Correct understanding load density

tpcollins · March 20, 2009, 10:00 AM

My Nosler reloading guide indicates load densities for .243 Winchester. For a Nosler BT 70 gr bullet, it lists 43.0 grains of 4350 with a 90% load density. For a Nosler BT 80 gr bullet, it lists 43.0 grains of 4350 with a 88% load density.

I look at this two ways:

- 43 grains is 43 grains. Load density should be identical for the same size charge for a given powder.

- considering the same COL for all, the heavier bullet would be seated deeper into the case and therefore reduce the amount of room available for powder in the case. 43 grains should occupy a larger percentage of the available room in the case with the longer (heavier) bullet than the shorter bullet. The heavier bullet should have a higher density . . . ?

But the percentages in my guide appear to go in the opposite direction of either of my thoughts. So there must be a third and correct explanation that I don't know about. Any help in understanding this would be appreciated, thanks.

a7mmnut · March 20, 2009, 10:05 AM

Load density is also based upon the area left in the case mouth to seat the bullet. Therefore, a longer or heavier bullet will have to be seated deeper to yield the same approx. OAL. So, there is less room for a powder charge. -7-

**Unclenick** · March 20, 2009, 02:58 PM

I think he said that? But yes, load density is the percent of total available powder space under the bullet base that is occupied by the volume of the powder charge. Fixing the charge at 43 grains and the projectile at one bullet design, then changing COL will alter load density. Load density is useful to know, as low enough load density can result in more erratic ignition and less MV consistency. I like to see at least 90% load density in match loads.

Nick

SL1 · March 20, 2009, 08:11 PM

tpcollins,

I looked at the info you provided and see your point. I don't have the manual you referenced, so I can't look to see if you missed something that explains the apparent discrepency. But, I do agree that it looks like a discrepency. Only 2 things come to my mind that MIGHT explaon it.

(1) Maybe they used two different "4350" powders. There are AA-4350, IMR-4350 and H-4350, which are all slightly different. But, ususally a manual will use the same one(s) for all bullet weights in a particular cartridge section, rather than one 4350powder for one weight and another 4350 powder for another weight. So, I don't think that is the likely explanation. Or,

(2) The bullets might be 2 REALLY different shapes, allowing the lighter bullet to be seated more deeply in the case than the heavier bullet. A VLD shaped bullet with its very thin, streamlined nose is a lot longer than most bullets of its weight. Conversely, a round-nosed or flat nosed bullet is a lot shorter than spitzer bullets of the same weight. So, for the same COL, a VLD would probably be seated deeper than a round nose IF the limiting factor is the rifle's magazine. Seating bullets so they are the same distance from the lands is a different thing, and the VLD bullet might be farther out of the case than the round nose.

But, frankly, neither of those explanations seems likely for Nosler .243 bullets in the Nosler manual.

Well, maybe there is a third possibility, and that involves bullets that don't have a lead core. All-copper and all-gilding metal bullets are longer than cup-and-core bullets because they are made completely of a material that is lighter than lead. Most manufacturers are coming out with those, now, and I think Nosler's are called E-tips. It would be possible for a 70 grain E-tip to be longer than an 80 grain cup-and-core bullet. But, last I heard, Nosler had not put their E-tips loads in their manuals, yet.

Anyway, you do understand loading density correctly. And, you demonstate an inquiring mind and careful reading of the data. Both real good qualities in a handloader.

SL1

wncchester · March 20, 2009, 08:46 PM

In real world load density terms, 88% is equal to 90%.

SL1 · March 20, 2009, 08:56 PM

Quote:

In real world load density terms, 88% is equal to 90%.

True, but he was expecting to see a real world INCREASE in loading density, not something lower that might actually be the same.

SL1

tpcollins · March 20, 2009, 10:24 PM

Thanks for the help guys. Actually it's getting worse. In the Nosler #6 reloading guide, page 157 indicates for the 70 gr Nosler BT, a load of 41.5 grains of IMR4064 has 3478 fps with a load density of 90%. On Nosler's website reloading forum, it shows the same identical info except the load density is listed at 82%. They have a phone number for reloading questions so I'll be calling them Monday to find out why this descrepancy and the reason for a lower density percentage when going from the shorter 70 gr to the longer 80 gr bullet with the same amount of powder.

SL1 · March 20, 2009, 10:37 PM

Please post what they tell you.

**Unclenick** · March 21, 2009, 12:11 AM

It is curious. Could be a typo. Watch out for a change in case brand, too.

