For hunting, cold bore zero is what matters. Shoot one shot every day and record its position. Compile about 10 and use that as your zero. Light profile barrels shift a lot and with very few shots in my experience.

thirty years ago I had purchased a rem model seven, it shot 1 in groups when new, sent it off to have the barrel action refinished with dull finish, was very shinny bluing. the gunsmith refinished the rings and mount also. put rifle back together and it still shot good for about 2 years deer hunting, less than ten shots total and four deer in the freezer, then every thing went to crap, 3-4 inch groups. glass bed the stock, no changed, it sat in the gun safe for twenty five years. recently I pulled the old classic rifle out of the safe and did a completed relook, come to find that a tally base was loose, I knew right away that was the culprit. lock tight the bases on and the rifle now shoots just under 1 inch groups. life is good again !

I shoot PRS and when I have a zeroed rifle in Indiana and go to Northern Michigan or Southern Indiana or even 2 hours west in Illinois the following day, I have to re-zero because sometimes it's still off even if your equipment is not loose. Temperature, barometric pressure, density altitude, all kinds of stuff can affect your zero from one day to the next.

I think cold bore “shifts” come predominantly from people cleaning their barrel between range sessions or between zero’ing their gun. You scrub that barrel and you will absolutely have POI change for a shot or so. You commonly hear cold bore shift discussions with fairly inexperienced shooters or casual shooters. I don’t ever hear precision shooters have issues with cold bore POI problems.

One point not mentioned is if you wear glasses. This can impact your parallaxes without realizing. I never realized cold bore issues with my Model 70 or my Blazer. This usually is a thing with extremely thin barrels e.g. Kimber from my experience or can be caused by a barrel with improper stress relief due to incorrect heat treatment which should very very rare. I like the turret stickers.

I totally agree with you in that everyone wants to focus on group size, but none of that matters especially in a hunting rifle if it can't consistently hold zero.

Everything starts with the shooter. If your shooting form is consistent then you go looking at equipment and other potential issues. We all must pay attention to pressure, humidity, wind, lighting, thermals, etc. At the end of the day the best rule to follow is that if you're not sure of where your shot impact will be, don't take the shot. There's nothing wrong with an ALL STOP if things are wrong. In fact, that's the safest thing to do. Great video. Thanks for all the work you and the crew (family and friends) have done to provide these videos and information for us so we can all learn.

A quick trick a friend of mine told me was to use nail polish around the screw heads. every time I take the gun out, I now look at the rings and the pic mounts for the nail polish to be intact, if something moves, the polish will be cracked.

Man... thank you. It so easy to forget to tighten everything down. Had my rifle out to the range two weeks ago and it was perfect, went out yesterday and couldn't hit a thing. Just now checked it after watching this, my rear scope mount was loose, bipod was loose, and my suppressor was backed off about 1/8th of a turn!

What about scope cant ?….I shoot out at a buddies property, but the ground isn’t always level where we shoot. I’m running Holland levels on all my scoped long guns now. You hit the light conditions point very well. I used to get frustrated sighting in, I’d shoot on a weekend, & get the gun dialled in during mid day. Then I sometimes ran out to the shooting range after work when the sun was going down, and my point of impact would change, not a lot, but enough to frustrate me. I soon started sighting in later in the evenings when the sun wasn’t hitting my scope at different angles and noticed my point of impact was never far off week to week.

Also. Lifting your head off the rifle and changing your cheek weld will cause accuracy issues. If your action and magazines are working properly, there is no reason to lift your head. Watch competitive shooters, they only lift their head when changing targets and distances.

this was the exact problem i had ,missed an ibex about 9,10inches down, at 350 meters, i rechecked everything at last it was the suppressor that was lil bit loose, i thought i cant be the problem so went to the range to check , you know what happened,

Your brave. Baffle strikes occur when your suppressor is loose.

Suppressors …another thing to go wrong in the bush . Great idea

Ambient temperature and powder temp tend to cause a shift in both velocity and point of impact.

