amount of compression used in original .45-75 black powder cartridges

[w44wcf]

I dissected 2 original .45-75 b.p. cartridges to learn how much compression was used.
One is headstamped W.R.A. Co. and the other, S UMC H (solid head).

Surprisingly, they both contained an average of 76.3 grs. of b.p.

The bullet seating depth was .54" in both cartridges.

The average amount of factory compression that was used was .20" (settled charge).

w44wcf

[Hobie]

Interesting!

[Grizzly Adams]

Any idea as to the granulation size of the powder used?

[w44wcf]

According to the book "Complete Guide To Handloading" by Philip B. Sharpe,
FFG granulation would be in the 16 to 24 mesh per inch range
and that is what the powder screened to. 

In addition, there was a very small amount of fines, probably as a result of the
powder being compressed in the loading process.

w44wcf

[john boy]

John ...
*  What is the case length of either the WRA or UMC?
*  What is the length of the pulled bullet?
*  What is the thickness of the wad?
*  Where is the bullet crimped - above, at or below the driving band?
(Have to ask because the original you gave me is in Marmora)

Here's what I did for a compare:
Case -  1.886"
Bullet - 0.900"
Powder - 76.3gr Express FFg
If bullet was seated 0.54 ... it would be crimped 0.06" above the driving band

Powder - settled but not compressed = 0.26" to top of mouth. Add 0.20 for compression.  Subtract 0.03 for fiber wad.
Math = 0.43" for the bullet to be seated
Bullet seated 0.54 leaves 0.11" difference 

[w44wcf]

John Boy,

In answer to your questions:

Case length of either the WRA or UMC = 1.880"
Length of the pulled bullet = .90"
Thickness of the wad = There was no wad in either cartridge.
The bullet is crimped above the 1st driving band.

Original .45-75 Cartridge dimensions:
2.24" Cartridge OAL
1.88" Case Length
0.36" Bullet protrusion (2.40"-1.88")
0.90" Bullet length
0.54" Bullet seating depth (.90"-.36")

Powder settled but not compressed - .34" from case mouth (solid head button pocket case).
Powder Density - I have not checked but will compare to Goex, Schuetzen and Swiss and post
the result in the next few days.

If bullet was seated 0.54 ... it would be crimped 0.06" above the driving band

That would be about right .......closer to .04" using the 1.88" case.

w44wcf

[w44wcf]

For what it's worth (Inquiring minds want to know these things.  ) I compared the powder volume / weight of the b.p. used in the original .45-75 cartridges against the current lots of Goex, Schuetzen and Swiss that I have. To do that, I used the original balloon head case that was of the solid head button pocket type. I settled 75 grs., by weight into the case and measured the amount of headspace (distance fom case mouth to top of the powder).  I then determined the amount of each powder that would fill the same volume.

Result:
Goex: 72 grs.
Schuetzen: 75 grs. ( same volume / weight as the b.p. in the original ctgs.)
Swiss: 78 grs.

Happy New Year!
w44wcf   

[john boy]

John ... Happy New Year!
Interesting comparison.  Your lot of Goex is one of the better ones.  The density of Goex usually runs 10 - 12% less than Swiss.  Your lot is only 8% less.  I'd save that can! 

Since I have many cans of Schuetzen ... I'll start loading the 45-75's with it