Most efficient process to diagnose and fix problems with loss of zero or change in precision?

[Macintosh]

This topic of troubleshooting a loss of zero or a gun that seems to suddenly be less precise than normal comes up so frequently that I'm surprised I haven't seen a dedicated thread on the topic. I am interested in what people's specific process and order of operations is for diagnosing a problem with a rifle holding zero or a change in accuracy or precision. By this I mean, in a situation where a gun that was zeroed suddenly and inexplicably starts putting shots off the zero (shots were dead-on, now it's low and left), or precision changed noticeably (groups were 1.25", now it's 3"), what exactly do you do, and in what order do you do it, to determine exactly what part of the gun system is the problem (stock/action/rail/rings/scope/shooter), and go about fixing that? ie it doesnt do you any good to replace the scope if the stock-to-action interface is the problem, and vice versa--so what is the MOST FOOLPROOF AND EFFICIENT way to make that determination of which part of the system needs attention?

• What do you do ahead of time to anticipate a problem that facilitates a quick diagnosis? (before you have a problem--clean/degrease and torque, witness marks, loctite or paint, etc on initial setup). Perhaps the "scope mounting to maintain zero" process, but what else? Record keeping? other?
• Zero process so you know the true cone for the gun and can determine if something is truly a shift versus when you are just seeing a group that includes a shot or two from the fringe of the cone of fire.
• When you notice a problem what is your first step--try to repeat the sequence of shots, tear something apart, etc? Second step, etc.
• What is the most efficient process (from a time, equipment, effort and ammunition requirement perspective) to isolate the issue to one part of the system?
• anything else?

I'm guessing @Formidilosus has a relatively concrete process so hoping he can chime in at some point, and interested to hear how others approach this as well.

 

[JohnJohnson]

I'm in the middle of changing some stuff regarding this, including building on a LP Fuzion that has an integral scope base so I have fewer screws to worry about. I also switched to a Foundation stock for that build since it's basically like having a bedded stock. I am considering having my rifles in my KRG chassis bedded as well, due to what people have been finding about unbedded chassis when it comes to impacts to the barrel shifting zero.

Up to this point the first things in my process have been:

1. Check tightness of suppressor
2. Tighten every screw I can get to without removing the scope from the rifle entirely

• Action screws
• Scope ring screws
• ARCA rail screws / forend screws

3. Take scope off and check scope base screws if there's still an issue (those are blue loctited though)

Once my new rifle is put together I'm going to test my stock/barreled action for impact shifts the same way Morgan Lamprecht and those guys have been testing theirs. Cover the end of the barrel with some kind of cloth and then hit it solidly with a rubber mallet. A lot of competition guys are bedding their chassis now because it helps a lot with zero retention after impacts to the barrel.

 

[TaperPin]

The process is very context dependent for me. The human part is the most likely source of problems, then the optic is the next weakest link, then the ammo, then the rifle.

If a shooter is new and has only fired a centerfire rifle 500 times, is much different from someone who has a long history of shooting accurate guns - these guys have worked out many of the bugs in their shooting techniques. The newbie might have issues with every part of their technique and understanding of the gun. New shooters don’t know what they don’t know.

The background of the rifle is also important - it isn’t reliable or accurate until it’s proven over time. A pawnshop purchase is treated differently than someone’s pet varmint rig that has been reliable for years and 1000’s of rounds. One 30 round group isn’t a reliable source of information, other than that day that shooter made the one group - everything might have been schitt - 30 rounds of schitt is still schitt.

One of the best ways to have a consistently accurate rifle is to have two accurate rifles. There are so many benefits to having a second accurate rifle, the added cost is quickly recouped in headaches avoided. If both rifles shoot bad it’s an environmental or shooter issue. If an accuracy problem changes rifles with a simple scope swap, then it might have just saved hundreds of rounds to figure out.

Isn’t it interesting how one of the first questions we ask someone with accuracy issues is how they clean the rifle? If we were in person rather than an Internet forum, the first thing I’d do is bore scope the barrel. Hard carbon deposits are well known to cause problems, yet many insist on not cleaning, or not knowing how to clean, or not being able to tell if they actually cleaned out the carbon. It’s also easy to tell who cleans blued guns based on the bore damage - pitting from normal amounts of moisture in all but the absolute driest climates will ruin a bore eventually. You don’t have to believe me - look at any 30 year old hunting gun that hasn’t been cleaned - it’s littered with pits.

