this rule.

5yds = 500yd zero
10yds = 400yd zero
20yds = 350yd zero
40yds= 300yd zero
50yds = 200yd zero
100yds = why do you have a bore sight tool?

The bore sight tool only does a fixed point in space where the line of bore and when adjusted, the line of sight meet.

If i do a 5yd bore sight i get my line of sight to meet the laser, then take off 15moa of elevation.

So to clarify for ballistic apps, if I am shooting a target that calls for 60 MOA holdover and inclination is zero, angle of departure = 1°
and
The app will ask for either mechanical offset or scope height above bore but never both because they are two terms for the same thing.

Is my understanding correct?
 
So to clarify for ballistic apps, if I am shooting a target that calls for 60 MOA holdover and inclination is zero, angle of departure = 1°
and
The app will ask for either mechanical offset or scope height above bore but never both because they are two terms for the same thing.

Is my understanding correct?

Yes and no.

The angle of departure is a developed set value, in an angled unit of measure. Let's call that unit MOA. Upon attaining a zero of let's say 100yds, you have now built in the angle of departure to align with a fixed point that both the line of sight and line or bore agree with. aka 100yd zero. This sets the system to "0" and works from that base point forward. the set value of zero has windage and elevation consumed in the sighting system to gain "0". Now we clear the deck for all readings moving forward.

To your question, to shoot at a target and to get the 60 moa holdover, you must have zero "0" established before starting. Now you are adding the 60 moa or 1deg of adjustment on top of the zero.

This is why quality gunsmiths for precision rigs retap and align the bases mounting holes to square to the bore. This removes excess windage, a 20 MOA base lowers the erector of the optic to 20 MOA LOWER upon zero to give more "up" adjustment. This is also why if you run stupid tall rings and base, you can run out of total travel, it took too much internal adjustment and the resting zero of the erector is in a jacked up spot.

to the second question,

Scope height above bore = mechanical offset.
 
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JBoyette, this is the way that I think if it. The scope does not move, it raises or lowers the cross hairs. To keep the cross hairs on target you have to raise your barrel (scope is fixed to the receiver which should not be moving) which cause the upward path of the bullet.
 
JBoyette, this is the way that I think if it. The scope does not move, it raises or lowers the cross hairs. To keep the cross hairs on target you have to raise your barrel (scope is fixed to the receiver which should not be moving) which cause the upward path of the bullet.

100% right path.

Lets do a small shift in moving pieces in your words.

Replace cross hairs with line of sight.

The unmoving line of sight is the foundation everything adjust from, and is what all measurements are taken from.

A line of sight is the visual line from your eye to the target. The tools you use to make things impact with the target all are based on the line of sight.

Mechanical Offset: the physical distance how high the sights are above the line of bore

Point of aim: the orientation of the firearm and sights towards a target.

Point of impact: the relationship of bullets impacting near the line of sight.

Sight picture: how you place the sights onto the target

Cant: the rotation of a firearm in relation to the line of sight

You get the idea.

John
 
The assumption is the laser emitter in the boresight "body" is centered. They are not.

As JBoyette states,
Test one...
Turn it 90* and then 180* and see what it does. Take one of the "cartridge" chamber bore sighters and spin it in a lathe or chuck one up in a drill clamped in a bench vice and watch the "dot" wiggle all over the place. Not precision at all...


My procedure is similar to Tims..
I use a white paster ( or masking tape) on a USPSA target at 25 yards. I clamp the upper in the table vice and sight the barrel bore visually. The white paster is easy to see and align with the bore. Make reticle adjustments as needed for alignment and take 3 to 5 shots. You should be very close to where you need to be.
 
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So to clarify for ballistic apps, if I am shooting a target that calls for 60 MOA holdover and inclination is zero, angle of departure = 1°
and
The app will ask for either mechanical offset or scope height above bore but never both because they are two terms for the same thing.

Is my understanding correct?

4FDBFCBB-2610-4DB2-B350-110841940DE6.png 6EFF2EA3-4398-4122-84BA-FC86CD84E0EA.png

For ballistics apps, the offset is used when you have 2 loads for the same gun.

