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Bore Sighting an 870

1K views 12 replies 8 participants last post by  Don Fischer 
#1 ·
I've got a few choices of red dot type sights and have one mounted on the gun, but I need some way to bore sight it prior to find tuning in order to save my shoulder ! I've got a lazer bore sighter, but all of the bore adapters are for rifle or pistol calibers, not shotgun bores. Anyone with a clever, ( and preferably cheap ) solution to getting this thing on paper ?
 
#3 ·
I've been thinking about this for a bit, and though it's not a perfect solution, it's an approximate one.

Do you have access to a drill press? If not, forget I mentioned it, but if you do, adjust its chuck central axis to as perfect a perpendicular to the table as you can achieve. Drill a hole in the center of a wooden plug cut from a dowel larger than the bore of your gun that will accommodate your laser bore sighting tool. Run a bolt that will fit snugly through that hole and fix it to the plug with a bolt, washers and nut. Install the plug in the drill press, securing it by the bolt, then use a flat file to reduce the plug diameter to fit your barrel. Remove the bolt and replace it with your boresighting tool. Press the plug into the breech of the shotgun and turn on the laser.
 
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#4 ·
You are going to spend some money either on ammo or adapters for your bore sighter.
Just use a lead sled or sand bags. Start at 25 yards and shoot adjust and go to 50 yards and adjust.
It should only take a few rounds(3) at both to sight it in.
I have found that a new scope is centered pretty good already. And if it is mounted correctly you should not have to shoot it much to sight it in.
Mike
 
#8 ·
Set up a target at 25 yards, a big one. Fire the first shoot off a bench rest at a small portion of the target, and adjust scope/reddot sight. Move target to 50 yards, repeat.
 
#9 ·
Guess I'm missing something here. You want to bore-sight a Remington Model 870 shot gun? You could make up some sort of adapter to "bore sight", but it would be a complete waste of time. A shotgun patterns (or groups the shot pattern) mostly because of the choke or reduced interior of the barrel at the tip or muzzle. The only thing a bore sight would do for a shotgun it to tell you where the barrel is pointing - not where the shot will be sent.

I understand that you do not like the recoil of shooting, but the only way to see where your shot pattern will be on paper is to shoot it. You need to build or buy a frame to hold a large sheet of card board or paper, maybe a 48" size. Set it up at say 25 or 40 yards. Draw a large (maybe 30") circle on the paper with a visible dot in the center for an aiming point. Like Carver said - shoot at the center of the paper from a bench or supported rest.

After you carefully aim and shoot one shot at the paper, go down and look at where the pellets have hit. That will tell you where the shotgun shoots at that range. Don't be surprised if the shot group is not exactly where you aimed. Not too many shotguns will actually pattern exactly where the bead lines up at.
 
#13 ·
Doubt you'll be able to bore sight it but, fairly easy fix. Set up a target at 10' and center the sight on it. Fire one round and then move the sight until it is about 1 12" directly above the first shot. To do this mount the gun on very steady platform or have someone help you. Next shot would be right on target but 1 1/2" high. At that point move to 25yds and do the same again. Then move to what ever range you want to zero and do it again. Pretty much the same as zeroing a scope on a riffle except on bolt rifles I can look through the bore at 25yds right from the start then move to 100' and fire the second shot and be well on the paper!
 
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