When someone doesn’t clean a barrel, I tend to think what else do they not clean. Is the bolt full of crap, maybe rust, that is causing inconsistent ignition. Is the trigger gunked up? Is there dirt and crap between the receiver and stock? Lazy cleaners are usually hard on their rifles in other ways - odds of muzzle or crown damage go up.

I’ve been part of a troubleshooting fiasco that went on for way way too long, until we figured out he had no idea how to shoot from a bench, and if I remember right the bench was rickety. Most portable shooting benches, or wire reels turned on their side are so bad as to be worse than just shooting over a pack. It’s hard to take poor accuracy seriously if they aren’t capable of at least good bench technique.

Trying to judge a person’s mechanical aptitude via how they post, is difficult at best - hell, even in person some guys talk a good game, and are barely able to poorly use a screwdriver. I’m often reminding myself of the guy who sounded sharp - torques all his screws, seemed very meticulous, but turned out to have horrible judgement and was barely putting any torque at all on action screws - the receiver was just flopping around in the plastic stock.

Whenever, I think no new craziness has been invented in a while, a shooter will surprise the world by winning the Ultimate More Stupider Award with something that is so off base that I would have never expected it.

I know a guy who bought a $4k gun and shoots fist size groups at 700 yards, but is still very green and makes simple mistakes - new shooters don’t know what they don’t know. It’s fun talking with him, because the rifle is dialed in, and most of the minor accuracy issues can be quickly identified as shooter issues. Normally, the poor accuracy of an average gun on an average day creates a lot of fog that has to be dealt with.

I don’t think there’s any way to avoid assuming everything, every body and every technique is broken, and go from there. Lol

 

[cjdewese]

If a shooter is new and has only fired a centerfire rifle 500 times, is much different from someone who has a long history of shooting accurate guns - these guys have worked out many of the bugs in their shooting techniques. The newbie might have issues with every part of their technique and understanding of the gun. New shooters don’t know what they don’t know.

I feel like this sums me up pretty good. I have no mentors to teach me the proper shooting technique so I know some of my issues are definitely ME. I want to take a class but right now time and funds are limited or tied up with other ventures. I am putting in quite a bit of practice, but still feel like I have a long way to go.

Do you know if any good online/free resources to help teach proper shooting technique to help minimize that issue?

 

[Macintosh]

The process is very context dependent for me. The human part is the most likely source of problems, then the optic is the next weakest link, then the ammo, then the rifle.

If a shooter is new and has only fired a centerfire rifle 500 times, is much different from someone who has a long history of shooting accurate guns - these guys have worked out many of the bugs in their shooting techniques. The newbie might have issues with every part of their technique and understanding of the gun. New shooters don’t know what they don’t know.

The background of the rifle is also important - it isn’t reliable or accurate until it’s proven over time. A pawnshop purchase is treated differently than someone’s pet varmint rig that has been reliable for years and 1000’s of rounds. One 30 round group isn’t a reliable source of information, other than that day that shooter made the one group - everything might have been schitt - 30 rounds of schitt is still schitt.

One of the best ways to have a consistently accurate rifle is to have two accurate rifles. There are so many benefits to having a second accurate rifle, the added cost is quickly recouped in headaches avoided. If both rifles shoot bad it’s an environmental or shooter issue. If an accuracy problem changes rifles with a simple scope swap, then it might have just saved hundreds of rounds to figure out.

Isn’t it interesting how one of the first questions we ask someone with accuracy issues is how they clean the rifle? If we were in person rather than an Internet forum, the first thing I’d do is bore scope the barrel. Hard carbon deposits are well known to cause problems, yet many insist on not cleaning, or not knowing how to clean, or not being able to tell if they actually cleaned out the carbon. It’s also easy to tell who cleans blued guns based on the bore damage - pitting from normal amounts of moisture in all but the absolute driest climates will ruin a bore eventually. You don’t have to believe me - look at any 30 year old hunting gun that hasn’t been cleaned - it’s littered with pits.

When someone doesn’t clean a barrel, I tend to think what else do they not clean. Is the bolt full of crap, maybe rust, that is causing inconsistent ignition. Is the trigger gunked up? Is there dirt and crap between the receiver and stock? Lazy cleaners are usually hard on their rifles in other ways - odds of muzzle or crown damage go up.

