In shooting two different AR15s at 300m today, both had a horizontal dispersion of 4", and a vertical dispersion of 9". I shot one five shot group with each rifle. Both had 1/5 shots hit about 3" higher than the upper-most hit of the rest of them. I have no way of knowing whether or not this outlier was the first shot, but that's what I would guess, if I had to bet on it. It's worth mentioning that the first shots were on cold bores; not cold/clean bores. Could the presence of more oxygen in the bore and silencer on the first shot make for a hotter round? This person experienced a similar phenomenon, which he attributed to moisture...
https://www.snipershide.com/sh...sible-cause.6979238/

Before people jump down my throat, I am not seeking excuses for groups that I thought should have been tighter. Consider the question in the context of a very controlled environment, where we know these outlying high shots were the first rounds fired.

An interesting question I’ve given a lot of thought to, but I’ve never seen any discussion like the one you linked, so thanks for that.

I’ll have to ponder things a bit more, but as one poster in that linked discussion pointed out, it’s virtually impossible for changes in external humidity to affect the burn rate from one cartridge to the next. But humidity could affect the conditions inside the barrel.

For starters, though, I’ll mention that as one contributor here put it, there are no “cold” bores, only cold shooters. I.e., depending upon the shooting position and other factors, if we’re not set up the same way as we settle in for subsequent shots, that could be the actual reason for a point of impact shift. I believe that I myself have experienced the phenomenon and therefore now make a concerted effort to ensure my position, etc., are consistent and stable when starting a string of fire, and it’s helped.

I have no way of knowing whether that could be at all responsible for what you experienced, but it’s something to keep in mind.

In either case: The first round POI is mechanically altered by conditions outside the shooter's control, assuming the shooter doesn't hold to compensate for a known first round POI phenomenon; or the "cold shooter", himself, causes the first round phenomenon; is that first round discounted, in assessing the "system's"(shooter included) accuracy potential? If a shooter fires ten rounds, and one of them doubles the group size, due to a known and repeatable first round POI phenomenon, is it excluded from the measurement?

Edit: If the cause is known to be the shooter, can the first shot be discounted in gauging the rifle's accuracy potential? If the cause is known to be outside the shooter's control, can the first shot be excluded in gauging the system's potential?

Yes, in fact for me shooting a Mini-14, it's always the first two shots, and pretty consistently. The first shot out of a cold bore would be offset about 4"; number two would be 2", and then any successive rounds would hit point-of-aim, unless I allowed the barrel to cool down in which case the process repeats.

All the data I've published while doing R&D for the Accu-strut are based on warm bore. Not stone cold, neither extremely hot bore from any kind of rapid fire. About a minute between shots.

quote:

Originally posted by KSGM:
If a shooter fires ten rounds, and one of them doubles the group size, due to a known and repeatable first round POI phenomenon, is it excluded from the measurement?

Not if we’re depending on the precision and accuracy of the other nine shots to tell us where we’re going to hit.

As I say, I’ve given this issue a lot of thought.
First, many people, including the Army Marksmanship Unit believe that the first shot POI shift is a genuine phenomenon independent of the shooter; there’s at least one video that supports the contention. On the other hand Army sniper policy was that the sniper should fire at least five shots before going on a mission. That may take care of any POI shift problem due to a clean bore or due to something like solvent residues. That practice, however, does nothing if the problem is caused because the bore isn’t warmed from subsequent shots.

In addition, experiments conducted by Bryan Litz support the contention that any POI shift isn’t due to actual warming of the barrel with a single initial shot. His experiments demonstrate that POI shifts can occur with long strings of fire, but that’s with tens of rounds fired very quickly. For most barrels, there should not be enough heating to affect anything from the first shot to the second. What’s more, if one to two causes a major shift, then why none at all two to three, three to four, etc.?

In my opinion, if there is a genuine cause for first shot POI difference, it would be due to the presence of lube, solvent, or other substance in the bore. The linked article blames it on condensed moisture, and seems to support that idea with the breath experiments. I live and shoot in a high, dry environment, so if I can eliminate first shot shifts by other means, moisture may not be something I need to worry about.

I usually clean the bores of my precision rifles after every range session, even those of just a few rounds. For a time I was concerned about the effect of solvent residue on first round POI, and would scrub the bores with 99% isopropyl alcohol before a session. I then tried shooting without doing that, and as long as I did my best to eliminate the “cold shooter” effect, I found that was unnecessary. It’s still probably a good idea, especially if using a solvent that has some lubricating and/or rust prevention characteristics, but I finish up my cleaning sessions with TM Solvent that reportedly has neither and then remove any excess with dry patches at the end.

