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Old October 17, 2008, 10:03 PM   #1
DaveInPA
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How to bore sight a red dot sight?

I have questions about boresighting. I really don't want to waste ammo trying to get on paper.

1. I mounted my scope on my flattop AR today. The mechanical boresighter I use on my other rifles sits WAY too low, so I'll need to use a laser one. Would this get me on paper at 25yds?:

http://www.cabelas.com/cabelas/en/te...006&hasJS=true

2. What about boresighting my red dot sight? Line the red dot on the sight up with the laser dot on the target?

3. If boresighting isn't a good option, does the old fashioned way really work? In other words, secure the upper with the carrier removed, look through the bore and line it up with the bullseye, and adjust the crosshairs to match? Could I also use that method with the red dot?

Thanks!
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Old October 17, 2008, 10:31 PM   #2
dmazur
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I put an Eotech on a scout mount on a Garand and that's what I did. The laser got me onto paper at 25 yds, and I had to adjust for what I wanted after firing several rounds at 100 yds, which was 1.5" high.

The model I used was the "cartridge type", not the barrel insert, but the theory is the same I believe.

Remember, the laser boresighter projects a straight line, and the POI follows a curved trajectory. So, if you use the laser at too great a distance you will encounter this difference. IMO, only good to save ammo when fitting a new scope. Some report these are also good to verify zero, if you keep a card you mark up at short range with both laser location and crosshair location, after you have established your zero by shooting at range.

As far as I know, if you can clamp the rifle in some sort of improvised vise (or a cardboard box with two V's cut in it) and look down the bore while you adjust the scope, you can boresight it. That's where the term came from. Red dot or conventional scope, should be the same. (Except holographic red dots have less trouble with head position & parallax)
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Old October 17, 2008, 10:52 PM   #3
roach4047
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I too was considering a laser boresighter. I'm leaning more towards the Cartridge type though. I think there is less a chance of the cartridge type being inaccurate since it will be shooting it's beam the entire length of the barrel and then onto the target vs the one that you linked in your post. With the one linked in your post having to mount in the very end of the barrel even the slightest bit of misalignment would unknowingly project the laser into the wrong direction. With the cartridge laser sighter that's not as likely to happen since it projects it's beem from the rear of the barrel instead of 3 inches in front of the front of the barrel. Just my .02.

DMAZUR... was your shot 1.5" over @ 100 yrds? It sounds like you may have been right on the money for a 200 yrs shot if so.


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Old October 18, 2008, 01:56 AM   #4
dmazur
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Yes, for .30-06 150gr bullets at 2700 fps, 1.5" high at 100 yds is a typical adjustment to get a "zero" at 200 yds.

Regarding accuracy of the laser compared to the bore, IMO it depends on how "tight" your chamber is for the cartridge style, and how parallel the chamber is to the bore. The length of the barrel doesn't help the laser any.

For the muzzle insert style, it depends on the machining of the studs compared to the diameter of the bore.

Assuming the length of the stud is around the same as the length of a cartridge (2 to 3 inches, estimated) and assuming the same manufacturing tolerances, I'd expect the accuracy of the two systems to be about the same.

(Each system must also have x/y calibration screws, to adjust the laser so it is parallel to its machined reference "cartridge" or stud. The factory usually adjusts these and instructs the user to leave them alone. )
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Old October 18, 2008, 04:20 AM   #5
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I use the catridge type laser bore sighter and it works great. The problem I had when I attempted to use the muzzle design was that the stud was too short and my AR has a flash suppressor so it didn't have enough bearing in my bore to sit straight. I also didn't care for having to mess with all the little o-rings for different calibers. The catridge style works like a charm, it's a little more expensive but well worth it in my opinion. Natchez Shooting Supply usually sells the Aimshot catridge kit fairly reasonable, you save quite alot buying the kit if you own several calibers as the price of arbors adds up quickly.
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Old October 18, 2008, 07:40 AM   #6
JDG
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I just clamped my uppers in a B&D Workmate, looked down the bore at the neighbors hubcap, and adjusted the optic. Both times put me on a paper plate at 25yrds. Remember the adjustments are opposite of what your optic says, while boresighting.
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Old October 18, 2008, 07:08 PM   #7
Ruger4570
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I guess I have a different take on the subject. Even for the low price of $40.00 plus shipping etc for a bore sighter, you can buy an awful lot of ammo. Try a single shot at 12 yards, adjust what is needed and move out to 25 yards. I think I could be centered with 2 maybe 3 shots. Good luck in any event or choice.
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Old October 19, 2008, 08:18 AM   #8
Alleykat
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Ruger4570, aren't you ashamed of interjecting common sense into a thread like this?
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Old October 19, 2008, 08:26 AM   #9
22-rimfire
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The old way works for me. Just keep your distance to 25yds or less to start. I used a bore sighter for a SRH that was giving me fits until I figured out what was wrong. (Mounts worked loose after a couple shots.) The problem is always if you can't look down the bore. Then the laser or old style bore sighter is useful.
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Old October 19, 2008, 11:30 AM   #10
T. R. Allen
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One shot sight in

As long as you can put a shot anywhere on the paper, make it a LARGE sheet, you can be on with one shot. Fire one shot from a solid rest, with the crosshairs on the bull. Find that hole, and with the gun still on the rest and crosshairs on the bull, adjust the scope to the hole without moving the gun. The scope now points to where the bullet goes. Now adjust to 100 yds or where ever you want.
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Old October 19, 2008, 02:18 PM   #11
overkill556x45
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Here's a trick we use in the Army. I hope you have some irons on your rifle, and that they are zeroed. Also assumes a co-witness sight picture.

You need two people and to do this. It's better if the guy holding the rifle is in a supported position. Make sure the weapon is clear. MAKE SURE THE WEAPON IS CLEAR.

The "firer" (Guy #1) assumes a firing position and aims through the irons while the red dot is turned on. Guy #1 tells Guy#2 which direction to move the dot so it appears to be sitting on top of the front sight post, looking like a lollipop.

This WILL get you on paper at 25m. I was a line safety on the zero range last weekend and some guys hadn't boresighted or done the above process. I helped them out, acting as Guy #2. I got them on paper every time! Usually about 4-6" off the correct impact area. I like this method because it is simple and can be done with no extra equipment. You can also do it anywhere, not just at the range! It won't get you as close as a real bore sight can, but it gets you close enough to finish zeroing with your allotted 18 rounds.
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