I’ve been part of a troubleshooting fiasco that went on for way way too long, until we figured out he had no idea how to shoot from a bench, and if I remember right the bench was rickety. Most portable shooting benches, or wire reels turned on their side are so bad as to be worse than just shooting over a pack. It’s hard to take poor accuracy seriously if they aren’t capable of at least good bench technique.

Trying to judge a person’s mechanical aptitude via how they post, is difficult at best - hell, even in person some guys talk a good game, and are barely able to poorly use a screwdriver. I’m often reminding myself of the guy who sounded sharp - torques all his screws, seemed very meticulous, but turned out to have horrible judgement and was barely putting any torque at all on action screws - the receiver was just flopping around in the plastic stock.

Whenever, I think no new craziness has been invented in a while, a shooter will surprise the world by winning the Ultimate More Stupider Award with something that is so off base that I would have never expected it.

I know a guy who bought a $4k gun and shoots fist size groups at 700 yards, but is still very green and makes simple mistakes - new shooters don’t know what they don’t know. It’s fun talking with him, because the rifle is dialed in, and most of the minor accuracy issues can be quickly identified as shooter issues. Normally, the poor accuracy of an average gun on an average day creates a lot of fog that has to be dealt with.

I don’t think there’s any way to avoid assuming everything, every body and every technique is broken, and go from there. Lol

This is good insight and I cant say I disagree with it, but its slightly off from squarely addressing the topic. What is YOUR step by step process to isolate where the source of a problem is and address it with one of your guns? What is your mental checklist that you go through, in order, when you have a problem? That’s the topic. If step 1 is hand the gun to a known good shooter to address if its a shooter issue, thats perfect…so what is step 2-through-whatever after you determine it isnt the shooter? #2 borescope…assuming its fine or you are on a trip and dont have your borescope, what next?

 

[SBR Sarge]

I feel like this sums me up pretty good. I have no mentors to teach me the proper shooting technique so I know some of my issues are definitely ME. I want to take a class but right now time and funds are limited or tied up with other ventures. I am putting in quite a bit of practice, but still feel like I have a long way to go.

Do you know if any good online/free resources to help teach proper shooting technique to help minimize that issue?

Check out snipershide. There is a wealth of info there about precision shooting how-to. I am a 36 year cop, with 30+ years being an instructor, including rifles. Studying snipershide’s articles tightened my groups noticeably.

There are probably the same resources here, I just haven’t taken the time to look.

One good technique, is to set up a video cam and film yourself shooting. It is a great way to reveal stuff you did not think you were doing. And it can be humbling!

 

[Rippey715]

1. Check torque on every screw/look for broken or unaligned components.
2. Check ALL your data inputs/DOPE.
3. Check environmentals. (Mirage/barometric pressure)
4. Check yourself.

I torque and look everything over before matches or after I clean the barrel. Found a broken scope ring that way once. If my scope is within .2mils I generally dont want to mess with it or rezero it if I knew it was zeroed last time I shot. Could be a tiny change in environment or myself posture or even clothing wise. Don't chase your zero is a good phrase to remember.

Check and recheck your data and inputs. Garbage in, garbage out. It's gotten me more than once. Worst is when it works for a bit and then falls apart randomly. Amazingly a 308 profile and 22lr profile can share dope and still get hits depending on target size and then 2 stages later you cant hit anything and realize the mistake... Height over bore, environment, velocity, temp, G7 BC, etc. It all matters and you need to check all of it before going rabbit holing.

I generally use a Kraft Drill or other positional process to zero. So 9-12 shots from 3-4 positions between low kneeling and standing. Do a build and break between each shot and shoot the positions round robin. Then take a photo of the target with an app that will plot your shots and adjust your zero to the center of the group. It's easy and most closely represents my shooting. I keep shooting drills like this and generally its always the same. I big change in a drill would be a tell that something was wrong.

If something is wrong I am going to assume it's me. Everytime. It's hard to blame yourself as the most inaccurate part of the system but it really is almost always the correct answer. I wouldn't tear anything apart until I could actually prove something was wrong consistently.

Hope this helps. Good Luck

 

[Macintosh]

1. Check torque on every screw/look for broken or unaligned components.
2. Check ALL your data inputs/DOPE.
3. Check environmentals. (Mirage/barometric pressure)
4. Check yourself.

