Since it's easier to get to the computer than it is to the range, AND since I don't have rifles chambered in 7 different .30 caliber cartridges, I thought I'd do some more ballistic pencil-whipping.
 
It has long been "taken for granted" that "large" capacity cases, while they do make bullets go faster, do so with a non-linear increase in powder. The "large" cases are referred to as less "efficient" than "small" capacity cases. While, to my knowledge, the term "efficient" so used has never been specifically defined, it was always 'understood' that it meant that you can make bullets go faster with big cases, but you're gonna hafta use a lot more powder to do so. So I thought I'd just test that "truth".
 
I decided to use .308 caliber because it is so universally (in the US) considered the "yard-stick" by which every caliber must be compared. That galls me, but it is nonetheless the parochial reality. So, I chose the following cartridges. Their case capacities, in grains of water, follow in parentheses:
 
.308x1.5 - (38.00)
.308 Win - (56.00)
.30-06 AI ("Improved" because I wanted an increase in case capacity of about 15 grains between each case) - (70.00)
.30x.338 Win Mag - (85.00)
.300 Weatherby Mag - (98.90)
.300 Rem Ultra Mag - (113.00)
.300 Pegasus - (132.01)
 
For bullets, I chose the Speer 110 HP, the Nosler 180 Partition, and the Barnes 250 RN. This represents essentially the spectrum of bullet weights available in .308. Plus, there is a 70 grain difference between each bullet and the one adjacent to it.
 
While there are relatively slight differences in max chamber pressures between the cases, in order to keep things as simple as possible, "oranges to oranges" and all that, I kept the max chamber pressures all equal at 60,191PSI.
 
Again, in order to keep things simple, I kept seating depth uniform for all bullets and cases - 66.7% of the caliber, or .205".
 
Finally, I kept the bullet travel equal. In other words, I compensated for over-all cartridge length so that all bullets in all cases traveled exactly the same distance before exiting the barrel. Bullet travel was 23.807". This resulted in bbl lengths ranging from 25.1 in the .308x1.5, to 26.5 in the .300 RUM. Those are reasonable bbl lengths without getting into extra-long "custom" lengths.
 
The bullet travel of 23.807" was selected because I started with the .308x1.5 and the 110 HP and a muzzle velocity goal of 3000 f/s. In order to achieve this AT A SPECIFIC BARREL TIMING NODE, the barrel needed to be 25.1" long, leaving 23.807" of bullet travel. All other bullets and bbl lengths were adjusted to that length.
 
The results for each bullet in each case were obtained by caclulating the bbl timing nodes, and selecting the one that gave the maximum MV. In other words, the load was determined by the charge that gave the maximum velocity AT AN OPTIMAL TIMING NODE. In more 'other words', I made conditions optimal for every case with every bullet. In even more 'other words', I made things the best they could possibly be for each bullet in each case. There are no "disadvantages" to one bullet/case combo by having to "fit" to some other bullet or case's constraints.
 
I found the results intersting. (Obvious, I suppose, or I wouldn't be presenting the results here.) Before I present my personal conclusions, I'll present the graph of the results and let youse guys mull it over.
 
The graphs have 3 lines, one each for the 110, 180, and 250. In the first graph - Case Capacity vs Average Muzzle Velocity - the lines you see are the 'best fit' of the data points using a linear regression. The slope and intercept data are in the corners of the graph. The slope and intercept for the 110 is in the upper left; the 180 in the upper right; and the 250 in the lower right. The slopes are:
 
110 - 7.6727
180 - 7.5577
250 - 6.1822
 
The intercepts are:
 
110 - 2754.7
180 - 2166.6
250 - 2002.4
 
An "R squared" value is a measure of how well the regression line fits the data. The "R squared" value for the 110, (0.99), is very high. (A perfect fit "R squared" value would be "1.0".) The 250 "R squared" value, while not as 'tight' is still a good fit.
 
The second graph - Average Efficiency vs Case - is the "efficiency" of each bullet/case combo, with "efficiency" defined as the ratio of Muzzle Energy in foot-pounds to charge weight in grains. In other words, how many foot-pounds of muzzle energy do you get for every grain of powder. These models are 'second order' hence the square functions, but ignoring the math for the most part, note that the fits ("R squares"), are very good.
 
Have a look at these and I'll offer my conclusions after we've had a chance to discuss them a bit.
 
