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  #1  
Old 08-18-2008, 11:33 AM
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Accuracy of bore sighting?


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I just had my scope put on my .270 the other day and went to sight it in this morning. The guy at the place where I had my scope put on bore sighted the gun. I took the first shot a 50 yards and missed the paper, so I took another shot at 50 which also missed. So I shot a few at 25 yards. Still I missed the target. So now to my question, does getting a gun bore sighted always work. Any other help would be appreciated.

Thanks.
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  #2  
Old 08-18-2008, 11:45 AM
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Bore sighting a gun is a lot like a wheel alignment: It depends on the guy doing the job.

You clearly got a cross-eyed dyslexic working with his off hand and who really needed to take a whiz.
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Old 08-18-2008, 11:55 AM
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Originally Posted by thebigcheese109 View Post
So now to my question, does getting a gun bore sighted always work. Any other help would be appreciated.

Thanks.
Does it "always" work? Apparently in your case it didn't.

As a gunsmith, one of the requests that frequently came to my Dad was to bore-sight scoped rifles and to my knowledge it was usually pretty good at getting things close enough so that the shooter could dial in using a sight-in target without completely missing the paper.

Is it possible that your guy didn't hook up the bore-sighting properly?
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Old 08-18-2008, 12:13 PM
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Properly done, it'll at least get you on paper. Note, I said "properly done". Experience has taught me that "guys in a gun store" don't necessarily know what they're doing.
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  #5  
Old 08-18-2008, 12:29 PM
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If you've got a bolt gun or any gun that allows you to look down the bore then you can do it yourself with nothing more than a cardboard box and a place where you can sight in on a target or something else you can see thru the bore.

Cut two notches in the box to rest the rifle in. Set it on a table or shooting stand or bench. Make sure the scope is attached correctly and all screws are tight. Adjust the box so that you can see your target thru the bore. Now all you have to do is adust the scopes cross hairs so they match what you see thru the bore.

You'd be surprised how accurate this simple bore sighting technique is and it doesn't rely on an expensive bore sighter and can be done by anyone with a rifle that allows you to look down the bore with the bolt removed.

As far as gun store clerks with boresighters, some do a good job and some don't know the front from the back end of a gun..
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  #6  
Old 08-18-2008, 12:34 PM
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Thanks for the help guys.

I talked to a couple of my friends that had rifles bore sighted there and they said that the guns weren't even close too.

I have heard of looking through the bore to bore sight a rifle and have actually done it to my inline but I didn't really think of doing that. I'll give that a try before I go to the range again.

Thanks again.
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  #7  
Old 08-18-2008, 01:29 PM
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Depends on boresighting equipment

I bought a BSA boresighting tool two years ago. I read the instructions, which seemed pretty easy, used the right arbor for my rifle, and had the same results that you just had at the range.

I used that same BSA boresighting tool for my muzzleloader, and used the .50 cal arbor - same thing.

HOWEVER... When I used the "Shotgun" arbor, which is an adjustable arbor that gets a really tight fit, my .50 was pretty dang close to the bullseye when I tried it out again. I used that arbor on my 20 gauge slug gun with the same results.

So... I purchased a laser boresight tool with the different adjustable arbors for using with my .270 and .22's, and I was on paper with my first shots on each.

I came to the conclusion - those "spring tension" arbors included with my kit are junk.

Guess what? That's the same kit my local gun store used on my buddies gun, and he wasn't on paper either. They used the spring tension arbors also.

I've heard the Leupold boresighter is great, but that would stand to reason, knowing that companies reputation. However, I haven't used one myself, so I don't know for certain.

All the best,
Glenn
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  #8  
Old 08-18-2008, 03:16 PM
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The boresighter itself may need calibration. I have two of the Bushnell boresighters, one with the adjustable arbors and the other with fifteen fixed arbors. Both seem to do as well as the other. If the ring is taken off of the lens end of the boresighter four tiny screws can be seen. If one was to use the boresighter with calibers with similar ballistics these screws can be used to calibrate the boresighter so that it will be very close the first time. I don't bother with calibrating my boresighters because I use them for calibers from .22 BR to .25-06 Remington. Obviously this would not work for my situation.
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  #9  
Old 08-18-2008, 03:33 PM
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Have owned several of the laser and optical boresigters. Nothing will beat the old fashioned eyeball bore sighting from a solid rest and centering the target in the bore.