Jim, great video. One thing that I would love to see addressed is the condition of the bore during the cold bore shot. I would love to see your advice on storing a gun (clean barrel, dirty barrel, or an oiled barrel and pushing a few clean patches through.. etc). This might be an explanation to why the shots after the first shot seem to be more consistent (oil is gone and barrel is fouled). Competition shooters could just foul the barrel with a few shots before competing, but for hunters this often is not an option and certainly it isn't ideal. Would be an interesting topic to address, and maybe combine it with a barrel cleaning video (should you clean a bore to bare metal, should you keep it consistently 'fouled-clean' or maybe shoot x amount of shots and then clean and foul the barrel and never touch the barrel until accuracy drops off again). Lots of things to think about :)

Hahaha lost it when you started hammering that scope

Very good information. I really enjoy your videos and your honest, unbiased opinion on equipment. I agree with you about the "Cold Bore Shift" phenomenon.

Incredible. Very well done video that covers a lot of common reasons for losing zero. I learned something new. Thanks!

The second point is really fascinating. It’s call the Law of Large numbers in stats. You’ll know when you’ve shot enough rounds to zero when the center of the groups no longer moves a significant distance. Great video!

2:00 Last time at the range, I had this exact thing happen. I was shooting a new barrel and getting decent groups. Then I started noticing my point of impact shift. At first I thought it was just the barrel settling in. Then I was letting the barrel and suppressor cool down between shot strings. I reached up to feel how hot the suppressor was and noticed a tiny bit of play. I re tightened it (maybe a 1/10 of a turn) and then magically my original POI came back to the original spot. I learn this lesson first hand that day. Now I check the suppressor for snugness often

That must be why California makes it a felony to possess a hearing protection device. They're really looking out for us!

I learned a lot from this informative video, thanks Jim. My comments are in regard to the effect of barrel temperature on the POI: 1. there was no discussion of the effect of barrel temperature on barrel harmonics; 2. there can a very broad range of variation in barrel temperature - which will vary with the barrel material, mass, and surface area - e.g. from ambient temperature, which could be 30 degrees F to > 106 degrees F after 8 shots in my rifle; 3. Eagleye Hunting Gear showed quite a bit of difference among rifles in the change in POI with increasing barrel temperature in a KZfaq video; 4. It is important to distinguishing between the effect of increasing barrel temperature and fouling with repeated shots. Of course when you're hunting the most important shot is going to be with a cold bore.

The cold bore subject is really a cool one to dive into to. One thing was missed that I have run into. Action screws miss torqued make a huge difference.

Thank you for sharing all your wisdom I as a new hunter I like to learn from people like you who have experience and you explain well thank you I didn’t know there was a difference being a little lost that’s why it didn’t hit them

People may be confusing clean bore vs cold bore. I have had many different rifles and especially mussel loaders that shoot horrible when they are clean. So maybe what some would consider a fouling shot is being blamed on cold bore

Great video Jim. Excellent information, even for experienced shooters.

Greetings from Australia...thanks for your work on these vids, always helpful.

@backfire Jim, Great channel!! Great advice!!! My gun strings hard after the third shot so that's where's its zeroed. Its a pencil barrel so you have to wait what seems like all day for it to cool all the way. Ive been going through this gun as it had issues which you stated in this video which were affecting the zero along with my shooting it hot. I'll double check three cold shots next time i shoot it as its a hunting rifle and i doubt i will get more than two or even three shots at anything.

I free floated the barrel of my Ruger m77 and bedded the action in the stock because it was shooting wild. Tried all kinds of different torque on the stock screws to no avail. Finally realized it was just a piece of wood and sanded the forend away from the barrel and bedded the action. It really helped the rifle a lot. The variability from shooting from a bipod vs resting on a bag is much less than it was. Will find out next month if i drew an elk tag this year or not. Deer tag for sure.

Bro at 12:22 in the Video you can see Jesus over your shoulder. I love that Christus statue. That warms my heart. ❤🤍💙

Thanks for the information regarding light changing the zero

solid informational video as usual! Ordered some turret tags - what a great idea...that I wish I would have thought of. LOL

Enjoying the content of your videos from over the pond in the Uk.👍

Thanks for this video! Keep making more like it! Back to the basics

Some really great points in this presentation - some thoughts, the instructors comments on Sun position are real but are a much smaller issue with very good glass and coatings and point of aim being through the centre x hair, (centre glass) but can be well off with on cheaper glass, with fewer coatings and when using large holds well away from the centre of the glass. In my view there is little point to a Christmas tree style reticle with poor glass and coatings (as the error will increase away from the centre of the glass). Good glass, good coatings (and plenty of them) plus relatively simple reticle e.g. 1/2 mil dot is the way to go (in my view).

