CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.
Oyster Stew,
The ways of copyright law are complicated. Data itself, or any other sort of fact, cannot be copyrighted. However, the arrangement or graphic representation of something can. You've avoided the latter by not using the same typeface. For the former, if you simply reorder the data, for example, to emphasize some aspect of it, you avoid that element as well. Cut and paste needs to be avoided unless you ask and receive permission from the author.
One change to make is what the author calls the volume ratio. Given the 20" barrel, that matches what interior ballisticians normally call the expansion ratio of the gun (volume of fired case and and bore with bullet gone, divided by case water capacity under the seated bullet). I'll go ahead and changed that for you.
EDIT:
I noted that six powders and six loads were listed in the second portion. I expected, when I first posted this, that the loads were in order for the powders listed, respectively. But that's not what evaluating the numbers showed. That shows the same charge weights being suggested for all those powders, even though their burn rates and energy densities and bulk densities are not the same. The authors probably just looked the powders up on a burn rate chart and decided they were close enough to be OK. That's very sloppy and shows lack of understanding of powders.
The other problem I'm having, aside from the badly organized data, is that my eyeball and QuickLOAD are telling me the pressures and velocities are not plausible. If you look at the load page on that site, it says the loads were developed with Load From a Disk, an obsolete interior ballistics program based on the old Powley computer which was originally developed for IMR stick powders and for a narrow range of case fill from 85% to 100%. Homer Powley was ahead of his time and something of a ballistics wizard, but except for 3031, I do not believe he worked with the powders listed. That means someone else interpolated their characteristics for the calculator or they just guessed they would be about the same, as I indicated, above. I have no faith in either approach, so I'll add
the forum's obligatory warning to your post.
I've shot and measured both pressure and velocity for sabot loads in a Savage ML10. The main thing that jumps out on the pressure curve from such a gun is that because there is little significant friction between the plastic and the bore, start pressures are slow developing and peak late, when more expansion has occurred than would be the case with a jacketed bullet of groove diameter. This reduces peak pressure and velocity, requiring more powder than a same-weight jacketed bullet does. I don't know that there is any way to enter that low start pressure into Load From a Disk, though I don't have a copy, so perhaps someone who does have it can verify this. The bottom line is, nothing I'm seeing on that site gives me a warm fuzzy feeling about the technical acumen of its authors.
QuickLOAD has a more sophisticated ballistic model and does let me enter low start pressures as I found the ML10 needed to get a matching performance prediction (around 350 lbf, IIRC; but don't take that as gospel, as I haven't dug out my data from five years ago and looked it up). QuickLOAD is also telling me that none of the powders listed can reach the pressures or velocities listed. Indeed, the slowest rifle powder in QuickLOAD that was able to exceed the SAAMI .30-06 MAP (Maximum Average Pressure) and still fit in the case without too much compression was IMR4227. IMR4198 looks usable, but will fill the case without exceeding SAAMI MAP. A case stuffed 105% with IMR 3031 (56 grains and change) is down in the 30-35 kpsi range in QuickLOAD getting about 3500 fps with your bullet weight.
Slower spherical powders like 748 behind a too light bullet can cause a situation where the powder mass gas and movement lag the bullet position in the bore, but catch up when the bullet is part way down the bore, causing a rear-end collision of the powder mass with the bullet. That can ring barrels, and in extreme cases, bulge or break one. This usually happens at around 20" down the tube, so it's possible the folks testing with their 20" barrel didn't see it, but could be an issue with longer barrels than that.
Example of a load producing a severe rear-end collision, whose expansion strain is reflected down the barrel to appear like a pressure on a strain gauge instrument plot. Either increasing bullet weight or changing to a faster powder eliminates these spikes. Notice this is a commercial load, and the maker is unaware of the pressure event because it doesn't show up on either copper crushers or piezoelectric transducers because of the way they are mounted. This plot is reproduced with kind permission from Jim Ristow at
shootingsoftware.com.
As others said, sabot's and accuracy in .30-06 (e.g., Remington Accelerator) have never gone hand-in-hand, but you can get some astonishing speeds with the right powder. And there is nothing intrinsically inaccurate about sabot loads. The sabot loads in the Savage ML10 are very accurate. So are the ones fired from the Abrams M1 tank, so I'll suggest this is not necessarily a waste of time.
The main technical obstacles in high power rifle sabots are that they have to enter the rifling carefully to avoid being off-center and the bullet can't slip inside them and fail to pick up adequate spin. An eccentrically spinning bullet mass gets lobbed at a drift vector tangential to side of the bore it is closest to at exit, giving it drift in that direction that accumulates over a distance. So, centering has to be really perfect. A smooth bore, like the tank, which has fin stabilized projectiles, or a muzzle-loaded sabot that is thin on the bullet sides and that you press carefully into the rifling can do well. But the thicker wall .30-06 sabot under high pressure is sort of like trying to use your thumb to force a plug of butter to center perfectly in the barrel. It's not necessarily a trivial undertaking as a technical problem.
You can test for the sabot slipping against the bullet under angular acceleration by the rifling. It is perfectly possible for a bullet to exit with too little spin, even though the rifling pitch should be adequate. You can test for this by using Trail Boss or other reduced loads to see if you get a sudden jump in accuracy at some reduced velocity.
Anyway, while I don't want to discourage you in an absolute sense, I would not trust the load information from that site. Bear in mind that my QuickLOAD information, even though I have a lot more faith in it than what comes from Load From a Disc, is still just a computer model and could be wrong for some technical reason I'm not identifying. This is the kind of gray area where you need experimental validation of your computer predicitions. I don't want to send you out filling cases with 4198 thinking it is safe, only to have your gun blow up because I hadn't worked an experimental confirmation up first.
Personally, I would not want to get into this very far without the ability to verify
pressure by strain gauge, specifically, so I could see the gun wasn't being abused by secondary powder mass collision with the bullet and to verify pressure value. I would also want a good chronograph. It appears to me the Magnetospeed would be safe from sabots. An optical chronograph will need to be a safe distance downrange from the sabots.
Trail Boss loads should be just fine. Follow Hodgdon's data and see how these shoot? The low velocity and pressures should all favor accuracy with the sabot to give you an accuracy baseline without investing in fancy equipment.
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