However, after doing that, I use the newer style Leupold tool and carefully note where the crosshair alignes in the tool. Take it with me to the range, get sighted in and check again. This reference and the tool make my hunting trips in the ammo bag and is available to check the scope if there is a question as to the scoope being bumped or not.
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  #10  
Old 08-18-2008, 07:26 PM
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The muzzle-fitting laser bore sighters are beginning to get inexpensive now, though they certainly haven't come down to the cost of laser pointers. The ones with bore spuds on the back end and a taper that self-centers in the muzzle nearer the laser module itself have the advantage that they work with any kind of action, including those that don't let you see through the bore without a small dental mirror. Gas-operated guns, for example. You pop them into the muzzle and point at a wall and look through the sights to see the dot and adjust the scope knobs until the crosshairs cover it. This works for initial adjustment of iron sights as well as of optical sights. However it will throw the shots high at 100 yards unless you make a target with two dots separated by the height of your sights above your bore line. With that you can put the spot on the lower dot and adjust the sights to align with the upper one. That should put your line of sight parallel to your bore axis. After that you just have to adjust the sights to compensate for bullet drop to the target (from trajectory tables) plus the height of the sites above the bore.

Another good trick relies on the scope rings to be aligned correctly in parallel with your bore line. This is not 100% reliable. However, you can usually get on paper with it. You build a scope spinner (picture attached). It just takes a piece of 2” x 4” and four ” Nylon round head bolts that you drill and tap pairs of holes for in the board, with the pairs having the same spacing as your scope rings. You lay the scope on the Nylon bolt heads, using them like V blocks, and turn the scope in them while you look through it. You adjust the elevation and windage until the crosshairs stay centered on one point while you turn the scope. That puts the crosshairs on the centerline of the scope optics. When they are not centered you see the crosshairs orbit the center. With alignment achieved, you mount the scope. If the rings were properly centered and the barrel perfectly made, your scope should now have its line of sight parallel to the bore line. As before, you need to look up the total drop for your bullet at the sighting distance you want to use and adjust the elevation knob to raise the impact point by the number of M.O.A. needed to compensate for that drop plus the height of the sights above the boreline.
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Last edited by unclenick; 08-18-2008 at 07:36 PM.
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  #11  
Old 08-18-2008, 07:43 PM
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another way to opticaly center the cross hairs is to place the objective lens flush against a mirror. now look into the ocular and you'll see the cross hairs and a second set in the back ground as a result of the mirror reflecting them back to you. now just turn the turrents until both sets of cross hairs align as one set. you are now opticaly centerd.
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  #12  
Old 08-18-2008, 10:27 PM
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Good info I had not read either of the centering methods before, thanks.
Has anyone any experience with the magnetic bore sighter Leupold is selling?
Kdub; does it seem to realign advertised?
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  #13  
Old 08-18-2008, 10:46 PM
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Having worked in a gunshop with 3 different boresighting tools, I can tell the tools are approximate at best. We have two Leupold laser models and one collimator type with the various pilots for each caliber. You can boresight a rifle with one, and the other two will not agree. One of the Leupolds often agrees closely with the "looking through the bore" method, the other does not. The collimator is not adjustable for scopes mounted at different heights above the muzzle, so elevation often does not agree with "thru the bore." Also, I have taken the collimator off the rifle, then put it right back on to check it, and found it to be off. None of this considers the scope's paralax, which can be considerable.

Bore sighting with any of the available tools is an approximation, at best. You still need to start close when you shoot.
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  #14  
Old 08-19-2008, 03:36 AM
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Originally Posted by MarlinF View Post
Good info I had not read either of the centering methods before, thanks.
Has anyone any experience with the magnetic bore sighter Leupold is selling?
Kdub; does it seem to realign advertised?
I have one of the Leupold magnetic bore sighters, and consider it useless. For one thing it is nearly impossible to "square" the bore sighter, while it is on the muzzle, as it's always crooked. I have an old Sweany "Site-A-Line Bore sighter, and it's much more easy to use and accurate. PLUS it is made in the U.S.A. NOT China!
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  #15  
Old 08-19-2008, 05:56 AM
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hey unclenick, do me a favor sometime. next time you have a scope that needs to be re-centered, place it against the mirror and note the offset. then center it the way you usualy do and then place it against the mirror once more and note the alignment.
or center as i describe then use your set up to verify. i've centered several this way and am confident it is within a click or two. however way you do it though it is only an advantage if you have a mount system that will allow you to center the scope with the bore of the rifle. this is where i like the burris rings with the plastic inserts to align it all.
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  #16  
Old 08-19-2008, 08:17 AM
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Jim,

