I have a really nice 243 Win FN Mauser barreled action in a Bishop Mannlicher stock. I haven't completely dialed it in or done many groups, but I've noticed it is pretty far off a careful bore sighting. So far off I might be off the paper on a small target at 50 yards. I'm usually pretty good at getting very close when mounting a new scope and have had rifles sighted in with very few shots after a careful bore sighting. I mount the rifle in sand bags and look through the bore at an object a half mile away, then line up the cross hairs to the same point. I live on a lake and can use the water level across the lake to check elevation, and power poles on the dam to check windage.

This rifle seems to not shoot to the same pont as a bore sighting and I've wasted some shots by thinking my bore sighting wasn't good to start with and started over. Could this mean a bent barrel? Or something else?

Maybe it doesn't matter if it groups and is just a minor annoyance. Ever had a rifle that did this?

Well, bore sighting is often just a guide to where the bullet will impact and it works better with some kinds of rifle than others. A rifle with a free-floating barrel would be most likely to correspond but it doesn't work with double rifles and less often when there are bolts or bands holding the fore end on to the barrel. Mannlicher fore ends probably fit that situation.

Something else that worries me is the distance you are boresighting at. Try it at, say, 50 yards and expect that once zeroed at the range your scope may be looking an inch or three below the bore when you check the bore sight next.

Once you do get it zeroed at the range, take a bore sight at a convenient mark 20 to 50 measured paces out your back window at home (from a darkened room). Whatever the relationship between bore and reticle is then, remember it, draw a picture of it and put it in your gun case. Then before you go hunting or after any bump, check it again, and if that relationship has remained the same, your zero should still be where you left it.

You can bore sight your rifle using a target marker on a wall inside your house.
At the range, set up a blank sheet of paper at abut 25 yards (you can just turn a target over)
Shoot a shot at the center of the paper. Now then, shot a second shot at the first bullet hole. This will tell you exactly how far your scope/bore is off. Adjust your sights until you are hitting the original bullet hole. Don't forget that at 25 yards, the click values of the scope will only be .25%.

I was at the range at the weekend and shooting next to a guy who was trying to sight in a Bergara single shot 308W with 16.5" barrel mounted with a red dot sight of some sort. He was shooting at a 25m target but having little luck adjusting the sight. I noticed he was then attempting to bore sight using a soft pillow type of rest and with the gun broken open it just wasn't working.

I was shooting my sons 7mm-08 and then my 404J which he had a look at while waiting for barrels to cool and others checking targets.

He asked if I could have a look and see if I could check the bore sighting. Using my bags and only just opening the action for a good solid rest I could see it was well off the bore so adjusted the sight to the bore, fired a shot (bloody muzzle blast even with Grade 5 muffs). Shot 6" low and 2" right. Holding red dot on the bull adjusted the dot down to the bullet hole. Second shot 1" right, adjust dot to bullet hole, third shot dead centre.

After he had expended most of a packet of ammo he was most impressed with my technique.
Moral of the story is that often rifles don't shoot to their bore and there in lies the problem when using reticule shifting scopes where the cross hair can be awfully off centre in the sight picture when the rifle is shooting to the required POI.

quote:

Originally posted by eagle27:
Moral of the story is that often rifles don't shoot to their bore and there in lies the problem when using reticule shifting scopes where the cross hair can be awfully off centre in the sight picture when the rifle is shooting to the required POI.

Touche! But better another shim and an extra trip to the range than a life of delusion.

quote:

A rifle with a free-floating barrel would be most likely to correspond but it doesn't work with double rifles and less often when there are bolts or bands holding the fore end on to the barrel. Mannlicher fore ends probably fit that situation.

I'd say an Mannlicher stocked rifle is likely at the other end of the spectrum from free floated barrels since the muzzle end is enclosed with a steel forend cap.

"Moral of the story is that often rifles don't shoot to their bore and there in lies the problem when using reticule shifting scopes where the cross hair can be awfully off centre in the sight picture when the rifle is shooting to the required POI."

Event though the action was likely drilled at the factory, the mounting holes or the mount could have the scope off center. Could fix it with Burris Signature rings with the off center plastic ring inserts. I have done this on one rifle. Don't care to replace the mounts on this FN Mauser since they are lovely period Redfield mounts that go nicely with the rifle.

Thanks all for your input.

A slightly bent barrel is likely your issue. It is difficult to see such a slight bend looking down the bore. Such barrels can shoot just fine, and, although they might be subject to walking their shots as they warm, this usually isn't a problem with a hunting rifle where it is essentially the first shot from a cold barrel that counts.

It is also possible that, particularly with a full stock rifle, there is an uneven stock pressure point that is skewing the shots away from the bore line. Again, if the rifle groups okay, this isn't a problem once sighted in.

Ditto on bore sighting at 50 yards.

Then walk the shots out to farther targets.

quote:

Originally posted by RaySendero:
Ditto on bore sighting at 50 yards.

Then walk the shots out to farther targets.

