Hypothetical load guesstimation.......

[ar15barrels]

I've found precision based trades like machinists and uber specific technicians have no need for touchy feely things like manners or courtesy.
If they're good, they get the work and keep chugging along.

Spot-on observation.

[bigbossman]

I still think OP's original reasoning made some sense and will wait for someone to address it. I'm not optimistic but I can always just use that bottle of Windex I guess

That ship has sailed, my friend.

[JMP]

So - here's the hypothetical question....... would it be SAFE to assume that the mystery powder is of a similar burn rate as these two powders, and therefore would be OK to substitute the load data of these known powders with lighter bullets for the mystery powder I pulled down? Does it work that way, or am I missing something?

That ship has sailed, my friend.

I am not comprehending your initial question. Is it that you want to reuse the "mystery powder"? Or, do you want to substitute it with new powder and components? If you are using new powder, why not simply go to the Hodgdon site and look up the charge you'd need. I am assuming that you are talking about the 8mm Mauser. That ain't a new cartridge. Just look up your rifle and see what specifications that it would have required.

[hambam105]

[QUOTE][this is a hypothetical exercise/QUOTE]
And this is a hypothetical answer, don't do it.

[3RDGEARGRNDRR]

I guesstimate triplex loads as well. Its pretty straightforward. I see no problems

[bigbossman]

I am not comprehending your initial question.

The question is pretty simple, but either I didn't express myself well or it just got lost in the noise.

Ok, let me see if I can make it more succinct:

I have some Milsurp ammo with a given cartridge (8mm) with a given bullet (200gr), using 44gr of an unknown powder.

I see that (for example) the min/max charge weight for a 200gr bullet using H4895 is inclusive of 44grs..... the max of H4895 is 45gr or so.

The question is, supposing I wanted to use the same unknown powder that I have, but use a lighter bullet (say 150gr), could I use the charge min/max data for the apparently similar H4895 as a starting point, or not?

And, if not, why not?

In general, when you go to a lighter bullet with a given caliber/powder, the max charge weight goes up. If this is the general case, then I should be able to either:

A) Use the 150gr bullet with the same 44gr charge weight of the unknown powder that works fine for the 200gr bullet without a safety issue.

B) Use the 150gr bullet with the 44gr of unknown powder, and work it up slowly over a chrono while watching for pressure signs and grouping, without a safety issue.

Is there an error in my line of thinking? If so, what is it and why?

"Don't do it" and "learn how to clean after firing corrosive ammo" are OK answers I guess, but don't answer my question and I've learned nothing in the process.

[ar15barrels]

In general, when you go to a lighter bullet with a given caliber/powder, the max charge weight goes up. If this is the general case, then I should be able to either:

A) Use the 150gr bullet with the same 44gr charge weight of the unknown powder that works fine for the 200gr bullet without a safety issue.

B) Use the 150gr bullet with the 44gr of unknown powder, and work it up slowly over a chrono while watching for pressure signs and grouping, without a safety issue.

Is there an error in my line of thinking?

Your option B should be fine within the SAME cartridge/bore size.
Guessing your powder and then trying to use book data would not be a good practice.

[pacrat]

A) Use the 150gr bullet with the same 44gr charge weight of the unknown powder that works fine for the 200gr bullet without a safety issue.

GTG

B) Use the 150gr bullet with the 44gr of unknown powder, and work it up slowly over a chrono while watching for pressure signs and grouping, without a safety issue.

GTG, with stated safety precautions.


Is there an error in my line of thinking? If so, what is it and why?

Part of your OP

So - here's the hypothetical question....... would it be SAFE to assume that the mystery powder is of a similar burn rate as these two powders, and therefore would be OK to substitute the load data of these known powders with lighter bullets for the mystery powder I pulled down? Does it work that way, or am I missing something?

You know that the existing mystery powder works. You also know that reducing bullet weight with same powder and charge will reduce OA pressure.

Blindly substituting by guesstamation another powder would not be a known.

