Home Forums Hunting & Shooting Gunsmithing Cerrosafe tips?

Got 1/2 pound of cerrosafe on it's way from Midway to do a chamber cast. Have read a bit on how to use it and the plan is to plug the bore with a tight fitting patch run in from the muzzle to just ahead of the throat.

As part of Brownell's tips they mention "Melt the entire bar of Cerrosafe in a heatproof container that you can easily pour the hot Cerrosafe out of."

I had planned to use my RCBS lead dipper and just melt one dipperful, as I only need a cast of the shoulder, neck and throat area. But they say to always melt the whole bar.

Guess I could melt the whole thing in a clean ingot mold on the stove and then ladle it out of that with the dipper, but would like to hear what you guys use to carefully pour the holt melt into the chamber.

Also, any tips or gotchas that you have learned would be appreciated.

I never found it necessary to use the whole bar. I just melt it down in a cut off soda can. Make a pour spout in the can, and if your real careful, you don't even need a funnel. Cerrosafe melts between 150 and 190 degrees. A cotton glove on the hand you're gonna pour with is all you really need.

One thing I might add is be very careful with the crown. It doesn't take much to damage it with the rod. Fold a small patch in half and carefully work it past the crown, preferably with a coated, 1 piece rod so as not to inflict too much damage. Insert a round in the chamber holding it in place with your finger. Carefully advance the patch with the rod until you feel it touch the bullet. This should put the "plug" right where you need it. Remove the rod and round.

Clamp the barrel vertically in a padded vise with the loading port in a convenient location to allow a clear path to, and, a clear view of the chamber. I prefer to pour the cast with the barrel at a slight angle. Don't let the casting sit in the chamber too long before removing it.

Don't go crazy looking for something to cook and pour the stuff with. This is a Tuna can I've been using for somewheres around 30 years.

Thank you! These are just the kind of tips I was looking for. Wouldn't have thought of using a can like that.

I put some water in an old frying pan, and use my ladle like a double boiler.

Keeps direct heat off the ladle and Cerrosafe, if that's important.

Paul

Not to sound like an 'ol lady but WASH yOUR HANDS!!!!!
Cadnium and all.

I use my thumb to push the metal in, just to fill voids.

Yes while its still hot.

The size will change with time.

But yes get it out fairly quickly, the man speaks the truth.

I'll find he size curve if needed, but change is small.

Clean chamber of course.

Sorry I nag on;

Watch the anvil on your mics, if carbide they will cut in easily on tapered surfaces.........like a chamber cast.

One more question: I'm going to do a bore casting of a Marlin 38-55 Cowboy. Which end is cast/measured? Muzzle? Ahead of Chamber? Both? Excellent tips. A keeper.

You will cast the whole chamber.

Reread Malm's post.

If you're just wanting to find the bore measurements then I would simply slug it by driving a lead slug from one end to the other and then measuring that. This requires considerable care as you are inserting the lead into the bore at the muzzle. The best results will be obtained if you expand the lead into the walls of the bore before pushing it with the rod. You do this by removing the bolt and inserting a good 1 piece rod from the chamber end to act as an anvil while you carefully tap the other end of the lead to "squeeze" it into the sides of the bore. Don't forget to run a lightly oiled patch through the bore first. And watch that crown.

Just for reference, here are Brownell's tips for cerrosafe, quoted from this site: http://www.brownells.com/.aspx/lid=10387/guntechdetail/Hints_For_Using_Cerrosafe

�The basic ingredient of Cerrosafe is bismuth. Bismuth is a heavy, coarse, crystalline metal which expands when it solidifies, up to 3.3% of its volume. When bismuth is alloyed with other metals, such as lead, tin, cadmium and indium, this expansion is modified according to the relative percentages of bismuth and other components present. As a general rule, bismuth alloys of approximately 50% bismuth exhibit little change of volume during solidification.

Alloys containing more than this tend to expand during solidification and those containing less tend to shrink during solidification.�

What all this means for the gunsmith is that you can make chamber castings using only Cerrosafe and a few, simple hand tools. To make a chamber casting, first clean and degrease the chamber. Use a tight-fitting, cotton patch that�s wrapped around a bore mop or brush to plug the bore just ahead of the throat. I usually leave the cleaning rod attached to the plug until it�s time to remove the plug. Melt the entire bar of Cerrosafe in a heatproof container that you can easily pour the hot Cerrosafe out of. You can use a propane torch or heat over a hot plate or the burner of a stove. Cerrosafe melts easily at 158�-195� F. While the casting metal is still liquid, stir very well, skim off the dross and pour your chamber. The real trick with Cerrosafe is not to overheat it. If you heat the solid slowly, and keep it within the required temperature range, you shouldn�t get any dross.

Note the time the casting was poured. The casting will take only a very short time to solidify, usually within a minute. Wait 30 minutes and then remove the plug from the bore. Turn the muzzle upward and the casting will fall from the chamber. At 30 minutes after initial solidification, Cerrosafe shrinks slightly, so removal is very easy. Allow the new casting to cool thoroughly then measure the casting exactly one hour from the time it was cast. The casting will give you an exact measurement of the chamber. Cerrosafe casting metal can be used over and over. Remelt the entire amount back together and pour the Cerrosafe into a small mold of the appropriate size. Always melt the entire Cerrosafe ingot to make a chamber casting. For best results, never cut off, or use, just a part of the ingot.



From Midway's instructions:
Contraction - expansion factor versus time, measured in inches per square inch:

2 minutes -.0004"

6 minutes -.0007"

30 minutes -.0009"

1 hour +-.0000"

2 hours +.0016"

5 hours +.0018"

7 hours +.0019"

10 hours +.0019"

24 hours +.0022"

96 hours +.0025"

200 hours +.0025"

500 hours +.0025"

Thank you Jim in Idaho;

I knew it moved but wasn't sure of the rate.

