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S.D. as guide for working up reloads

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S.D. as guide for working up reloads

Old 07-21-2013, 08:19 AM
  #1  
Spike
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Default S.D. as guide for working up reloads

Pressures in the 7x57 'family' and 30-06 'family' vary from 270 Winchester levels to 257 R levels, maybe more.

Is it feasible/wise to use the S.D. of a cartridge in one of these family's in the other cartridges of that family since case capacity will be virtually the same?

examples -
270 Winchester cartridge for lower pressure 35 Whelen?
244 Rem for 257 R?
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Old 07-21-2013, 08:39 AM
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IMO there is alot more to safe reloads than SD. The Model / make /year of construction of your gun all play into reloading.Measuring your cartridges expansion and using a chronograph would be safer than using SD . I dont load anything faster than the new reloading books say to.
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Old 07-21-2013, 05:54 PM
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Spike
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Well, thanks for your interest.

Type of firearm not really relevant to my question. Expansion check fine if you are working up max loads, I'm not. Chronograph good for seeing how fast you're going, I'm not interested yet. Current reloading books always play it safe in the listed cartridges.

Maybe this isn't best place to put my question - which is a little theoretical but also practical. If a 270 Win load is in the book, it is safe for rifles designed for that cartridge, but can I apply that load to an equally strong 35 Whelen? I think I can, if I work up slowly, but ...

Oh, just we're together, "S.D." is "sectional density".

Last edited by Catchem; 07-21-2013 at 05:57 PM. Reason: define S.D.
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Old 07-22-2013, 04:28 AM
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I really don't know the answer to your question. But on one hand, all the cartridges you mentioned have reloading data available. And on the other hand, I would not use the data for a .270 to load a . 35 Whelen. It is my thought that the differences in bullet weight alone (+40%) would be cause for excessive pressures.
I suggest that if you want to use lighter loads out of your rifle then use the lightest bullets available for the task you want and use the starting loads listed in the manuals you have
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Old 07-22-2013, 12:13 PM
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Originally Posted by Catchem View Post
.................... If a 270 Win load is in the book, it is safe for rifles designed for that cartridge, but can I apply that load to an equally strong 35 Whelen? I think I can, if I work up slowly, but ...

Oh, just we're together, "S.D." is "sectional density".
What i just now did was visit a powder supplier website and compare 270 loads with 35 Whelen loads. First thing i noticed was mostly different powders were used for the two caliber. Then..................it took me some looking, but i finally found a powder used for both caliber.

IMR 4895 was the common powder.

The 150g .277 bullet and the 250g .358 bullet have the same SD of 0.279.

The .270 load with the 150g bullet, was 44.5g which produced 50,600 cup.

The 35 Whelen load with the 250g bullet was 53.5g @ 50,300 cup.

It seems to me, you can safely work up from a 270 load to the 35 Whelen load. However, it will take so long you will miss hunting season. Another problem i foresee, is if you are using a popular/common 270 powder, the 35 Whelen case will fill up and overflow, before you reach a suitable charge.

Going from 244 to 257 could be doable, and should be safe, but i didn't research any loads for these caliber.
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Old 07-22-2013, 02:10 PM
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My question is a simple one...why? All of the calibers you mention are standard calibers and have SAMMI specs to work with...so why not simply use known data that is available.
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Old 07-22-2013, 05:03 PM
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Originally Posted by emtrescue6 View Post
My question is a simple one...why? All of the calibers you mention are standard calibers and have SAMMI specs to work with...so why not simply use known data that is available.
Well said.
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Old 07-23-2013, 09:21 AM
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Originally Posted by emtrescue6 View Post
My question is a simple one...why? All of the calibers you mention are standard calibers and have SAMMI specs to work with...so why not simply use known data that is available.
Thanks to all for your feedback.
My interest is limited to seeing how high SAFE reloads for the 257 R and 7x57 Mauser can be made. Both have low SAAMI specs, and both safely could be shot faster.

257R +P = 58,000
7x57 = 51,000
6 MM Rem= 65,000

It seems to me at first glance that a bullet with a given S.D./velocity/pressure relationship in 6 mm Rem in a reloading manual would be shot at the same velocity/pressure in the other 2 as long as the S.D. and type of powder was held constant. By using a chronograph and going up slowly performance of the calibers would be improved safely(?).

I realize that theory and practice don't always match up.
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Old 07-23-2013, 01:06 PM
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Originally Posted by Catchem View Post
Thanks to all for your feedback.
My interest is limited to seeing how high SAFE reloads for the 257 R and 7x57 Mauser can be made. Both have low SAAMI specs, and both safely could be shot faster.

257R +P = 58,000
7x57 = 51,000
6 MM Rem= 65,000

It seems to me at first glance that a bullet with a given S.D./velocity/pressure relationship in 6 mm Rem in a reloading manual would be shot at the same velocity/pressure in the other 2 as long as the S.D. and type of powder was held constant. By using a chronograph and going up slowly performance of the calibers would be improved safely(?).

I realize that theory and practice don't always match up.
Based on that I would say no....using another caliber to gauge reloads probably isn't a good idea. As a few said, the only safe way to do this would be to slowly build up loads using classic methods signs of high pressure like proud primers, stiff/tight bolts upon case extraction, cracked cases, etc...also using a crony would be a good idea as well to check for consistency, a lack of which may indicate high pressure.

I have a 257 Roberts AI I recently built and am in the same boat of having to slowly build up a load watching for signs of pressure.

Just remember...speed doesn't always equate to accuracy....I build accurate loads watching for signs of pressure.
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