Hunter Select US 308 Winchester 7.62x51mm .243 7mm-08 Remington Caliber Cartridge Laser Bore Sighter Boresighter

This one is just like my other one, also from Amazon, also under $15. You don't get a large, complex, or terribly precise instrument for 15 bones. You get a useful, inexpensive, simple item like this bore sighter. You can set up your rifle at home, and when you go to the range you can set up your sighting in target at 25 yards and you'll be on the paper first shot, every time. 100 yards, you'll probably be on the paper first shot. If you've ever been through one of those 'I can't see the hit' affairs where you spend 5 or 10 rounds getting on paper, you know what this item is for. It's cheaper than lunch at a lot of places, and makes sighting in a rifle more fun. 8^)I got one of those 'alumi-wallets' you see on TV on a whim; it's crap for a wallet, doesn't fit a dollar bill folded in half, but with a little packing foam it makes a fabulous case for my boresighters! If you set the foam up so the boresighters are held in place between the case and the foam, that bit of pressure holds the base in place and prevents the things from coming on and killing the batterys. If you don't constrain the thing in some way, keep spare batteries around, because they tend to find a way to discharge. If you take the batteries out and put them in a ziplock, they'll lay on each other and get discharged. (this from experience) You can roll them separately in a kleenex and keep them in a ziplock that way and they'll stay good.Bottom line: if you are a gunsmith, get a big, expensive, sophisticated boresighter. If you are a hobbiest who would like a boresighter for occasional use, this thing is excellent.ADDED: By the way, .308, .243, and 7mm-08 cases are identical except for the neck area. This gizmo is a case without a neck with a lazer inside. It fits all three calibers the same, even though it only lists ".308" on the side of the boresighter. There was some confusion about that on here, as I recall, hopefully that helps clear things up for someone.

This works fine, if You understand how these work.First off one must realize the angles and precision You're working with. A thousandth of an inch tilting this tool, will equate to inches off target at 100 yards. Rifle chambers vary. They're never exactly on specification as each mechanism to extract varies in strength and speed. There is always some clearance to allow spent brass to expand slightly, contract slightly and then extract without tearing. Know that this is built into the rifle and not a fault of a laser bore sighter.It is fairly easy to overcome this with minimal effort. On bolt actions I simply remove the bolt, press the brass with my finger into the barrel. I then point (at night or dusk) at a target about 100 yards away. I push in a circle and let the laser "draw" a circle on the target (for me a blank white wall) while looking through the scope. This shows You the "ring" of slop in the chamber but WILL show You the approximate impact circle. I adjust the scope so that the laser's "slop" when pushed in every direction is about equally away from the center of the reticule. Using this method I have been as close as 2 inches, and as far as 8 inches at 100 yards. Both are VERY acceptable for this type of device. After final scope adjustment with live fire, You can "verify" with this device where it should be at a given distance, then recheck the gun anytime it's in question to see that it is at least "close"With semi Auto's it will vary based on mechanism. Some will put tension on this (cetme/g3/hk-91/ptr) which seems to actually make it easier. Just check by pulling back part way and closing the bolt numerous times. You're looking for center of the "average" so to speak.No boresighter will have the precision required to get much closer than 6 inches reliable unless it was custom built for Your exact gun. Expecting any better than "on paper" is a fault of improper expectations. These are to make it easier and get You in the ballpark not fine tune. No laser or any other sighting device can take bullet drop into account. It helps to figure the approximate drop ahead of time and then sight accordingly. (I expect the laser's circle to be 2 mil dots high at 100 yards for instance, one for drop, and one because I sight 1 mil high at 100 for a longer range zero)