Wednesday, June 17, 2009

Rifle Sight-In Made Easy

A gentleman sent me an email asking if there was an easy way to sight in a rifle. He said he had gone through several boxes of ammo to sight in his rifle. I have heard this many times and always wonder what is wrong to take so many shots. Remember the scope must be mounted correctly and all must be tight in order to sight in properly. I won’t go into that here. If you do not know how to mount a scope correctly have someone that does help you the first couple of times or have a professional gunsmith do it for you. Do not let some kid in a box store mount your scope. I have had to remount lots of scopes for clients through the years. Bore sighting a firearm is not having a firearm that is sighted in properly. Bore sighting will usually get the shots on the paper but not always. I have seen lots of people miss with a gun that has been bore sighted. Every barrel and different ammo will impact differently and must be shot in properly on a target.

Remember that if your rifle barrel has been cleaned since firing or it is a brand new rifle to fire a couple of fouling shots before sighting in. Many rifles will not shoot to the same point of impact with a clean oiled barrel as they will with a fouled barrel.

Here is the fastest and simplest way I know to sight in a rifle. I usually start at 25 yards so I will be on the paper. Even a bore sighted rifle may not be on the paper at long range. I get a solid gun vice or some way to hold the rifle in place where it will not move. A cardboard box with two v cutouts to rest the rifle can be used in a pinch. I fire one shot at the bullseye and then make sure the cross hair is lined up on the center of the bullseye. Making sure not to move the rifle adjust the elevation and windage until the crosshair is exactly centered on the bullet hole where the shot you just fired hit. This means move the center of the reticle to the actual center of the bullet hole of your shot. Next carefully fire a second shot at the bullseye. If you did not move the rifle while adjusting the scope and you can shoot, the second shot should be in the bullseye. In reality most will need a few more shots for small adjustments to get into the center of the bull, but this is a lot faster that most other methods and uses less ammo.

Now move to the one-hundred yard target and finish sighting in with whatever small adjustments are needed to get you where you want to be on the target.
Good shooting, Wild Ed

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tom said...

I've seen a WHOLE LOT of rifles where the mounts aren't true. Those are the ones where people have cranked insane amounts of windage and/or elevation to get sighted in. Good to check that too and get adjustable mounts if need be. Sometimes barrels are drilled or dovetailed wrong even when they look correct because the bore isn't concentric with the outside contour of the barrel. Receiver mounts can easily be installed wrong too, as above. It's not always exactly the fault of the person "installing a scope wrong" as the fault of who set up what they were installing it into. Could be a mix of both.

If it's not a new scope, it's not a bad idea to count clicks for both adjustments and re-set both in the center of the ranges of adjustment.

Simple poor man's boresight with bolt, break action, and falling blocks and their relatives is to mount the gun in a firm rest and look down the bore at the target and then look through the scope at the target. It'll get you close-ish.

The various bore-sighters and collimators that use a barrel spud depend somewhat for their accuracy that the barrel crown isn't too banged up causing them to misalign from the bore. If the crown is significantly damaged, you aren't going to be able to get it to shoot well anyway and you need to get that fixed anyway before you worry about a scope. Farmer I knew got a scope and said "it shot well with iron sights but it doesn't shoot well with the scope". To his 50 year old eyes, he was getting acceptable performance with iron sights for his taste but it wasn't a tack driver when he mounted a scope because the crown and a portion of the bore near the muzzle were damaged. Something else to keep in mind.

One other thing. If you're one of those removable muzzle brake people: Brakes move the rifle to some degree before the bullet has passed the ports. This is because the bullet is shoving atmosphere ahead of it in the barrel that bleeds out the ports even before the bullet passes and the propellant gas starts exhausting through the brake's ports. Therefore such a rifle won't shoot to quite the same point of aim with and without the brake.

Scopes mounted on the barrel change the resonance of the barrel and may cause what worked in barrel bedding or contour for free floated barrels without the scope or a different mass scope to become less than ideal with the new one.

It's all the tiny details that matter if you want a tack driver.

Wild Ed said...

Pay attention Tom is giving you some good information in his comments.

tom said...

Don't Blame me.

Blame a lot of good influences, and my family that let me start shooting at a young age and decided if I was to bother I should learn to be good at it (same as piano and guitar lessons)...and excessive free time to study and try out things and a machine shop helps.

I just try to keep my ears open and not let my personal bigotries prevent me from hearing what somebody is saying. Especially when it's elders in the trade.

On the adjustable sight mounts, they can seriously salvage a rifle where holes or dovetails were cut just a bit off, but enough to make a difference. One other thing. If you intend to shoot particularly long range most times (+500 or so, cartridge dependent), you may wish to set your scope mounts so that they are pointing a bit "downhill" on your rifle barrel to compensate for muzzle elevation so you don't have to crank the heck out of elevation to get them on target as to parallax. Most Long Range rifle manufacturers offer this option in the mounts for your rifle, but if you like to shoot 600 yards or some such, it might also be relevant to your scope mountings. Same thing, as far as physics, as the sliding scale flip up rear sights on old military rifles with range markings, except you kinda have to pick how far you usually intend to be shooting.

Random thoughts from a hyperactive mind on scoping things.

Glad to be of help,