The internet is great isn't it. 30 years ago a few would know those numbers in the shop and a small handful would have the reference book it was in.

Hey guys, thanks again for all the tips. The cerrosafe arrived yesterday and I was able to get a good cast of the chamber last night.

Still have something that doesn't seem right with my fired cases but at least the casting assured me that the neck and throat of the chamber are properly dimensioned.

Such as what?

Since you asked...

A bullet should be a loose slip fit in a fired case. From my .243, a bullet can be forced into a case but it won't just slide in like every other chambering I load for. The case mouth is pinched ever so slightly. Once you get past the mouth it slides okay.

The barrel was an unfired factory take-off .243 I got from a poster here, the gunsmith set it back 1/2 turn and ran another .243 reamer in to set to minimum headspace. At first I thought maybe the neck wasn't long enough so I trimmed cases a hundreth shorter than needed - 2.025" instead of 2.035. Max case length allowed is 2.045".

Fired cases still wouldn't let a bullet slip in. If you take a chamfering tool and run it around a couple spins, the bullet will generally fit.Note that cases were already chamfered and deburred normally before ever being fired. Once the bullet gets past the mouth (very tip of the neck) it slides in okay. I figured maybe the chamfering tool was reaming open the mouth ever so slightly. Also, these cases were handled carefully after firing, not just dropped on the ground or something so they might be dented. I've checked the fit at the range right after removing the case from the chamber, for some reason they won't let a bullet slip right in.

A fired case neck should be .276" outside diameter all the way to the mouth. With .015" neck walls, this allows an ID of .246". Measuring as carefully as possible I thought the cases went from .276" OD all the way along but then tapered right at the mouth to about .274 or .273, giving an ID right at .244 or .243. The was with a micrometer and was as good as I could measure with the relatively large anvil on it.

I figured somehow it had a tapered chamber neck, maybe the reamer was ground or sharpened incorrectly? The gunsmith measured his reamer and he said it checked out just fine.

The chamber casting backed him up, exactly one hour after pouring it showed a chamber neck diameter of .278" from the shoulder junction to the end of the chamber neck. A cartridge drawing shows a .243 neck as .2406" long from shoulder to mouth, my chamber neck runs .285" long so it has a good 40 thousandths clearance past a maxed out case neck.

So, the chamber is good, neck is straight and there is plenty of room for cases to release the bullet.

But why do my fired cases still resist the entry of a new bullet? The measurements just don't add up.

But - all I really wanted to know was whther this was safe. Everything I can see from the chamber dimensions and actual firing shows it is, so I'll just go on shooting it. The rifle, like every .243 I've owned, is phenomenally accurate. Just last week I fired six 4 shot groups with 6 different loads. Four of the six groups were sub 1/2", and if I was a decent bench rest shooter and didn't tend to throw flyers all of them would have been under 1/2".

I'll continue to scratch my head on this until the barrel is worn out, but at least will not lose sleep over it being unsafe.

Wild ass guess, just because I'm feeling lucky today.

Could it be a tiny extra spring back right at the case mouth because it's supported by more metal on one side only? Does this make sense, and would trying a case that's annealed dead soft at the neck be telling?

trimmed to 2.025... What does your fired case measure? What does the mouth of the fired case measure with your calipers?

Another tip that worked well for me with Cerrosafe is to heat the chamber just prior to pouring the Cerrosafe-I got better "fill-out" and a cleaner cast that way. I used a hair dryer to gently warm the chamber. Clean and dry is essential as well-no oil. I use my lead dipper and a propane torch to carefully melt just the portion I need for each cast.
I see you have already gotten a good cast-just a suggestion for any future users.

Outside diameter of the necks is .276" for most of their length, exactly what cartridge drawings show they should be. If I put the blade of the caliper right at the very mouth then OD seems to run about .274 or .2735". "Seems" since even the thin beveled part of the caliper blades is .030" thick, so it covers that much case mouth. If you get too far up on the case neck you are measuring the outside bevel which is obviously a bit narrower. Neck walls are a consistent .015" thick.

Outside diameter minus (2 times wall thickness) = inside diameter

.276 - (2 * .015) = .246 which is what I think most of the neck ID is, since once the bullet gets past the case mouth it slides easily enough.

Yet the inside diameter of fired cases measured with the caliper at the mouth is .244 to a whisker over .243. Necks are round and not pinched on one side, I measured at 90 degree points around the circumference to verify this. Mouths are chamfered and beveled well so it's not a lip or burr at the mouth which causes this.

That's what is weird. It doesn't seem to matter if cases are 2.025" long or 2.035" long, they all have this narrowing right at the case mouth. I blackened the mouth of a new case that was a good 2.042" long and after chambering it did not show any rubbing against the front of the chamber, the casting verified that the chamber neck is plenty long enough.

Factory ammo shows this same effect, but my handlaoads aren't crimped so it's not some left over springback from that.

Figured my measurements were just screwed up, but bullets definitely do not slide easily into a fired case mouth, and bullets do slide easily into all other fired bottleneck cases - .30-30, .308, three .30-06's, two .223's, two .270's, etc. That is a fact. My worry was that the chamber neck was too tight but case measurements and the casting show everything right where it should be. It's a mystery but I'll just keep shooting.

Yes, a can with 1/2 pound of cerrosafe will fill that chamber really fast! A dipper might be a good idea next time, or at least be very careful and pour the melt really slow. I filled the chamber right to the brim before realizing it and almost ran it into the locking lug recesses.