I have a Sightmark boresight tool that fits in the chamber of a rifle (.308) and sends the beam down the bore of the rifle to the "target".

I am thinking that in a low light situation I should be able to pick a target at 100 yards and see the laser through the scope to boresight so that when I go to the range I am within an inch of the impact point I am trying to achieve.

at about 40 feet with the elevation bottomed out I am seeing the dot about four inches above the crosshairs (MOA crosshair in an Athlon 6-24x50 with 30mm tube). I know at 100 yards I will probably see the dot from the laser below the crosshair.

Thoughts?

Just FWIW, I have tried a few different laser bore sighting devices. I've had exactly ZERO positive results with any of them.

I have however boresighted or got on paper at least a couple hundred different riflescopes but simply pulling out the bolt and sighting down trough the bore at a round target or a large cross hairs.

Since the latter method is FREE requires no additional widgets and has been near 100% successful in sighting in my scope I would suggest you don't waste your money on Laser bore sighters.

You might also reduce what you expect by bore sighting. Use a large target, get on paper and adjust with your turrets. Don't expect ANY bore sighting method to get you within an MOA, it's blind luck if you ever do.

And just like in the African Movie, NEVER trust a rifle you haven't sighted and tested with exact ammo yourself.........

Waste of money and time IMO.
As mentioned I just look down the bore and adjust.
I do it at 50 yds and adjust the reticle to be about 1.5" high then go zero at 100 yds and am usually really close.

I look down the bore at times, with a steady rifle hold. I’m not sure how well it works, but something.

I recently sighted in from scratch, newly mounted scope. I know it’s not easy at a formal range, but I start short, adjust on one shot until time to fine tune.

That start distance may be 25 yards, larger cardboard. Usually in 5-7 shots things are close.

The way I set up, not sure a dedicated ‘bore sighter’ would be of benefit.

Thank you all.

this is on an M1A so looking down the bore isn't an option; but the looking down the bore works well on a bolt gun.

I know I won't get MOA at 100 with any bore sight tool as laser goes in a straight-line while a round travels in an arc.

My expectation is that I can at 100 yards first with the laser in the bore get it sighted so I am within eight to ten inches on paper with a live round. Once the first round is on paper I can make the adjustments for windage and elevation to get the rifle hair on a gnat's behind accurate.

I already have the bore sight device (I have many so I can do multiple calibers)

Follow the directions. IIRC they usually say to used them pretty close. They're made to get you on paper, that's what it'll do.

Your bullets flight path isn't going to be flat like a laser beam, so doing it at a 100 yards will pretty much guarantee worse results when you shoot it.

The "theory" part in laser bore sighters comes after you sight it in. You bore sight it again with a grid target at a set distance, making notes of where the laser dot is on the grid. Then at some later date, you can do the same with the grid and make sure it's still in the same spot. Say after a long car trip, or a flight etc etc. In theory.

Like Lizardman, the rifle I recently tried to boresight was a pump-action .22lr, so sighting down the barrel isn't an option.

I have a laser boresight but the jury is still out as to how well that works. I just did it today and will take it to the range next week and see what happens.

What is your experience with the ones that use a "grid" approach? Are they any better than the laser boresight?

quote:

Originally posted by lizardman_u:
Thank you all.

this is on an M1A so looking down the bore isn't an option; but the looking down the bore works well on a bolt gun.

Just FWIW they made bore inspection mirrors for the .303 Enfields so you could look down the bore with a mirror. You can just take the bolt out on Enfields so I never used my bore mirror for sighting in.

Of my M1A I just moved a Large target in to 25 yards shot on paper and made 4x adjustments to make up for the 1/4 MOA distance. Still Simpler than figiting with a laser, OR bore mirror! :-)

I agree with just shooting at a large target backer to get started with zeroing, but if one wants to look down the bore from the breech of a rifle like the M1A, a cheap dental-type mirror works. (I have one in my range box for that and other purposes.)