cold-bore-shot

The Cold Bore Shot

In Blog by Rich16 Comments

There’s a lot of talk about ‘cold bore’ shots in the precision rifle community. Hollywood has made the term popular and so many a new shooter finds themselves overly concerned with their cold bore shot. They want to know how the cold bore shot is different than other shots, and how to account for the difference to increase chances of a hit. The goals are all well and good but some of the information is a bit misleading. Having been involved with long range shooting for several years now we can discuss this and hopefully put some of the rumors and voodoo to rest!

The Cold Bore Shot Myth

That’s right, we’re calling it a myth. When I got started in precision shooting I thought this was something to be concerned about. After some training, many rounds of experience, and reviewing training material from knowledgeable folks at Sniper’s Hide and Rifles Only, we can pretty much call it what it is. This is a myth. As the story goes a cold barrel, unfired for the day or whatever, will exhibit a shift in point of impact from the zero. This point of impact is different from where the bullets land after the barrel has warmed up, so the myth goes.

Personally, I like Frank Galli’s take on this. He said something to the effect of, “If your barrel shoots to a different point of impact cold than it does warm there is something wrong with the gun.” That’s pretty blunt and pretty true in my experience. There is often a difference that you can see on paper with regard to where rounds impact on the first shot versus shots fired later in the day. However, as the folks at Rifles Only have termed it, what you really have to deal with is ‘cold shooter.’ The point here is that the gun is a mechanical device. There are things that will cause shifts but the barrel being warm or cold isn’t one of them.

Frank Galli even did a video to disprove it, burning through 20 rounds or so quickly after leaving the gun in the sun and dialing back down to zero. He put the final round right next to the initial round of the day. If this video doesn’t convince you this is a myth I’m not sure what will!

Clean Bore Shots?

There is such a thing as a clean bore shot. This is where some of the myth comes from. A barrel that has been scrubbed clean with solvents and patches and has a bore that is unfouled by bullets and powder likely will exhibit a shift in the point of impact initially. A barrel that has been ‘fouled’ by several rounds will usually have some copper, powder, and miscellaneous grit that works its way into some of the small pores and imperfections of the barrel. Having those pores filled will guide the bullet in a different way than a completely clean barrel. A clean bore may exhibit a shift in point of impact the first few rounds. After which it will settle in and stabilize.

This is also why the common recommendation is to avoid cleaning your barrel constantly! Every time you give it a good scrub you need to fire a few fouling rounds afterwards or you risk taking a shot that will be affected by the clean bore shift. We talked about rifle cleaning practices in our article on Cleaning a Precision Rifle. Generally I suggest you clean your rifle every 300-350 rounds or sooner if you notice accuracy degrading. Certainly don’t clean it after every shooting session when you get home or you set yourself up for a few rounds that aren’t going to go where they should, even with a good zero on the rifle.

Testing the Cold Bore Myth

This is another suggestion I have to give Rifles Only credit for, and it’s a good one. If you are one of these people that refuses to believe that cold bore shots are a myth give this a whirl. If you have a rifle you are convinced has a cold bore shift, bring it to your next range session. Set it aside. Shoot the first half of your day with another rifle, or a buddy’s gun, whatever. Come back to the problem rifle after you have had some shooting time logged and you feel pretty loose and warmed up and see how the problem gun shoots. Chances are it will shoot the way it always does. If it doesn’t, try having a buddy shoot your gun using the same process to test it. There shouldn’t be a temperature induced shift, if there is, you may need a new barrel because a properly assembled gun shouldn’t have this issue.

Other Shifts?

Another thing that may give you a shift in point of impact is shooting with a suppressor. This has nothing to do with the temperature of the barrel and everything to do with muzzle velocity and barrel harmonics. Shooting with a suppressor will often times give the rifle a small boost in muzzle velocity. Obviously, given enough distance, the difference in muzzle velocity between suppressed and unsuppressed fire will produce a shift in the point of impact. Additionally, you are affecting the harmonics of the barrel by hanging a suppressor on the muzzle. This happens by adding weight to the front of the gun. This shift should be consistent and repeatable but since we are talking about shifts in point of impact, we thought we’d mention this. We’ll talk more about suppressors and shifts in future articles!

