OT: how do rifle scope adjustments work?

I don't know if anyone uses actual crosshairs anymore. Etched lines on a glass reticle are common. The reticle is fixed inside a metal ring. The adjustment screws move the ring and the attached reticle (or crosshairs) up/down and left/right against a spring. Better scopes have an individual spring opposing each screw, while cheaper ones have a single spring at a 45 degree angle so moving the elevation can also move the windage a bit.

And the theory behind that sort of thing (if this is what you're _really_ asking) is that it's already pretty close to being in adjustment before you start -- if it's way out of whack look to how it's mounted.

That is because it is mounted in the focal plane of the scope.

The wiki is worth reading:

Of course, I now have a question, the link points out two different focal planes and places to put the reticle. I was thinking camera but on reflection I suspect you can have many focus points with enough elements.

My air rifle sports iron sights so I have no idea of what increment of adjustment at a said distance is normal.

How far is it off out of the box and what range are you trying to shoot it?

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

uspect you can have

Re: Scope focal plane reticle location

Most US-retailed scopes have the reticle fixed so that when you change power on variable-power scopes, the cross-hairs, dots, numbers, whatever, stay the same apparent size. Europeans prefer that the reticle stays the same REAL size, so that the bits subtend the same area at low power as at high. Makes the reticle appear to grow larger as the power is increased. Some imports have this arrangment, usually have a post reticle or derivative, too. Not popular here for the general deer hunting crowd. One is first focal plane, the other is second, forget which is which.

As far as the O.P.'s question as to if he can break the crosshairs adjusting things, the screws are moving a tube inside where the reticle is, the opposite side is spring-loaded, so the answer is "no". Go too far and the tube ends up hard against top or bottom or left or right side. Some scopes intended for hard-recoiling guns have snubbing screws that can be set up against the tube after sight-in so it doesn't move. Have to loosen them to make adjustments again.

For bore-sighting, laser is the way to go, you're just wasting ammo any other way. You can get a trimmed-down Laserlyte outfit from wally world or order a more complete one from Natchez Shooter's Supply for cheaper still when on sale. You can instantly tell if you've got ring or mounting problems. I would recommend Burris Signature rings, have plastic spherical bearing inserts and offset inserts can be had for mounting deficiencies. Don't mar the tubes, either.

Stan

I'm a fan of move in close, adjust alot, move back adjust less method. Keep in mind the scope position above the bore line.

Now for rifles, such as bolt actions where you can remove the bolt or Marlin lever guns where you can remove the screw for the lever and then remove the bolt, cradling the rifle on bags, looking at a target through the bore and then setting the scope to match is the cheap and easy way to go. I do that at 50 yards during sight in days at my shooting club which is held just before whitetail deer season in Michigan. I like to get the gun on paper leaving some ammo left for the guy that came out to hunt with.

As you can tell, I don't have much use for bore sighting devices. Good mounting and a scope that is delivered optically centered should get you in the game to start. That is my opinion for what it is worth.

This is likely a religious issue as far as shooters go.

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

Rifles don't always shoot where boresight would indicate. I have a .22-250 that groups well under 0.5 MOA that boresights nearly off the paper to the right at 100 yd when POI is dead center on a calm day. This isn't with a boresight gizmo, it's my eyeball looking at the target thru the bore with the bolt removed. I have no idea how this can be, but it certainly is so.

I just last week remounted a previously-zeroed scope on that rifle, took it to the range. Boresight indicated I should dial in maybe 20 clicks of windage but I knew about this anomaly so I aimed and fired hoping it'd be on the paper at 100. It was: within a couple of clicks of bingo in windage and a couple of inches low.

Bore not straight? I sure wouldn't try to do anything about it since she shoots good.

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

Thanks for the insights guys! I can get a 2" cluster with the Gamo at 50 feet, but it's always in the lower left quad of the target. The rifle is not rigid mounted (it's a break barrel pump action so it would be pretty unwieldly), so there's plenty of room for human error. I was concerned because my scope adjustments don't seem to be able to bring me to target center. So I was concerned I'd broken the scope by tweaking it beyond range.... Chet

Might want to check both free float and action screws.

But I agree..if it works..dont fix it.

Gunner

"A conservative who doesn't believe? in God simply doesn't pray; a godless liberal wants no one to pray. A conservative who doesn't like guns doesn't buy one; a liberal gun-hater wants to disarm us all. A gay conservative has sex his own way; a gay liberal requires us all to watch and accept his perversion and have it taught to children. A conservative who is offended by a radio show changes the station; an offended liberal wants it banned, prosecuted and persecuted." Bobby XD9

Springer airguns are very particular about hold. Forestock should rest on your hand just ahead of the trigger housing.

Thanks for that interesting tip! Chet

You are welcome, but that was the very short version. you have to be consistent in the way you hold it, and let it recoil naturally. Don't try to clamp it down. There are quite a few airgun smiths who tune these things for a living. A big part of it is the grease used to dampen the spring. Quite a science, and lots of information online.

Probably irrelevant but hits in the lower left quadrant (for a right handed shooter) are an indication of jerking the trigger - for a pistol shooter.

Cheers,

John B. (johnbslocombatgmaildotcom)

If your group location is consistent, then moving it is just a matter of scope adjustment.

If your scope can't be so adjusted, it may well be broken.

Spring-type air guns have an odd recoil that, while quite mild, can tear the hell out of some scopes that would have no problem on a .30-06 or .308. Scopes used on air rifles must be rated for use on same. I think all Bushnell scopes are air-rifle rated.

IIRC, it's the reversal of thrust that's a scope killer with spring-type airguns. There is recoil both ways, with a sharp, snap reversal in the middle. It bothers scopes more than shooters.

Float is free, action screws are torqued.

I do intend to pillar-bed this rifle with Devcon 10110. Had it disassembled to do that but ran out of time because I don't want to hurry that job and SIL Hassan is gonna want to bring home a "sniper target" to show his mates back in London. I think daughter Karen might also enjoy that with some of her foo-foo artsy pals in NYC. I also have an NRA baseball cap for her, I'll about guar-un-tee that she's gonna love that! Karen's a bit of a rebel and renegade, takes after her mother I suppose.

I'll bed it this fall. Stress-free pillar bedding did significantly improve my inexpensive Savage .243. Though just a consumer-grade "package rifle" sporter, it now shoots smaller groups than the significantly heavier .22-250 Savage BVSS varmint rifle. The .243 does shoot to boresight, don't know how or why the .22-250 doesn't but it's still a shooter at any range where that caliber makes any sense.