I am sure many of you have experienced this before.

You get one rifle, that seems to shoot different loads, and different bullet weights, to the same point of impact at 100 yards.

Then you get one rifle that seems to throw its groups all over the target as soon as you change powder or bullet.

I wonder if anyone has any theories on this??

I would have thought there are any number of contributing factors, that can be accredited to this.
From metallurgical compounds changing within an individual pour of steel, to it's distressing prior to or following the profiling/boring and rifling (button,cut,hammer forged) process.
In cheaper barrels there is also the problem that some come with the bore far from central within the barrel profile, which I can well imagine will make a real mess of trying to balance any given load with another....
And then there's always.... Murphy

Saeed:

Yes I have ideas. Thanks for the invitation to comment.

I went into this very extensively many years ago and it is quite involved.

* Barrel type and construction.
* Bedding.
. Barrel harmonics.

X Bullet type and construction.
X Type gunpowder.
X Amount of gun powder.

& Caliber
& Case type

There are some calibers that have proven to be inherently more accurate than others, and less sensitive to variation. In other words more stable. The 6mm PPC is the renown grand champion more accurate than any other caliber.

By observation some of the smaller calibers seem to be inherently more accurate than the big bore heavy duty calibers in the upper echelon.

There is a whole lot more but two salient features seem to be barrel harmonics and the combination of bullets and powder.

I went over the load data here on your site rather extensively and as you are the first to now it changes dramatically from load to load in the same rifle.

Rifles can be sent to gunsmiths for "accuratizing". However, if one particular rifle is acting erratic, cantankerous and troublesome then best just get rid of it.

One mystery that perplexes me is - fliers. Sometimes I get them and sometimes not. Just haven't figured that one out yet. Or I should say more specifically - I haven't as yet figured out how to get fliers under control and remedied. From what I gather bench rester's shoot 3 preliminary shots to clear the barrel and heat it to uniform temperature.

Kindest Regards and Best Wishes:

Bill Tibbe

I do have a theory....except that I believe it's been proven by all of us. "Each rifle is an entity unto itself".

In my experience, the thicker/stiffer the barrel is, the more likely it is to shoot different loads close to the same point of impact. A theoretical, perfectly stiff barrel would exhibit only vertical stringing due to differences in time of flight; there should not be any horizontal separation between different loads. I have some heavy-barreled rifles that behave almost like that.

Gremlins, Saeed. That and differences in machining tolerances.

quit using walters blaser

I've noticed this on occasion. I've attributed it to differences in barrel quality, a non-trued action, and/or subtle differences in bedding. Sometimes it will go away when the rifle is re-bedded and/or the action is trued-up by a good gunsmith. Sometimes it will go away by adding a fixed pressure point further down the forend. Sometimes it only goes away when you get a new first-rate aftermarket barrel.

A case of split personality...



I have 2 barrels for my Sauer 202, one in 7x64 and another in .30-06.

The former's petload is 160 SGK/N 160 x 56.0 AND CCI 250 primers (std. primers produce oval groups and this barrel demands magnum primers).

Same rifle with .30-06 barrel. Pet load is 165 SGK/N 160 x 60.5. WLR or other std. primers OK ?!?

Also, I have 2 .300 Win Mag rifles : a Blaser R93 and a Rem 700 Sendero. The Blaser insists upon CCI 250, while the Sendero accepts any magnum primers (it will even group very well with mixed brands of Mag primers)...

Go figure...

quote:

Originally posted by Saeed:
I am sure many of you have experienced this before.

You get one rifle, that seems to shoot different loads, and different bullet weights, to the same point of impact at 100 yards.

Then you get one rifle that seems to throw its groups all over the target as soon as you change powder or bullet.

I wonder if anyone has any theories on this??

Yes, I have two 270W - 1 shoots most all 130s, 135s, 140s and 150s into a small group. The other is very finicky.

And Yes, I have 3 general theories. Two are already listed above = Barrel thickness and barrel harmonics. The 3rd is groove diameter verses bullet diameter.

The one most important factor I've found in getting this 2nd to group is bullet. In This rifle - Its not the bullet weight nor is it general bullet design, As different bullets at the same weight and the same flat base design can group from as larger as 2 1/2" down to 1/2"!!!

But that also shows that, with the right bullet, that 2nd rifle can group very well, too.

Good juju vs Bad juju.

Bedding, barrels and luck. Heavier barrels tend to be less finicky, and I've cured quite few finicky rifles by bedding with forend pressure. Since its barrel whip that changes the close range POI, dampening it a bit with the stock can help.

I've always been confused by the "third shot" flier. For example, "every time I shoot my rifle, the first two are touching and the third is a little off." How does the rifle always know which shot is the third? Do they count? I've heard many, many people say this exact same thing, but never understood it.

upon firing, the barrel acts like a tuning fork.

A good true barrel in a good true action bedded well will always shoot more consistently and shoot well with more combinations than something that is....well....not as true....


.

quote:

Originally posted by BaxterB:
I've always been confused by the "third shot" flier. For example, "every time I shoot my rifle, the first two are touching and the third is a little off." How does the rifle always know which shot is the third? Do they count? I've heard many, many people say this exact same thing, but never understood it.

