Boresight off POI in one rifle, on POI in the other

[stumpers]

As the title says, I boresighted two rifles prior to a trip to the range, but have varying results with the chamber/laser boresight.

Both are ARs, with lightweight 14.5 inch barrels plus extended flashhiders to make 16.25 inches.

One is a BCM BFH barrel, the other is a BCM standard. Both 5.56.

After boresighting, I zeroed both with M855. One rifle was nearly dead on L/R, but a couple inches low. The other was way off low and left.

Now when the rifles have been zeroed on paper, the laser boresight says the one is dead on, and that the other is way off.

The boresight works on one gun, but not the other - or so it seems.

The question is: why would two zeroed ARs be so drastically different when it comes to checking with a boresight?

 

[Certaindeaf]

The rifle isn't a laser.. barrel harmonics are an interesting thing.

 

[wally]

The laser ignores aerodynamics, barrel harmonics, irregularities in the muzzle crown etc. whereas the flying bullets do not.


If you are on the paper with your first shot the boresighting has done its job.

 

[Carl N. Brown]

I trust boresighting to put the sights on target board only, and expect final adjustment to vary gun to gun, barrel to barrel.

 

[chaser_2332]

Sell the laser and buy more ammo, it's the only sight in I would trust.

 

[splattergun]

If you are on the paper with your first shot the boresighting has done its job.

My Lazerlyte bore sight gave me the same results you're getting. In my Howa 1500 30-06 the light dot vs actual zeroed POI was 4" low left. In my friend's Rem 700 06 the light dot was 1 1/2 high right. In my .243 the light dot is 1" high center. In my friend's 22-250 it is 3" high left. I worried and wondered and fidgeted until I finally realized exactly what Wally said. It got me close and rounds down range did the rest.

Why the varied result? I'm in agreement with all the previous. I might add that I suspect that there is really no way to insert and tighten the rod of the tool in exactly the same point in every barrel, so the light point will vary. We might get tighter tolerances from a laser sight tool that inserts into the chamber, but my muzzle-type laser gets the job done, so I have no current plans to change.

 

[jerkface11]

Boresighters are a waste of time and money. Give me 10 shots and I'll have a rifle zero'd every time.

 

[rcmodel]

What everyone else said.

You wasted your money on a gadget that you could have matched or exceeded the results with by taking the bolt out and looking through the hole in the barrel.

My son bought one last December (against my advice) to sight in his new STAG AR-15.

His new laser chamber insert shows my old Colt SP-1 is off 3" at 10 yards, in the basement.

But, in fact, it isn't off 3" at 100 yards, I would have to say.



Barrel harmonics with different loads.
The way you hold the gun, etc, make it a waste of time for anything other then getting on paper a close range.
Which you could have done just as well by looking through the hole in the barrel.


rc

 

[Haxby]

Boresighters work about 50% of the time. But if you don't boresight at all, you'll only be close about half the time.

 

[PedalBiker]

I have two barrels for my Savage 110. The factory barrel hits so far to the left I had to get Burris Signature rings and 20 shims. The cheap A&B barrel shoots almost dead on with the receiver.

Tolerances stack up.

BTW, the boresighter confirms this behavior to within an inch at 25 yards for both barrels, so I can still check the zero on both barrels with a muzzle mounted laser.

All of my rifles will hit to within 3" at 25 yards with the laser - not good enough for hunting, but good enough to get the scope dialed close - since I don't have a "favorite" load yet I'm constantly sighting the rifles every fall anyhow.

If the laser saves me 2 rounds per rifle per year I'm ahead already.

 

[jerkface11]

Changing loads won't make you have to totally resight the rifle. Just change the zero. So a boresighter won't do you any good in that situation.

 

[stumpers]

The laser ignores aerodynamics, barrel harmonics, irregularities in the muzzle crown etc. whereas the flying bullets do not.

That was a thought I had, but obviously wasn't sure. Just odd how one was on and one was off with nearly identical setups.

 

[Deer_Freak]

Once the gun has been sighted in by firing it. Even if the laser is a little off You see how much it's off. They are handy for checking you scope after the rifle has been dropped or handled rough. After all you don't want to ride up to your hunting area and test fire your weapon as soon as you get out of the truck.

 

[herrwalther]

My laser boresighter has always worked great. Handguns or rifles I use it to get sights, scopes and other lasers on paper. Then fine tune it with live ammo. That is all they were really designed for to get "close enough."

 

[jpwilly]

Everyone is wrong, send me the upper I'll take it off your hands cheap!

 

[jmr40]

Boresighters are a waste of time and money. Give me 10 shots and I'll have a rifle zero'd every time.

I agree, they are a waste of time and money, but I don't need 10 shots. I'll have a bolt rifle dead on at 100 yards on the 3rd shot. With something where I cannot see through the bore it might take me 4.

All those things do is get you on paper for the 1st shot. I can do that faster, easier, and less expensive without one.

They are handy for checking you scope after the rifle has been dropped or handled rough.

All they will do is verify you can hit a 12"X12" box at 50 yards. If you are checking your rifles zero after dropping the rifle you could still be off by more than 6" at 100 yards even though the boresighter says you are perfectly zeroed. I wouldn't trust anything but firing the gun.

 

[jerkface11]

I agree, they are a waste of time and money, but I don't need 10 shots. I'll have a bolt rifle dead on at 100 yards on the 3rd shot.

I don't even bother with looking thru the bore. First shot goes into the dirt berm adjust accordingly. Then you're on paper. 10 is a max number.

 

[stumpers]

Even if the laser is a little off You see how much it's off.

But in my case, that's only true for one of two rifles.

Laser confirms actual zero in one, shows that the other is off, but the other is actually zeroed as well.

 

[gamestalker]

I would never sacrifice good money on a bore sighting device, that could be much better applied to reloading components. I've had customers complain every hunting season about missing game, because their rifles were not properly bore sighted, as if bore sighting is some magical substitution to properly fire sighting in a weapon.

GS