Wrapping Up

The whole cold bore thing is a lot of myth and superstition. Don’t buy into the hype. If its too late and you’re already convinced this is true, try testing it and see if you can disprove it! At the end of the day, assuming you fired a few fouling rounds after the last cleaning session, your rifle should shoot the same on the first round as it does on the 200th round. If it isn’t, chances are that it’s the shooter that is introducing the difference. Try focusing more on the Fundamentals of Marksmanship! Videotape yourself at the range and see if you can see a flinch or slap of the trigger that isn’t there after you have warmed up. Like many things in the shooting world this really boils down to a training issue. If you train properly you can mitigate and eliminate the effect completely.

Owner and Proprietor of AccuracyTech, LLC. Rich is a Firearms Enthusiast, Precision Rifle Competitor, and Writer. He is committed to bringing readers quality reviews and articles related to the Precision Shooting Sports. If you have any questions for him, please use the contact form on the site.

Comments

  1. I know this is an old post but I thought I would mention that maybe some of this myth comes from Ammo Temp. In Arizona I notice a POI shift (long range) from when I start shooting in the morning to midday and my ammo warms up creating higher velocities.

    Something to think about.

    1. Author

      You can avoid that discrepancy with a 100yd zero and density altitude cards, but you’re 100% correct! Environmental shifts are at the basis of the myth, along with cleaning regimens, and a cold shooter

    2. I have noticed that with different powders in the same rounds and guns. say IMR 4064 is a moderately temp. sensitive compared to IMR 8028 XBR wich is a pretty stabil temp. powder.

  2. Cold bore shot with a suppressor that may be related to FRP?
    this was 100% reproducible

    gun AIAE MK3
    suppressor YHM Ti QD 308
    bullets are HBN coated…
    tested with 4 5 round groups, to see if it was FRP related, i took a 5 gallon air tank and blowgun with me…
    1st shot .9 to 1″ high from group center
    if i shoot another 5 after, they group with the 1st 4…
    if i blow 30sec of air down the barrel to clear gases from the can then shoot another 5, the 1st shot will be 1″ high.

    each time i did that, 1st shot was 1″ high..
    to me, that says FRP “1st round pop” is causing this… BUT… in the past with the same can on a different barrel, i didn’t notice this…

    what i would like to test, is if i preload the can with CO2 or canned air what will happen?..

    1. Author

      I sincerely doubt your can is causing a shift of an inch on the first round. Isolate some variables. Does it happen without the can? Does it happen on other rifles with the same can?

      Try doing 10 good dry fire presses before a live round, is there still a shift? Have somebody else shoot the rifle, still a shift? Etc.

  3. Just becouse it has not happend to you is no reason to doubt it…… Its very common in black powder shooting, in fact the first shot is usually only good shoot there. In this instance its about the bore condition.. still a cold bore shot..I was in black powder competition and most of the winnders cleaned between shots…… Ive noticed continually as i hate to clean guns that the first shot will get the gunk warmed up in my .223 rock river arms in condition to shoot just fine, To a point, every gun is different….
    The real stumper was my hk usp (clean or dirty with cold barrel ) would put first round about 4 inches right and the next three (four shot group) in very tight at 25 yards, inch and a half to two inches, four- five inch group with all four shots… I did everything mechanically i could to stop this but it would not stop..(mechanically means, crimp amount, powder amount, case sorting, gun cleaning etc, I read up on cold bore shot and finnaly looked thru my huge stack of targets for this gun and found two powders that did not do it.. Bottom line, tite group and some other powders would do it, and aa5 and power pistol would not… Changing powder and or sysematic cleaning can sometimes clear this up.. The semi auto forum on the fireing line helped me alot on this issue.. What i needed to do was search for loads that give me the smallest group, and smallest velocity deviations, and not worrying about first shot, last shot etc.. This will eventually get you to the best load for your weapon… dave

    1. Author

      There’s a lot of common myths out there that people continue to advance, it doesn’t make the myth true.