I'm done bore sighting this rifle. I'll just start the next session with large close targets and adjust as needed.

I bore sight everything from .17 to .458 at 100 yards.
I look down the barrel and move the crosshairs so they are just UNDER the center of the target. I usually see it about 4" low, because for most of my rifles, I want to hit 3" to 4" high at 100 for MPBR.
Then I shoot at 25 yards once to make sure. It should hit nearly point-of-aim at that distance. Then I move out to 100 yards.
Takes very few shells to get on target.

If you bore sight at 100 and have the crosshairs dead on or over the target, you will shoot way too low and waste ammo.

That 100 yards boresight makes some sense - but I like to do that part before I leave home. The aiming mark depends on what you can see out your window.

I use the insulators on a power pole I've stepped out to be 45 yards away. Our 338WM, .30-06 and .22RFs, once zeroed at the range, show the reticle about three inches below the target, even at that range. My 270 WSM, however, is a much flatter-shooting rifle and points straight at it.

For certain other rifles, we have to use slivers of mirror, which can create some head scratching. To cut the confusion, I just set them up to point straight at the target when setting up - but have forgotten how that played out after going to the range. Must check 'em out.

quote:

Originally posted by Lucky Punk:

quote:

Originally posted by RaySendero:
Ditto on bore sighting at 50 yards.

Then walk the shots out to farther targets.

I'm done bore sighting this rifle. I'll just start the next session with large close targets and adjust as needed.

LP, That will work.

I only bore sight to get on paper.

After that I have a preprinted trajectory for that cartridge and just walk the target out step by step to the farthest distance I plan to shoot it.

PS: Keep shooting fun - Don't make it work!

WITHOUT bore sighting, if you can't just mount the scope and hit a 12" x 18" sheet of paper at 25 yards, you've got one fucked up rig. Most likely, the barrel is bent or canted or the mounting screw holes on the receiver are misaligned.

strips of metal from beer or soda cans make nice shims.

quote:

Originally posted by Lucky Punk:

quote:

Originally posted by RaySendero:
Ditto on bore sighting at 50 yards.

Then walk the shots out to farther targets.

I'm done bore sighting this rifle. I'll just start the next session with large close targets and adjust as needed.

If going this way I would set the scope adjustments to be centred for up and down and side-ways, i.e. wind adjusters fully in then back fully out counting number of turns. From fully in again back out half the number of turns. If your shot is wildly away from the bull on target then you will likely have problems with holding a scope setting as the erector lense is compensating too much for a misaligned scope mounting, bent barrel or bedding problem. If this is the case I would leave the scope adjustments centred and shim a mount to bring the bullet impact closer to the bull then use scope adjustments for fine tuning. If you had a reticule moving scope you would have to do this as otherwise your crosshair or post would be visually way out of centre. In extreme cases with image moving or reticule moving scopes you actually run out of adjustment on the scope even though the adjustments may still turn. This is where you are sometimes driven to slinging a noose over the nearest tree at the range Been there done that but didn't quite get to the noose stage, thankfully

That's a worry, eagle27, but a considerate way to take your quietus in regard to range reputation and cleaning, at least.

Years ago gunsmiths would mount a reticle-movement scope to boresight or, at additional cost, centralised impact for you - and I don't recall seeing any shims in their work. I assumed they must stone or mill metal off the bases or elsewhere instead. A lot of Holland & Holland rifles of the time seem to sport reticle-movement Zeiss/Hensoldt or Nickel Supra scopes; I'd be interested to know if they used shims in those mountings.

Usually if the barrel is bent so much that you can't hit the back board, then you can see it. If you look down the bore of a straight barrel you will see the bore exit as a round circle inside the other round circle of the barrel walls. If both don't look round then your barrel is bent.

I have a rebarreled CZ that shot 60 inches lower than the bore sighting at 100 yards! It is a lot larger caliber than yours. Had a Smith check it out and all is correct. He rebeded it, now it is only shoots 45 inches lower! The receiver is 20 MOA negative! So I put a plus 20 MOA rail on to zero it out. I ended up putting Burris rings with the plastic inserts to keep the scope at zero. I even polished the bore with JB red and that helped a little. I have killed several pigs with it. I could try and explain why I think it does but that would start a fuss!

I have never had good luck with bore sighting; either manual or with lasers. Many times the scope was on paper and I ended up adjusting it further off center. At my range we have freestanding target frames that hold 3'x 3' cardboard squares. When I want to setup a new scope I set the target at 40-50 meters and cover the cardboard with a piece of butcher paper (or use a new piece of cardboard) with a splatter target attached in the center. Using this method there has never been a time the scope wasn't punching holes somewhere on the paper. I then adjust the scope to the bulls eye and move the target to 100 meters; at this point the rifle has always printed on the splatter target.

quote:

Originally posted by onespeedbiker:
I have never had good luck with bore sighting; either manual or with lasers. Many times the scope was on paper and I ended up adjusting it further off center. At my range we have freestanding target frames that hold 3'x 3' cardboard squares. When I want to setup a new scope I set the target at 40-50 meters and cover the cardboard with a piece of butcher paper (or use a new piece of cardboard) with a splatter target attached in the center. Using this method there has never been a time the scope wasn't punching holes somewhere on the paper. I then adjust the scope to the bulls eye and move the target to 100 meters; at this point the rifle has always printed on the spltter target.