Hornady podcast #50 on group size is very interesting. Basically, you should shoot a 10-20 round group and use the center of the group as the center of your zero. and that group should be what you consider your rifle actually capable of.

Great content as always. I do have a comment on the cold bore discussion. My favorite hunting rifle shoots the cold bore shot 3/4in high and 1/4in right every time. I have shot 1/2moa 5 shot groups by cooling the rifle in-between shots with a barrel fan. Once the rifle is warmed up the group stays tight until round 15ish and then things open up again. I always sight my hunting rifle to "cold bore" zero...... I think it comes back to every rifle having its own little nuances and the only way to be prepared is to put rounds down range. Practice makes perfect!

Some good stuff again. Now I have check my guns again. Just when I thought I had all my guns dialed in. Good job Jim makes very good sense. CW

Very informative Jim ! Thank You .. Just read ottokite post and reminded me of a drifting zero on a GA Precision 300 WSM and couldn't figure the culprit until I took the scope off and one of my Premium rings had a hairline stress crack .. Called the company and he told me they had some metallurgy issues with a batch of rings and I returned the ring to them and they sent me a new one ... Back in business ... Hasn't moved again...

Cold bore shift is absolutely a real thing, Although it is not necessarily something that is present or significant enough that you will see it in every rifle. I had an Accuracy International rifle in 308 with a night force scope in the night force rings and the first shot out of this gun was consistently in the 7 o’clock position between a half and 1 inch out from the rest of the group. After that first shot, the gun would shoot a half to 5/8 minute five shot group every time. Before I sent it back to Accuracy International for warranty, I had other shooters test the Cold bore. It didn’t matter who shot the gun. It was always in the 7 o’clock position a half inch to 1 inch from the rest of the group. The factory could not figure out the problem or wouldn’t tell me what the problem was. They ended up replacing the gun with an upgraded model.

Expert advice for those of us who are new to shooting. I feel like I stumbled upon gold with this one.

Fookin quality content mate you guys just have something no other channel has (no idea what specifically) Bloody love ya work! Would be hella keen to see some reviews on the woox stocks, at least the less common reviewed ones

It’s mostly shooter input that makes groups open or zeros to appear to wander on a great rifle. Also atmospheric pressure, wind, temperature and humidity will affect the zero. Ammo is also not perfect. It is impossible for a human to put the exact amount of pressure on the cheek weld, same pressure on your shoulder, or your grip, much less trigger pressure. You can have a 1 lb trigger and crack it at 1 lb or 4 lbs. Then as he said your eye can be a touch off of center up, down, left or right. Most people don’t shoot nearly enough of conscientious practice to be remotely good enough to wring out a great rifle’s accuracy.

Its common knowledge that pencil barrels are less accurate and shift after heating up. Heavy barrels are more accurate and have little to no shift after heating up. Three shot group adjust the scope then check and adjust another Day. Patience is a virtue

Hey Jim, When culling deer, after 2-3 shots we check the mod. Although, it happens you drop 4-8 in one salvo but try to not rush and if possible to keep in mind the heat is building and mod could shift. I am lucky in that my mod never moves when culling.

Regarding cold bore shots, I have a hypothesis in its infancy that I really want to test more. I picked up a garmin chronograph and decided to just chrono everything my buddies and I shoot, along with some other guns we get to use through our job (Bergara b14 and hmr in 6.5 cm, seekins hit 6.5 cm, dmr 556, and sp10 in 308, Marlin trapper 45-70, Christensen ranger 22 lr so far). I noticed the velocity of the first recorded shot was generally one of the closest to the average over 10-20 shots. I want to test this much more before I put any stock into this but perhaps taking a lot of time between shots to allow the rifle to cool would improve zeroing. This would mainly apply to hunting scenarios where having the best zero cold bore is essential, but also developing a dope chart closest to that cold bore shot’s velocity and average velocity would be extremely helpful. But in reality, most people don’t shoot well enough for it to matter, whether it’s abilty to adjust for elevation/wind, ability to create and use a stable position, rifle/optic quality and gear setup, or what I just like to chalk up to fudd lore.

