Internal Ballistics?

[86alaskan]

So, here's the question..... What is the approximate pressure change btween the chamber and the end of the barrel? Suppose you have a full tilt 300WM at 60Kpsi and a 26" barrel. Anyone have any idea as to the pressure of the gas as it hits open air? I'm looking at running an AAC TiRant suppressor on a 45 Colt carbine. The standard 250gr LRN 45 Colt cowboy load is approx. 12k, but then a more realistic hunting load 250gr XTP-HP is at 30k. i wonder what the actual pressure experienced by the suppressor would be.

 

[FearNoWind]

... Anyone have any idea as to the pressure of the gas as it hits open air?

Zero...

 

[86alaskan]

? really, how bout the pressure just behind the bullet right before it exits the barrel and dissipates? is that better? as i understand it there is a pressure spike and then it falls off as the bullet travels down the bore.

 

[shaughn]

You might want to call the suppressor manufacturer

 

[Ridgerunner665]

Right at 11,000 psi, varies some depending on powder burn rate....its the "Pmuzz psi" column below.

Cartridge          : .300 Win. Mag.(SAAMI)
Bullet             : .308, 190, Berger Hunt VLD G7 #30514
Useable Case Capaci: 80.404 grain H2O = 5.221 cm³
Cartridge O.A.L. L6: 3.340 inch = 84.84 mm
Barrel Length      : 26.0 inch = 660.4 mm
Powder             : Alliant Reloder-26 ?

Predicted data by increasing and decreasing the given charge,
incremented in steps of 0.676% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step    Fill. Charge   Vel.  Energy   Pmax   Pmuz  Prop.Burnt B_Time
 %       %    Grains   fps   ft.lbs    psi    psi      %        ms

-06.8   87    68.99   2890    3524   50602  10667    100.0    1.374
-06.1   87    69.50   2909    3570   51783  10705    100.0    1.360
-05.4   88    70.00   2927    3616   52990  10742    100.0    1.346
-04.7   88    70.50   2946    3661   54225  10779    100.0    1.332
-04.1   89    71.00   2964    3707   55487  10816    100.0    1.319  ! Near Maximum !
-03.4   90    71.50   2983    3754   56777  10852    100.0    1.305  ! Near Maximum !
-02.7   90    72.00   3001    3800   58096  10888    100.0    1.292  ! Near Maximum !
-02.0   91    72.50   3019    3846   59445  10923    100.0    1.279  ! Near Maximum !
-01.4   92    73.00   3038    3893   60825  10958    100.0    1.266  ! Near Maximum !
-00.7   92    73.50   3056    3940   62236  10993    100.0    1.253  ! Near Maximum !

 

[Mikecr]

+1 Ridgerunner665
Biggest variance to what he shows is burn rate to barrel length.
My max acceptable Pmuzz is <8Kpsi, and I chose barrel lengths and fast enough powders to get it.

26" is pretty short for such a large capacity cartridge. While not tacticool, I'd likely go 30".

 

[86alaskan]

Excellent, that's just what I was wondering. My 300wm is actually 22", but that blast is harnesseD by a SilencerCo Omega, so I'm not too worried about blast. Thanks ridgerunner