Downloading Magnum Cartridges

07 June 2001, 16:57

<Guus Verheijen>

I would welcome suggestions for downloading the following cartridges to .30-06/.308 Win/8x57 IS performance levels: 300 Win Mag, 308 Norma Mag, 300 Weatherby Mag & 8x68 S. What kind of accuracy may be expected? Suggestions using Vihtavuori powder(s) are especially welcome.

Thanks in advance,

Happy hunting,

Guus

08 June 2001, 02:40

Dutch

Guus, I'd just load it with a too-slow powder. You'll get some flash and some muzzle blast, but you are not looking for that far of a step down. Here we have the option of going with the IMR SR series, which is a very bulky, but fast powder, but then you are in the 700 M/s range. HTH, Dutch.

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For evil to prosper, good men must do nothing. (Burke)

08 June 2001, 03:25

1894

Have a look at the speer manual which has some SR4759 loads which take velocities well below what you require. Alternatively use the slowest Viht startload.

Downloading magnum cartridges is said to be frought with danger. A lot of loading books do not reccomend reducing magnum loads beyond their start loads, they are generaly correct in most things.

If flashover/detonation/ destructive interferance of pressure waves in the case doe indeed exist (the reason this practice may be dangerous) then it probably takes a specific combination of powder burn rate, powder position, bullet position and temperature to occur. Just because it hasn't happened to someone who reccomends such a practice doesn't mean it won't happen to you (or them) at some point.

This is not to diminish this forum which is an excellent resource but you cannot safely test for this condition (if it exists), if it happens it will destroy your gun. Published data will have been tested not to produce it.

08 June 2001, 03:36

<Bill Tompkins>

Guus,
1894 makes an excellent case for reduced loads, but with today's powders it is not necessary to take the chance.
You can use V V N170 for all four cartridges and have not only reduced velocity but reduced pressure. These loads will not burn completely in the barrel so there will be extensive muzzle flash. Accuracy is impossible to comment on. We used to do this with .264 Win. Mag. and cast bullets.
Bill

08 June 2001, 05:00

John Frazer

You probably don't need to go to the point of danger to achieve the types of velocities you're talking about.

I've personally played with several light loads *within the limits of the manuals* -- you just have to have the right manuals.

Best results so far in the .270 and .30-06 have been with the reduced loads in Speer #13 (especially their 110-gr. .30-06 loads using XMP-5744) and starting loads in the Lyman manual, using the powders that are on the fast side for the cartridge, e.g., IMR 3031 and IMR 4895. These loads have low recoil and little blast or flash.

The IMR manual also shows lower-velocity loads with most bullet weights in most calibers using powders such as SR 4759, IMR 4198 and IMR 4227.

Good luck,

John

08 June 2001, 16:43

LE270

Others here are overdoing things -- they are writing as if you want to use cast bullets or achieve velocities that are in the range of 1/2 of top. But you asked for 308 - 30/06 velocities from a 300 magnum.

Such velocities are easy to achieve, and you can do it without danger. Go to a reloading manual such as the Lyman, and look at their minimum loads for the caliber in question. You will find a number of loads that give you what you are looking for. Typically they use a bit faster burning powder -- e.g. IMR 4064 instead of IMR7828 or H4831 in a 300 Weatherby.

If you think of 2800 fps as the standard max load with 180 gr. bullets in a 30/06, and 2650 fps as the standard max load using 180 gr. bullets in a 308, then the Lyman Reloading Handbook, 46the Edition lists a number of starting loads for 180 gr bullets in the 300 Weatherby, for example, that go from about 2600 to 2800 fps; these meet what you are trying to achieve.

I once did experiments in my 300 Weatherby with the same goal in mind. I found I could reach the velocities I was looking for, with good accuracy, following the method I outline here.

08 June 2001, 17:12

<Bill Tompkins>

LE270,
It would be a good thing if you would read the above posts correctly before making contrary remarks. There is no mention of Guus wanting to shoot cast bullets, only a mention of past experience. The discussion of reduced loads I'm sure is based on common sense and a desire to impart a need for safety. Yes, you make a good point about being able to use faster powders, but that is not the sense of the original question.
Bill

09 June 2001, 14:38

LE270

quote:
Originally posted by Bill Tompkins:
LE270,
It would be a good thing if you would read the above posts correctly before making contrary remarks. There is no mention of Guus wanting to shoot cast bullets, only a mention of past experience. The discussion of reduced loads I'm sure is based on common sense and a desire to impart a need for safety. Yes, you make a good point about being able to use faster powders, but that is not the sense of the original question.
Bill

Well, no slight was intended. John Frazer gave essentially the same answer as I gave. But several respondents wrote about using special powders that are appropriate for very much reduced loads, and at least one spoke of making loads with cast bullets. But those suggestions do not speak to Guus's question, which was about making loads for magnum calibers that duplicate standard 30-06, 308, and 8x57 loads. To do that, the best way to proceed is to look at the beginning loads given in various loading manuals, as I and several others suggested.

Concerning the problem of unsafe loads with reduced powder charges, I suggest that people here read the thread under Jack O'Connor's loading scale. Someone there comments on this problem -- it seems/seemed to arise especially with the old surplus H4831 powder, and possibly with other slow-burning powders. I do not know of ever hearing or reading about it coming from reduced loads using such medium-speed powders as IMR 4064, the 4895s, IMR3031, and so on. (If I'm mistaken about that, I'm sure someone here will point it out.) In any case, if you use loads that are given in recognized loading manuals, you can be certain beyond reasonable doubt that they have been tested and found to be safe.

09 June 2001, 15:24

John Frazer

Maybe I did go a little far in suggesting the Speer manual reduced loads--which are basically cast bullet velocities with jacketed bullets.

I concur in trying the starting loads with the faster powders. The Lyman manual is great for this because their starting loads are lower than most manuals and they list faster-burning powders.

E.g., their starting load for the .270 150-gr. with IMR 3031 gets about 2400 fps in my rifle with very good accuracy using Ballistic Tips, which should be a nice mild short-range deer load.

And, the starting load (can't remember which manual or manuals) for IMR 4895 in the .30-06 150-gr. was right around 2475 fps in my rifle with sub-MOA accuracy.

I would check the Lyman, Hornady and Sierra manuals since they seem to start with the lightest charges. Hornady lists several with N160 and N165 in the calibers you mention.

09 June 2001, 18:18

<Bill Tompkins>

LE270,
I made the response regarding cast bullets and slow powders only as a reference to a practical experience, not as a suggestion for Guus. Using slow for bore or capacity powders is a way to reduce not only velocity but also pressure.
As far as Secondary Explosive Effect(S.E.E.) is concerned; it has application to any powder in any case based on the volume of that case where the volume falls below the top of the the primer in a cartridge in a rifle held level or below level. If the primer is ignited under these conditions, the flame bowl of the primer passes OVER the top of the powder, igniting it from the top down instead of from the back foreword. The increased square area of powder under ignition creates an instantaneous ultra high pressure spike of catastrophic proportions.