I first became interested in this question in connection with the issue of law enforcement sniping. Unlike the competitor who can fire a number of “sighters” or even just into the berm, or the military sniper who can crank off five shots before moving into position for the day, the LE sniper must have confidence that her first, and hopefully only, shot will go exactly where she wants and expects it to. The LE sniper admittedly usually has the advantage of shooting a much closer ranges than the competitor or miliary sniper, but the consequences of a miss are also usually much greater.

A couple examples (of many) of “cold, clean bore” 100 yard groups that I’ve posted before:

308 Winchester




6.5 Creedmoor




And I will add that the rifle may have a significant effect on whether the phenomenon occurs. Even the bedding can affect whether the receiver and barrel stay in place after the first shot. My thought and research have been about rifles suitable for long distance precision shooting.

Another observation. I reread the topic title and noted that the question was originally about the semi-auto rifle. I haven’t seen any claims about rifles, but at one time there were shooters of semiautomatic pistols who believed there could be a significant difference in POI from first to subsequent shots. A long time ago on a different forum the question was raised, and the owner flatly denied that it occurred. My response was that when I had a Colt Combat Elite in 45 ACP, it was something I experienced to such a degree that it prompted me to sell the gun. I didn’t have the handgun shooting skills that I do today, but the effect was so great—3-4 inches at 7 yards—that I’m still confident it was genuinely the fault of the gun and not me. I’ve never seen it raised about AR type rifles, but could there be some difference in how the first manually-chambered round would have a different POI than the rest? I strongly doubt it, but ….
Any thoughts?

I don't think something like an AR is affected in the same way an automatic handgun potentially is. I specified semi-auto in my title because that is what I was using today, and I think that, of course, by their very nature, a semi-auto enables a quicker firing cadence, and is more often applied in circumstances that call for such a cadence. The quicker cadence obviously exacerbates heat build-up and post-shot bore atmosphere retention between shots, which are two potential culprits of POI shift after the first shot. The severity of potential shift phenomenon is likely also influenced by a semi-auto's operating system and/or construction though; kkina's experiences with Mini14s may be evidence of that.

My father-in-law and I were contemplating dusting off his chronograph the other day, and this discussion further motivates that. I am curious as to the viability of my bore atmosphere theory, especially when a silencer is in play. The internal volume of a silencer has quite the supply of oxygen to potentially boost the velocity of that first shot, before subsequent shots are left to travel through the oxygen-starved silencer cavity.

I completely agree, when it comes to the LE sniper, and I applied that mentality when gathering dope for my AR10. I was patient, and insisted that every round I fired was "cold bore", because that's what I wanted for that gun: I wanted to be able to use a laser range finder, and use that information combined with my dope, to attain a first-round-hit. So far, it has proven effective. However, I have not grouped that gun, since gathering the dope. I grouped it to narrow down the ammo that was most accurate and consistent for me, but I have not grouped it to determine if there is a meaningful shift after the first shot. It's been on my to-do list, but that ammo ain't cheap.

I don't know that it has a bearing on the progress of this discussion, but you could say there are two contexts, when it comes to the first round shift phenomenon: The LE sniper context, where you need to know your cold POI, to make that first shot count (and know your shift afterwards, if follow-ups are required); and (perhaps) the general tactical context, where you have a more conventionally-derived zero, but ought to know your first-round POI phenomenon, if a precision shot on a "cold" bore is required.

My work AR15 11.5” barrel has a different poi every time. Not much but, it’s there. When I was one of the snipers for my agency my Remington 700 police had a different poi for the first clean bore shot. It find the matter if the weather was hot, cold, wet, or dry it was almost an inch high and half an inch right. Everytime. Like clockwork. No biggie. You just took it into account.

Now M1 Garands are notorious for putting the first round in a different place than the rest of the 7 shots. The old timers explained it was because of the first round being cycled by hand the rest the action/rifle was doing the “feeding”. I suppose the same can be said with other auto loaders as well.

I have multiple AR-15 rifles/uppers in 223, one in 300blk, one in 9mm. I have AR-10 rifles/uppers in 6CM and 6.5CM. I've shot a few other calibers, and have buddies with more still. For many years I've shot suppressed only, with my Surefire SOCOM and Thunderbeast cans. All my rifles have quality barrels with proper chambers. With quality factory ammo, they shoot with great accuracy. The only time accuracy suffers is when I use FMJ ammo, which is reserved for short-distance targets, limited stability shooting positions, and rapid shooting.

In my early days of rifle shooting, I did not possess the fundamentals to accurately call my own shots. As I have improved upon those fundamentals, I am better able to determine when wayward accuracy is due to me or equipment/environment.

