Pressure and Velocity comparison......

[Mus408]

Trying to get an idea of pressures with my .45 Colt "Cowboy Special" loads by comparing velocity of these to velocity of my standard .45 Colt loads. Will this be a valid indicator?
My Special load is the Starline Cowboy Special case with 5.5 and another batch of 5.7 gr. of Unique powder under the Xtreme plated 255 gr. cone shaped flat point bullet.

I plan on loading up some standard Colt .45 ammo using same bullet over 8.0 gr. of Unique and compare bullet speeds using same test gun...the Ruger Bisley NM Blackhawk with 5.5 barrel.
The Bisley has the .45 ACP conversion cylinder which will be used with the "Special" loads.

Not an expert here on ballistics but could you take from this that the .45 Colt load at lets say 800-850 FPS which is normally within the 14000 psi. range, would compare pressure wise with the Cowboy Special at 5.7 gr. of Unique powder IF velocity is within same range?

My .45 Special loads are to be used in my Ruger New Vaquero Birdshead revolver with 3.75 barrel length and the velocity would most likely be less than what the Bisley tests will show.

As a note...I had already tested these "Special" loads using above mentioned bullet with 5.5 of Unique powder which was giving speeds of 760-790 FPS.
Just curious to see what the pressures might be using this test.

Any thoughts here?

 

[Jimbo357mag]

The Quickload Reloading Software will give you very good comparisons of various loads. I actually think this might be more accurate for pressure than a chronograph on the firing line. Maybe somebody with that software can run some numbers for you.

 

[WIL TERRY]

A shorter 45SPECIAL case can cause markedly higher pressures with the loads that equal those from the SAAMI standard 45COLT 1.285" case length.

And so it goes...

 

[Chuck 100 yd]

A shorter 45SPECIAL case can cause markedly higher pressures with the loads that equal those from the SAAMI standard 45COLT 1.285" case length.

And so it goes...

^^^ I agree ^^^ You would be better off comparing data with the .45 ACP.

 

[Mus408]

A shorter 45SPECIAL case can cause markedly higher pressures with the loads that equal those from the SAAMI standard 45COLT 1.285" case length.

And so it goes...

^^^ I agree ^^^ You would be better off comparing data with the .45 ACP.

Hard to do with that since the bullet I'm using isn't normally used in a .45 ACP.

I seat the 255 gr. Xtreme at just below the knurled crimp area for a 1.235-1.230 COL.

Now even with this the bullet does sit about .030 deeper than a typical 230 gr. ACP ball nose bullet which is why I started the loads at 5.5 gr.

My thinking is that given same powder and bullet and test gun it will take X amount of pressure to accelerate the bullet to 800 FPS. With the shorter case it would take a X amount of smaller powder load to accelerate same bullet to the 800 FPS speed and still be around same pressure as the longer Colt case with more powder.

Will test this out later next week when I get back down to my range and will video the results!

 

[Greenjoytj]

I think the whole purpose of the short 45 Special case is to make reloading to milder power levels as used in the cowboy action shooting game. By nature of the game light loads win so your bullet weight should be closer to 200 grains than 255g the lighter the better. This presents to the reloader the broad array of 45 ACP load recipes to use in the 45 Colt, this was the purpose of introducing the short case.
By using light 45 ACP load recipes you'll keep pressures low for use in historic Colt revolvers. If your shooting a modern Ruger SA I'm sure they with stand full powder 45ACP loads, but again that's not the purpose of the new short 45 Special case it for gaming. Mostly I load my full length 45 Colt cases with a 261g bullet (that's how my 20:1 alloy and LEE 452-255 RF-DC mold drops them) over 35 grains of GOEX 2fg real black powder. It's more fun that way.

 

[wwb]

Pressure and velocity are only slightly related..... the burn rate of the powder used, and the weight of the bullet are big factors. Staying within recommended loads, fast powders with heavy bullets result in high pressures, but not necessarily high velocities. Barrel length also plays a part - long barrels produce higher velocities at lower pressures when used with slow powders.

There is no simple "one size fits all" rule for pressures and velocities.