I'm getting ready to do a chamber cast, and maybe slug the barrel, of an old English rifle that I have acquired (.242 Rimless NE). I'm using cerrosafe from Brownell's. Are there any precautions or tricks of the trade that I should be aware of before doing these little tasks ? Thanks for any input.

Frank,

If you send me an email I will send you a PDF file I have on casting chambers. Lots of good info and pictures.

My E-Mail is joycebeller@msn.com ..... thanks.

No secrets at all. Just plug the barrel 1/2 inch or so into the rifling with a small piece of cloth and pour in the cerrosafe. It may do a bit better job if the barrel is preheated with boiling water and dried before pouring. Measure cast just 1 hour after cast is made to get exact dimentions.
You are doing this cast with the barrel off the action arn't you.

The trick is taking it out at the right moment. It is not unheard of to get the casting stuck in the chamber, especially if the chamber is rough or lacks taper. The longer you leave it in, the more likely it is to get stuck.

On the other hand, if you mess with it before it has fully solidified, then the liquid cerrosafe will spill out and make a huge mess. It does take a long time for the cerrosafe to solidify, 5 - 10 minutes.

If it does get stuck, you can dunk the breech in boiling water to melt the cerrosafe out. Then start over.

Contrary to what a certain vendor claims, it will not give you exact dimensions. It starts expanding as soon as it solidifies, and ends up being 0.001" - 0.002" larger than the true diameter.

My practice is to cool it as soon as it is removed by dunking in tap water, and then measure immediately. And chances are, it will still be slightly oversize.

pope

I have made hundreds of chamber casts and my experience is definitely different than yours. Cerrosafe will solidify, even in a heated chamber, in less than a minute. It will shrink slightly at first and then begin to expand. You can see the changes with your mic. The trick is to know exactly when to make the measurements. I believe that the makers have established the timing based on actual tests and would trust their judgement over a quick cool off and then a measurement. JMHO

Frank, you can pre-heat the chamber with momma's hair dryer.

Ray

For me, timing and preparation is everything. I generally leave the barrel on the action unless I can't gain access to the chamber otherwise. Where I can, I wipe the chamber with a "lightly" oiled patch and then warm the area with a propane torch to impede the rapid solidification which prevents the cerrosafe from becoming crystallized. If done right, this gives me a beautiful, un-galvenized looking copy of the chamber. If done wrong, it sucks.

The reason I'm doing the chamber cast is so I can send off the casting to RCBS so they can make me custom dies. If the cerrosafe changes demensions to any great degree, how can RCBS properly make my reloading dies accurately ???

quote:

Originally posted by Frank Beller:
The reason I'm doing the chamber cast is so I can send off the casting to RCBS so they can make me custom dies. If the cerrosafe changes demensions to any great degree, how can RCBS properly make my reloading dies accurately ???

Since RCBS is making your dies, and has been doing this for years, talk to them and get their advice. They have a pretty good idea on what the dimensional change will be based on when you did the cast. Be sure to include that. What caliber is it and why can't you just send some fired cases?

quote:

Originally posted by Cheechako:
pope

Cerrosafe will solidify, even in a heated chamber, in less than a minute. It will shrink slightly at first and then begin to expand. You can see the changes with your mic. The trick is to know exactly when to make the measurements. I believe that the makers have established the timing based on actual tests and would trust their judgement over a quick cool off and then a measurement.

Hardly. Because of its low freezing point, cerrosafe may take several minutes to cool enough to solidify. Or at least, the center may remain liquid for several minutes. I learned that lesson the hard way when I tried to remove a casting too soon, spilling liquid cerrosafe into the action and all over the wall and floor.

Any metal (or ALMOST any metal) will shrink slightly as it cools. If you are measuring a still warm casting, you may indeed see some shrinking as it cools. However, if you quench it in water immediately as I do, then the temperature effect disappears and only the time effect is left, and you'll see constant expansion for 24 - 48 hours.

I have never seen any published data that noted the temperature or how the reference diameter was determined. My data is based on comparing the chamber cast to measurements taken with a calibrated internal micrometer accurate to 0.0002". At no time, with any method, have I seen a cerrosafe casting reproduce the true diameter. It is always oversize, and only a question of how much.

Chambers that have a reverse taper or tooling marks may not let go of a casting even if you do everything right. I have a 357 rifle that I have tried over and over again to cast, and it'll stick every time. A smooth, tapered chamber shouldn't be a problem.

A cast sent to RCBS should be just fine for them to make dies.

So am I the only luddite still using sulfur?

Great thing is you can write the date on it with a fine sharpie and be able to compare castings over time, or at least that is the idea since a lot of stuff I can't seem to find when I need it.

But it is nice to have a record of throat erosion.



Somewhere.

pope

I think you might be heating your cerrosafe too hot or the chamber is too hot. I was working on a wildcat cartridge just this afternoon and made 5 casts. 4 of them solidified in less than a minute and one took a little less than two minutes because the barrel was hot - too hot to handle comfortably.

Cerrosafe is used by tool and die makers and it's properties are well documented.

First you said that a casting shrinks slightly and then you said you have never seen one that wasn't oversize??????

I have never seen a reverse taper chamber. How do you extract the fired cases? An even better question is why is it reverse tapered?

Ray

quote:

Originally posted by Cheechako:

I have never seen a reverse taper chamber. How do you extract the fired cases? An even better question is why is it reverse tapered?

Ray

I have and it's the result of over zealous polishing.

quote:

Originally posted by malm:I have and it's the result of over zealous polishing.

I'd call that a Ruined Chamber or a One Shot Chamber.

Ray

quote:

Originally posted by Cheechako:

quote:

Originally posted by malm:I have and it's the result of over zealous polishing.

I'd call that a Ruined Chamber or a One Shot Chamber.

Ray

Me too!