Check my math.

PinnedAndRecessed · March 7, 2006, 07:59 AM

Is this math correct?

Powder conversion factor:
1 gram = 15.4 grains
1 pound = 453.6 grams
6985.44 grains in a pound

If I load a 9mm with 4.3 Unique, then:
6985.44/4.3 = 1624.5 cartridges per pound.

Therefore I get 16 boxes of 100 out of every pound.

If powder is $15/pound, then the cost per box of 100 = $.94.

Sport45 · March 7, 2006, 08:32 AM

Close enough for what you're doing. The direct conversion from pounds to grains is 1# = 7000 grains (exact).

HSMITH · March 7, 2006, 08:32 AM

I came up with 3.5 more rounds per pound than you, and $.92 per box of 100.....

For all intents and purposes our math is the same.

Smokey Joe · March 9, 2006, 01:28 AM

Pinned and Recessed--and others--Yr math is impeccable but you're forgetting one factor that plagues every reloader I know: Spillage. It is next to impossible to reload 1624.5 cartridges without spilling a bit of powder here and there. Which will throw off yr calculations.

With my target loads of Win 231, I get 2058 rounds per pound. Yeah, right! Due to the occasional spill, I don't believe anyone can be that precise in their calculations.

BTW, P 'n' R--What does the .5 cartridge look like??

cdoc42 · March 9, 2006, 11:41 AM

Your math is correct, but there's a difference of opinion regarding the actual values for the conversion tables.

The use of "grains" is really a pharmaceutical term and dates back to when Apothecaries filled prescriptions. Today, things are rounded off so loosely it is hard to get accurate numbers.

It used to be that 64.8mg = 1 grain, so that 1 Gram (1000mg) would be 15.43grains. Today's Remington's Practice of Pharmacy says there's 60mg in a grain!

It has always been generally accepted that there are 454Gm in a pound, or 28.38 Gm in a ounce. But I was taught there are 28.35 Gm in an ounce, so that means we have 453.6 Gm in a pound!

So if we accept that, 453.6 x 15.43 = 6999.05 gr in a pound.

As such, I have always used 7000 grains as my reference.

The only concern I would have with your numbers is when the cost goes from under a buck to over a buck.

Leftoverdj · March 9, 2006, 12:21 PM

You must be buying kegs to get Unique for $15 a pound.

Y'all might recall a hubbub a few years back about "slippery math". That's the concept that reasonable approximations are often as useful as exact calculation.

The slippery math approach would be 7000 grains to the pound, 2000 3.5 grain charges, about a 3/4 that many 4.7 grain charges or 1500 to the pound so about a buck a hundred.

Easy to do in your head, allows a little for spillage, and plenty close for our purposes.

March 7, 2006, 07:59 AM	#1
PinnedAndRecessed Junior member Join Date: November 12, 2004 Posts: 449	Check my math. Is this math correct? Powder conversion factor: 1 gram = 15.4 grains 1 pound = 453.6 grams 6985.44 grains in a pound If I load a 9mm with 4.3 Unique, then: 6985.44/4.3 = 1624.5 cartridges per pound. Therefore I get 16 boxes of 100 out of every pound. If powder is $15/pound, then the cost per box of 100 = $.94.

March 7, 2006, 08:32 AM	#2
Sport45 Senior Member Join Date: May 25, 1999 Location: Too close to Houston Posts: 4,196	Close enough for what you're doing. The direct conversion from pounds to grains is 1# = 7000 grains (exact). __________________ Proud member of the NRA and Texas State Rifle Association. Registered and active voter.

March 9, 2006, 01:28 AM	#4
Smokey Joe Senior Member Join Date: July 14, 2001 Location: State of Confusion Posts: 2,106	You're all forgetting something! Pinned and Recessed--and others--Yr math is impeccable but you're forgetting one factor that plagues every reloader I know: Spillage. It is next to impossible to reload 1624.5 cartridges without spilling a bit of powder here and there. Which will throw off yr calculations. With my target loads of Win 231, I get 2058 rounds per pound. Yeah, right! Due to the occasional spill, I don't believe anyone can be that precise in their calculations. BTW, P 'n' R--What does the .5 cartridge look like?? __________________ God Bless America --Smokey Joe

March 7, 2006, 08:32 AM	#3
HSMITH Senior Member Join Date: June 21, 2002 Posts: 2,019	I came up with 3.5 more rounds per pound than you, and $.92 per box of 100..... For all intents and purposes our math is the same.

March 9, 2006, 11:41 AM	#5
cdoc42 Senior Member Join Date: March 13, 2005 Location: Pennsylvania Posts: 1,687	Your math is correct, but there's a difference of opinion regarding the actual values for the conversion tables. The use of "grains" is really a pharmaceutical term and dates back to when Apothecaries filled prescriptions. Today, things are rounded off so loosely it is hard to get accurate numbers. It used to be that 64.8mg = 1 grain, so that 1 Gram (1000mg) would be 15.43grains. Today's Remington's Practice of Pharmacy says there's 60mg in a grain! It has always been generally accepted that there are 454Gm in a pound, or 28.38 Gm in a ounce. But I was taught there are 28.35 Gm in an ounce, so that means we have 453.6 Gm in a pound! So if we accept that, 453.6 x 15.43 = 6999.05 gr in a pound. As such, I have always used 7000 grains as my reference. The only concern I would have with your numbers is when the cost goes from under a buck to over a buck.

March 9, 2006, 12:21 PM	#6
Leftoverdj Senior Member Join Date: October 15, 2004 Posts: 934	You must be buying kegs to get Unique for $15 a pound. Y'all might recall a hubbub a few years back about "slippery math". That's the concept that reasonable approximations are often as useful as exact calculation. The slippery math approach would be 7000 grains to the pound, 2000 3.5 grain charges, about a 3/4 that many 4.7 grain charges or 1500 to the pound so about a buck a hundred. Easy to do in your head, allows a little for spillage, and plenty close for our purposes.