Extrapolating powder usage


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BlessYoreHeart
February 10, 2013, 09:21 PM
Hi folk,
I like the vihtavuori powders and wish to use them exclusively.
In order to develop various loads safely, I need a way to find a starting point for using a powder with no published data for a particular use. I'm wondering if anyone has come up with a method to find such starting points via comparison of components.

Example:
For 20ga, Lyman's 5 shows N330 at 16.5gr for 2-3/4 Remington STS hulls using 7/8oz. But nothing for N340.

However, turn the page and find N330 (16.5gr) AND N340 (17gr) using Winchester HS or compression formed plastic cases with a 7/8oz lead charge.

Problem 1:
I can only get (and have done so) N340 locally. So, comparing the two hulls, both use 16.5gr of N330.
The Winchester uses 17gr of N340.
So...it seems to me I could I safely start with 17gr of N340 in the Remington STS hulls.

Anyone experienced experts see a problem with my thinking?

Problem 2:
I also have N310 locally and I use it in loading .380 cartridges from the VV 2002 manual recipes.
Is there some method of correlation one can apply to get to a start load for the 20ga STS 7/8oz load using N310? Perhaps comparing powder densities of each powder or some such?

Any pertinent info would be appreciated :) Please don't suggest a brand change or start a debate on 12 vs 20 lol! :) The post is about methods to analyze published info. within a powder family to begin developing unpublished recipes for one's own use.
And no, I don't have pressure testing equipment or access to a lab ;)
So I'm looking for the tried and true tactics some of you have established to arrive at a load you're comfortable with using observation as your main tool. I do have a chrony but that is my only analytical hardware :)

Thanks much!

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blarby
February 11, 2013, 05:06 AM
There are very few powders that appreciate in burn and gaseous disposition rate along a linear force curve.

In short- many of them are not linear in power/pressure in relation to charge weight at all- and the curve is very unforgiving in most fine powders far before the math should catch up with you.

If this language confuses you- stop. Do a lot of homework until it does not.

What you are proposing is obviously doable- but will require a great deal of experimentation, when referenced to my current manuals.

If you could find a charge weight table that showed the pressure levels of your chosen powder in "X" cartridge, some extrapolations could be made to other cartridges- but the effect of different volumes of space in your cartridges is going to be .......tricky.


Start low, and KNOW what you are looking for in pressure signs in each type of cartridge you are loading. 20 ga has a very narrow bandwidth between useless, useful, and kablooey- be wary of that. you can good from good to very bad in very short order.

This is before wads are considered even in the least- which is another variable.

If you are going to seriously stray from published data in pursuit of a loading shelf stocked only with fairly obscure and hard to obtain powders- I would consider a pressure monitoring system of known repute before doing so.

Good luck, and godspeed !

BlessYoreHeart
February 11, 2013, 04:05 PM
Thanks much! Good information and appreciated :)

GLOOB
February 11, 2013, 08:17 PM
I dunno where you buy your powder, but VV is expensive stuff where I shop.

VV powders might be amazing for specific uses, making it worth the extra dough. But I am astounded one would choose this blessed holy water of powders to use in ways in which it was not intended.

Isn't that what surplus powders and Promo are for?

Walkalong
February 11, 2013, 09:30 PM
You are stretching your "interpolations" quite a bit.

kingmt
February 12, 2013, 04:20 PM
I do it work cheap $4 lb power & find nice loads but I have a hard time telling someone else to do it. Blarby have good advice tho.

oneounceload
February 12, 2013, 06:05 PM
Remington hulls and Winchester AA hull data is interchangeable as they are both the same type of hull

I agree, VV powder is the MOST expensive out there - I saw 1# containers costing more than I pay for 4#

However, turn the page and find N330 (16.5gr) AND N340 (17gr) using Winchester HS or compression formed plastic cases with a 7/8oz lead charge.

Problem 1:
I can only get (and have done so) N340 locally. So, comparing the two hulls, both use 16.5gr of N330.
The Winchester uses 17gr of N340.
So...it seems to me I could I safely start with 17gr of N340 in the Remington STS hulls.


NO! STS uses 16.5, you use 16.5 and err on a little less. This is NOT metallic where you start and work up - the recipe is as the recipe is. If you do not have a manual, perhaps you should put things aside until you get one and read one - for your safety and those around you

homatok
February 12, 2013, 08:39 PM
Try calling the powder manufacturer.

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