I am going to use common cartridges, not schuetzen cartridges, to try to shed some light on a phenomenon that interests me.

Using small capacity cases, e.g. .30 Carbine, you can shoot cast bullets successfully at full pressure (40,000 lbs)and full velocity of it's jacketed counterpart. However, using large capacity cases, you cannot (e.g. .30'06). If we accept the Carbine full velocity as being 2,000 fps, we can easily get 2,000 fps with the 30'06. However, we can neither get full .30'06 velocity (2800 fps) nor can we shoot cast bullets successfully at 40,000fps. At least that has been my experience. I am speaking of doing it with target accuracy. That has now become one half minute accuracy. Now understand, my experience with modern cartridges and cast bullets is somewhat dated. My big sport for the past several years has been Schuetzen shooting, and fifteen years before that, the BPCR Silhouette rifle. 

I do note that some fellows in the CBA have been shooting faster than previously with excellent results but I have not really kept up with what is happening on that front. Someone feel free to bring me up to date.

At any rate, the point of this topic, is to simply try to find the elements that allow somewhat better results with small cartridges in OUR sport (Schuetzen shooting). When I say small, I am referring to the .32/357 Dell and the .32 Miller Short as compared with the larger capacity traditional cases, the .32/40 and .38/55, etc.

Now, it is obvious that one of the benefits (highly touted) is that less powder room allows smaller deviations. The powder simply has less "room to roam" leading to more consistent velocities. Powder position has long been known to have a serious effect on consistent or inconsistent velocities. I definitely subscribe to this theory as being at least one of the advantages of the small case.

Understand, when we drive a bullet at the desired (for me, at least, and I believe Mr. Borton and Mr. Darr have suggested this) velocity of 1450-1500 fps our small cases require higher pressures to effect this. The larger the case, everything being equal,  less pressure is required to gain the desired velocity. In fact, it is difficult to make use of the same level of pressure without bad shooting in large cases. So, I wonder if there are not OTHER benefits of using the smaller case than just powder position?

I, personally, have had more consistent results using my .32/357 Dell than I have the .32/40. I am NOT saying that it is not possible to be competitive with the .32/40 or .38/55 but I DO suggest that it is easier to perform well with the smaller case.

I hope that this has not been TOO muddled....

Dale53

Quote:


I don't think that this is true.
In order to make a given bullet go at a given speed, a force must be applied to the base for a certain time.
There are a large number, probably an infinite number, of force/time profiles that will result in the bullet going at the specified velocity.
These profiles would be unique to the powder type, AA#9 has a different profile than IMR4227 for example.
For a given powder, less would be required in a smaller case than a larger case for the specified bullet/velocity combination, because of the larger expansion volume in the larger case.
It is probably true that higher PEAK pressure is required in a smaller case than in a larger, for the bullet/velocity. Or, another way of looking at it, the smaller case doesn't have room for enough slower powder to get the bullet to speed, but the bigger case has the room to burn at lower peak pressure for the required bullet/velocity.
The energy, I think, imparted to the bullet, is a function of the area under the pressure curve-not the peak pressure.
Now E = MV^2/2g, so velocity isn't linear-not at all.
To summarize, I think that for a given velocity/bullet:
Smaller cases need less, faster, powders at higher peak pressure 
Bigger cases can use more, slower, powders for lower peak pressures; or the more, faster, powders at lower peak pressure.
EX: 32MS needs AA#9, high peak pressure
32/40 can use IMR4831, low peak pressure, or
AA#9, more than 32MS, lower peak pressure than 32MS but higher peak pressure than IMR4831.
joe b.

In both cases we still have to be careful not to ring our chambers. This is not so much a product of pressure but how the pressure is applied. When Charlie Dell did his studys on ringing he found that  a. In most cases chamber ringing happened slowly over many shots. and  b. That seating the wad off the powder was critical to not ringing the chamber. The powder must slump to 1 side in the case. The powder can still be restricted but the case has to leave enough room to seat the powder off the wad.

40 Rod