Edited to add good points from comments! Thanks RHT/jrg
I got a question in email about this, so here ya go… From 2010…
Tips, tricks and lessons learned…
Sighting in rifles is always interesting, even more with scopes. Here’s what I’ve learned over (mumble) years of screwups, multiple tries, and lots of help from people that actually KNOW what they are doing…
1st assumption- You have already bore sighted, laser sighted, used a collimator to get the sights/scope pretty close to on…
2nd assumption- You have reviewed your ballistics tables for the round you are going to zero/hunt with (and it’s the same round). You’ve recorded the altitude, weather (temp, humidity, etc.). This becomes the base for the ‘dope’ for that rifle/scope/round combo. If you know you are zeroing at/near sea level, and know you will be hunting at 4-6000 feet of altitude, you will know what corrections you will need when you get on site to re-zero the rifle.
Target- Use a target that has the 1 inch blocks printed on the target, makes it MUCH easier to determine how far off one is…
Spotting scope- Nice to have, or you’re gonna be doing a LOT of walking back and forth…
Rifle Rest- If you are using something like a Caldwell’s Lead Sled (which are NICE, but pricey), don’t exceed 25 lbs of weight on the sled. You DO want the rifle to be able to recoil at least a little bit. If you put too much weight on it, you risk damaging the stock due to the action and recoil lug slamming back into the stock with NO movement (remember, most rifles are NOT fully bedded so only screws and the recoil lug are the only thing holding them in the stock). You want the front arm to hold the rifle as near the barrel end of the scope as possible, and seated as well as possible in the pad; for the butt, place it firmly into the pad and rest your shooting hand on the rifle, use the other hand to manipulate the front arm to get the proper height and aimpoint for the rifle.
Note: Recoil will move the rifle to the rear. It is now in a DIFFERENT position. Put a piece of masking tape with a witness mark on the forend. Have a corresponding witness mark on the front rest. After each shot, lift the rifle just enough to break contact and move it forward to line up the witness marks.
If you use a bipod for the front, you are stuck with its position on the forward end of the stock. if you use a tripod /rifle rest/sandbag for the front, position it at the barrel end of the scope, or just forward of the receiver group at the thickest part of the stock (this should also be just forward of the balance point of the rifle). For the butt, use your choice of bags, but here is where it gets interesting…
Use the bags to get the proper aim point WITHOUT having to squeeze the bags. What you want to get in either case is a STABLE, REPEATABLE position for the rifle. Trust me, you can’t do that if you’re sitting there trying to squeeze a bag up, or pressing down to try to ‘flatten’ one out to get your aim point.
Clean barrel or fouling shots-
You can clean your barrel with acetone to remove the light oil you (hopefully) put in the rifle the last time you cleaned it. One patch with acetone should remove the oil and allow a ‘clean’ shot on the first shot. If you choose fouling shots, run a clean patch through the bore before you start, then 2-3 fouling shots (don’t look at this as a group, because they may be flyers).
Wait 20 minutes… Why? Give the rifle time to cool down. You want to shoot what are effectively cold bore shots out of any rifle that doesn’t have a heavy barrel (heavy barreled rifles have a different procedure).
If you’re bored, go google rifle barrel harmonics- Harmonics and barrel flex are real, and play a significant part in rifle accuracy (more on that later). Also, heat weakens the barrel and allows more flex/harmonics (e.g. wider pattern of flyers). It may be that your rifle doesn’t ‘like’ a particular load, so it is always advisable to have at least a couple of different weight bullets available to check grouping (for example, my rifle does not like 168gr bullets, but does like 173-175 gr bullets (to the tune of about ½ inch tighter groups; while a friend with the identical rifle is just the opposite).
Get into a comfortable, stable shooting position, minimizing tension on the body (preferably similar to the shooting position you will use in the field). Confirm your sight picture is correct or adjust as required (no squeezing the bag)…
Do NOT put your off hand on the weapon anywhere, put it flat on the shooting bench or curled under your shooting hand. WITH THE CHAMBER EMPTY, assume the position, get a good cheek weld, put your shooting hand on the weapon such that your palm is touching the stock in the proper position to place your finger on the trigger, DO NOT wrap your thumb over the top of the stock. Re-confirm your sight picture is correct or adjust as required (no squeezing the bag), (some people use mnemonics to confirm position, breathing, trigger pull), continue pulling the trigger until you get a surprise break on the dry fire (the sight picture should NOT change). Look at the sight picture again, if it is off to either side, you are not getting a straight pull back on the trigger and your rounds are NOT going to go where you think you’re aiming.
Lather, rinse, repeat until you get the correct finger position that does not move the rifle/change the sight picture during the trigger squeeze. Once you have done that, fire three rounds using exactly the same sight picture, hold, mnemonic, and trigger pull.
Note- you don’t need to do this fast, as you want the barrel to stay at/near ambient.
If you shoot a called flyer, shoot one more to get a good three shot group.
Once you have that group, look at the error (hopefully a fairly small one). Let’s say you are 2 in high and 1 in left. Make the BIGGER correction first, tapping the turret after you make the change, and shoot three more rounds (using the techniques above). Confirm that correcting ‘worked’, then make the smaller correction, tapping the turret after each chage and repeat. At this point you ‘should’ be on target. If your scope is a ¼ min/click you can further refine if you desire, if it’s 1/2 or 1min/click, you’re done, same if it’s iron sights.
Note: Some scopes will not ‘seat’ the reticle properly until shot, unless you tap the turrets.
I know people claim they can zero a rifle in 2 shots, but honestly I’ve never been able to do that… Guess I’m just a dummy…
If you need to zero for 200x and only have a 100x range, look at your ballistics curve for the ammo you are shooting, look at your 200x zero and it will give you the ‘over’ at 100x (usually around an inch with most ammo).
Very carefully loosen the caps on your scope and readjust to the new zero position and re-tighten as necessary. If you have a BDC cap, I’d recommend another three shot group with a different range to check zero (e.g. select 300x BDC and the rounds should be appx 2-3 inches high depending on ballistics table).
If you have standard caps, I’d recommend zero of 200x for hunting as anything between 100x and 300x will hit within about +/-3 inches of aim point across those ranges with most ammunition.
The next thing is to shoot the gun in the position I will be using it in the field. I’ll usually take three shots to confirm my zero.
NOTE: If your zero is significantly off, you may need to rezero using your shooting position instead of a bench position! I have seen this happen once, with a gent that put the front rest all the way out at the end of the forestock on a Winchester.
At this point, I’m done; I don’t clean the rifle again until hunting is complete for the year. I also will always do at least one cold bore shot at 100x before I go into the field to hunt, just to make sure nothing got knocked loose in transit!
Disclaimer- There are tons of how to sight rifle links on the net, and plenty of forums and blogs that detail this also. These happen to be mine, based on MY experiences. YMMV, INAL, etc… 🙂
Shoot em good folks!