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Old November 10, 2010, 08:09 PM   #1
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Heavy and Light Loads with bullets????

Had a discussion with a gun dealer about reloading:

Heavy bullets require lighter powder loads
Lighter bullets require heavier powder loads

Or is it vice versa?

I wrote it as I think it is.... Cuz, I think a bigger bullet takes up more space which delays it leaving the round/chamber. A lighter load of powder is required due to free space thereby it will have more time to burn and increase pressure to send the round forth to hither or yound.

Any words of wisdom out there to guide me down the yellow brick road?
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Old November 10, 2010, 08:15 PM   #2
Brian Pfleuger
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Generally, a heavy bullet uses less powder than a light bullet. The bullets inertia means that it takes longer to get moving and pressure builds faster behind it that would be the case for a lighter bullet.

All else being equal.
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Old November 10, 2010, 11:38 PM   #3
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These questions are fun as us "regular guys" toss our answers in before some of the real sharp minds show up and tell us exactly what is actually happening!

While it seems to me that a heavier bullet allows for less space in the case, which raises the pressure with less powder, it seems to make more sense (to me) that the heavier slug is more work to move down the bore -- which creates more pressure in the reaction -- which pushes enough given a lighter power charge weight.

Now I'm not even sure that came out in a way anyone can understand what I'm trying to say.

Remember that while a heavier bullet requires less powder than a light bullet, it's not to make it run the same velocity. It's merely to make the cartridge run at a similar pressure. When you run a heavier bullet and do so with less powder, you typically get the same/similar pressure, and less velocity.

Published load data typically shows an array of different bullet weights and data for them, but most of the loads listed have a similar goal... not velocity, not energy and not bullet weight or momentum or Taylor KO value-- but a similar pressure, somewhere just under SAAMI maximum.

To get to that spot, you use less powder for a heavier slug and more powder for a lighter slug. (assuming you are comparing the same powder)
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Old November 11, 2010, 08:37 AM   #4
Uncle Buck
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Lighter bullet, more powder...
Heavy bullet, less powder...

I wonder how heavy a bullet needs to be before we get to use no powder?

I think those loads are called rocks.

Anyway, that is the rule of thumb I learned.
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Old November 11, 2010, 08:41 AM   #5
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Reminds me of how when you buy more the price gets cheaper so I always ask if I buy enough are they free.
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Old November 11, 2010, 12:24 PM   #6
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It all depends on the type of load--if someone told me my 300 grain .44 bullets required small powder charges I'd laugh in their face. I've got light loads with heavy (for caliber) bullets, and I've got heavy loads with light bullets. I've also got heavy loads with heavy bullets as well as light loads with light bullets.

Heavy bullets absolutely do not require light powder charges, and light bullets absolutely do not require heavy powder charges.
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Old November 11, 2010, 09:29 PM   #7
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Its a matter of degree

Between what you call "lighter" and "heavier". Because you are limited to a given pressure, when you up one part of the package, you reduce another, and vice versa.

Pick a standard, lets say 158gr bullet and 14gr of powder X is a full pressure load. Go to a 180gr bullet and it maybe only 12gr of powder gives a full pressure load. Go to a 125gr and you might get 17gr of powder for a full pressure load. Since the pressure is the same, the heavier bullet is going to go slower, and the lighter one faster than the "standard".

Heavier bullet needs a lighter charge (weight) to keep the pressure the same. Lighter bullets can use a heavier charge weight while keeping the pressure the same, but they don't need to. You can load a "standard" weight powder charge with a light bullet, and still get some more velocity, you just won't be at full "standard" pressure if you do that.

Load a heavy bullet with the "standard" powder charge and you will be overpressure, possibly dangerously so.
All else being equal (and it almost never is) bigger bullets tend to work better.
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