I torque and look everything over before matches or after I clean the barrel. Found a broken scope ring that way once. If my scope is within .2mils I generally dont want to mess with it or rezero it if I knew it was zeroed last time I shot. Could be a tiny change in environment or myself posture or even clothing wise. Don't chase your zero is a good phrase to remember.

Check and recheck your data and inputs. Garbage in, garbage out. It's gotten me more than once. Worst is when it works for a bit and then falls apart randomly. Amazingly a 308 profile and 22lr profile can share dope and still get hits depending on target size and then 2 stages later you cant hit anything and realize the mistake... Height over bore, environment, velocity, temp, G7 BC, etc. It all matters and you need to check all of it before going rabbit holing.

I generally use a Kraft Drill or other positional process to zero. So 9-12 shots from 3-4 positions between low kneeling and standing. Do a build and break between each shot and shoot the positions round robin. Then take a photo of the target with an app that will plot your shots and adjust your zero to the center of the group. It's easy and most closely represents my shooting. I keep shooting drills like this and generally its always the same. I big change in a drill would be a tell that something was wrong.

If something is wrong I am going to assume it's me. Everytime. It's hard to blame yourself as the most inaccurate part of the system but it really is almost always the correct answer. I wouldn't tear anything apart until I could actually prove something was wrong consistently.

Hope this helps. Good Luck

This is great, and I appreciate the zeroing method, it has pluses and minus’s but I get it. Question though: you said “I wouldnt tear anything apart until I could actually prove something was wrong consistently”. My question is what your process is when you actually strongly suspect you have an equipment failure. What is the gist of your process to eliminate shooter error, and THEN what is your process?

 

[ElPollo]

The info already posted is good, but I’ll throw my options/order on the pile. But before you start diagnosing look up some info on shooting fundamentals, like THLR’s YouTube channel. Make sure you are straight behind the gun, make sure you have your parallax set correctly if it’s an option, try to ensure you have a good natural point of aim, that your rear hand is relaxed and putting only rearward pressure on the trigger, that you have good front and rear rests, and that you are not putting pressure on the forend that causes flex that would contact the barrel or result in lateral torque on the gun. Now…

1) Rings and mounts—I’m a 25 inch-pounds guy whether the manufacturer says less or not. Clean the screws and loctite. If I have an issue, I’ll mark them on the outside.
2) Action bolts—65 inch-pounds if I can, but never less than 50. Cleaned and loctited.
3) Barrel channel clearance—you need to have enough clearance so that you cannot flex the stock to touch the barrel, and make sure there is no debris caught in there to cause contact. If the barrel channel isn’t big enough to do that, sand it out. I personally don’t do full length bedding.
4) Make sure you have a reliable scope—See drop tests in the long range hunting forum. I hate chasing zeros and wasting ammo on a scope that doesn’t work.
5) High round count zero—10 minimum, but every one of my guns does some 20-30 round groups. Trying to zero on 3 round groups is chasing your tail and wasting ammo. Make sure the center of your group is less than 0.1 mil or 0.25 MOA off of POI.
6) Barrel—If patterns show up in the 20-30 round groups that indicate a directional heat shift and you’ve made sure you have no stock contact, stop there and send the gun or the barrel down the road unless you are prepared to deal with that BS.
7) If I’m still having issues, I swap the scope with one I know is reliable and check the action bedding to ensure it’s contacting the lug correctly and around the rear tang.

 

[Macintosh]

@ElPollo, Yes, thats the gist of my question. So if your friend who didnt get the memo is at the range with you and is having an issue, does your list above change? Example, “make sure you have a reliable scope”…regardless of scope, some have problems. What is your step by step process to isolate it as a scope problem versus a shooter problem versus a gun problem, and when you have determined positively that it is an equipment problem what are the steps you take to isolate what part if your equipment is the problem?

 

[Rippey715]

This is great, and I appreciate the zeroing method, it has pluses and minus’s but I get it. Question though: you said “I wouldnt tear anything apart until I could actually prove something was wrong consistently”. My question is what your process is when you actually strongly suspect you have an equipment failure. What is the gist of your process to eliminate shooter error, and THEN what is your process?