Paul

Hello Paul. Nice charts. I would have predicted those results. I would have liked to see the vanilla '06 as well. The 308 was designed with the aid of fairly modern technology and was selected as the NATO standard for good reason as it is a highly effecient case. The big Magnums poor effeciency is very predictable in my view. I would have liked to see the 300 win mag as this one doesn't seem to devour as much powder as most. The 7Mag also loves copious quantities of powder to get fairly marginal results. However, the name of the game is speed and STW, Lazzoroni and Weatherby sell gobs and gobs of the things. Regards, Rick.

Rick,
 
With regard to "I would have liked to see the vanilla '06 as well." and "I would have liked to see the 300 win mag as this one doesn't seem to devour as much powder as most."
 
The reason I chose the cases as I did was so that the roughly even spacing would allow a good model development. The "R squared" values show that 99%, 98% and 77% of the variability within the data is explained by the models. With a model in which one could have confidence, like these, all you need to get the '06 Springfield value is the Springfield case capacity - which happens to be 68.20 grains of water, and the bullet weight. Let's start with the 110 HP.
 
7.6727 * 68.20 + 2754.3 yields an estimated MV of 3278 f/s. The estimated MV for the 180 is 2682 f/s, and 2424 f/s for the 250.
 
The 300 WM estimated MVs are:
 
110 - 7.6727 * 91.5 + 2754.3 = 3456 f/s
180 - 7.5577 * 91.5 + 2166.6 = 2858 f/s
250 - 6.1822 * 91.5 + 2002.4 = 2568 f/s
 
As for the issue of "efficiency", I was actually a little surprised at how well the bigger cases did. Of course they're not as "efficient" as the smaller cases, but when one considers how much more MV they provide - at least some of them - a little extra powder seems a trade-off I might be willing to make. Of course there are other considerations such as cost of reloading components, custom chamberings, and barrel life. Still, pushing a 110-grain HP up near 4000 f/s has some appeal to me. :)
 
One of the interesting observations was how the .308 Win did in comparison to the '06. When one keeps barrel timing (accuracy) in mind, the .308 Win does very well indeed when compared to the '06. This is keeping the pressures the same and the bullet travel - (effective barrel length) - the same, and picking the highest-speed timing node for each. In each bullet weight, when compared to the Springfield '06, the .308 is always less than 100 f/s slower than the '06 and in the 110 and 250, its less than 50 f/s slower.
 
Instead of "beating" the magnums up, I'm in fact a little more interested in what they might do with light bullets.
 
Paul

Well, I know you love your .308's but they will always be almost as fast as the '06. That's not being smartass or anything else......The '06 case holds more powder and more powder makes bullets go faster although they may be less effecient. The 308 was developed IMHO to fill the need of a reliable machine gun....hence the M-60. The US government cleverly masked this entire concept with the standard NATO round all dreamed up by McNamara and the standardization/interoperability weenies. McNamara also forced the Navy to buy the F111....bad idea. Ever wonder why an F111 has a landing gear bigger than most commercial airliners?
 
Anyway, I happen to like the 308. It's effecient, tame, and wonderfully accurate. I shot expert rifle in basic with an M-14.....darn right I like the 308.....that was a 3 day pass!:D :D :D :D . Regards, Rick.

Quote from: sakorickWell, I know you love your .308's but they will always be almost as fast as the '06.

Waaaallll, only kinda sorta. What this analysis has demonstrated is that when barrel timing is considered, (and completely ignoring "efficiency"), there may actually be bullets for which the .308 Win even beats the MV of a properly timed '06.
 

QuoteThe '06 case holds more powder and more powder makes bullets go faster although they may be less effecient.

Actually that's exactly what this analysis demostrated wasn't absolutely true - if the prime consideration is accuracy, not speed. If we're talking about starting out building a custom rifle, then absolutely your statement is undeniable. However, if we start with "factory" rifles, meaning they have pre-made, unmodifiable chambers and bbl lengths, AND if we insist on having the charges produce the correct timing for maximum accuracy, I suspect there is a bullet or two in which the .308 Win's MV, may actually exceed that of the '06 with the same bullet.
 
Let me quickly make two very important points: First, I'm not trying to "elevate" the .308 Win to the "status" of the '06. That's not necessary. Second, I'm not trying to "lower" the status of the '06. That's simply spitting into the wind. I'm simply trying to point out that bbl length, as a method for increasing MV, and more importantly, case capacity as a certainty for increasing MV, ain't necessarily certain if one is more interested in 'accuracy' than MV.
 