I do see some levels of unexpected POI shift with cold/clean bores. It's minimal on most of my barrels. I don't recall in recent years a POI shift for the first shot (or first few shots) with a fouled cold bore. This is for quality ammo, out to the practical targets distances for a given rifle -- meaning out to transonic distances.

I do see unexpected POI shifts when changing ammo types, and it can take quite a few rounds for accuracy and POI to settle down. I have seen quite a few WTF flyers from FMJ ammo, and that's why I just won't use it when accuracy counts.

I suggest your positively confirming which shot of a given string produces flyers. Guesses are often wrong. Use quality ammo. Shoot from stable positions. Document results over multiple days, in different weather.

quote:

I am better able to determine when wayward accuracy is due to me

I admittedly have yet to master this craft. I find myself getting better at it, but it's still got a ways to go.

quote:

I do see some levels of unexpected POI shift with cold/clean bores

So, the "cold bore shot" of precision rifle lore, and the LE sniper context presented above, has actually always been more specifically about cold, clean bores? I suppose it makes sense, as a LE sniper's rifle may sit in the armory for extended periods, and it wouldn't be good to leave it in a fouled condition. This bodes well for my particular AR10 though, as I gathered dope with "cold" bore shots, not cold/clean bore shots.

quote:

I suggest your positively confirming which shot of a given string produces flyers. Guesses are often wrong. Use quality ammo. Shoot from stable positions

I intend to. The ammo should be good: Sig 5.56 77gr OTM. The position on the day these observations were made was prone, with the front end of the rifle supported by the edge on a barricade. So much of my shooting lately has been impromptu and squeezed in around other obligations, that I seldom have the time or wherewithal to be properly set up. I'll try to grab a rear bag next time.

Thank you for your notes, fritz.

quote:

Originally posted by KSGM:
a LE sniper's rifle may sit in the armory for extended periods, and it wouldn't be good to leave it in a fouled condition.

Not in the context of LE sniping, but I have seen much more discussion of not cleaning rifle bores too often than cleaning them after every session. There are Internet references to “good copper” and many claims of shooters’ firing many hundreds of rounds and cleaning their bores only when there is a noticeable drop off in accuracy. Some shooters say that after they clean the bore thoroughly following an extended period with no cleaning, they have to fire the gun 20 or more times to get it back to peak precision.

If all that plus the fact that many casual shooters seem to take pride in not cleaning their bores at all means anything, I don’t believe that leaving a bore fouled has any harmful effect except making the fouling harder to remove when it is cleaned.

As a side comment, I believe that most LE snipers keep their rifles in their possession when not in use. There are clearly some exceptions, but having to go to a central armory to draw the weapon just increases deployment times in situations that need quick response. If an LE sniper’s rifle must be stored in an armory, it’s a cardinal rule that it must be secured separately so no one else has access to it.

Short answer is yes, and is generally predictable.

For whatever reason.

I almost always clean my ARs after a day of shooting -- clean & lube the BCG, and run wet patches down the bore until carbon residue is minimal. Which means the majority of my first shots of the day with ARs are with clean cold bores.

At the home training location, I tend to shoot the first shots of the day from prone. I have 2 commonly used shooting locations where I keep most of my barriers. Once I've done a few rounds from prone to confirm that dope is still good, I generally switch to shooting from the barriers. I almost always place steel targets at 2 locations with good berms, then add additional target locations as I see fit. My primary targets locations result in distances of 320 & 440 yards from the forward barriers, and 340 & 460 yards from the rear barriers. The majority of the time my initial cold clean bore shots with an AR15 are at 320 yards.

Ammo for these initial shots is generally Hornady 75 Black HPBT or Federal GMM 69. Sometimes it's Hornady 55 Vmax or a load that uses 69 SMK bullets. Regardless of which AR15 I'm using, if my vertical dispersion is more than 3-4 inches at 320 yards, something's wrong. Usually the problem is me. Rarely is there a pattern of flyers from a round count standpoint. It's often that I've worked pretty hard around the ranch earlier in the day and I'm not yet in shooting mode. When I dry fire a bunch before going to live ammo, my cold clean bore vertical dispersion tends to be quite small. Hence the cold shooter challenge.

After a course of fire, I almost always walk to the steel targets to repaint and/or reposition. Being on a ranch, that generally means shovel in hand, and a circuitous path out and back to inspect/work the pasture. Such that in almost all but the hottest of summer days, I'm back to cold (but fouled) bore for the next course of fire. I don't see noticeable changes in the way my rifles shoot with subsequent courses of fire.