Eliminate shooter error by having a friend watch my fundamentals or filming myself. I'd also repeat the scenario, prop, stage, situation again on another day and see if its repeatable. I had one issue where I shot my worst match ever and was a full target high almost all day. Mirage. Rifle was perfectly zeroed day before and then couldn't hit anything. Also effected my mental game only making everything worse. Similar but different shooting a 22lr match in -14f. Totally erratic. So I'm not going to deep dive changing things when It's possible it was things that arent the rifle or scope. I went back a day or two later, checked zero, and did some practice and the system was hitting again. So environment and operator. Make notes of these scenarios in case they come up again.

As far as scope, you can do a tall target test.
barrel heating up you can do various strings and watch for dispersion.
Chrono a larger sample of your ammo for consistency
Use known good components both for gear and ammo
and maybe the biggest of all PRACTICE. Practice enough that you can be more certain of when and why something is wrong. Dry fire training and range sessions and drills like the Kraft or MDS 21 dot.

 

[ElPollo]

@ElPollo, Yes, thats the gist of my question. So if your friend who didnt get the memo is at the range with you and is having an issue, does your list above change? Example, “make sure you have a reliable scope”…regardless of scope, some have problems. What is your step by step process to isolate it as a scope problem versus a shooter problem versus a gun problem, and when you have determined positively that it is an equipment problem what are the steps you take to isolate what part if your equipment is the problem?

I think I see where you are going now. People get attached to scopes and other brands and can get a bit butt-hurt if they think you are belittling their long-term friend. I would try to isolate the issue with tests. Make an adjustment, shoot it, let the rifle ride around in a vehicle for a while, document what happens when you shoot it again, and try the next thing. Marking the ring and mount bolts with paint like Form does makes it clear when you have a failure. And you can pick a more manly color than he uses. If it’s not the scope attachment, or the action screws, and it’s not heat-related, and your bedding seems to contact if you use a dry erase marker, then what does that leave? You at that point you can offer a personal scope as a test. I would also suggest you keep a running total of ammo used to solve the problem. If someone says, I don’t want to spend Nightforce money on a scope, they usually aren’t calculating how much they blow on ammo trying to resolve their problem.

And you don’t necessarily have to talk your friend into throwing their rifle at the floor to prove a point. Most of the zero losses I’ve had have been from my rifle riding around in a truck in the desert. If it doesn’t survive that, it won’t survive falling over on the ground when it’s leaned against the truck.

 

[TaperPin]

This is good insight and I cant say I disagree with it, but its slightly off from squarely addressing the topic. What is YOUR step by step process to isolate where the source of a problem is and address it with one of your guns? What is your mental checklist that you go through, in order, when you have a problem? That’s the topic. If step 1 is hand the gun to a known good shooter to address if its a shooter issue, thats perfect…so what is step 2-through-whatever after you determine it isnt the shooter? #2 borescope…assuming its fine or you are on a trip and dont have your borescope, what next?

My method or check list will be different from others based on what’s been done to the rifle up to the point groups went to crap. My maintenance is good - rarely would enough shots be sent down the barrel in between cleanings to amount to much, but on a varmint shoot it could. The bolt is pretty clean, but some crap could have made it into the firing pin hole causing poor ignition, or a firing pin spring might have developed a crack or a defect is just making itself known. Pull the bolt apart, spay carb cleaner inside the bolt over a clean paper towel and see what comes out. Lightly oil everything and put the bolt back together.
Having had accuracy issues with bedding in the past, now all stocks are bedded, so that’s not a concern, unless the action was taken out of a stock and then the issues started - maybe something fell between the receiver and bedding, or the magazine box is bound up somehow.

I keep a shooting journal, so if I couldn’t remember the last bench group it just takes a minute to look it up. Gradual loss of accuracy is different from something sudden. If the barrel is fresh, wear and tear probably didn’t cause the problem, but the closer a barrel gets to a normal range of burnout, the more I’d consider that.

I’d reach in the shooting bag and grab a backup scope to swap and shoot a group. It’s just a fun thing to have a variety of scopes, but the rifle has 1x, 4x, 6x, 8x, 12x and 20x scopes all in their own rings that can be easily swapped. I’ll probably get a Nightforce sometime this year just to be one of the cool kids.

At this point I’m fairly certain the problem isn’t me, the scope, the stock, the shooting setup, cleanliness of the barrel. This is a switch barrel rifle and the barrel isn’t torqued as tightly as a factory gun, so that would be worth checking, as would the crown in case it hit something and has a burr. I might even put a known good barrel on and shoot a group just to rule out anything related to the action.

