Settle a argument about bore sighting

[spiker44]

Friend has a 7600 Gamemaster and put a set of see thru scope mounts on it. So since he couldn't bore sight down barrel he went and bought a bore sighting rig. The kind that has a spud and device that sit on the spud on the end of the barrel. You see a graph in the scope and center the cross hairs on the center of the graph. Ok. here is where it gets good. He bought this BSA bore sight kit for big bucks. Does what the instructions tell him to plus he read where he can set it higher for long distance shooting. I tell him to start at battle sight zero and work his way back making adjustments. He says no way man. I got it all zeroed in already. So off we go to the range. Start a the 100 yard marker and boom. Nothing on paper. half a box later, no holes anywhere but in the wind. So we move closer and closer until we are close enough to hit the target with the muzzle and it hits high. He tells me he is going to get a replacement for the bore sighter as he thinks it is broke. I try and tell him with the see thru mounts the plain of the scope is much higher than what the bore sighter was designed for. He tells me the POI still wont change no matter the difference between regular rings and see thru. I don't see it. It has to make a difference but maybe I am wrong. I only wish he just shot closer and worked his way back because it still is not sighted in because he ran out of rounds :banghead: Can this type of bore sighter be used for see thru rings and if so how?

 

[rcmodel]

No, you are right.

Spud bore sighters can only get you so close to true zero.

See-Through mounts complicate it even further because the scope line of sight is so far above the bore.

Just a WAG, but I think you would have to set it well above the X in the bore sighter to even get close to paper at 100 yards.
Or the bore sighter would have to have adjustments for scope height.

In all, I think they are a complete waste of money.

I can use a simple 12" ruler, and fire one round at a 25 yard target and be on paper.

Then use the ruler to measure the distance the bullet hole is fron the aiming point.

Then do the simple match tot convert the scope click from 25 to 100, and a just it.

And bet I will be very close to zero on the second shot.

rc

 

[Hookeye]

Friends don't let friends shoot see through rings.

 

[JDGray]

With irons, you don't need a bore sighter. Bench the rifle , get on paper, adjust the optic to the hole you made...

 

[jmorris]

I am with JD, if you already have a sight that is zeroed and can use them at the same time, that is the wayI would do it.

In fact I even built this rig to be able to swap from one optic to another and have both zeroed on the same spot.

Clamp it to the barrel and adjust it so the projected dot lines up with the crosshairs, then swap optics and adjust the new optic to the projected dot.



Much more accurate than any bore sight device I have ever used.

 

[Bart B.]

Bore Sighters 101

First off, bore sighters come in two types; the laser ones and the optical ones. They work differently.

Laser bore sighters project a beam of light on the bore axis down range and put a spot of light on the target. That beam is an extension of the bore axis. It points to the same place as what's seen looking through the bore from the back and centering the target image in the bore center.

Optical collimators project thousands of parallel beams of light backwards towards the back of the rifle. Collimate means making light rays travel parallel to each other. If the lens is 1 inch in diameter, all those beams of light inside a 1 inch diameter circle are parallel to the bore axis. Once the sight is zeroed on the optical collimator reference, the line of sight is above the line of fire (bore axis) that same amount from the muzzle to infinity. Iron/metallic sights have to be high enough above the bore axis to see the lowest beams of light emitting from the optical bore sighter. With see-through rings, the bottom of the scope's objective lens should still be low enough to catch the light rays coming out of the top of the bore sighter; a 1/4 inch overlap's enough. As long as the scope's objective lens overlaps that tube of target light the same diameter as the collimator's lens, the collimator reference will be seen through the scope regardless of scope height above the bore axis.

With an optical collimator and after the scope's zeroed on it, you adjust the scope elevation up some MOA value to compensate for bullet drop and scope height above the bore axis. That moves the scope reticule down below the collimator reference. The bore axis has to point above the line of sight, doesn't it?

Laser bore sighters put a spot on something down range on the bore axis. You have to align the scope reticule some place below it to compensate for bullet drop. Scope height is automatically compensated for as the line of sight is angled down to cross the point of aim where the laser spot is. If your scope's 1.5 inch above the bore axis and the laser spot's 25 yards away, the line of sight is 6 MOA angled down from parallel to the bore axis when its on that spot.

