I'm in the process of trying to teach myself "more precise" shooting with rifles and starting up reloading at the same time and I could use some insight into what I have going on with the group in the upper right hand corner of the target in the picture. The rifle in question is a Tikka T3 Stainless in .243. The load in question is Nosler 95gr Partitions over 40.5gr of Hybrid 100V. The distance is 100yds.

1) The six rounds that are just above the bullseye - is this coincidence or is this what the load or gun is good for?
2) I'm assuming that the loaner round above the group of six is my fault, is this a correct assumption or is this potentially a hotter round from poor loading attention to detail?
3) What do I make of the three rounds to the left of the target?

Was the one out by himself your first cold shot? That is what it looks like to me-my 243 does that if I clean the gun then shoot it, the first one is always a flyer.

But those three over at 9 o’clock could be you doing something about your hold. They are still pretty small group, just moved or you did something different (face closer to scope, grip too tight)

I have a factory barrel and it’s pencil thin, if I rip off ten rounds back to back the group moves or opens up. If I shoot a few and pour water across the barrel to cool it, it’ll stay in an inch.

I don’t remember the exact quotation, but paraphrasing something I read in a science journal, “The answer to puzzling questions is more data and experiments, not more speculation.”
A single shooting group doesn’t tell us much and therefore it’s important to shoot more to better understand what we’re trying to determine.

There are several possible reasons for the type of result you got.

I have come to distrust the “cold bore” explanation for a single shot out of a group like that. As one competitive shooter here remarked, “There are no cold bores, just cold shooters.” That is, it’s common for shooters to throw initial shot(s) because they haven’t settled into the position that will be used for subsequent shots. Since I’ve heeded that comment and have made a concerted effort to ensure I’m in the proper position and using the proper marksmanship techniques from the beginning, my “cold bore” flyers have all but disappeared, especially when shooting from a solid bench rest. If “cold bore” POI shifts occur, they would actually be more noticeable in a situation like that.

But even if the phenomenon does actually exist (at least sometimes), it’s more likely to be due to the condition of the barrel, i.e., oil and/or solvent residue than its temperature. If the barrel has been previously fouled with a number of shots and then a new string is fired and the first shot is out of the group, that’s almost certainly (IMO, of course) due to shooter error. If the barrel is perfectly clean for the first shot with no residues, the POI could conceivably change with multiple shots, but it will probably take more than one to get things to settle down.
Likewise, according to Bryan Litz, heating a barrel due to extended firing can affect point of impact, but it requires much more than a single shot.

If there is a break in position during a string that can also result in a clustering of shots outside a preliminary group. That’s something else I’ve confirmed for myself.

And as for a loading difference being the reason for the high, out of group shot, I ran some figures for that bullet under standard atmospheric conditions. If the velocity of the group was, for example, 2650 fps, to result in a point of impact about 1 inch higher at 100 yards and all else being equal, the velocity would have to be about 3400 fps, and I doubt anything you could do with loading would result in such a higher muzzle velocity. Minor velocity differences have much less effect at close ranges than we may think.

quote:

2) I'm assuming that the loaner round above the group of six is my fault, is this a correct assumption or is this potentially a hotter round from poor loading attention to detail?

In general, a higher velocity round will impact lower, not higher. This is due to the bullet exiting the muzzle sooner in the recoil cycle.

If a gun is able to move a significant amount during recoil, it’s possible that a more powerful load will result in a higher point of impact. An extreme example in my own experience is shooting a hot cartridge from a S&W model 340PD revolver. It has a very short barrel and the projectile’s time in the gun is extremely short, but due to the gun’s very light weight (not to mention its small grip) the recoil causes the muzzle to rise significantly before the bullet leaves the barrel and the point of impact is also high.

The time the bullet is in the barrel may have an affect on the point of impact with a freely-recoiling gun, but I find it hard to believe that it’s greater than the recoil itself that affects the movement of the gun.

In any event, I also believe that the variations in cartridge power due to minor load differences are unlikely to have significant effects on points of impact at close distances (e.g., 100 yards). There are many other variables ranging from the quality of the bullets to shooter skill that are more important.

If, however, there is something that demonstrated my belief is wrong, I would be very interested in seeing it.

quote:

Originally posted by MikeinNC:
Was the one out by himself your first cold shot? That is what it looks like to me-my 243 does that if I clean the gun then shoot it, the first one is always a flyer.

But those three over at 9 o’clock could be you doing something about your hold. They are still pretty small group, just moved or you did something different (face closer to scope, grip too tight)

I have a factory barrel and it’s pencil thin, if I rip off ten rounds back to back the group moves or opens up. If I shoot a few and pour water across the barrel to cool it, it’ll stay in an inch.

Your pencil thin barrel comment has me wondering a bit now. So, the day started off with the 5 shot group in the middle, 5 shot group in the lower right, 5 shot group in the lower left, and then the 10 shot group in the upper right. The typical cadence would be to get 7-8 shots off before the line was called cold, check targets, and then get another 7-8 shots off, go check targets, repeat. I'll usually grab my barrel after I check my target and see if it's warm or hot and usually not resume shooting until it's just warm. However, I always start shooting the smaller charges first on my reloads to check the empty brass and see if the brass show any signs that would make me not want to shoot the next higher charge amount. Since my groups typically open up as my amount of powder had increased I had just assumed that my barrel didn't care for the higher velocities, but now I'm wondering if the cause was more that I typically have a colder barrel for the lowest charge weight and in theory a hotter barrel for the highest charge weight.

quote:

Originally posted by kkina:
In general, a higher velocity round will impact lower, not higher. This is due to the bullet exiting the muzzle sooner in the recoil cycle.

Not in my experience with both AR15 and bolt action rifles.

Lighter, higher velocity loads may exhibit a POI that is about the same as the slower, heavier bullets at 100 yards. Or they might be a little higher. As the MV difference increases, the more likely the bullet's POI will be higher. I've really noticed this with Hornady's Superformance loads, which used the same bullets, but with MV increases of 100-200 fps.

When I've chrono'd ammo, I see no difference in POI at 100 yards which can be attributed to MV changes of 10-30 fps, which is the ballpark of MV variation seen in factory ammo.