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  #1  
Old 12-16-2004, 09:43 AM
mobocracy mobocracy is offline
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Accuracy of laser bore sighters?




How accurate are laser bore sighting devices, particularly with pistols?

The reading I've done from google and other forum archives varies from "almost extacly zero" to "gets you on the paper", although it seems most of this refers to rifles, not pistols.

The reason I'm interested is a pistol I have shoots left consistently. I used to blame myself (it's a DA/SA gun), but I've put nearly 1000 rounds through it and the last 400 or so have been shot trying lots of different trigger pull strategies, grips, stances, etc with no real movement. I'm grouping my shots well, it's just they're 2-4 inches left of POA @ 8 yards.

If a laser bore sighting system was accurate enough I could figure out if the sights really were off and then pay a gunsmith to adjust them and give him an idea how much to adjust them. If they sights really were on and I'm just a crappy shooter I could spend more time trying to get it right (and then eventually give up and have a 'smith adjust away my error..).

The sights are the dovtail "driftable" kind and visually they appear to be about 2 or 3/64" biased to the left I've actually had a go at adjusting them, but they won't drift with any force I've been willing to try, and there's a certain "mark with chalk, cut with axe" level of accuracy involved with just tapping a sight as stuck as mine.

Even though it seems like a one-time purchase, it'd come in handy for re-scoping my .22 rifle and scoping my S&W Model 41.
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  #2  
Old 12-16-2004, 10:25 AM
malynch malynch is offline
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bore sighters

are designed to get your scope on the paper. The are not designed for open sights.

That being said, since a laser boresighter works by being inserted into the muzzle it is parallel to the barrel. So in theory you could use to to see if your open sights are off. I don't know how large the dot will be at be at 25yds however.
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  #3  
Old 12-16-2004, 11:34 AM
1saxman 1saxman is offline
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From what you've posted I see no reason why your problem would not be solved by drifting the rear sight to the right. The point of impact follows the movement of the rear sight. Like the man said, lasers are for 'roughing in' a new scope set-up on a rifle, but could be used for a pistol, particularly for line (left and right orientation). On a recent build of mine, I sporterized a 1953 Hungarian M44 carbine in 7.62x54. I added a pistol scope in the 'scout' position ahead of the bolt. Going to the Norma Ammunition site, I used their ballistics calculator to analyze the trajectory of the 200 gr ammo I intended to use with a far zero of 200 yds. This yielded a near zero at 31 yards. I put a laser in the muzzle, set up a piece of paper in my backyard at 93' and adjusted the scope to the laser dot. The adjustment was very small, which indicated to me a good scope installation. I expect my shots at 100 yards to be close to the predicted impact point of 2" above the point of aim, needing only minor adjusting. Then I'll check and make any adjustment needed at 200 yds. The rifle should then be set. The laser just made it easier and safer to get on the paper.
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  #4  
Old 12-16-2004, 11:47 AM
mobocracy mobocracy is offline
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Quote:
Originally Posted by 1saxman
From what you've posted I see no reason why your problem would not be solved by drifting the rear sight to the right. The point of impact follows the movement of the rear sight.
I'm sure it could be, but how do you determine how much drift to apply? I wish the sight was easily hand drifted at the range, hell, even trivially drifted at home, but the dovetail fit is so tight that it needs a pro to move it and I'd hate to spend a month and multiple smith trips to get it accurate.

It just kind of struck me that an accurate (not super cheap) laser bore sight that actually shines its beam on the bore axis would be excellent for determining lateral error, especially at 10 or 15 yards.
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  #5  
Old 12-16-2004, 12:00 PM
Jim Watson Jim Watson is online now
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Trigonometry, similar triangles.
Three inches (midpoint of 2 to 4) at 8 yards (288 inches) corresponds to .062" over a six-inch sight radius. Right at 1/16" of movement. To the right, if your gun is shooting to the left. Since your sight is visibly offset to the left, try centering it up and shooting some more. From a rest, this is not a test of your holding ability.
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  #6  
Old 12-16-2004, 12:45 PM
steveno steveno is offline
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any bore sighting device is nothing more than a guide. it can't make adjustments for gravity and the vibrations of the firing of the gun and the bullet itself
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  #7  
Old 12-16-2004, 01:40 PM
1saxman 1saxman is offline
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To drift the sight, you would treat it with a penetrant, then using a hard plastic or brass drift, you tap it to the right. If the sight could be moved by hand, it would be useless because you could never depend on it being in the correct position.
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  #8  
Old 12-16-2004, 01:57 PM
mobocracy mobocracy is offline
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Quote:
Originally Posted by 1saxman
To drift the sight, you would treat it with a penetrant, then using a hard plastic or brass drift, you tap it to the right. If the sight could be moved by hand, it would be useless because you could never depend on it being in the correct position.
I haven't tried penetrant, but I have tapped the sights pretty darn hard with a brass rod without any movement. I don't have a great vise setup or other tooling (like some kind of universal drift tool), and I'm afraid if I hit it any harder I'm going to break something. I'm not real sure that penetrant would help, but I should give it one more try.

As far as them being easier to move, isn't that what the darn set screw is for? A touch of loc tite on the set screw and it ought to not go anywhere AND be adjustable as needed vs. tolerances so close you need a hydraulic press to fit it.
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  #9  
Old 12-16-2004, 02:09 PM
Chuck S Chuck S is offline
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With the use of proper targets a laser boresighter will get you much better than "on the paper." Of course much of this depends on the quality of the bore sight device. You need to fix the weapon to a secure mount and then rotate the device in the bore observing the dot on the target to ensure it doesn't move. A device which can't rotate may work well on only one particular weapon.

Unless you're spending several hundred dollars, though, getting on the paper may be all you get.

-- Chuck
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  #10  
Old 12-16-2004, 02:40 PM
chuckshoun chuckshoun is offline
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Sight Adjuster

The Brownells catalog lists a sight adjuster for $125 that will drift either front or back sights on a slide. You have to remove the slide from the pistol, but the thing does work. I found that I had to work up a method of measurement so I didn't move the sight too far (a vernier caliper with a dial gage on it). I used it at the range, just disassemble the pistol, move sights, reassemble, shoot, then I had Io do it a couple of more times. It was a heck of a lot better than a drift and a hammer, and I felt well worth the money spent. Sight drifting is frustrating as can be to me.
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  #11  
Old 12-16-2004, 02:56 PM
mobocracy mobocracy is offline
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Quote:
Originally Posted by chuckshoun
The Brownells catalog lists a sight adjuster for $125 that will drift either front or back sights on a slide. You have to remove the slide from the pistol, but the thing does work. I found that I had to work up a method of measurement so I didn't move the sight too far (a vernier caliper with a dial gage on it). I used it at the range, just disassemble the pistol, move sights, reassemble, shoot, then I had Io do it a couple of more times. It was a heck of a lot better than a drift and a hammer, and I felt well worth the money spent. Sight drifting is frustrating as can be to me.
I *just* discovered them. Now there are two in their catalog for that same price (both made by PI, Inc) -- the "P500 Universal Sight Tool", and the "SEMI AUTO UNIVERSAL SIGHT TOOL". I knew Sig sold something like this, but I haven't found one that claimed to be universal until now. Which one do you have -- the P500 or the more portable SEMI AUTO UNIVERSAL tool?

The former looks like it would be a better buy due to the superior adjustability, while the latter looks more portable and easier to use. Sadly for the former is out of stock and the latter shows "Dropped by factory" which means either the factory drop-ships it, or they dropped the product from their line.
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