  4. I experienced this problem yesterday at the range. Testing new reloads; .308 Win, 22″ barrel (free floated), 1 in 12 twist, 130g Barnes TTSX, 46.1g TAC, Lapua brass, COAL 2.735″. First shot (Cold Bore), three inches high. Shots two and three, right on the money. I waited 20 min and shot again. Same results. The rifle typically prints sub MOA groups at 100 yards. The only thing new was the 130g bullet.

    No idea why.

  5. This is not an opinion, it is a matter of physics, metals expand when heated, the way a barrel is fitted to an action and the differences/similarity in metals used for barrel and action can also affect precision of bullet placement. Every weapon, pistol or rifle that has a cantilevered barrel (attached at one end) will react differently to different amounts of heat – these are facts, not myths! Fly in the ointment is, there are ways to minimize the difference, we mistakenly call these “accurate rifles” (they are actually precise!) anyway, cherish them, but even a precise weapon will fail when it becomes so hot the barrel deforms. The “myth” is only a reality is the weapon is sighted with only a cold barrel, otherwise you are tracking the change in zero. Being an engineer, and having over 50-years of shooting experience helps me know these things!!!

    1. Author

      There was a whole chapter on this in Modern Advancements in Long Range Shooting Vol. 2, and yes…with enough shooting heat will start to affect any barrel. However, the volume of fire you’re talking about to achieve that is fairly significant. 100+ rounds in 20 minutes. Of the barrels tested, the common contours had a variance of less than Half Minute of Angle. It’s a factor under heavy volumes of fire. Yes if you burn through a hundred rounds, then set your zero on a hot barrel, you’ll likely experience a shift with a cold barrel.

      Most people aren’t doing that and most people aren’t burning through 100 rounds in 20 minutes. However, we like to blame material items for our flaws before we look inward. If your first round shifts from your zero you’ve either got a case of cold shooter, a hot barrel zero, or there’s something mechanically wrong with the gun. For example screws on the base are loose, or a bad bedding job, or a barrel not cut straight. Something.

      Most folks tanking their first shot are doing just that, tanking their first shot.

  6. Any suggestions for helping me fix the cold shooter problem? Have you trained it out of yourself? Because like you mentioned I do shoot better once I am warmed up!

  7. Hi there. This is a bit off topic but I’d like to get your thoughts. I generally only get to shoot once a fortnight and if I miss that day it can be once a month. I have always cleaned after use and do find it takes upward of 10 rounds to get consistent although as you say 90 percent of that is the shooter. With regards to not cleaning the bore, how long would you say a gun can be stored like that? Im assuming alot of you guys are shooting multiple times a week? Can I leave it fouled for weeks on end without use?

  8. To a friend and pasted here:

    You and I have talked a bit about the muzzle velocity of the first round out of a clean barrel versus a fouled barrel. Many shooters when referring to this effect attribute it to a cold barrel. I think the low velocity of the first round of the first group is due to a clean barrel instead of a cold barrel as my testing described below indicates:

    The “cold barrel” comment is bogus in my opinion. The comment should be “clean barrel” or “fouled barrel”. A single round from a 6 mm cartridge does not heat a match barrel much, about 5-degrees F on average for a typical match load and match barrel. If the effect was caused by barrel temperature rise then then the muzzle velocity should continue to rise, on average, with each successive round fired relatively quickly but it does not. Last month I chronographed the load for my deer rifle, which I do not clean during hunting season, thus the first round was from a cold but fouled barrel. That first round was 1 f/s above the average of 10-rounds with the 6 th., 9 th. and 10 th. rounds firing bullets at muzzle velocities well below the first round. The first round out of a clean barrel is always the lowest muzzle velocity round. That hunting rifle barrel is 26” long and much lighter than the typical match barrel thus will heat more with each round fired.

