Min/max powder charges


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wworker
March 10, 2008, 07:58 AM
How is it that the loading manuals will have starting values for powder charges and then maximum values for loading charges and then the manufacturers will have much greater powder charges?

I pulled Winchester white box 9mm ammo and found a spread from 5.4 grains to 5.9 grains of W231 in the cartridges.

The loading manual says 4.8 grains is the maximum charge.

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USSR
March 10, 2008, 09:15 AM
wworker,

A couple of things. First, ammo manufacturers don't use cannister grades of powder like is sold to the public. So, if it is W231, then it probably has different burn characteristics than your or mine W231. Second, reloading manuals are vetted by the publisher's lawyers before going to publication (i.e. the lawyers make sure there are no truly max loads listed as max loads). Hope that helps.

Don

rcmodel
March 10, 2008, 02:13 PM
+1
No way factory ammo has plain old W231 powder in it that you & I can buy. It may look just like W231, but it does not have the same burn rate as W231.

The factories blend batches of bulk powder to meet pressure & velocity requirements for a specific load & lot number.
But they don't sell it to reloaders, and very likely will never use the same exact powder blend again in the future.

And not all load data is lower in the bullet companies manuals then in the powder companies manuals.
If anything, it's the other way around.

Winchester lists 26.3 grains max of W748 with a 55 grain .223 load.

Hornady lists 27.7, Speer lists 28.0, and Lyman lists 30.0.

There are many others like that one example.

rcmodel

Shoney
March 10, 2008, 02:28 PM
When looking at max loads, you must also consider the weapon they were using, compared to the competitiions listed weapon. Then there is a wide vaiety of factors that can created pressure and velocity changes.

A few factors which affect velocity (presuming same powder charge and primer):
Powder - - - powder varies from one batch to another
Weapon - - - tightness of chamber & lockup, length of barrel, tightness & condition of bore, height & condition of lands or is it polygonal
Case - - - thickness, capacity, alloy, trim length
Bullet - - - diameter, alloy of jacket, design of tip and base
Cartridge - - - fit in chamber, bullet distance from lands, crimp on bullet

All can and do influence the pressure and velocity.

dagger dog
March 10, 2008, 05:50 PM
You can shoot that 9mm (you didn't specify Luger) in a 1908 Luger or a state of the art new S&W M&P or a AR chambered for 9mm Luger . You can bet the bank that that round isn't going to cause any damage. The powder that Winchester uses isn't the same powder they sell on the reloading market. So equal powder weights on factory ammo does not equate to handloading!

wworker
March 11, 2008, 01:14 PM
Ok, the powder in the cases is probably not W231 even though it looks like it.

That said, it is still easy to see why the accuracy isn't so great with the powder varying from 5.4 grains to 5.9 grains.

When I reload 9mm Luger, I can usually maintain the accuracy of the powder to within .1 grains, thus improving the accuracy.

Steve C
March 12, 2008, 06:19 PM
The factories blend batches of bulk powder to meet pressure & velocity requirements for a specific load & lot number.
But they don't sell it to reloaders, and very likely will never use the same exact powder blend again in the future.


Actually you have it a bit backwards. Factories blend different bulk powders lots to achieve a specific burn rate for the canister grade powders they sell to reloaders, so data and pressures will be as close as possible the same from a can mixed 15 years ago to can mixed today.

The ammo manufacturer on the other hand, uses their ballistic laboratory to determine the load for each lot of bulk powder they purchase. If they are loading on several machines with different lots of powder the boxed product may have quite a mixture of powder weights in the individual rounds but the pressures and velocities will be very close. If you ever chrono factory ammo you'll find it to be usually less than 15 fps in STD.

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