Cold Bore Zeroing Process

[Evilsports]

Good morning fellas. I'm going to load some shells up this morning and hit the range. Decent groups yesterday and today will be some cold bore zeroing.


I have a few questions...

How much POI walking from cold bore to warm bore do you typically expect? I'm zeroing for a cold/fouled barrel so I'm planning on firing at 100yd and then adjusting scope, waiting 10 minutes or so for a cool barrel and then shooting again until I can confirm cold zero. I'm planning on repeating at 200 and 300 to confirm drops. Does this sound like an effective/efficient process or do you sort it out some other way?

Load is shooting just fine with a warm barrel but I did notice a few slightly concerning first shot POI's yesterday when I moved from 100 to 200, and also from 200 to 300 and the barrel had time to cool.

Shooting 140gr TTSX with 60.5gr of H4831SC, 24" 8.7T Rock Creek carbon fiber barrel in .280 AI

Thanks,
Kevin

 

[Seabeeken]

This depends on how well the rifle was set up at the start. My trued actions have no change at all from cold to warm barrel. Pressure points in the stock and action will cause impact shifts between cold and warm as well as other factors. I do mine in a simialr way. I use a chamber chiller to help cool it and I only shoot 2 rounds before cooling since id likely never shoot more than that when hunting. Good accurate powder in 280ai, mine likes that and RL-22

 

[FEENIX]

Good morning fellas. I'm going to load some shells up this morning and hit the range. Decent groups yesterday and today will be some cold bore zeroing.


I have a few questions...

How much POI walking from cold bore to warm bore do you typically expect? I'm zeroing for a cold/fouled barrel so I'm planning on firing at 100yd and then adjusting scope, waiting 10 minutes or so for a cool barrel and then shooting again until I can confirm cold zero. I'm planning on repeating at 200 and 300 to confirm drops. Does this sound like an effective/efficient process or do you sort it out some other way?

Load is shooting just fine with a warm barrel but I did notice a few slightly concerning first shot POI's yesterday when I moved from 100 to 200, and also from 200 to 300 and the barrel had time to cool.

Shooting 140gr TTSX with 60.5gr of H4831SC, 24" 8.7T Rock Creek carbon fiber barrel in .280 AI

Thanks,
Kevin

Kevin,

Each barrel behaves differently. "I" always sight/zero with a cold bore. Your first two shots (follow-up shot) are your most important shots. Good luck and happy, safe hunting.

Ed

 

[Evilsports]

Thanks guys. I'll see how well it behaves this morning.

I didn't really pay attention to cold shots during the load work up so I'll do some comparisons and see. I should have paid closer attention, I will in the future.

 

[imyourhuckleberry]

Experience has shown me that shooting at 100 yards will not repeat the same results at 2 or 300 yards. For me if you already know your ballistics of your particular round my first cold bore shot would be taken at 300 hundred yards and not 100 yards. My reasoning for this is that atmospheric conditions will change with time by either increasing or decreasing the density of air depending whether it gets hotter or colder from the time you started your testing.

If this is for hunting purposes in my opinion and take it for what free advice is worth it becomes easier to adjust your shot to 200 or 100 yards. Now in my defense I zero all my rifles at 200 yards because of where I hunt and seldom have I taken game at 100 yards or less. Your situation could be different.

Also the exterior part of your barrel may feel cooler than inside the barrel. I would use one of the laser infrared digital thermometer and check the inside of your chamber to see how hot it really is if you want to be OCD about it.

 

[MagnumManiac]

I see how your wanting to verify your cold bore shots, which is a good thing, however, the only way to do it justice is to do it at different times of the day, and on different days.
Also, you want to pick several ranges, not just 100, 200 & 300. Go 450 one day and 250 on another. I assume you are twirling knobs for this.
I have to say, if ANY of my rifles or barrels walk shots from cold to warm to hot, they don't hang around long.
I do my very best bedding a stock so that it is totally stress free and the barrel free floated from the recoil lug forward.
If this is done correctly, the only cause for a barrel walking shots as it heats up is from a stress relieving poorly done. It can also be caused by a bad blank that has defects, not all barrel steel is x-rayed, even though they may say it is.
A barrel cooler is a good thing when working up loads, but you can't use one while hunting, so just keep track of where your prints as it heats up.