Thank you for correcting me on LE sniper rifle storage protocols, sigfreund. That, of course, makes perfect sense. As for the cleanliness of the bore, I guess this thread was never about that, as my bores weren't clean on the day that inspired the discussion. They were cold; I was cold.

Fritz, in saying this in your first reply:

quote:

I do see some levels of unexpected POI shift with cold/clean bores. It's minimal on most of my barrels.

, and this in your second:

quote:

if my vertical dispersion is more than 3-4 inches at 320 yards, something's wrong. // my cold clean bore vertical dispersion tends to be quite small.

, are you saying that the minimal "first shot phenomenon" POI shifts that you see are still inside a ~five inch diameter group, along with the following shots? at 300 yards? I got the impression, from your first reply, that you do see the phenomenon, though it is always small, and perhaps only with certain guns/ammo. Your second reply seems to imply that the phenomenon doesn't occur outside the shooter's control. I know you're an experienced shooter; are you of the opinion that the "cold bore" shot is a myth? If not, then what are the factors that make it real? It seems to me, based on this discussion, that a trained shooter ought not fall victim to the "cold shooter" phenomenon, and any known consistent mechanical anomalies unique to the first shot should be able to be taken into account, to make for a predictable first shot impact point.

I intended to chrono the first and second shot out of the same two rifles I shot yesterday, this evening, and I did try, but, in my chrono ignorance, I didn't know that the waning light of evening would present a problem in detection of the rounds passing through the hoods. So, I wasted some not cheap ammo, thinking I was doing something wrong with the equipment, when I was likely doing everything right, but in the wrong conditions. I hope to try again tomorrow morning, or perhaps Sunday.

Edit: Accomplished chrono this morning, and my bore/silencer atmosphere theory is certainly bunk. I believe the only example with the notable difference is a fluke. The ammo ought to be consistent, but the chrono is at least thirty years old. However, that gun does have the largest silencer internal volume, so who knows. Either way, I saw the first shot phenomenon across both guns the other day, not just the one. Results are as follows, for those interested. Ammo is 77gr 5.56 Sig OTM. My question to conversation participants is, if that one recording is not incorrect, is a 40 ft/sec difference enough to see a different POI at 300m, with that ammo weight?

11.5" with carbine gas and HALO GMT
1st 2562
2nd 2557
14.5" with mid gas and OCM5
1st 2759
2nd 2718
16" with rifle gas and Trek-T
1st 2796
2nd 2789

This message has been edited. Last edited by: KSGM,

I am interested in your further input, Fritz.

Mention of the chronograph measurements prompted a “Duh!” moment for me. I had simply forgotten the fact that I’ve examined the clean bore question from that perspective before and concluded that velocity figures should be the final answer to the question of whether the internal ballistics of a shot are the cause of point of impact differences between the first and subsequent shots in a string. In other words, if the cleanliness of a barrel affects the velocity of a shot and that’s why there is a major POI shift, then the velocity differences should be obvious.

Below are the recorded velocities, including the first cold bore shot, of a 10 shot string using Hornady 147 grain ELD Match from a Tikka T3x rifle chambered 6.5 Creedmoor. According to my records, I had not cleaned the bore after the previous 25 rounds on earlier days. The average of all shots was 2659 feet per second, its extreme spread was 39 fps and the standard deviation of the lot was about 13.2 fps, both of which were not too bad for precision shooting.

2676
2641
2661
2664
2655

2676
2669
2657
2653
2637

Now, the groups:





The first shot fired from the prone at 100 yards hit significantly higher than the next four in that group, or than the next five in the second group.
Note that the first shot that hit high had a highest velocity of 2676 fps, or 17 fps greater than the average. But the sixth shot had the same 2676 velocity, and the lowest velocity of 2637 was 22 fps different than the average. Coincidently, both the second highest-velocity shot and the lowest-velocity shot were in the second group that measured 0.697", or ~0.67 MOA, well under Tikka’s guarantee for five shot groups for that rifle. Further, I have fired much tighter groups whose individual shots had significantly greater extreme spreads than 39 fps.

It should be obvious that the first extremely high impact was not due to the bullet’s velocity and which in turn could not be blamed on the fact it was the first shot from a cold barrel. In fact, I later decided that it might have been because the bipod hadn’t settled into its final position in the dirt as completely as when firing the rest of the shots. Or it could have just been the cold shooter’s fault.


I’ve consistently found in measuring the velocities of shot strings that the velocities of first shots even from clean bores are usually well within the extreme spread, and for the first shot of the above string to be right at the maximum is unusual. I usually have not been recording velocities when I’ve had problems with the POI of a first shot and therefore cannot be certain that a huge velocity variation was never the cause, but it would be quite a coincidence for the velocity to vary so much in those situations, and not when I was recording velocities.