    It is a fact that a flat base bullet heats more due to barrel friction than a boat tail bullet of the same caliber and same core weight.

    Why? The entire lead core mass of a flat base bullet, when exposed to the typical acceleration of about 100,000 to 200,000 g’s, goes into applying force to the inside of the jacket which then applies force to the rifle bore resulting in friction and heat. In a boat tail bullet only the core mass above the bearing/boat tail junction is in effect to increase friction through the method just described.

    Thus tests were conducted with 6 mm, 121 grain flat base bullets in a dry bore, wiped with clean patches, then patches soaked with a solvents to remove traces of bore cleaners, oils and the like.

    Result: 100% of the flat base bullets failed, i.e. spewed molten lead on a paper screen 20-yards from the muzzle or they fragmented when shot from a dry bore. A few boat tail bullets failed but not close to 100% failure rate of flat base bullets. That test followed by firing the same make of bullet, flat base or boat tail, immediately out of the now fouled barrel resulted in no failures.

    That shows that powder fouling is an excellent lubricant. Yes the powder is coated with graphite but likely most or all of the graphite burns with the powder.

    Then tests to find a lubricant to apply to a clean and dry bore that would work as well as powder fouling—none were found. Lubricants tried: Croil; several bore cleaners; powdered-moly; lubricating oil; Hoppie’s grease and bore treatments claimed to act like powder fouling to eliminating the low velocity of the first round. None of those “lubricants” worked as well as powder fouling. They did reduce the failure rate of the bullets but did not eliminate the failures as did powder fouling does.

    In chronographing thousands of rifle loads with precision chronographs it has been noted that the first round out of a clean barrel is always the lowest velocity round.

    Why? Because the bore is free of powder fouling and is coated with one of the “lubricants” described above and thus friction is higher than a bore with powder fouling, resulting in a lower muzzle velocity. A second effect is that the “lubricants” in the bore is evaporated, thus reducing gas temperature and pressure and reducing muzzle velocity somewhat. Once a round is fired the bore is coated with powder fouling thus reducing friction, resulting in higher muzzle velocities and reducing bullet to bore friction and bullet failure. However powder fouling can not save a bullet from failure that is fired in a barrel that has several thousand rounds of full loads fired in it. The bore in the throat area and just beyond the throat area becomes rough and combined with maximum gas pressure in that area creates enough friction to overheat the bullet, weakening the jacket, melting part of the lead core and resulting in bullet failure.

    I have probably around 100-targets showing failure of lead core bullets fired from dry bores and clean bores with many of them fired out of a 10” twist match grade barrel with well under 1000 rounds fired through that barrel.

    After many tests over the years and after writing the above message, a search was made on the internet for “First shot out of a cold bore”, turning up this site: http://www.accuracy-tech.com/the-cold-bore-shot/. It is easy to see that my findings agree completely with the information at the just named site.

    Henry Childs

  9. I own a .308 savage 1:10 bull barrel hs precision stock. I use the federal 168 sierra match kings. As most people know metal expands and contracts with change in temperature. If not research that instead lol. These magic barrels apparently don’t do that. Bore diameter is normal at ambient temperature as long as the temperature of the ammo matches. As your barrel heats up the friction will suffer the difference in the two. Mine expands after two shots then slightly reduces my initial friction in the barrel therefore a very minimal loss of velocity but enough to show beyond 300 yds. No one can tell me where to find these magic barrels that don’t shift down. But if I am a cold bore shooter i accept it. I can draw a straight line down through my holes at 600yds. If im a bad shot shouldnt i hit left or right of the target. I enjoy the sport of targets. Let your gun rest 5 min between each shot record your data and move on. Using this method should get you sub moa results.

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