Most people don't believe how far off their line of sight is relative to the alignment point (laser spot or alignment x/grid) after they've refined a zero for 100 yards. If the scope's 1.5 inch above bore axis and bullet drop is 2 inches, the scope does not point exactly 3.5 MOA below bore sight. It could be anywhere depending on how the rifle's held and its bore axis moves while the bullet's going through the barrel.

 

[Bart B.]

What I think happened due to:

He bought this BSA bore sight kit for big bucks. Does what the instructions tell him to plus he read where he can set it higher for long distance shooting. I tell him to start at battle sight zero and work his way back making adjustments. He says no way man. I got it all zeroed in already. So off we go to the range. Start a the 100 yard marker and boom. Nothing on paper. half a box later, no holes anywhere but in the wind. So we move closer and closer until we are close enough to hit the target with the muzzle and it hits high.

After zeroing his scope on the collimator reference, he moved the scope elevation up some MOA value to compensate for some long range zero. The scope's reticule will move down relative to the collimator reference because the line of sight has to be angled down from the bore axis. That moved the line of sight angle down that many MOA's. When he put the line of sight about level and shot at the 100 yard target, the bullets naturally go high. He just set the scope elevation too high to hit the target paper 100 yards down range.

If you move the scope reticule to somewhere above the collimator reference, the line of sight will be some angle above the bore axis. The LOS axis always has to be at a lower angle below the line of fire (bore axis) to compensate for bullet drop.

He should have moved the scope's elevation up from collimator zero an amount to get close to zero at 100 yards. If the scope's 1.5 inches above the bore axis and bullet drop at 100 yards is 2 inches, he needed to move the scope elevation up 3.5 MOA then shoot the darned thing at that 100 yard target. Most folks will end up making a 1 to 2 MOA change due to how they hold the rifle, but the first shot should be on letter size paper. If not, there' something bad about how the rifle's put together. Then do more come ups on the scope for longer ranges as desired.

If see-through rings position a scope so the line of sight's only 1 inch higher, a 100 yard zero on the scope needs a 1 MOA come up in elevation. A 1000 yard zero only needs a 1/10th MOA come up. Bullet impact only changed 1 inch down at both ranges.

Exactly what is "battle sight zero" for a Rem. 7600 pump action rifle?

 

[Zeke/PA]

See-Thru Rings ??
A joke of the past !!

 

[jmr40]

With the money your friend wasted on see through mounts and a useless bore sight tool he could have bought a much better scope. Even without being able to see through the barrel I could have had it zeroed at 100 yards in 4-5 shots. With a bolt gun, 3 shots.

 

[CraigC]

You were right, he was wrong. And he has those silly see-thru mounts to boot. He needs to stop arguing with you, ditch the boresighter, get some proper scope mounts and maybe let you get him on paper. If I couldn't get on paper without a boresighter, I wouldn't call myself a shooter.

 

[Bobson]

With the money your friend wasted on see through mounts and a useless bore sight tool he could have bought a much better scope. Even without being able to see through the barrel I could have had it zeroed at 100 yards in 4-5 shots. With a bolt gun, 3 shots.

Yep.

Not sure why people think they need a boresighter.

 

[kwg020]

I have the laser type. It gets me on paper with windage pretty easily (left and right) but I have to measure from the center of the barrel to the center of the scope. I set mine so the point of light on the sight-in target 20 feet away (how long my basement room is) is the same distance to the center of the scope. If it's 2.5 inches from the scope center to the barrel center, I set the point of light 2.5 inches lower, at 25 yards my POI is 2.5 inches lower than the point of aim. Raise POI by 3/4 of an inch and move to the 50.

At 50 yards you want your POI be roughly 1.25 inches lower than the bulls eye center. At 100 yards you will be pretty close to center bulls eye. Adjust windage as needed to stay in the center. I have never used the collimator type of scope sight in tool.

kwg

 

[Zeke/PA]

I've owned a spud type bore sighter for years and truly it has done a great job of getting me "on paper".When I sight in, I shoot at a target pasted onto a large cardboard sheet and go from there.
I know some guys however, who take the bore sight as gospel.

 

[Bart B.]

Bobson, people think they need a bore sighter because it helps them install then zero sights inside their shop and get the lines of sight and fire close enough to get on letter size paper at short range; with one shot.

And they've got the aptitude, skills and knowledge to do it right the first time. Everyone else may not have the wherewithall to do that.

Some years ago, a USA International Rifle Team Captain used one to get his team's rifles (issued by the match sponser as required by the rules, no sight dope on them at all) roughly zeroed for a long range match, All team members got on target with their first shots and went on to win the match.

