Larry Gibson, re-Cerro-Safe

[44man]

I made a casting today of my .475 revolver throat. This throat measures .4773 with both a boolit pushed through and a small hole gage. A .4775 and .478 boolit will NOT go in unless pounded with a stick so I know the measurements are right on. The .478 boolit takes a LOT of force. These boolits will be sized all the way around.
The Cerro-Safe casting came out of the cylinder at 12:16 and measured .4765. At 12:28 and 3 hours later, it measures .4788.
That is .0015" larger then the throat.
Sorry, Larry, I will not depend on the stuff. It expands more then chamber, throat or bore size.
By the way, that is almost exactly the difference I get between an expanded slug and a casting in my 45-70. Give or take .0001".
Have you ever made a chamber casting, let it sit an hour and then try to chamber it? You will NOT get it in!

[44man]

Here it is. It would take a BIG hammer to get that thing even started.

[Onlymenotu]

I haven't made any cast with it but every thing i've read says take measurements after one hour....

[montana_charlie]

44man,
Not to dispute your findings, but...

I guess everybody knows that Cerro-Safe 'changes' over time.
I haven't read the instructions for quite a while, so I don't remember 'how much' it's supposed to change...or when.

But, many of the well-known makers of custom moulds ask for a Cerro-Safe chamber cast in order to fit the cavity to the customer's rifle.
It's my impression that those guys are so familiar with the properties of the stuff they can 'make adjustments' for it's 'changes'...and produce good results if they know how old the cast is.

I've never ordered a mould from Paul Jones or Steve Brooks (to name two) but those who use their moulds have only good things to say.

Since you don't particularly like Cerro-Safe, it's probable that you haven't used it enough to come to 'know it' (in the biblical sense). But, I doubt that you wish to prevent others from liking it...if that is their desire. Right?
CM

[44man]

That picture was taken after ONE hour. What you have to realize is that custom mold makers either know Cerro-Safe's properties and adjust or just go with it because a mold cut to that size will actually give a right size boolit after it shrinks.
I don't really know!
I have made castings with this stuff for more years then some of you have been alive and in every case, I get a larger reading with it and is the reason I use many other measuring methods in conjunction with the casting.
I never said that I don't like the stuff but it has limitations. It has many good uses but to depend on it for the exact size does not always give you that exact size.
To depend on any one method just does not work in all cases. The caliber alone can change the rate of expansion of Cerro-Safe.
Unless you have very sophisticated measuring devices, you are in the same boat as I am.
As an aside, I shoot .477 to .478 boolits from that revolver and all shoot the way I want them to. I KNOW they are larger then throat size because I would have to pound one through with a hammer.
Some of you are reading between the lines again and think I hate the stuff when all I am saying is you have to make a determination on your own if you are getting the proper dimensions and not to depend on what you are seeing. Make other measurements for a comparison. NOW you have to read between the lines.
To just pound a slug all the way through a bore and say that is the size of it is just as wrong as just making a casting and saying that it is the exact size. Have you noticed that both are very far apart?
All that I know is that the expansion rate of Cerro-Safe is more then the instructions say it is. Take that any way you want to.
Maybe I have to put it another way. The measurement MUST be taken exactly 15.98452072 minutes after casting to get the exact measurement. Otherwise it is either to small or too large.

[Phil]

The last time I read the instructions they said to take the measurements an hour after casting.

On the casting not fitting the hole, any machinist will tell you that you cannot put a .5000" pin in a .5000" hole, it will NOT fit.

Cheers,

Phil

[John Boy]

44man ... the best $65 investment to add to your reloading area ...

.251-.500PLUS PLUG GAGE SET (http://www.use-enco.com/CGI/INSRIT?PMAKA=616-8130&PMPXNO=5215208&PARTPG=INLMK3)
They are ISO certified and do a fast job measuring bores, chambers and cylinder throats

[floodgate]

Phil:

Right! From my recollections of the Brownell cerrosafe instructions, it shrinks for about 1/2 hour after casting, then starts to expand, reaches the ID of the chamber at one hour, and then expands further, stabilizing at 0.4% over the reference diameter (a bit over 0.001" oversize for a 30 caliber bore cast) after three hours or so. Used properly, it can be a very accurate reference. BTW, the alloy contains cadmium, so DO NOT overheat it to the point of releasing any vaporized Cd! Nasty stuff!

