Chamber presures

[PacMan]

After reading some post about rechambering a handgun from 45 colt to 454 Casull i have a question.
Lets use the 38/357 or 44spl/44mag therefore taking out the large/small primer debate.

Using the same bullet, powder and primer and fixed test barrel.
Using the 44spl case loaded to a velocity of 1400fps and a 44mag case loaded to the same velocity would both generate the same chamber presures?

Thanks

[303Guy]

Do you mean by loading to the same overal length? If so them my answer would be yes, the pressure would be the same. That's because case volume would be the same with boolit seated further out of the shorter case. There were boolits designed with two crimp grooves for loading 357/44 magnum loads in 38/44 special cases.

[HeavyMetal]

On the other hand if you use a boolit like the 429421, use the same 1400 FPS load, and seat the 429421 to the crimp groove in both 44 spec and 44 mag case's the pressure in the special case will be much higher!

One of the Speer manuals, in the 9mm section, cautions against a loose bullet fit. If the bullet "accidentally" seats itself futher into the case when it hits the feed ramp pressures can spike very high. A .020 "extra" seating depth generated an additional 20,000 psi over the standard load If I remember correctly, please read the 9mm section in a Speer manual to confirm.

All in all same load, smaller "combustion chamber" (read less case volume) means higher pressure as a general rule of thumb. I'm sure odd case's exist but for safety this is the rule I always go by.

This is one of the many reasons you need to work up a load, and particularly high performance loads in a specific lot of brass. Replace the brass or any other component and you start over.

[PacMan]

I did not spell it out so here goes. Using the same bullet in both cases would mean seating to the same depth/crimp grove in each case. I understand that reducing case capacity increases chamber presures and that is the reason both would be loaded to the same velocity using the same powder not charge.
My corny is down so i have no way to check but using the same load in both case should not produce the same velocity.
I fat fingered the velocity in the OP and meant to say 1200fps.Will edit and correct.
We are not talking same load but same velocity
I would think that the preasures would be the same but dont know.

Thanks for the replys guys.

[wiljen]

I ran a couple loads through QL 3.4 to show the numbers:

Assumptions: 429421 at 245gr bullet loaded to crimp groove. Blue Dot powder. 10 inch barrel.

44 mag:
Overall length 1.610
Charge to Reach 1400 fps 15.1gr Blue Dot
Pressure (Peak) is 30043 PSI

44 Spec:
Overall Length 1.485 (same amount of bullet inside case as in the 44 mag)
Charge to reach 1400 fps 13.9gr Blue Dot (Dangerous Overcharge DO NOT USE)
Pressure (Peak) 36877 PSI


A second run using the same OAL for both shows the following:

44 Mag 1.610 OAL, 15.1gr Blue Dot 30043 PSI at 1400 fps
44 spec 1.610 OAL 15.1gr Blue Dot 30090 PSI at 1400 fps (Again, not a safe load in 44 special)

So when loaded to the same OAL, they share the same pressure. When loaded to the proper OAL for the cartridge to the same velocity, they do not.

[PacMan]

wiljin- that answers my question and i thank you for your time.
I have heard you guys talk about Quick Load before and i realize that it may not be exact sience but where can i get the program?

Thanks again guys
Dwight

[Iron Mike Golf]

wiljin- that answers my question and i thank you for your time.
I have heard you guys talk about Quick Load before and i realize that it may not be exact sience but where can i get the program?

Thanks again guys
Dwight

You can order it here (http://www.neconos.com/details3.htm).

[ColColt]

Does it tell you the proper BHN boolit to use based on your choice powder, etc.? I looked at it and saw a lot of different qualities it displays but, I didn't see that.

[lwknight]

Most big boomers have 6 to 8 inch barrels and the only way to maximize velocity is to use a powder slow enough to burn throughout the launch. Slower powders require more case capacity to build up to the max desired pressures.

Barring short barrels , the right load can always benifit from more case capacity

[BAGTIC]

Including short barrrels too.

The powder that gives highest velocities in longer barrels almost always gives highest velocities in shorter barrels also.

[Bret4207]

Does it tell you the proper BHN boolit to use based on your choice powder, etc.? I looked at it and saw a lot of different qualities it displays but, I didn't see that.

You're kidding, right? If not, then absolutely nothing I've said to you sunk in.:sad: There is no "proper" Bhn for a given load. The number of variables involved are too great. If you want a supposed pressure for the point of plasticity, then the Lee book has a chart or formula, but it's not a "rule" that determines "proper" Bhn.

Damn the idiot that came up with the "hardcast" advertising slogan!:takinWiz:

[ColColt]

Why, Bret-I thought everybody knew you have to match your chamber pressure and BHN values to get the boolit to obturate properly...:p Yep, just joking. I knew better than to delve into that so, you can relax.:razz:

[Bret4207]

Sunamagun! You got me big time with that one!

[ColColt]

My M29 doesn't seem to care what alloy you use with your loads. Sizing boolits to throat diameter in that revolver worked perfectly whether it be BHN 12, 15 or more-no leading(knock on wood). That should tell you something.

[BAGTIC]

Why, Bret-I thought everybody knew you have to match your chamber pressure and BHN values to get the boolit to obturate properly...:p Yep, just joking. I knew better than to delve into that so, you can relax.:razz:

Make it big enough in the first place and you don't need to worry about it expanding to fit the grooves.

[ColColt]

Make it big enough in the first place and you don't need to worry about it expanding to fit the grooves.

Thanks for the astounding advice.