Will do. I'll probably geet to that some time in the next month. I'll bookmark this thread so I can find it easily when I have the data.

I'd never heard of the mirror approach, but it sounds like nifty simplicity to me. Nothing to buy or make. The only advantage the scope turning method has over it is its inherent immunity to parallax error. Once the crosshairs are adjusted to stop orbiting a point, they remain stationary during turning no matter what the observer's angle. Only what they cover in the distance will change if that distance is one its parallax is not corrected for.

The idea for the Nylon screws on the block came to me because I'd bought a commercial equivalent; two plastic V-blocks made for the purpose and sold by Stoney Point. When a friend in another state needed to set up a scope in a hurry and didn't have time to order a pair, I cooked that block and screw and 2x4 improvisation up for him.

The parallelism of the scope mount is an issue. Also, if you are setting up a gun with long range scope rings, there will be an intentional 20 M.O.A. of downward height differential to be subtracted from the adjustment. If you have a Weaver type one-piece scope rail, you may be able to lay a cylindrical shaped laser pointer onto the center channel on top to check for left to right misalignment with respect to some point you've spotted by looking through the bore? The Weaver style ring should not give you an offset issue with respect to the base.

Offset on conventional mount rings would need to be cleaned up before mounting the scope, but that is true anyway if you don't want to ring the scope tube. I have the 1" and 30 mm scope ring aligning points that Brownells sells for the purpose, but using those plus doing a little lapping adds up to a lot more work than the Burris Zee Signature rings do. I think those are a good idea. There used to be another scope ring maker who advertised in Precision Shooting who did those ball joint mounts. I've forgotten who? It was long ago and Burris may have bought him out to own the IP, if there was any?
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  #17  
Old 08-19-2008, 09:32 AM
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MarlinF - Contrary to what others have stated, I have no problem getting the new model Leupold bore sighter to be square. The calibration on the stem of the optic will allow to compensate for scope center above bore center. Just need to measure the scope height. Reinstalling after denoting crosshair alignment with the sighter grid, I can come close enough to verify if the scope has taken a hit or not and could easily regain center, if needed.
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  #18  
Old 08-20-2008, 11:25 AM
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Quote:
Originally Posted by faucettb View Post
If you've got a bolt gun or any gun that allows you to look down the bore then you can do it yourself with nothing more than a cardboard box and a place where you can sight in on a target or something else you can see thru the bore.

Cut two notches in the box to rest the rifle in. Set it on a table or shooting stand or bench. Make sure the scope is attached correctly and all screws are tight. Adjust the box so that you can see your target thru the bore. Now all you have to do is adust the scopes cross hairs so they match what you see thru the bore.

You'd be surprised how accurate this simple bore sighting technique is and it doesn't rely on an expensive bore sighter and can be done by anyone with a rifle that allows you to look down the bore with the bolt removed.

As far as gun store clerks with boresighters, some do a good job and some don't know the front from the back end of a gun..
I had never heard of that or even considered it, but it makes perfect sense - once again, great advice from Bob!

I had thought about buying a bore sighting tool, but it seems to me that your method would be more reliable.
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Old 08-20-2008, 12:08 PM
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Looking thru the bore at the distant street light at the end of the block works for me and will put me on paper at 100 yds. everytime.
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  #20  
Old 08-20-2008, 02:51 PM
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Thanks again for the help.

Went outside last night and looked through the bore at an archery target and adjusted the scope. I went to the range this morning and with the first shot at 50 yards a hit the ring I made with a role of duck tape approx. 2 inches left of the bullseye. I adjusted and on the second shot I hit dead smack in the middle of the circle. Moved it to 100 yards and after 4 shot I was hitting the bullseye.
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