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.

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.

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.

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.

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

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.

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.

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.

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!

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

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

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.

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).

@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.

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

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,

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

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

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

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!

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 :)

Thanks for the information regarding light changing the zero

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

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

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.

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

nice I was really pumped for this video

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

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!

Hahaha lost it when you started hammering that scope

Hello from Canada! Could you do a video on SCOPE RINGS alone? I find quite a difference between various rings, some close nicely around the circumference of the scope, while others have a slight gap even though they have been tightened to the recommended torque. I wonder when we get a large temperature shift, if the scope could then move under recoil. I shoot a custom 375 H&H magnum as it has been my favourite cartridge for 40 years. Between the several sets of rings I have, the ones that do end up with a slight gap always seem to be the least consisted and I’m not really sure why. The last time I used such rings was three years ago. The rifle had been zeroed with a new Whitworth barrel installed into the Mauser action ( also new). I took it hunting that fall ( within two weeks of zero) and also took a few test shots after the fly-in. Second day of moose hunting, a hot fall day and an easy 300 yard shot presented with no crosswind at all. I took the shot using a rest, and while it was still a decent hit, it was a fair bit forward and high. Later after recovering the animal, I shot another 200 yd group at the camp after the hunt only to find my zero had shifted three inches left and two inches high. After returning home, I changed out the rings and have not had the same isssue since. I knew it wasn’t the optic, I knew it wasn’t me, as I’ve put thousands of rounds of .375 down range over the decades and I’m very comfortable with the recoil of the rifle which fits me very well. I’d love to hear your opinion on rings, how you set them up, and your experiences. Cheers.

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

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

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...

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.

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.

Good stuff, great video 👍

Great video Jim, good stuff

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.

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

Great stuff Jim. Pretty interesting stuff.

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.

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.

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

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.

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.

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.

Jim, you definitely get a 👍. Good video.

Excellent and very useful

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

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.

Great video mane! 🤙😎

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.

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.

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.

Hahaha love the editing on the sun/light effect on impact

great job!!!!👍👍👍

Good info 👍

Great video!

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

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.

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.

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.

👍👍👍 great info

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.

In my experience, there IS a different in bullet impact between a cold barrel and a hot barrel, but unless you’re using the same rifle for hunting and competition, most people won’t be able to tell a difference out to about 300 yards (give or take depending on the caliber, MV, bullet weight, etc.). I don’t shoot competitively now, but in the past I’ve always used the cold bore method of zeroing for my hunting rifles and shooting various amounts of rounds at a time for competition rifles. Of course, barrel weight and thickness, action type, and action quality all have an effect on this. In conclusion (as with most things shooting), how much a cold bore vs hot bore zero varies greatly depends on a multitude of factors and there really isn’t one right answer.

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.

In my opinion, using a hard case, people usually put the gun in upside down. When they pick the case up by the handle, the gun is carried upside down. The weight of the gun is weighing down on the scope. I dont know if that could change impact or not.

Not sure if it applies to centerfire but if i remember right there was a couple people that proved the "cold bore" shift in 22lr was moisture related. They could do a breath of air through a straw into the chamber and down the barrel and the shift was gone. I think Josh on pursuit of accuracy had a video on it. I think some of the center fire shift is cold shooter and positioning of youre face and eye behind the scope

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

As with the suppressor this affects PCP air rifles just the same. Either you hunt with or without.

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

Cold bore that’s more than 1/2 moa is barrel that’s not made right, had a bergara HMR that they warranties and replaced the barrel for me. It was shifting 6 inches from cold bore over a 4-5 rd shot string

Very interesting. Around the 15:51 time frame you talked about positioning where someone shoots a tight group and gets up and checks the target. Then shoots another tight group but it is not in the same place ( precision but not accuracy). The group has shifted. You speculated that the person is not in the same shooting position on the 2nd group. What if .... it is the sun position? I was a Professional Surveyor who was trained by the Army at Fort Sill in star shots and sun shots for determining the position of the object being aimed at . When we took sun shots we followed the sun in the scope by turning both knobs and noted the exact time ... exact to the second. When I looked through the scope the sun was moving rapidly. I had to make adjustments so that I had the center of the sun in the cross hairs by constantly turning the two turrets and when I got the sun in the exact center I called out to my partner and he noted the exact time. When someone gets up to check the target and gets in position to make a second group he is not seconds away from the shots he made on the first group. He is minutes. The sun has moved a lot in those few minutes. You talked about the position of the sun affecting the scope. I knew about parallax but never thought about the position of the sun rays hitting the scope and the shot placement being a click off in the opposite direction. You opened my eyes. I am going to check it out.

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

What do you think about a “clean bore” impact shift. In other words, have you noticed a different impact point with a clean barrel as opposed to after fouling shots? Thanks and love all of your content!

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 .

Hey Backfire! Where did you get that cool Collimator tool???

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.

Hey Jim, thoughts on a lead sled as apposed to using a bipod and a bag in the back. I am 6 6 and the lead sled let me sit at the bench in a little bit better shooting position as apposed to hunched over a bipod and a bag in the back. On another note, Love your content! It is awesome content for the normal guys out here!

One thing you missed mentioning is a clean gun. My first two or three a lot of times aren’t true if I just grab a clean rifle out of the safe that’s been sitting a while. I have found some lighter fluid on a few patches before shooting to get oil out tightens things up though

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.

What about barrel whip because of the weight of the suppressor?

Saw Tiberius Rex video several years ago speaking also about the importance of the temperature of the cartridges being consistent. Any thought on how important this is as another variable?

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

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

Oof, I have a Leupold scope so to see him smack it around I was for certain that scope was messed up. Nope, 'it returns perfectly to zero'. Thankyou for that. Seriously, I've been so worried my scope was going to be off if i jumbled it around in the hunting rig going to the hotspot. I needed that verification.

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.

How much did the barrel heat up during the 10 shot or 20 shot group. Barrel heating will affect grouping size. I trust a 3 shot group more that a 10 or 20 shot group.

I've experienced a POI change between the first shot and subsequent shots and was able to correct this shift by remounting the scope or bedding the stock. I've not seen where this shift cannot be corrected. There is a real and measurable difference in velocity, not POI at 100 yards, between the first clean bore shot and subsequent dirty bore shots with some rifles.

I wonder about thermal expansion differences between actions, scope rings, and the scope body.

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.

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 have noticed the bolts on bottom of stock. And on picatinny rail and scope mounts need to be checked.

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

I usually settle at half an inch north and a half inch left from the center point. No idea how I settled on that.