Often that is the case with me to where I want to move the bullet impact left but adjust right ie confuse bullet position with turret adjustment. That is why after getting a couple of grouped shots on target, not just a single cold barrel shot, I then hold on the target bullseye or other aiming point and adjust the cross hair/post to the bullet hole. That way you can come from 2 foot out to the bull in one shot or so close only a small adjustment is needed.
Otherwise you can end up chasing all over the target and frustrated.

In regard to moving bullet impact: R --> should mean turn the knob that way to move bullet impact to the right; H --> should take the shot higher.

This may seem too obvious to mention but I can recall when young wondering if it referred to the direction the reticle would move - which may be the opposite, physically.

In terms of bore sighting, if your barrel is centred on the target but the reticle is to the right of the 'bull', that should be equivalent to having the reticle on target but the shots hitting to the left - so, turn the knob in the R--> direction.

quote:

Originally posted by sambarman338:
That 100 yards boresight makes some sense - but I like to do that part before I leave home. The aiming mark depends on what you can see out your window.

I use the insulators on a power pole I've stepped out to be 45 yards away. Our 338WM, .30-06 and .22RFs, once zeroed at the range, show the reticle about three inches below the target, even at that range. My 270 WSM, however, is a much flatter-shooting rifle and points straight at it.


In regard to moving bullet impact: R --> should mean turn the knob that way to move bullet impact to the right; H --> should take the shot higher.

This may seem too obvious to mention but I can recall when young wondering if it referred to the direction the reticle would move - which may be the opposite, physically.

In terms of bore sighting, if your barrel is centred on the target but the reticle is to the right of the 'bull', that should be equivalent to having the reticle on target but the shots hitting to the left - so, turn the knob in the R--> direction.

Yes, when boresighting the reticle movements are counter-intuitive.
If 45 yards is all you have, it's all you have. I sight in off my back porch, so....
The reason I pick 100 yards is because I know how far I want my crosshairs to be below the bull at that distance. The larger the bull, the easier it is to center it in the bore and be more precise. I can usually be ready to start shooting groups for fine-tuning after 2 or 3 shots.
The toughest are the varmint rifles with the high comb. Hard to see down the bore well enough to center it.

quote:

Originally posted by onespeedbiker:
I have never had good luck with bore sighting; either manual or with lasers. Many times the scope was on paper and I ended up adjusting it further off center.

I can understand your reluctance with those bad experiences.
But, My experience, thank God, has been better.

Depending on scope ring height, I bore sight my bolt action rifles to get on paper at 25 yds with the POI at about 1/2" low. This normally allows me to easily walk a target out to 50, 100 and onto 200 yards. Past that distance, I switch to an 11x17" target and use a trajectory curve to guide me.

quote:

Originally posted by eagle27:

quote:

Originally posted by onespeedbiker:
I have never had good luck with bore sighting; either manual or with lasers. Many times the scope was on paper and I ended up adjusting it further off center. At my range we have freestanding target frames that hold 3'x 3' cardboard squares. When I want to setup a new scope I set the target at 40-50 meters and cover the cardboard with a piece of butcher paper (or use a new piece of cardboard) with a splatter target attached in the center. Using this method there has never been a time the scope wasn't punching holes somewhere on the paper. I then adjust the scope to the bulls eye and move the target to 100 meters; at this point the rifle has always printed on the spltter target.

Often that is the case with me to where I want to move the bullet impact left but adjust right ie confuse bullet position with turret adjustment. That is why after getting a couple of grouped shots on target, not just a single cold barrel shot, I then hold on the target bullseye or other aiming point and adjust the cross hair/post to the bullet hole. That way you can come from 2 foot out to the bull in one shot or so close only a small adjustment is needed.
Otherwise you can end up chasing all over the target and frustrated.

What I meant to say was after bore sighting, it appears if I had done nothing (not sighting the scope to the bore sighter laser dot) the scope as already adjusted to center target. But the bore sighting lead me to adjust the scope 2 feet to the right and a foot high, which pretty much matched the scope adjustment with the bore sighter. Today I went to a range to sight in another scope. An inside the chamber laser, showed the laser dot a foot left and low. But rather than adjusting the scope to the bore sighter, I left the scope alone and my first round at 50 meters was horizontally centered on the target and 2 inches high. So much for bore sighting.

Of course it doesn't, its not supposed to, all bore sighting does is get you on the paper somewhere, sometimes its close, sometimes dead on, but that's rare indeed... Mostly its as much 3 inches to as much as a foot off. that's what the adjustments are for. It saves ammo is its only redeeming quality..