Cheers.

 

[Evilsports]

I see how your wanting to verify your cold bore shots, which is a good thing, however, the only way to do it justice is to do it at different times of the day, and on different days.
Also, you want to pick several ranges, not just 100, 200 & 300. Go 450 one day and 250 on another. I assume you are twirling knobs for this.
I have to say, if ANY of my rifles or barrels walk shots from cold to warm to hot, they don't hang around long.
I do my very best bedding a stock so that it is totally stress free and the barrel free floated from the recoil lug forward.
If this is done correctly, the only cause for a barrel walking shots as it heats up is from a stress relieving poorly done. It can also be caused by a bad blank that has defects, not all barrel steel is x-rayed, even though they may say it is.
A barrel cooler is a good thing when working up loads, but you can't use one while hunting, so just keep track of where your prints as it heats up.

Cheers.

I don't have a barrel cooler but I'm thinking I'll take a small battery air pump with me to the range today just to hurry up the cooling. I am planning on shooting some warm/hot groups as well because I definitely want to know if/what the variance is.

I am spinning knobs for drop, was thinking about zeroing cold barrel at 200 or even a bit longer. I won't be shooting over 400 on my upcoming hunt (cow elk and cow moose), just because I got tangled up fighting for a VLD load and ate up a lot of my shooting time with that. I'm not confident any longer than that for now.

Hopefully won't be an issue. We've done some heavy scouting and the numbers are way up there. Coupled with my friends father inlaw owning a big portion of the valleys I'm hunting in has me feeling relatively optimistic. I

 

[Mikecr]

I do a lot of cold bore testing, but for more than confirming zero.
I do it for best cold bore accuracy.

So what's the difference?
Let's say you have a solid 1/2moa hot grouping load. You take your first cold shot at the range and adjust your scope. A 2nd shot confirms. [you would do this off a bipod in the dirt, as you would in the field][I do it at 200 and 300]
A few hours later, or next day, you try again. How accurate is this shot?
Over 5 days you shoot a single cold shot each at the same bull, what was the furthest impact from center of mark, over those 5 shots?

Whether the gun is expensive or off-the-rack cheap, you might have anything here.
I've seen competitive level hot bore grouping guns that fared poorly for cold bore accuracy here.
And I've seen poor hot grouping guns that turned out very cold bore accurate.

Sometimes a 'problem' can be the scope. I had a NF NXS scope that caused a lot of excess testing for me. Hot grouped fine, cold bore wandering.. The ONLY way I figured out that it was the scope, was to buy another & swap them ($$$). According to NF, it was a lens bedding issue. They actually fixed it (same scope), 2 day turn around.

What I do is adjust powder for this, departing a bit from what was the best hot bore load.
This is adding a kernel at a time.
With that, I'll tighten the true cold bore accuracy.
You can use a 1" shoot-n-see dot at 200yds. Just hit the dot (seems simple), never miss it.
Same setup at 300yds,, 1" dot. 2" dot at 500.

Oh, unless you just want to add to the challenge, avoid 10min shot rate. Terrible..
Here & there I enter a local accuracy contest. It's a 3/4" dot at 200yds (what led me to this testing). You step up, drop your gun on sand bags, fire one shot, if you hit the bull you move to the next round. It's one bench, and with 50+ shooters it takes pretty much all day for one to win.
At round 10, we go closest to center & wrap it up. There is normally only a couple still shooting by then.
What I notice every time is that the late rounds cause ~10min shot rate, and every shooter does worse there.
Sunlighting has also shifted by then, and that throws shots out (somehow). Slight alcohol factor..
There is betting, and pig pickens, and booze, oh yeah

 

[FEENIX]

I don't have a barrel cooler but I'm thinking I'll take a small battery air pump with me to the range today just to hurry up the cooling. I am planning on shooting some warm/hot groups as well because I definitely want to know if/what the variance is.

I am spinning knobs for drop, was thinking about zeroing cold barrel at 200 or even a bit longer. I won't be shooting over 400 on my upcoming hunt (cow elk and cow moose), just because I got tangled up fighting for a VLD load and ate up a lot of my shooting time with that. I'm not confident any longer than that for now.