I always wonder as a white tail hunter isn't the first cold bore shot the most important as usually the first shot after hitting your stand is the most important

Good info, makes you realize once you found the right ammo and zero it, there are still things to keep track of👍

My muzzle break went loose on me at my NRL comp, I started missing and did a check on my gun and realized my break was all loosy goosy. Tightened it up and was back on.

5:32; there's a huge difference between "not tiny little groups", and having a target that looks like you were using a shotgun

Great stuff Jim. Pretty interesting stuff.

nice I was really pumped for this video

Good stuff, great video 👍

I have a Ruger M77 Mark II .30-06 and I have only had to re-zero my scope on this rifle once in 30 years of hunting. And I have hunted with it every year for 30 years. I even have a fairly cheap scope on it. It is a Bushnell Trophy 3-9X40mm. The reason I had to re-zero is because I lost a screw gromet my sling and the rifle fell off my shoulder and the end of the barrel hit the gravel road!! OUCH!!

Great video Jim, good stuff

I remember reading a long time ago that you could eliminate "cold bore" shift by breathing into the barrel before the initial shot. If I recall it has to do with the level of moisture in the barrel. I have tried it with my rifle, and it worked for me. Get a straw, and shoot a puff of air or 2 down the barrel prior to first shot and see what happens compared to when you dont.

Great topic. One thing I have always done is have my action bedded and barrel floated and triggers set to the same weight.

I had the same issue with the suppressor not tightened all the way. So now I have witness marks to prevent that.

Great video, I may have missed it but I didn't see anything on a fouled barrel vs clean bore, this can cause the first shot fliers.

I wouldn’t necessarily say the zero is off if it’s on when things are secure but off when things are improperly fastened, however this information is valuable, don’t go shooting with a loose muzzle device

For a hunting rifle I really believe in establishing a cold bore zero. What was the shot spacing on the shots. Maybe use a laser thermometer and record the barrel temp for each shot. From what I have read cold bore variation can be affected by the barrel manufacturing process and stress relieving the barrel.

5” POI change with a quart turn of the suppressor is definitely on the extreme side in my experience. I’ve had one gun (a Keltec RDB survival) with an absolute pencil barrel that has around a 4” POI change at 100 yards between suppressed and unsuppressed, but between suppressors only minor POI changes. Every other gun, suppressed, unsuppressed, different suppressors, exc, only around 2 moa difference.

Cold bore shift is real. A primary cause comes down to how the barrel is made. As steel is being forged and shaped, it can build up internal stresses where different grain patches in the steel want to naturally flex some direction. If the steel isn't properly stress relieved, the barrel will bend itself one way or another when it heats up. The hotter and thinner the barrel, the easier it is for the internal stresses to flex it. The stories of early M16s shifting zero as they heated up are at least partly true because metallurgical processes have advanced greatly in the last 60 years. A barrel that was properly stress relieved during manufacturing should have minimal shift as it heats up, if any at all. But it's also important to remember that your groups will always open up as the barrel gets hot. Lightweight hunting rifles, those with thin sporter barrels, can start opening up after only a couple shots. I had a Creedmoor that could place the first two shots relatively close, but couldn't hold better than a 3" group if you fired more than three rounds in five minutes. So it's possible what one person thinks is cold bore shift is really just the barrel quickly getting hot and the opening up.

every savage rifle i have bought new has a ton of oil under the mounting rail. after zeroing, it would shft. removed the rail, cleaned and dried the rail and action, then mount again with loctite. the 338LM 110 even had mounting rail holes that went through to the action into the bolt area. any cleaning fluid used would wick into the hole and loosen the loctite. had to be diligent.

I remember Johnny’s Reloading bench had a little fan gadget that you put into the chamber and blow air down the bore to speed up cooling the barrel back to “cold” bore status. That helped him speed up the process when trying to fine tune his hand loads.