Let me generalize the results a bit more, and remove this discussion from the eternal ".308 Win vs .30-06" argument. I submit that this 'paper' exercise suggests strongly that if one were to take any two cases in the same caliber, whose capacities were less than 15 grains apart, there is a very real possibility that the case with the lesser capacity might be able to exceed the MV of the larger case (using the same bullet in each), as long as accuracy, (barrel timing), was the prime consideration, not simply MV.
 
Of course one can always cram more powder into a larger case and get more velocity. That IS a certainty. However, if the timing of the barrel, as an indicator of most stable precision, guides the load work-up, then a larger case capacity does not absolutely dictate a faster MV.
 
In the end, I guess I'd summarize by saying that in general, for cases whose capacities differ by 15 grains or less, there's really going to be only academic differences in their "performances" (MVs) as long as accuracy, NOT MV, is the primary interest.
 
Paul

Why did you use a 250gr bullet instead of a 220? There are very few 250s available in 30 cal. I agree that in many cases that the most accurate load is not the fastest. So it is indead possible to excede the speed of a larger case within specified accuracy requirements. I guess tha tit is up to the shooter to decide what is the most important thing to him, speed or accuracy.

Quote from: HunterbugWhy did you use a 250gr bullet instead of a 220? There are very few 250s available in 30 cal.

For three reasons: First, because it represented a 70-grain step up from the 180 which was a 70 grain step up from the 110 - uniformity of the data set. Second, because it represented the top of the weights for the .30 caliber. Somebody would have complained that you wouldn't see the real advantage of the big cases until you got to the really heavy bullets. Third, some people insist that the really heavy bullets are the "best".
 
The make/design of the bullet is almost immaterial. It does make a small difference if it's a boat-tail (smaller bearing surface for a given length). But otherwise, this is internal ballistics, and weight is the most important factor by a long, long way.
 

QuoteI guess tha tit is up to the shooter to decide what is the most important thing to him, speed or accuracy.

Yup.
 
Paul

Hello Paul. In reality....not paper, rifles seen to tighten up groups the faster you go. I have worked extensivelly with 4 Sakos, a Tikka, a Parker Hale, A Steyr and a Zavodi during the past 5 years. These rifles ranged from a 243 to a 300WM. Save for my son's '06, every single one of them shot their very best groups between .5 gr of and up to max published load. Come to think of it, Eric's rifle may even shoot better than the 3 hole cloverleaf I fired.....it was so good, I just quit about 1 1/2 short of max. He shoots a 150gr Game King in his L61R. I just may try the 165gr Sirocco in his rifle today...It will give me a project while the Tro-Oil dries. His '06 has a longish freebore....perfect for the long Siroccos. Off to the reload bench....Regards, Rick.

QuoteIn reality

A relevant comment in this thread...
 

Quoterifles seen to tighten up groups the faster you go.

While I too have observed this phenomenon, I wouldn't go so far as to say it was "the norm". On the contrary, on the rifles I have worked with, I'd say it was 'uncommon'. And that's in light of the fact that my tendencies are to "push the envelope" as opposed to "stopping short of the edge". HOWEVER, let's take the observed as "reality" and see if there isn't a way to have our pencil-whipped barrel timing "cake" and eat it too. :)
 
According to wave theory (in our case, "barrel timing" theory), there are equal numbers of "good" nodes, and "bad" nodes. The "good" nodes occur when the ignition-induced wave is at the receiver, and the "bad" nodes when the wave is at the muzzle. The bad nodes occur - timing-wise - exactly half way between the good nodes. That part of "theory" is undeniable. So let's take the situation where the rifle in question has its precision "improve", (group sizes decrease), as the charge approaches the maximum load. This does not contradict Optimal Barrel Timing theory. Again, on the contrary, that particular observed response supports it.
 
Let's say a "good" node occurrs 'back' from the max published load by half a millisecond. At the same time, we calculate that the timing of good node simply can't be reached without exceeding the published pressure limits of the cartridge. Without benefit of OBT calculations, we reduce the max load by 5% and start our workup there. That 5% reduction from max gives us an unacceptably large group, so we up the charge in 0.1 grain increments. If that -5% load was at a "bad" node, then every increase in MV we take moves us - timing-wise - toward the "good" node, and the groups will shrink. At some point, we decide to stop increasing the charge, either because we've moved outside our 'comfort zone' or we've reached an 'acceptable' group size. That doesn't mean we have reached the "good" node, it simply means we have moved away from the "bad" node, and in doing so, must improve precision. By the same token, since we're dealing with published (paper) maxes, and velocity maxes NOT pressure maxes, we may actually have reached the "good" node.
 