Hopefully won't be an issue. We've done some heavy scouting and the numbers are way up there. Coupled with my friends father inlaw owning a big portion of the valleys I'm hunting in has me feeling relatively optimistic. I

Very few hunters have an opportunity for a second shot on the same game, esp. on elk; this only happened to me once after nearly five decades of hunting. Your first two cold bore shots are what matters, not when your barrel is warm or hot unless you wrap your barrel to keep it warm/hot afield. There is no need to complicate things unnecessarily.

For what it is worth >>> https://www.bevfitchett.us/sniper-training-2/cold-barrel-vs-warm-barrel.html

 

[thatguyshm]

When the weather changes for hunting season the final test of my loads are to put the rifle and ammo in the truck or garage overnight, to let it get to ambiant temp and then go to the range in the morning, early as I can, to check for cold bore zero. If you freeze your ammo, you've only checked the ammo. I do that before final check. When the gun is cold too it will be more representative of that early morning cold weather hunt.

 

[nealm66]

Would really like to hear your results with the carbon fiber barrel. From my experience, stock and bedding improved cold bore changes. Would be interesting to hear your findings

 

[Evilsports]

Would really like to hear your results with the carbon fiber barrel. From my experience, stock and bedding improved cold bore changes. Would be interesting to hear your findings

I'm happy with the range results from this morning. I didn't find much of a variance between cold bore vs a five shot group. I heated it up more and ran a run of 7-8 shots and it might have walked a half minute.

Brought a temp gun and a small battery compressor and cooled the barrel to ambient between cold shots and set a solid zero at 200yds that I'm confident in. I'll go back next weekend and shoot 300yd cold bores for drop, but as it stands I was concerned about nothing.

The barrel was quite odd. I shot the inside and the carbon wrap on the outside with the temp gun. The throat and inside the barrel hardly seemed to heat up after a few shots, but the carbon outside would get warm. I was guessing that it was maybe dissipating decently, but I'm not sure.

 

[nealm66]

Excellent. Thank you

 

[Pro2A]

Good morning fellas. I'm going to load some shells up this morning and hit the range. Decent groups yesterday and today will be some cold bore zeroing.


I have a few questions...

How much POI walking from cold bore to warm bore do you typically expect? I'm zeroing for a cold/fouled barrel so I'm planning on firing at 100yd and then adjusting scope, waiting 10 minutes or so for a cool barrel and then shooting again until I can confirm cold zero. I'm planning on repeating at 200 and 300 to confirm drops. Does this sound like an effective/efficient process or do you sort it out some other way?

Load is shooting just fine with a warm barrel but I did notice a few slightly concerning first shot POI's yesterday when I moved from 100 to 200, and also from 200 to 300 and the barrel had time to cool.

Shooting 140gr TTSX with 60.5gr of H4831SC, 24" 8.7T Rock Creek carbon fiber barrel in .280 AI

Thanks,
Kevin

If sighting for your "home" turf with known, consistent shooting distances, maybe....BIG maybe, in my world.....zero at a range other than 100yds. But, if you travel, hunt other locations/conditions, IMHO zero at 100yds always. Allows zero confirmation at most outfitter camps.....most have 100 yd range for that....outfitter will have more respect. Atmospheric and other ballistic affecting parameters are minimal/non-discernible at 100 yds. As you work on cold bore consistency.....assuming that is your objective....at longer ranges, more of those ballistic parameters....one cannot eliminate them.....begin to sneak in muddling the data/consistency. Personally, for any reason, I've never understood the wisdom of zeroing at longer than 100yds.......like those Ballistic Turret thingys gizmos......sorta like ballistic hand grenades in my perspective. From 100yd zero, I can hold for ballistics....always for wind as it's too variable to spin......with known DOPE for out to maybe 300-500yds (depending on caliber specifics) for those quick opportunities. Longer shots "always" afford time to spin the turrets for necessary longer range accuracy. If, one does not have time to spin at those longer ranges, then one is merely throwing a Hail Mary round down range....IMHO....YMMV.