I have experienced this same thing and found it perplexing. Even where the 'flier' wasn't predictable in the shot sequence. But the grouping would be consistent and repeatable; two touching and one an inch away.

And then I got even more perplexed when I got a chronograph. Two different powders would give me the same MV with the same bullet but one load would do cloverleaf groups and the other 2 MOA. I get the barrel harmonics/vibration thing with the pressure curve being different.

Now that I've mellowed and matured, I find a load that shoots good and call it good!

quote:

Originally posted by RaySendero:

quote:

Originally posted by Saeed:
I am sure many of you have experienced this before.

You get one rifle, that seems to shoot different loads, and different bullet weights, to the same point of impact at 100 yards.

Then you get one rifle that seems to throw its groups all over the target as soon as you change powder or bullet.

I wonder if anyone has any theories on this??

Yes, I have two 270W - 1 shoots most all 130s, 135s, 140s and 150s into a small group. The other is very finicky.

And Yes, I have 3 general theories. Two are already listed above = Barrel thickness and barrel harmonics. The 3rd is groove diameter verses bullet diameter.

The one most important factor I've found in getting this 2nd to group is bullet. In This rifle - Its not the bullet weight nor is it general bullet design, As different bullets at the same weight and the same flat base design can group from as larger as 2 1/2" down to 1/2"!!!

But that also shows that, with the right bullet, that 2nd rifle can group very well, too.

After reading the other responses and thinking some more about my situation; I'd like to add 1 more theory:

A possible interaction between throat dimensions and bullet jump into the riflings.

It's all about the harmonics of the barrel IMO, and no two are ever exactly alike. I do bed the action on all of my rifles, even if it's just a skim bed, if nothing else to eliminate this potential problem from the equation. I've also found that free floating barrels seems to be the way to go IME. After torquing all the screws to spec, paying extra attention not over torque the rings/base screws (most people waaaay over torque these). After that, it's still somewhat of a crap shoot, but I've also found good barrels will be much easier to find accurate loads for.

I am no expert.

I have a question - are you comparing apples with apples - like free floated barrel with similar free floated barrel?

My Simson M98 in 9.3X62 shoots about 3 or 4 loads of 285 & 250 gr bullets into 2.5 inch composite group at 100 meters. When I go to a 320 gr load it prints that 6 inches low - 250 to 350 fps slower velocity. The rifle had the barrel touching the wood stock in the channel AND a full length rib - octagon to round barrel.

Similarly my CZ 416 Rigby produced good composite groups with 4 or 5 different bullets. Barrel had pressure from the Kevlar stock.

On the other hand my Sako 280 Ack Imp will product several 1 inch 5 shot groups with many loads but the composite group could be 10 inches! The barrel is free floated.

I suspect this is to do with barrel harmonics from free floated barrels versus stock pressure.

JMHO

Barrels whip when you shoot just like a hose when the water is turned on. There is a difference though, unlike a hose a barrel has a natural state of rest to which it wants to return. As it whips it first gains speed, then as it reaches the extreme of its movement it slows, stops momentarily then reverses direction slowly accelerates in the opposite direction. Barrels that clear the muzzle when it is slowing, stalled out or just starting to move back will tend to cluster nicely at least at close range. Variations in velocity matter less, and that barrel will likely group to the same POI across a few grains on the powder charge sequence. It's the basic premise of the Auddette ladder and OCW methods of load development. An opportune sweet spot can also put several different bullet weights in the same close range group. Luck plays a part.

Bullets exiting at the worst case scenario of the barrel moving through the fastest portion of the oscillation will tend to move POI with minor changes is powder charge, string shots and put different bullets to widely different POIs. You can slow the oscillations and lengthen the sweet spots with a heavier barrel, of dampen the movement by having the forestock stiffen the barrel.

Further to my post above, I also tried the new CEB hollow point raptor & solids in my 9.3X62. The HP was 255 gr & the solids were 280 gr.

they shot 12 inches above the other loads! It might have even been 18 inches as it missed the entire target board and we saw the soil kick up on the mound behind.

This did not happen with Barnes TSX 250 gr!

The CEBs are bore-riders for the most part. If they hit anywhere near where a conventional bullets lands, just consider it a fortunate coincidence. My .458 will shoot them to the same POI as most others. Everything else I tried them in was a mile away

quote:

Originally posted by Dogleg:
The CEBs are bore-riders for the most part. If they hit anywhere near where a conventional bullets lands, just consider it a fortunate coincidence. My .458 will shoot them to the same POI as most others. Everything else I tried them in was a mile away

Interesting, in as much as bore riders I have tried in my CZ416, Rem 700 300SAUM, Steyr 270W, Rem (Aftermarket barrel) 700 6.8SPC, 35Whelen (After market barrel) throw to the same point as conventional bullets.

I dare say - with what very little knowledge of the subject I have- that most of what has been posted would cover the explination in most instances.

I will have to check the 416 again as I have just put it in a new synthetic stock.