Load A is your “zero” load and has no offset.

Load B impacts +2 when compared to your zero; so it has an offset of +2.

The pics below are from StrelokPro. The 77gr load is my “zero” load. When I shoot Wolf 55, I
need to add .2Mil to get that load to “zero”
 
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The apps will then ask for “scope height” to input the distance over the bore, what @JBoyette was referring to as “mechanical offset” above.

Every ballistic app that I’ve used, and I’ve used em all, definitely want BOTH height over bore and offset - the offset is only necessary when you have loads with different zeros.

This is why you’ll see the “offset” value associated with the load data and the scope height only associated with the rifle data, as it would be the same for all loads.



EFF38ED7-10FB-420B-9D3C-030BC2EE8F50.png
 
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The apps will then ask for “scope height” to input the distance over the bore, what @JBoyette was referring to as “mechanical offset” above.

Every ballistic app that I’ve used, and I’ve used em all, definitely want BOTH height over bore and offset - the offset is only necessary when you have loads with different zeros.

This is why you’ll see the “offset” value associated with the load data and the scope height only associated with the rifle data, as it would be the same for all loads.



View attachment 134437

I do not use apps, i just have a sharpie with dope written down in per-click scale.
 
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I do not use apps, i just have a sharpie with dope written down in per-click scale.

That’s why I answered since his question was in reference to the apps. It took me a lot of trial and error to get them figured out. I use them to get “close” and using their calculations. Then, use the apps truing functions to record actual.
 
That’s why I answered since his question was in reference to the apps. It took me a lot of trial and error to get them figured out. I use them to get “close” and using their calculations. Then, use the apps truing functions to record actual.

Understand, its my weak area, i do not trust them at all.
 
Understand, its my weak area, i do not trust them at all.


You should. I made 1st shot hit on a 2MOA target at 750yds the other day. Prior to that shot I only had verified data for 300 yards with that load/rifle.
 
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The more precise the data entered, the more precise the results of the app. They are spot on if good data is used. Confirmed Chrono numbers and Current weather can be big factors. I like Sierra Infinity. Sierra will download current weather conditions with one button push.

Download one and play around with selecting projectiles, entering data, and looking at the dope/drop, wind drift, and reticle charts. You will eventually be amazed at how you got along without it.
 
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So I zero'ed 3 rifles with the bore-sighter, and actually followed the instructions this time. The three rifles (12.5 inch/11 inch/ 10.5 inch) vertically all were within roughly 4 inches from POA. POA/POI horizontally was within 2 inches. So I am happy I can skip the 25 yard get on paper step.

I also tried some better ammo and discounting the flyer the rifle is obviously sub MOA capable, although I am not. Probably the best $800.00 I spent on a rifle.

8pxTLln.jpg
 
So I zero'ed 3 rifles with the bore-sighter, and actually followed the instructions this time. The three rifles (12.5 inch/11 inch/ 10.5 inch) vertically all were within roughly 4 inches from POA. POA/POI horizontally was within 2 inches. So I am happy I can skip the 25 yard get on paper step.

I also tried some better ammo and discounting the flyer the rifle is obviously sub MOA capable, although I am not. Probably the best $800.00 I spent on a rifle.



That wasn't a "flyer"... That hole is simply where the sights were lined up when the shot broke...

Glad you got your gear up and running!
 
Maybe I’ve bought junk boresighters in the past, but I’ve never had good luck with them.

I’ve started removing the BCG, clamping the upper to a vise and just looking through the bore to a 25 yard target. Adjust the reticle to be in paper and take a couple shots. 25yd Zero from there within a couple shots and easily on
paper for a final zero at 100 or 200.

Ditto! I boresight at home across the length of the house. I clamp the upper minus the bolt in a panavise on my desk and use a picture in the guest room about 30' away as the target (I set for scope for about the bore to scope height offset). When I did my AR-9, I was in the 10 ring at 75 yds.
 
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