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Hypothetically Speaking

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With the current uncertain availability of our favorite powders we are often required to pick something else which brings the question. Let's say you are dialed in and shooting tightly at your chosen distance and and have to switch to a different powder. Luckily you find one in the same family (IMR in this case) that has a burn rate within one number of your current fave. Based on the calculated velocity of your current load and using the same bullet, primer and brass you cook up a load that matches the calculated velocity of the original load.

Is this a reasonable approach to hopefully be hitting somewhere near the same spot on your target rather than starting low and working your way up one tenth of a grain at a time?
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Nope.

Typically, you won't find another powder from the same manufacturer that performs the same. On the other hand, it's usually fairly easy to find a powder from a different manufacturer that will perform very similarly.
 

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Even one or two steps different in the powder the burn rate is different. Which affects pressure. You cannot go by velocity in most cases. A faster burning powder might need a lesser powder charge and you might get the same velocities and you might not.

We make ammunition test barrels and bullet/ammo/powder manufacturers use the test barrels to develop loads for reloading data and for box ammo for a reason.

Don’t guess at loads….use a loading manual etc…

Also burn rates not only effect pressures but in regards to a gas operated weapon can effect how the weapon will function. Good or bad.

There are a lot of variables.
 

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Discussion Starter · #4 ·
I presented this because it seemed that with 168 grain SMK bullets the sweet spot for repeatable accuracy generally was reported back as 2600 FPS ± with a variety of powders . That's all. No further head scratching required.
 
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