My point is that if you have a chronograph and you’re experiencing extreme first shot POI shifts, see what the velocities of those first shots are and compare them with the rest. Keep in mind, though, that measuring only the first two shots won’t tell you much if they’re far apart. The question will be how the first shot compared to the overall average and extreme spread of velocities, not just to the second shot. If your first shots are close to the averages and within the extreme spreads, and other shots with velocities close to the first shot’s don’t show the same POI difference, what should that tell us? If two shots with the same velocity hit in largely different places, the cause wasn’t because the barrel was clean for the first, and not clean for the second.

(If you disagree with that last statement, please explain why I’m wrong. Thank you.)

quote:

If you disagree with that last statement, please explain why I’m wrong. Thank you.

Hell, I defer to you. All my musings are largely speculative. Folks like you and fritz are on another level. I am here to learn.

I think it's interesting that fritz implies that a first shot shift isn't a thing; at least not a thing of real significance. The cold shooter phenomenon is interesting to me. It certainly makes me want to really look hard at what I am doing. In talking to a couple other shooters about it over the past couple days, it seems people do subsrcibe to the theory that the first, manually cycled round in a semi auto can behave differently than subsequent shots. One fella I talked to, who has shot benchrest stuff for years, swears that it can be a thing in bolt guns as well. He says most of his guns do not expereince a first round shift, but one does; every time.

This message has been edited. Last edited by: KSGM,

quote:

Originally posted by KSGM:
I am here to learn.

My previous post was not specifically directed at you, and especially not the last.
My interest in a subject is often piqued by something and I go off into an explanation of my thinking that may be on a tangent from what it was that prompted it.

I would be interested in what anyone thinks about my belief that if only the condition of the bore (clean/not) affects the POI shift for the first shot, the velocity would have to reflect it.
On the other hand and even though I haven't really mentioned much about it, I believe/wonder if the bedding of a barrel allowed the barrel to shift when that first shot was fired whether that could be the cause of the issue. I don't see how that could be possible in an AR type rifle, but possibly traditional bolt actions in wood or even some synthetic stocks—?

I think "settling" could occur after the first shot in an AR as well. If the barrel to upper fit had any degree of jiggle, when the gun was assembled, there could be a similar effect to what you're referring to in a bolt gun action's marriage to it's stock.

I intend to pay special attention to the elimination of my "cold shooter" influences, from here on. I'd likely learn a lot about this topic, if I group the AR10. I know my "cold bore" shots are going to go where I want them to, but what of follow-ups? I guess I agree with fritz, in a way: There ought not be any such thing as a first shot phenomenon, because we ought to shoot well enough to negate any potential cold shooter effect, and, if your rifle does have a known unavoidable mechanical first shot deviation, you ought to know it, and apply a proper hold to cancel it out.

My knowledge of the craft is many years old. I start out my LE Special Operations career as a sniper. I actually wore out a rifle barrel over a period of about six years. I got to go to a bunch of schools. I got to shoot a lot. It was all bolt action, however.

On a bolt gun, the only significant POA/POI shift started when the throat started to really erode. I was at a course and a delta guy told me “a dirty rifle is a happy rifle”. After that, I started training, then I would clean it, and then I would fire 2-3 rounds to “foul” it. This minimized the amount of cold bore shift.

Some of my guys are training with some 5th group guys a couple times a year. According to what I’m being told, they are telling them to not worry about “cleaning” the bore. Just the chamber. They claim they get much better accuracy that way. Just what I’m being told.

quote:

Originally posted by jljones:
On a bolt gun, the only significant POA/POI shift started when the throat started to really erode.

That is something to consider that I hadn’t, and perhaps could explain what I was questioning.
If the bullet is damaged or otherwise affected by the erosion that may include other changes to the throat, then fouling may help mitigate the effect. In that case perhaps the velocities of bullets fired with fouled and unfouled throats might be the same, but there would still be POI shifts between the two.

Part of the problem, however, with analyzing the issue is that there are so many possible variables that are usually not known in detail when evaluating someone else’s experiences. In addition there are reported experiences that just defy explanation by the condition of the gun. I consider the example I posted above to be one. There was virtually no difference between its condition when the first shot was fired and then the following nine, and I couldn’t even blame it on an eroded throat because prior to that string the rifle had been fired (by me, the original consumer) 433 times, usually a few rounds per session, and never rapid fire. And in addition, my first round shifts with that rifle have largely disappeared since I’ve been paying more attention to my shooting positions.

In any case it’s an interesting question.