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Cerrosafe

courtiron

Aluminum
Joined
Mar 25, 2009
Location
Waukesha,WI
I have two 30 Herrett TC contender barrels, a 10" and a 14". I fire-formed and loaded the once fire-formed cases some time ago. Unfortunately I didn't keep the records regarding which barrel they were fire-formed in. My bad.

I am getting split necks on the silhouette loads in the 14” barrel. I stopped when that happened and did not switch barrels to see if the problem occurred in both barrels. I thought I should figure out what was wrong before trying the 10" barrel. I want to measure the chambers to find out if the problem is the old brass or the fact that I may have two different chamber sizes. Rather than stressing out trying to figure out what happened 20 years ago I opted for a comparison of the chambers to come up with an explanation.

I am going to make a chamber casting of each of the 30 Herrett barrels. Is there any advantage to preheating the barrel before pour the cerrosafe into the chamber?

paul
 
There's no advantage to preheating the barrel with Cerrosafe. Room temperature is fine for the barrel, a light oil film is good for a parting agent. Mind the time period when measuring the casting, Cerrosafe is a moving target to get an accurate measurement. One hour after the cast is made the casting is the same size as the chamber. At other times one must calculate the contraction or expansion from well known data but why add the complexity of doing that?
 
It is NOT the chambers causing the problem. It is the brass. Regardless of which barrel they were fire formed in the necks expand a little when fired and you will have the problem in both barrels. The brass is harder than it should be causing the cracks when the brass expands at the neck. You need to break down the loads and anneal the cases. Because this involves heating the case the bullet, powder and primer must be removed.

The easiest way I know of to anneal cases without a bunch of hassle is to use a pie pan deep enough to fill with water so that when you lay the case down it is COMPLETELY covered.

Place a cartridge standing up in the partial filled pie pan. Heat the NECK of the case to a dull red with a propane or MAPP gas torch (don't get it so hot that you melt the brass) then knock the case over into the water. Don't worry that the shoulder gets hot, that wont hurt a thing. By standing it in the water you insure that you do not get the cartridge head too hot (annealing the head is not a good thing). Once cool reload and enjoy.

I have seen this problem with new unfired brass as well as once fired brass. It is MOST common in cases that have been work hardened by re-forming. That may or may not be the case here. HOWEVER, if the cases are cracking in the neck the BRASS is too hard and needs to be annealed. Don't waste your time casting the chamber. You will learn nothing of value in this case.
 
MIBill
That certainly occurred to me as well. It's just that all this brass is on its first full power load, and I fired hundreds of rounds of this same stuff before... just that it was about ten years ago. I just don't remember which barrel. Could also be age hardening.
If I have to break it down, I would more than likely just reload it with low pressure lead bullet loads and replace the brass.
I have an induction heater which I could automate to anneal the brass if I go that route. The advantage of the induction heater is I can take it to a intermediate softness and repeat and replicate the results quite easily. The chamber casts are more for my curiosity at this stage. The TC barrels didn't exactly have the reputation as the finest barrels... I want to see if the chambers are the same.
The shipping confirmation just came for the cerrosafe. It should be here in a few days.
paul
 
Its a hard brass problem as mentioned above. The brass has not gotten hard because of firing, it has more probably gotten hard from being worked from its parent cartridge. I assume you made it from 30-30 or 225 Winchester. When brass is worked slowly in steps it gets hard but it can be worked in this manor without breaking but fire forming is different. The violence from being suddenly final formed is cracking it. Its to hard to be stretched that quickly. Stand them in 1/2 inch of water and heat the necks and shoulder angle to dull red and tip them over in the water. That will put them back to an annealed state.

You can measure any discernible differences in the cases with a with a $40 Walmart micrometer It will be accurate withing .001 inch which is fine for your purposes. If you insert a fired case into each chamber it will tell you which chamber is tighter. It will act as a very simple GO / NOGO gauge. You should be able to quickly tell which chamber is tightest and use that means to separate your brass. Throwing a chamber cast, while is sounds neat will provide you with nothing that can't gleaned from a fired case.

Occam's razor always applies.
 
I find it a good idea to heat the chamber area to about 100 F before pouring the Cerrosafe. You then get a clean, smooth casting with little to no wrinkles. Oiling the chamber lightly helps, too

RWO
 
Chamber size follow-up

I have cast the two chambers in question. All measurements taken 1 hour after casting.
The 10" barrel is .4265 ahead of the rim, .4125 at the shoulder and .3410 at the neck
The 14" barrel is .4270 ahead of the rim, .4150 at the shoulder and .3420 at the neck
Which begs the point of annealing, which I will do, but may help to explain why I was able to fire a few hundred rounds without a problem from the 10" barrel.
There is a threshold to everything, and the 14" barrel might have been the tipping point.

<completely off topic, but does anyone else experience the spell checker not working if they are using a Linux system vs win7?>


paul
 
Just don't overly heat the chamber area. The surface finish on the casting will go down dramatically. You will get a really large grain, rough surface finish. Just a little warm will help the casting to fill the chamber evenly. No hotter than you can comfortably hold in a hand for an extended time.
 
I have seen brass and silver crack when quenched too quickly. Brass does not need to be quenched to be annealed. I'd just heat it up to a dull red and let it cool by itself. You can stand in water to protect the other end of the case,but just let them air cool,and I'm sure your cases will last longer.

We ruined a few jewelry patterns made from brass by quenching too fast after heating,and knocking the cases over would be even faster than taking tongs and quenching.
 
Induction anneal

Part of the neat thing about the induction heater when used to anneal is the very small heat affected zone that can be obtained. I am pretty sure that I can heat an area about 3/16" wide to nearly any temp from boiling water to melting the brass and anywhere in between. The time to reach annealing temperature will likely be 2 to 4 seconds.

I can also control the residual temp in the brass before I cool it in the water. The case will be held at the correct height in the coil by a solenoid operated catch. When the brass is cool enough it will release the case into the water to complete the cool down. Due to the terribly narrow heat zone it may well be possible nor even quench them.

See:
The Art and Science of Annealing

specifically these two paragraphs which I referenced when conceiving my process..

“With this setup, the neck will actually reach a temperature between 750 and 800 degrees. Remember, it's the combination of time AND temperature that does the job. We have raised the temperature sufficiently to be able to anneal the case necks in 6 to 8 seconds.

The shoulder will be a bit cooler than the neck, and the body cooler yet. The case head will be below 300 degrees (F), which is well below the critical temperature of 482 degrees (F) at which the first changes in grain structure can occur.”

Because induction heaters concentrate the heat and no heating takes place when you de-energize the coil, I believe that I can hold the temp down to a point below 482 just below the shoulder let alone anywhere near the case head. You could probably hold them in your fingers... it just would be as fast as the automated method. You have got to realize by now that I enjoy building the mechanisms almost as much as shooting the end results.

Due to the fact that I am no longer employed, I find that I have less and less free time, don't know how I found time to work before I retired. :)
Parts are beginning to show up for the lathe/cnc project, and I just got an email informing me that my new shotgun has been shipped. Look out rabbits!

All distractions aside, I will try to video the prototype coil and case in action.

Thanks for all the suggestions.

paul
 
It was too hard to begin with. Properly annealed brass will not split necks for many decades, if at all, unless they are stored in a corrosive atmosphere and the rest of the brass would show that if it were the case.
 








 
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