I rarely have more than one load for any barrel, so the odds of mixing up a charge weight with a different bullet is rare. My reloading journal will show what lots of components were used - if the same lots were shooting fine before accuracy went to crap, it’s probably not variations in lots causing the problem. If the rifle was right on the edge of a poor shooting combination, maybe normal wear and tear put it over the edge, but that would usually be a slow creep up in increasing group sizes.

If it gets to this point and nothing stands out I’d just keep shooting rocks with it and see what happens - probably try slightly different powder charges, may a different bullet. Sometimes odd things happen that are never figured out. The worst thing that could happen is I’ll get a happy new barrel out of the situation. Lol

 

[TaperPin]

I feel like this sums me up pretty good. I have no mentors to teach me the proper shooting technique so I know some of my issues are definitely ME. I want to take a class but right now time and funds are limited or tied up with other ventures. I am putting in quite a bit of practice, but still feel like I have a long way to go.

Do you know if any good online/free resources to help teach proper shooting technique to help minimize that issue?

There’s more free online information now than there’s ever been - in many ways there’s too much and a guy has to sort through what works for him and what doesn’t. Just spend some time watching the videos guys are recommending and search for shooting fundamentals and a lot will come up.

Also keep in mind a bench technique is different from a bipod, which is different from prone, which is different from shooting over a pack. You have to practice them all and make little tweaks to find what works well.

Dry firing helps identify what is rock steady and what isn’t. At the bench when the firing pin falls, the reticle shouldn’t move - if it does, something about how the gun is being held isn’t right or there’s too much pressure being applied with the trigger finger, or muscles are tensing up. Making up dummy cartridges (or buying them) let’s you mix them in and see what happens when you’re surprised by the gun not going off. Shooting off a wobbly bench is never a good thing.

Personally, the amount of pressure on the gun makes a big difference. If too little pressure is applied to the buttplate, hand on the fore end, or trigger hand, it’s inconsistent and groups open up. Same for having a death grip and pulling it into the shoulder too hard - groups open up. I tend to have a medium/light grip with both hands, relaxed arms, and pull the buttplate to the shoulder just enough to take out any slack and have a few pounds of pressure. That is very consistent for me, but is slightly different for everyone. Follow through is relaxed at first, then the rifle has to get back on target. All the muscles of the hands and arms have to be neutral and not push or pull or twist, or jump in any way. You know how some hand gun shooters tend to want to push the pistol forward and down with every shot? You can’t do that and be accurate.

Keep working at things - you’ll figure it out.

 

[Drswoll69]

This topic of troubleshooting a loss of zero or a gun that seems to suddenly be less precise than normal comes up so frequently that I'm surprised I haven't seen a dedicated thread on the topic. I am interested in what people's specific process and order of operations is for diagnosing a problem with a rifle holding zero or a change in accuracy or precision. By this I mean, in a situation where a gun that was zeroed suddenly and inexplicably starts putting shots off the zero (shots were dead-on, now it's low and left), or precision changed noticeably (groups were 1.25", now it's 3"), what exactly do you do, and in what order do you do it, to determine exactly what part of the gun system is the problem (stock/action/rail/rings/scope/shooter), and go about fixing that? ie it doesnt do you any good to replace the scope if the stock-to-action interface is the problem, and vice versa--so what is the MOST FOOLPROOF AND EFFICIENT way to make that determination of which part of the system needs attention?

• What do you do ahead of time to anticipate a problem that facilitates a quick diagnosis? (before you have a problem--clean/degrease and torque, witness marks, loctite or paint, etc on initial setup). Perhaps the "scope mounting to maintain zero" process, but what else? Record keeping? other?
• Zero process so you know the true cone for the gun and can determine if something is truly a shift versus when you are just seeing a group that includes a shot or two from the fringe of the cone of fire.
• When you notice a problem what is your first step--try to repeat the sequence of shots, tear something apart, etc? Second step, etc.
• What is the most efficient process (from a time, equipment, effort and ammunition requirement perspective) to isolate the issue to one part of the system?
• anything else?

I'm guessing @Formidilosus has a relatively concrete process so hoping he can chime in at some point, and interested to hear how others approach this as well.

Following

 

[Macintosh]

So far most folks initially concentrated on eliminating the shooter as the source of error first. Everyone hss their take, but there is commonality. I feel like this is a universal topic that a specific chain of tests and substitutions will apply for anyone, so Im hoping to arrive at a series of steps, in order, that will accomplish this for any shooter, any gun/scope.

