First time trying a cerrosafe chamber casting...

[guywitha3006]

Sorry in advance for the novel,

The story goes I have a Remington 700 I had rebarreled with an AAC 300 blackout. Haven't had a ton of time to shoot it but functionally it shot jacketed ammo fine. The problem was when I attempted to chamber some cast NOE 247s... Would not chamber. I initially wrote it off as I messed up the case forming step (even though they function my 10"AR fine). While reading another 300 thread a remember mentioned that AAC had a run of very narrowly chambered barrels...enter cerrosafe.

So I ordered some Cerrosafe alloy clone from roto metals and thought I would get some answers. As luck has it is not as simple as melt alloy block barrel warm barrel pour and measure. First mistake was I didn't remove the Timney trigger and got over flow in it :sad:
Then when I I tapped the casting out it was all wrinkled so I figured I'd remove the trigger and try again attempt 2 casting broke... Attempt 3 casting/patch stuck solution was to walk away at that point.

My plan is to drop the action and trigger group into boiling(or almost boiling water) and try to melt the overflow and stuck casting out. Then clean everything and stare at it for a while to determine if I want to throw the cerrosafe out and just neck turn my cases until the fit ...or try again. Any help is greatly appreciated. Tips tricks word to run away...all ears at this point.

Thanks for the help and sorry for the novel!

[OS OK]

I wanted measurements on my 8mm Yugo, not interested in leade length as that is pretty much established info out there in mil-surp of that variety. I wanted to know about I.D.'s of the neck, leade and bore.
Removing the bolt I had access to the chamber end easily.
I made a 1/2" wooden dowel resemble an 8mm case in length and body and neck dimensions (used a belt sander) so that it would fit easily and support itself laterally and hopefully not self destruct as I tamped the lead into the chamber. Also used a 'dead blow' type hammer with soft plastic face so as not to destroy the top end of the dowel.
Using a soft round lead ball of .350" and lubed, I dropped it in and tamped just enough to get that ball starting into the leade about 1/8" or so and then lightly tamped it back out from the muzzle with a rod and jag. The .350" ball widened out to the .360" I.D. of the neck and it engraved into the leade by 1/8" to give room to measure the leade at .326".
Next I put a new ball in and tamped it all the way into the leade and into the bore and tamped until I felt the dowel stop and become bottomed out. (Pencil marks on the dowel help to see how much it travels and when it is bottomed in chamber.) This drove the ball into the bore, then backing it and the dowel out with the rod and jag I had an engraved slug of the bore measuring .3233" and lands at .3176".
This didn't take long and if you mess one ball up there is plenty more in the buckshot box to work with.
It's about patience not pounding…just steady as you go.

Hope this helps…charlie

'Click' on the center picture...First from left….350" ball, Second...neck/leade, Third…leade, Fourth…bore
In the right picture you see the dowel.

[dilly]

I recently tried rotometal chamber casting alloy for the first time too. I wasn't at all successful either.

I haven't given up yet. I plan to tackle it with a better, more directed pouring system and a hair dryer to preheat the receiver, but that's another battle for another day.

[guywitha3006]

Thanks guys for the insight. I think I am going to boil everything out of the receiver tonight and then decide if I want to try it again or just make an impact slug, as that method seems like a lot less hassle.

[Jim_P]

I guess I got lucky casting a Pedersoli 45-70 Sharps with the RotoMetal material. I put it in a ladle and heated with a propane torch until melted and poured into the patched 'clogged' barrel. Cooled immediately and dropped out with a tap from a cleaning rod. Yes, it had a wrinkle or two. But it was very measurable. I've been holding off doing the two bolt actions I need to do, but that's a different story.

When you put that patch in, make sure it's oiled.

[John 242]

Remove the barreled action from the stock.

Place your plug patch about a 1/2 to 1-inch away from your throat. The patch doesn't need to be super tight. I leave the cleaning rod in the bore to support the plug. Secure the barrel in a padded vise, muzzle down.

I don't oil the chamber, but I'm a rebel. I also get very good castings with no wrinkles.

Heat the Cerrosafe with a heat gun until it melts. We use the bottom half of a soda can to heat our alloy in. Use gloves when handling.

Begin alternating between heating the barrel near the chamber area while keeping the Cerrosafe melted. The barrel only needs to be warm, not hot.

Pour the Cerrosafe into the chamber until it reaches the top.
Allow the alloy to harden. I wait about 10 minutes before pulling it out, but DO NOT WAIT MORE THAN 30 MINUTES. Cerrosafe shrinks and then expands.

Unless your chamber is very pitted, the chamber cast should pop right out. Careful with the casting, they are fragile and will shatter. Pop it out onto a folded towel.

After about an hour of cure time, measure the casting and compare it to reamer prints, which can be found on SAAMI's web page or elsewhere on the net (cartridge drawings will be several thousandths smaller than the chamber dimensions). Go to SAAMI's website and click on "SAAMI Standards" and download the PDF file. Save it, it's good info to have. http://www.saami.org/specifications_and_information/index.cfm

If you screw up, no problem. Remelt the casting with your heat gun and try again.
Stuck? No problem. Heat your chamber area with the heat gun and once it's hot, the casting will come right out. BE CAREFUL! Some heat guns will get hot enough to temper color small parts. Cerrosafe melts at low temperature (158 to 190-degrees) so take it easy!

More detailed instructions can be found here:
http://www.brownells.com/GunTech/Cerrosafe/detail.htm?lid=10614

[RobertS]

The one time that I did a chamber casting, I covered the extractor with a narrow strip of aluminum foil, which kept the cerrosafe from binding it up. The foil came out easily as part of the chamber cast.

[44man]

I never got the right dimensions with the stuff, timed to specs and all.