A scope don't go backwards in the scope ring under recoil 💡 If it's creeping, it creeps forward >> But you are totally right it's a bad thing to mount the scope in that manner from the beginning 🤝 Greetings from Sweden 🫡

None of my hunting rifles that were glass bedded had problems with zero shift. The Howa .223 i use would was very fussy with different ammo and would shift at different temperatures. A full action bedding job and now it is far more consistent, even though group size hasn't changed.

Good info 👍

Excellent and very useful

This might sound stupid but aging of the fouling in the bore can do it too. Even if that fouling is just the oil after cleaning. The carbon absorbs water, the copper oxidizes, the oil evaporates.

Check mounts and trigger pressure too high, pulling some shots. I zeroed my Savage model 12 with custom heavy barrel and many mods to 1/2 inch five group, then drove 3 hours to a deer hunt. The mounts (rings) fitted by the gunsmith moved by the time we got there. When i got home, i found he had not bedded the pic rail and didn't torque the mounts. I use a case too! Cold bore is bullshit. I've been an f class shooter for years and its best warm with heavy barrel. Cold bore only affects thin barrels. Biggest issue people forget is custom trigger, trigger weight (1.11-1.15) and plenty of dry fire practice.

I have had this problem on one rifle ( light barrel) where the first shot on a clean cold bore the shot is way off. Then it comes reasonable in grouping with subsequent shots. I put this down as the first shot is on a barrel with no lubrication from the powder. The burnt powder does provide lubrication. Barrel walking is also a problem with light barrels.

Here in Norway, we have mandatory practice shots. Minimum 30 of them spread over atleast 2 days before we have a practical shooting "exam". Every year. 5 outta 5 shots have to be inside killzone on a reindeer target. If we have problems zeroing in, we get help from our friendly neighbourhood gun and hunting guru ( he got 64 years of hunting experience and hangs on the shooting range every week )

There is no perfect solution. What works for me is a 5 round grouping at distance X, followed by a confirmation 5 round grouping at distance Y (for example X could be 100m and Y could be 200m). In terms of scope mounting, with your Sig Cross (or anything with a pic rail) - I avoid stand alone rings and just use high quality cantilever mounts. Moreover, any scope I mount is levelled and screws/nuts tightened to manufacturers spec. Also, I have a DOPE notebook which is invaluable. This recipe works well for me.

great job!!!!👍👍👍

I have a very accurate .22. I too have observed this group shift in impact due to position change.

Hey Jim, After reading several of the comments. There is another possibility that no one is saying. It's rarely thought of yet it happens. The ammunition. If you are shooting factory ammo a change in boxes different lot #s. Lets face it factory ammo is less dependable. Hand loads are usually more accurate and consistent. With that being said you can have a box of bullets for loading and change lot#s and their can be differences, just like powder and primers. I've run into this several times over the many years of handloading. There is no such thing as the perfect zero. The best we can do is the best we can do. Especially when there are so many things that are against shooters, some in our control and some not.

I learn3d to purchase double luggage scope rings with tape in the housing. I also use the sun shade as what you said about the light impacting your zero is true.

Very comprehensive testing with outstanding information I have found that the most accurate hunting zero possible is to shoot cold bore groups to establish an average zero Right on good stuff mate

That Winchester really did not like getting heated up.

That shift with a loose suppressor is wild 😮

Great video!

Thinking about cold bore. I’m just an average everyday shooter. I work in a machine shop. I could see a rifle bore changing with temperature. Variables might be material of barrel, thickness of barrel, tempering of barrel, consistency of atmosphere during machining causing a less accurate barrel. Maybe the bore isn’t directly down the center all the way; ie; barrel thickness varies around diameter, the rifling is inconsistent down the barrel. I’m not a gunsmith or anything. Not even a machinist. I just work manufacturing machined parts, some thick some very thin. Some of our parts have 2000 lasered holes .025-.030 diameter. The part changes.

May I suggest locating your rifle in the hard case with the scope closest to the handle. The rifle will then take the weight as you carry it and when you set it down.

Jim, you definitely get a 👍. Good video.

