I need some help. I am trying to make a chamber cast of a Jap type 38 rifle in 6.5mm and not having success. I am using "creosafe" and followig directions on the package. Have tried twice, both times could not remove the cast after 30 minutes.
Had to heat the barreled action to melt the creaosafe to remove it. What a mess!

Is there a trick to this? I leave the chamber dry - should I lube it?

This may be part of the problem - the reason I am making the casting. I loaded a few rounds - started low and worked up. The fired cases are enlarged in front of the case web. .007" at .3 from the base of the cartridge. No problems with extraction, primer edges are well rounded. No obvious pressure signs.
The bulge is concentric and tapers to the shoulder of the case. Think it may have been a poor chambering job or maybe someone hacked it up trying to remove a stuck case.

The gun shoots great- .75" 3 shot group at 50 yds with military open sights.

That seems to be the trait of Type 38 6.5X50 Japanese chambers. I have seen one "collectors grade" Type 38 (walnut stock, pristine bore and metal finish) and wish that I had bought it just to shoot so I could see if it too had the oval chamber.
Many were rechambered to 6.5X257 supposedly for brass availability, but I think cleaning up these chambers was another goal!
I have been considering chucking one up in the lathe and running one of the "new kid" 6.5 reamers in just to clean it up.

My rifle has a barrel that looks like a few miles of bad road, but holds about an inch and a half most of the time. More than minute of deer!
LouisB

trigger--

It sounds like you have a "jugged" chamber. There is a place that's not only not tapered, it's bigger than the portion behind it. That locks anything in the chamber when it swells or sets up.

Jack - Good to see you over here. Hope you come play more often!