Case head expansion.

[thezulu]

Hi Guys.

Another question from South Africa..

What is acceptable case head expansion?

I have a custom .240 Weatherby and load Somchem S385 powder. [very similar to MRP] One of my Favorite hunting loads is Norma Brass, CCI 250, 85gr XBT in front of 57gr S385 for 3686fps. The average increase in diametere over the belt is 0.01mm [sorry for the metric] every time I reload the case.

I know that this load is quite hot but was wondering what the actual pressure was like. The primers are nothing to write home about.

Accuracy is good and it is deadly on 350yrd Blesbuck.

Let me know what you think.

[Buffalobob]

I shoot a 240 Wby.

I am not sure case head expansion means anything in a 240Wby. Norma brass is relatively soft and hot loads will loosen primer pockets before anything bad happens. Some of my loads are so hot the primers are left in the action after I shoot.

A lot depends upon how your chamber was cut. I had a factory spec chamber with freebore in a Douglas barrel and took that off and had a minimum SAAMI chamber with no freebore cut in a Spencer barrel. Brass that had been shot with only moderate loads in the factory style chamber would not fit in the minimum SAAMI chamber because the belt had expanded by .001 inches.

I am not familiar with the powder you mention so have no understanding of amounts and pressure. I am using RL22 in a 30 inch barrel with 115 grain bullets.

[Black Diamond 408]

Usually you dont want the web area to expand more than .004"
yours is only .000393 Not too worry about that. If the primers get loose then you have exceded the case strength.

Like was stated earlier, Norma brass for Wby's is real soft.

Dave