Sunday 4 October 2009

This has got me thinking

I appears that Nitrochemie do not offer powders for reloaders any more. I will try and verify that tomorrow though. I have calculated two loads for the .338 Federal and the .338 RCM (which I had to fudge on the basis of the .300 RSAUM, since my QuickLoad doesn't have that cartridge yet).

**** Input data:                         Date: 4-Oct-2009     Time: 13:25:07
Cartridge................. = .338 RCM Fudge II - from .300 RSAUM
Projectile type........... = 8.58, 9., Möller 8,5 mm KJG S with boattail
 
Max.avg.pressure(Piezo SAA)= 448 MPa     Shot start / init pressure = 15 MPa
Projectile weight       (g)= 9.01        Groove caliber         (mm)= 8.59
Length of cartridge    (mm)= 71.76       Length of case         (mm)= 50.88 
Case capacity       (cu.cm)= 4.67        Length of projectile   (mm)= 30.48 
Length of barrel       (mm)= 560 
**** Values calculated:
Seating depth          (mm)= 9.6         Volume displaced    (cu.cm)= 0.55 
Comb.chamber volume (cu.cm)= 4.12        Projectile travel      (cm)= 51.87 
**** Input data:
Propellant type........... = IMR 4895
Charge weight...........(g)= 3.731       Load density......(g/cu.cm)= 0.905
Heat of Explosion   (kJ/kg)= 3860        Ratio of spec. heats cp/cv =  1.2431 
Solid density     (g/cu.cm)=  1.58       Weighting factor...........= 0.50
Burning rate factor Ba(1/s)= 0.61        Pro-/degressivity factor a = -0.15 
Burning limit ......... z1 = 0.6         Combust.Chamber Vb(m³)= 4.121772E-6
Factor.................. b = 1.6         X-S.Area of Bore A(m²)= 4.7291E-5
Bulk density      (g/cu.cm)= 0.890       Projectile mass mp(kg)= 9.007E-3
Loading ratio           (%)= 101.7       Projectile travel x(m)= 5.1871E-1
 
**** Results calculated:
Maximum pressure ........ =  430 MPa     Way of projectile at Pmax =  43.5 mm
Muzzle velocity  ......Ve =  978 m/s     Muzzle pressure .......Pe =  71 MPa
Project. energy at muzzle =  4310 J      Fraction of powder burnt  = 99.9  %
Projectile travel time from 10% Pmax to muzzle = 0.96 ms


and

**** Input data:                         Date: 4-Oct-2009     Time: 13:25:07

Cartridge................. = .338 RCM Fudge II - from .300 RSAUM

Projectile type........... = 8.58, 9., Möller 8,5 mm KJG S with boattail

Max.avg.pressure(Piezo Wil)= 440 MPa     Shot start / init pressure = 15 MPa
Projectile weight       (g)= 9.01        Groove caliber         (mm)= 8.59
Length of cartridge    (mm)= 71.12       Length of case         (mm)= 51.16 
Case capacity       (cu.cm)= 4.67        Length of projectile   (mm)= 30.48 
Length of barrel       (mm)= 560 
**** Values calculated:
Seating depth          (mm)= 10.51       Volume displaced    (cu.cm)= 0.55 
Comb.chamber volume (cu.cm)= 4.12        Projectile travel      (cm)= 51.93 
**** Input data:
Propellant type........... = Norma 200
Charge weight...........(g)= 3.031       Load density......(g/cu.cm)= 0.969
Heat of Explosion   (kJ/kg)= 3850        Ratio of spec. heats cp/cv =  1.239 
Solid density     (g/cu.cm)=  1.58       Weighting factor...........= 0.50
Burning rate factor Ba(1/s)= 0.555       Pro-/degressivity factor a =  6.5 
Burning limit ......... z1 = 0.3         Combust.Chamber Vb(m³)= 3.126928E-6
Factor.................. b = 2.2         X-S.Area of Bore A(m²)= 5.695E-5
Bulk density      (g/cu.cm)= 0.952       Projectile mass mp(kg)= 9.007E-3
Loading ratio           (%)= 101.8       Projectile travel x(m)= 5.1934E-1
 
**** Results calculated:
Maximum pressure ........ =  430 MPa     Way of projectile at Pmax =  32.1 mm
Muzzle velocity  ......Ve =  948 m/s     Muzzle pressure .......Pe =  46 MPa
Project. energy at muzzle =  4047 J      Fraction of powder burnt  = 100  %
Projectile travel time from 10% Pmax to muzzle = 0.92 ms

So this is pretty much 30m/s more muzzle velocity in exchange for a bigger cartridge, possible problems with sound moderation and maybe greater difficulties getting a licence. OTOH this increases the usable range of the KJG from 200m to just over 250m.

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