It's inversely related to the idea that some people think neck only sizing on bottleneck cases produces best accuracy.

 

[wild willy]

Were the open sights sighted in if they were there was no need for any kind of bore sighter.Put the gun on the bags or a cardboard box with slits cut in it line the open sights on something move the cross hairs to the same place.

 

[lobo9er]

just to pile on... you are right. and I have never felt any need to use a bore sighter. A fellow at a range once let me try his I did to be polite. It was no help. How hard is to shoot close and adjust? I'm not any rifleman or math whiz and it always works. Mid way through a box I am fine tuning usually.

 

[spiker44]

great

Great posts guys. I knew some but have also learned a lot more. I love this group. And since I am not one to rub his nose in it , I am going to print out all responses for him to read. Thanks guys..

 

[spiker44]

awesome Bart B!! Makes a lot of sense on how it works. Thanks for the knowledge. I will show your post to my friend and I am sure that is what he had done with his first settings...

 

[spiker44]

great looking rig jmorris

 

[Nom de Forum]

Yep.

Not sure why people think they need a boresighter.

This.

 

[jmr40]

Not sure why people think they need a boresighter.

I saved these targets a few years ago to prove just this point. I had purchased a new scope that needed to be zeroed and ended up playing musical chairs using that scope on a different rifle. Ended up having to zero 3 rifles that day. This is the 1st shot at 50 yards from each of them.

I never touched the scope adjustments and went straight to 100 yards for the 2nd shot since I knew it'd be on paper. After firing one shot at 100 yards I calculated how many clicks the scope needed to be moved and did so. Shot #3 was just where I wanted it.

No bore sight tool would have done as good.

 

[Trent]

I've never failed to get a bore sight within a few inches of true zero at 100 yards when I can see down the bore.

In my basement at 10 meters I affix two orange sticky targets to the wall. Use a bubble level to get them aligned vertically and space them from center of bore to center of scope line of sight.

Sandbag & books to get the rifle aligned. Bubble level to get the scope crosshairs aligned precisely with the line of bore.

Then it's a matter of aligning the bore (by sight) putting the center of the lower target in the center of the bore, and adjusting the scope to be dead on the upper target.

Then I fire up the Sierra Infinity software and figure out how many clicks to come up to get on target at 100, and done.

More often than not, I'm in the X. I'd trust my boresight enough to go hunting with.

It isn't difficult to do properly without any fancy gadgets or gizmos if you take your time and think it through.

As for the laser boresighter I bought? Frigging useless junk, I use it as a toy for the pets to chase.

 

[Bart B.]

I've used my Site-a-Line

http://www.alleysupplyco.com/default.asp?pc=sl

since 1971. Borrowed one a year earlier to get a rough zero at 200 yards on a Garand that had been rebarreled the day before. First sighter in that big match was the first one through that barrel; struck about 6 inches right and high from where I called it on the 200 yard target shooting offhand. Moved the rear sight to put the next/last sighter on call. Fired it; went an inch low. Rotated the NM sight aperture notch up then fired the first record shot. ''Twas called and went in the 10 ring at 3.

Fifty-nine rounds later, I fired the last shot. Won the match and the Remington shotgun it was for. That's when I decided to get one those Sweany things.

Have used it on several sporter and match rifles over the years and first shot from all at 50 or 100 yards no more than 3 or 4 MOA off call.

The optical collimators best use is checking scopes for adjustment repeatability. Fit one in the muzzle then zero the scope on it. Move an adjustment 1 click off and watch its reticle move. Move it back one click and it better go back exactly. Box the reticle 2 clicks on each side; then again with 4 clicks. 100 times more precise than shooting bullets whose groups are more sized by human error than anything else.

Collimators are also good to see how much the barrel bends if it's got a bedding pad between it and the stock fore end. Lots of people hand been surprised how much their barrels bend the bore axis when the rifle is benched on rests and the shooter bears down on them getting into position.

 

[69Precision]

With irons, you don't need a bore sighter. Bench the rifle , get on paper, adjust the optic to the hole you made...

You don't need one with a scope either. Starting close, getting on paper, adjusting works as well for scopes as irons.

 

[JDGray]

The bore axis has to point above the line of sight, doesn't it?

C'mon, everybody knows that bullets defy gravity, and rise above the bore axis!