Assume two cartridges are loaded equally except for bullet material. E.G.: same caliber, same powder, same charge, same bullet diameter and weight. Which will generate higher chamber pressure?
I have some thoughts on this and cannot get a straight answer from anybody. I'd like somebody that REALLY knows to help me with this.

Puncher

puncher,

That is a hard question to answer.
I have stuck both cast and jacketed bullets in the bore while working on squib loads.It requires
more effort to push the jacketed bullet from the bore than it does the cast bullet.Logic would seem to imply that the jacketed bullet would raise
pressures more than cast bullets do.

If you look in the Lyman Handbook # 47,you will see that the reverse is often true.It may be that
powder selection plays a part in this.

WC

Lead bullets obturate, to seal the bore more effeciently= higher pressure. My 2 cents. Jeff

There are so many variables that it is difficult to quantify: hardness of the bullet, amount of bearing surface, coefficient of friction, &tc. I have pondered this myself on many occasions, and searched for actual data that might give some clue. In 30-06, you can draw some comparisons because the third edition of the Lyman Cast Bullet book has published pressure data.

I did find one data point that correlates for bullet weight and powder charge: on page 106 of the Lyman 45th Edition Reloading book, for a load of 49 grains on IMR 4350 with 200 gr Winchester silver tip, Winchester Cases, Winchester primers, the published pressure is 39,900 CUP, and V=2380. On page 192 of the Third Edition Lyman Cast Bullet book, for a load of 49 grains IMR 4350 with 311290, 200 grains, No. 2 alloy, Winchester cases, Winchester Primers, the published pressure is 44,800 CUP and V=2403.

In this case, at least, the difference IS significant, and the higher pressure is obtained with the cast load. It is also significant that the 49 grain charge is listed as the "starting" load for the jacketed bullet, and the same charge is listed as the "maximum" load for the cast projectile.

FWIW.

Resp'y,
Bob S.

Howdy Puncher-

In your post you asked that someone answer that REALLY knows...

I suggest that the only folks that can answer your question quantitatively are the ones who perform pressure testing with calibrated equipment. A good source for that kind of info is usually the powder manufacturers who routinely publish their loading info. with accompanying pressure data. I've contacted the tech staff at Accurate Arms on a number of occasions and have always found them very helpful. In addition - their work has included a considerable amount of data on CB's as well as jacketed and so I'd recommend you give them a call.

Johan Loubser
Accurate Arms
Ballistic Lab Manager
800-416-3006

Best regards-

Horsefeathers,
BEST ANSWER I EVER GOT! Now, I've got something to work with!

Thanks so much! I owe Ya'!

Puncher