So far the universal step 1 is “set up for success before a problem” by a) using good mounting technique with quality equipment known for reliability, proper torque, threadlocker, witness marks to visually see a physical shift, b) have a perfect zero and known extreme spread of your baseline performance as a reference via a high round-count zero/group, and c) keep records for you to refer back to

Once a problem is suspected, the key is to make one change at a time to confirm the problem and isolate individual components of the system as the source of error, or eliminate them from being the source of error. Ie if you change only one thing and the result is the same, that thing was not the source of error.

So step 2 is “eliminate the shooter as the source of error”. A) is the issue consistently repeatable? If so, its not the shooter. B) Get a second known-good shooter to try if in doubt, if the problem persists with second shooter, its not a shooter-error issue.

Step 3 is still a bit in question. Perhaps checking any recent changes… “if anything else changed before the problem (new ammo, scope, tightened screws, cleaned, etc) take the gun back to the previous state” and repeat…if the problem goes away, that was probably the issue. If this cant be done (out of that ammo, etc) then try a different version if the same replacement to see if problem persists.

Step 4…?? Looks like some folks going right for the scope, others looking elsewhere. Whats next?

 

[TaperPin]

Step 4…?? Looks like some folks going right for the scope, others looking elsewhere. Whats next?

The problem with a simple checklist is it attempts to simplify and condense down all the things that make an accurate rifle/shooter, which is a big complicated set of topics.

As with any troubleshooting, from garbage disposal, to trouble codes on a new vehicle, check the low hanging fruit first and do the easy things, before digging deeper into the hard stuff. Lol

 

[Macintosh]

Well, yeah, but there’s a lot of low hanging fruit to go before we get to any hard stuff. So what’s next?

 

[Rippey715]

One option to prove the shooter is capable would be to let them shoot a known and easily accurate rifle. Trying to help a friend sight in this year and he could barely sight in or confirm zero with his BLR. like 5-6 MOA group at best. But then he shot a 1.5 MOA group from 5 different positions with my match rifle. So the shooter was capable, the platform was just very lacking.

 

[Marbles]

For a rifle I have 30 round groups for, I know my baseline when combined with the gun, and assume a deviation from that is equipment.

Roughly my steps
1. Look for anything obvious (loose muffler, cracked scope ring, broken or loose screw, cracked stock, Etc. Witness marks make this easier)
2. Start with a know accurate load and shoot a confirmation group. If that groups, go back to the other load, shoot it, if that one does not group, I would change the load.
3. If the known accurate load does not group, I would start by assuming it is a screw loose or something moving. If I have a known accurate scope mounted in rings that fit the rifle, then swap on the known accurate scope. If it starts grouping, then the problem is scope/rings. If it still does not group, then it is a rifle problem.

Scope/ring issue
1. Confirm by seeing if the problem carries over to another rifle, or I might just
1.1 Pull scope from rings, if rings look sound, degrease, remount using appropriate torque (I subscribe to the high torque school of thought, but whatever you consider appropriate). I will probably put loctite between the scope body and rings as well. If the issue continues.
2. Move to a new set of rings (though I would not pull the good shooting scope from its proven ring mounts to do this). If it still has a problem, can the scope and move on.

Rifle issue
1. Pull action from stock, check (full free floated barrel, no pressure points, no obvious stock damage). If that looks good, remount with 65 ft.lbs of torque on action screws and see how it shoots. If the problem persists, and I have a second stock, then swap stocks. If the problem still persists, consider checking the barrel.
2. I don't have a bore scope, so I can look at the crown for obvious damage. If I don't see anything their, I will probably shelve it for a while and consider replacement. I might clean it, for @TaperPin 's sake.



If it is a new rifle, particularly in a caliber that is larger than I usually shoot. I consider that the problem may be me, but much of the process is the same, except I try various types of ammunition I have on hand, then work through much of the above, then retry with various types of ammunition. Ideally have someone else shoot it, but I don't have many friends, much less friends that shoot better than me (something about having lost my marbles), so that usually does not happen.

Always consider how much effort I'm willing to invest, for some things I would have a lower threshold for canning it.

As always, free advice from a guy who lost his marbles is probably worth less than you paid for it.

Edit, if I don't have a second stock, I would consider bedding it once I had tried everything else that is easier.