I doubt very seriously that anyof the charges I calculated above would turn out to be the exact charge that produced the smallest groups. I simply argue that it is likely that those numbers are "close", adn better than simply shooting "in the dark" in trying to find a precise final charge, or even a good starting place for that matter.
 
Finally, it has been my experience that "published" load data is hardly more useful than suggesting what might be a reasonable starting place. As such, "max" loads rarely are - at least in my experience. That is precisely why I have worked so hard at acquiring pressure sensing equipment. Velocity alone is a very poor predictor of chamber pressure. Therefore, it is also a poor predictor of barrel timing.
 
Paul

Well, the 165 gr experiment with Eric's Sako was a 100% total failure. This rifle is the most accurate rifle I have ever fired and it hates, loathes and in general detests the 165gr Sirocco bullet. I shot one group that was a 4 shot 2 inch job that was fast (2886) but pitiful. Just when you think you know alot in the reloading world something like this bites you in the rear. Back to the Sierra Game Kings for this boy. This puppy hit a bad bad node with the Sirocco which only confirms my state motto "show me". Hey, when things go good, I'm fast to post.....when things go bad I'm even faster to post. I tell it like it is and in this case, is was aweful. :frown Regards, Rick.

Quote from: sakorickWell, the 165 gr experiment with Eric's Sako was a 100% total failure. This rifle is the most accurate rifle I have ever fired and it hates, loathes and in general detests the 165gr Sirocco bullet. I shot one group that was a 4 shot 2 inch job that was fast (2886) but pitiful. Just when you think you know alot in the reloading world something like this bites you in the rear. Back to the Sierra Game Kings for this boy. This puppy hit a bad bad node with the Sirocco which only confirms my state motto "show me". Hey, when things go good, I'm fast to post.....when things go bad I'm even faster to post. I tell it like it is and in this case, is was aweful. :frown Regards, Rick.

Well neighbor,

I shore like the way you think....and more importantly......the way you do!!!!:D

Always read your posts with great interest and appreciation!;)

Ol' John:cool:

Hey Rick, can you provide some numbers on that '06? Specifically; the barrel length (the more precise the better up to about a quarter inch), and case length - to a thousandth if you can, seating depth - again to a thousandth if you can. Case capacity in grains of water would be very good. If you don't want to fiddle with the case capacity, send me a fired case or two and I'll 'take them apart". Finally, if you know the throat or leade length, that would get us closer to reality.
 
The reason is, that figure of 2886 f/s for a 165 MV is by no means "hot" in a "normal" '06. Maybe we can get that Sirocco to shoot tiny little groups like the others do.
 
Paul
 
For example, the following chart is for the Springfield '06 cartridge in a rifle with a 24.25" bbl and a case length of 2.484". When I get the exact case capacity, we can look at the fill% more closely. Personally, considering the chamber pressures, (how low they are), these charges, regarless of being greater than 100% of estimated, usablefill capacity, would be of absolutely no concern to me. I would of course start 'down' and work up to them.
 
Paul

Quote from: gitanoHey Rick, can you provide some numbers on that '06? Specifically; the barrel length (the more precise the better up to about a quarter inch), and case length - to a thousandth if you can, seating depth - again to a thousandth if you can. Case capacity in grains of water would be very good. If you don't want to fiddle with the case capacity, send me a fired case or two and I'll 'take them apart". Finally, if you know the throat or leade length, that would get us closer to reality.
 
The reason is, that figure of 2886 f/s for a 165 MV is by no means "hot" in a "normal" '06. Maybe we can get that Sirocco to shoot tiny little groups like the others do.
 
Paul

Sure thing, Paul. The barrel length is 24 1/4 inches. Imperial brass trimmed to 2.484, 50.5gr IMR4064. OAL with 165gr Sirocco 3.342 touching the lands. Seated 3.302........whoa Nellie! That's wrong! His '06 likes the bullets up there close......015 off not .040. My '06 likes the 40 thousanths jump. To err is human....I'll recheck that load today with the bullet properly seated. In the meantime PM me your address and I'll send you some bress. I only use the Imperial for tatget shooting, I use Win brass for hunting loads. Regards, Rick.

Here's "my" chart with "scores" attached to the above powder selections.
 
Paul

Well, well well. I refired the sciroccos with exactly the same results. I then loaded 165gr Game Kings with the exact same identical load other that the seating depth as the ogive on these two bullets are miles apart. See the pic and you be the judge. PH= Game King, SIR=Sirocco. I thought they were the pro Hunters, however, these were the boat tails.