👍👍👍 great info

Cold bore shift is very real, especially for rifles that aren’t free floated. Thermal expansion in the barrel changes contact with the stock, changing the point as the forces of a bullet traveling interact in new and novel ways. Now you could say “just use only rifles that are floated”, which is fair I guess. But that is a limitation in picking the tool you want for the job. Knowing your rifle, and how it reacts, is important. I’ve had rifles I’ve sold for this reason, because their use case meant that multiple shots would require a warm barrel. I’ve had others I’ve kept, because they would never be shot very warm.

I think that a accuracy test using the same rifle, with different price point rings, would be really interesting.

I agree with everything you said , however your zero is only great if when you shoot after zeroing the external variables / day time conditions are identical from whe you zeroed the rifle . I always zero then go hunting . Bullet impact is different even with season or temperature change .

What we were taught through training at the S.O's office, is after cleaning the bore of the rifle run a patch through it with a little amount of oil, then run a dry patch through it. That little amount that is left almost mimics the first shot that "dirties the bore. The "cold bore" shot drastically changes the amount of shift.

As a hunter what i really want to know is where that first shot goes,when your satisfied you have your gun zeroed where you want it,shoot again on different days and different temps and conditions(cloudy,sunny,even rainy)if possible to make sure that first shot lands where you want it.I like letting my gun sit outside before i shoot and let it get close to outside temperature.A lot of modern powders are not very temperature sensitive but i want to know I’ve made every effort when the moment of truth presents itself.Great discussion👍

I would very much like to see a distribution graph of the 5 days worth of shooters group size and zero error. Seems like everyone thinks they are 1 MOA all day long shooters, but judging by the video most people are 4 MOA all day shooters with a 3" zero error. As for the cold bore shot, Erik Cortina and Speedy were talking on a podcast. I think it was Cortina that said he sent a puff of graphite spray down the barrel after cleaning and it resulted in his first shot grouping with the rest a.k.a no cold bore POI change. If this is repeatable, perhaps it's really CLEAN bore shift.

Cold bore is very real. The velocity on that first shot is different than the subsequent shots. You can let the rifle cool completely and shoot again... only to find that even though the bore/barrel is stone cold, there is no shift in impact. Go out the next day or next weekend, and the cold bore shift is back. This leads me to believe that the cold bore phenomenon has more to do with chemical changes in the fouling in the bore. We know that carbon fouling in the bore acts as a lubricant, that's why a clean bore shot has lower velocity due to higher friction, but what is happening to that carbon in relation to copper and other chemical deposits over 24 hours that doesn't happen in 1 or 2 hours? Maybe I'm smoking crack, but you decide whether or not this sounds plausible to you.

Good job, you covered many potential causes of zero shift. Might want to address mirage causing the image that you see to shift. Usually 1/2-1 moa.

Your group sizes will likely tighten up or spread out with inconsistent suppressor tightness. Just like using a barrel tuner.

Everything affects the way your rifle shoots and must be tested. I’ve seen barrels that shoot just OK till it gets fouled with about 20 rounds, then it stacks them consistently 1/2 MOA for about 200 rounds. So that gun does not get the copper removed until accuracy starts to go. Strip out the copper, re-foul it and it’s back to shooting 1/2 MOA. Some barrels shoot better clean and cold some like it dirty. Try that.

Your last factor is why the sig cross has a wondering zero. I see the same thing with AR type rifles. The reason I say is its pretty tuff to get those form factor guns to ride the bags the same. You want the gun to ride the bags the exact same when shooting, recoil back then side forward. look at how bench rest guys do it, its how to hold those guns exactly the same on the bench. YES the suppressor moving does that. The last couple of years I use white milwaukee paint pens to visually show marks on the barrel, the adapter and can, when tight all these line up and I can quickly see its lined up.

I’ve got levels on all my rifles, not having a level will probably be the main reason groups change place, it also explains horizontal stringing (other than wind). Try getting your gun set up horizontally and vertically when the landscape slopes, you have no chance because it’s impossible to see your cant. Cold bore shots in my experience tend to be shooter error, dry fire your rifle 2 or 3 times before the shot you will see your error and see it improve from shot to shot without the recoil of a live round.