Far too many things an average guy, even though an experienced loader just can't know. There is much more to actual pressure curves as they happen in a firearm than just burn rate variations. Different powders even though similar on burn rate charts, also react differently to variations in pressure vessels they are being burnt in. Some burn faster as pressure increases, some slow down as pressure increases. Skip the guesstamations. Leave it to the people with all the fancy expensive toys and knowledge to use them.

Stick with the knowns.

JM2c

[bigbossman]

Your option B should be fine within the SAME cartridge/bore size.
Guessing your powder and then trying to use book data would not be a good practice.

Ok, that's kind of what I suspected.

I was wondering if something could be extrapolated by comparing the powder "X" charge rate with similar charge weights of a known powder, but I'm satisfied from your posts and that of pacrat that this is just not the case.

You know that the existing mystery powder works. You also know that reducing bullet weight with same powder and charge will reduce OA pressure.

Blindly substituting by guesstamation another powder would not be a known.

Far too many things an average guy, even though an experienced loader just can't know. There is much more to actual pressure curves as they happen in a firearm than just burn rate variations. Different powders even though similar on burn rate charts, also react differently to variations in pressure vessels they are being burnt in. Some burn faster as pressure increases, some slow down as pressure increases. Skip the guesstamations. Leave it to the people with all the fancy expensive toys and knowledge to use them.

Stick with the knowns.

JM2c

Good advice, and thanks for bearing with me on this. As I stated just above, I was wondering if something could be extrapolated by comparing the powder "X" charge rate with similar charge weights of a known powder...... An intellectual exercise, if you will. Not looking to blow myself up, just tryng to puzzle things out and express my thoughts in public for scrutiny by those that know more/have more experience.

The whole point of this line of hypothetical reasoning was to see if there are ways to safely figure out what, if any use could be made out of pulled down powder that you can't ID but know one use for. It seems to me from our discussion here that one can only safely re-use the mystey powder for one of the two examples I stated earlier..... same caliber/same bullet or same caliber/lighter bullet with careful workups.

Trying to figure out how to apply it to something "similar" like a different caliber (.308, 30-06) or a known powder that looks like it has a similar burn rate would be a Bad Idea.

Thanks, guys!

[pacrat]

One positively safe use of unknown mystery pull down powder.

It makes great fertilizer to replentish nitrates in potted plants.

[rm1911]

Just get some trail boss, follow imr's recipe guide, and have fun.

[meaty-btz]

New loads are tested in labs..

They use tested burn rate data and math to get close enough idea to generally be safe before they build their first one.

They then test it in a test barrel and test chamber in a way that is safe if it blows and also rigged with sensors to record the pressures and other information.

Over time the data will be compiled and then the results published.

Wildcatters are a different kind of folks. The ones who come up with them often have a long history with firearms and are the slow, careful, exacting, kind of person. Heck many of them worked or were working in test labs for the major companies when they came up with the new cartridge.

Your average yahoo shouldn't even be reloading. Wildcatting? HAH!

Same thing about "working up a load" on a progressive.. yeahhh...

[JMP]

In general, when you go to a lighter bullet with a given caliber/powder, the max charge weight goes up. If this is the general case, then I should be able to either:

A) Use the 150gr bullet with the same 44gr charge weight of the unknown powder that works fine for the 200gr bullet without a safety issue.

B) Use the 150gr bullet with the 44gr of unknown powder, and work it up slowly over a chrono while watching for pressure signs and grouping, without a safety issue.

Is there an error in my line of thinking? If so, what is it and why?

That makes much more sense. If the bullets have the same diameter, similar composition, and are shot through the same bore with the same cartridge dimensions and charge, a lighter bullet will yield less pressure. With a lighter bullet, less force is needed to push it down the bore, so it will be propelled faster, leaving more space behind for the powder to expand, and this will result in a lower pressure.

I would caveat this by saying that you'd first need to assume the existing cartridge is safe, and of course, you will be using a different primer, which will result in some changes, but not that much.

I, personally, would not do it because it would be quite tedious and time consuming, but I'd not have an issue giving it a try from a safety perspective.