March 20, 2009, 10:00 AM	#1
tpcollins Senior Member Join Date: February 18, 2009 Location: SE Michigan Posts: 558	Correct understanding load density My Nosler reloading guide indicates load densities for .243 Winchester. For a Nosler BT 70 gr bullet, it lists 43.0 grains of 4350 with a 90% load density. For a Nosler BT 80 gr bullet, it lists 43.0 grains of 4350 with a 88% load density. I look at this two ways: - 43 grains is 43 grains. Load density should be identical for the same size charge for a given powder. - considering the same COL for all, the heavier bullet would be seated deeper into the case and therefore reduce the amount of room available for powder in the case. 43 grains should occupy a larger percentage of the available room in the case with the longer (heavier) bullet than the shorter bullet. The heavier bullet should have a higher density . . . ? But the percentages in my guide appear to go in the opposite direction of either of my thoughts. So there must be a third and correct explanation that I don't know about. Any help in understanding this would be appreciated, thanks.

March 20, 2009, 10:05 AM	#2
a7mmnut Junior member Join Date: February 27, 2009 Location: NC Foothills Posts: 1,150	Load density is also based upon the area left in the case mouth to seat the bullet. Therefore, a longer or heavier bullet will have to be seated deeper to yield the same approx. OAL. So, there is less room for a powder charge. -7- Last edited by a7mmnut; March 20, 2009 at 10:06 AM. Reason: spelling

March 20, 2009, 02:58 PM	#3
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,060	I think he said that? But yes, load density is the percent of total available powder space under the bullet base that is occupied by the volume of the powder charge. Fixing the charge at 43 grains and the projectile at one bullet design, then changing COL will alter load density. Load density is useful to know, as low enough load density can result in more erratic ignition and less MV consistency. I like to see at least 90% load density in match loads. Nick __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

March 21, 2009, 12:11 AM	#9
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,060	It is curious. Could be a typo. Watch out for a change in case brand, too. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

March 20, 2009, 08:11 PM	#4
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	tpcollins, I looked at the info you provided and see your point. I don't have the manual you referenced, so I can't look to see if you missed something that explains the apparent discrepency. But, I do agree that it looks like a discrepency. Only 2 things come to my mind that MIGHT explaon it. (1) Maybe they used two different "4350" powders. There are AA-4350, IMR-4350 and H-4350, which are all slightly different. But, ususally a manual will use the same one(s) for all bullet weights in a particular cartridge section, rather than one 4350powder for one weight and another 4350 powder for another weight. So, I don't think that is the likely explanation. Or, (2) The bullets might be 2 REALLY different shapes, allowing the lighter bullet to be seated more deeply in the case than the heavier bullet. A VLD shaped bullet with its very thin, streamlined nose is a lot longer than most bullets of its weight. Conversely, a round-nosed or flat nosed bullet is a lot shorter than spitzer bullets of the same weight. So, for the same COL, a VLD would probably be seated deeper than a round nose IF the limiting factor is the rifle's magazine. Seating bullets so they are the same distance from the lands is a different thing, and the VLD bullet might be farther out of the case than the round nose. But, frankly, neither of those explanations seems likely for Nosler .243 bullets in the Nosler manual. Well, maybe there is a third possibility, and that involves bullets that don't have a lead core. All-copper and all-gilding metal bullets are longer than cup-and-core bullets because they are made completely of a material that is lighter than lead. Most manufacturers are coming out with those, now, and I think Nosler's are called E-tips. It would be possible for a 70 grain E-tip to be longer than an 80 grain cup-and-core bullet. But, last I heard, Nosler had not put their E-tips loads in their manuals, yet. Anyway, you do understand loading density correctly. And, you demonstate an inquiring mind and careful reading of the data. Both real good qualities in a handloader. SL1

March 20, 2009, 08:46 PM	#5
wncchester Senior Member Join Date: December 1, 2002 Posts: 2,832	In real world load density terms, 88% is equal to 90%.

March 20, 2009, 10:24 PM	#7
tpcollins Senior Member Join Date: February 18, 2009 Location: SE Michigan Posts: 558	Thanks for the help guys. Actually it's getting worse. In the Nosler #6 reloading guide, page 157 indicates for the 70 gr Nosler BT, a load of 41.5 grains of IMR4064 has 3478 fps with a load density of 90%. On Nosler's website reloading forum, it shows the same identical info except the load density is listed at 82%. They have a phone number for reloading questions so I'll be calling them Monday to find out why this descrepancy and the reason for a lower density percentage when going from the shorter 70 gr to the longer 80 gr bullet with the same amount of powder.

March 20, 2009, 10:37 PM	#8
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	Please post what they tell you.