My set of pin gauges is specified to be 0.0002" UNDER the indicated diameter, so they will JUST slip into a clean bored hole of the specified size. You can also get sets 0.0002" over to use as "NO GO" gauges.

I need to try the sulfur / graphite method; years ago, I tried a straight sulfur cast in a very rough muzzle-loader bore and it stuck. I coudn't get the breechplug loose, and had quite a time chipping it out from the front.

floodgate

[IcerUSA]

OK, I've read both posts on this creo stuff and seen referance to the sulfir/graphite in both , but no where have I seen how to mix it hmmmm!
Could I get a ratio of sulfir to graphite ?
This is good stuff to know as I'll be working on a Marlin 336 soon and would be very interested in both to check out the bore on this rifle.

Thank Guys :drinks:

[montana_charlie]

Could I get a ratio of sulfir to graphite ?
It was in the other thread...
http://castboolits.gunloads.com/showpost.php?p=153147&postcount=2
CM

[Larry Gibson]

44man

Interesting results. Floodgate's recollection of the instructions matches mine. I loaned out my Gunsmith's Kinks" by Brownells some years back and haven't got it back yet. Might call Brownell's tomorrow and see what they say. Anyways I usually record the measurements within an hour, usually sooner. It works for me. I maight add that I've driven lots of slugs through revolver throats over the years I've notice that none of them once driven through are a slip fit back in. As noted an exact fit will not slip it. Also lead has a certain amount of spring back like any alloy. I use both methods and must admit I use lead slugs on revolver throats. I use cerrosafe in chambers in barrels. What works for you works and what works for me works. Seems like we're skinnin' the same cat, just gettin' it done two different ways is all.

Larry Gibson

[44man]

I kept checking the size the whole time and the casting actually reached maximum size before the hour was up. I just went with the hour specified in the instructions for posting since there have been many posts telling me that. But you see, it doesn't work!
Plug gages are the best but are expensive and to have a set for each caliber is not in the stars. As long as I know the size close enough and can make my boolits fit or a little larger, I don't need more.
I learned long ago not to depend on Cerro-Safe if you want the exact size.
All of you can jump on me and keep quoting the instructions for the next few weeks but I know what I know from several hundred castings, cold barrel and heated barrel.
All of you are invited to come over and work some hokus pokus to try and fit the casting back in my throats. Bring a file!
If you want to depend on it, you better know the exact time it takes to reach the size of the hole because in the short time it takes to make some measurements, it will have grown some more. Since this varies with caliber and size of the casting, good luck.
The only other way is to just let the casting sit for a few hours and subtract .4%. Figuring that for my .475, it is still .0004152 off correct size. Each caliber requires a different multiplier.
My whole argument has been that after the specified hour, you will not have the right size, don't depend on that reading.

[lovedogs]

Before we have a revolution, has anyone asked the people who make Cerrosafe what they recommend? Maybe get more info than is offered in the instuctions?

[felix]

All of these alloys must be calibrated on the day (hour) it is used. There is no way a mix is constant, day in and day out. Just like you cannot repeat the same casting session when making boolits. Might pour the measuring stuff into a honed pipe at approximately the same ID of the chamber, and the chamber at the same time. The percentage difference should be exact enough for what we are after. ... felix

[TAWILDCATT]

Hole Gages Can Be Bought From -harbour Tool.i Bought Transfer Punches And Hole Gages For Very Little Money Also Electronic Verniers
&15 For 6 In. They Also Have A Mini Cut Of Saw To Cut Cases To Length.(item 42307)$29.

[44man]

I have hole gages but the plug gages are different, like go-no go gages.

[Larry Gibson]

44man

I can see where the pins are used for revolver throats but do you use them for rifle chambers? If so how do you get the dimensons? Not being critical here just interested. Also if you use a lead slug do you use some sort of rod down the barrel as an anvil?

Larry Gibson

[44man]

Yes I use one rod for an anvil and I don't put the slug in too deep, just a short distance in. Then I do the other end the same way. They tap out with out deforming more and if I align the same rifling grooves, most will go back in a ways with a hard thumb push. If the rifling isn't the same as where the slug came out, it will not start back in. I use both a slug and small hole gages for throats.
The measurements are very close to actual and is good enough to fit a boolit.
What I don't like about depending on Cerro-Safe it that it expands over the reading you need. My throat casting went from .4765 to .4788 in 12 minutes. It read the same after an hour and now that it has sat a few days, it has expanded to .4789.. Now if a guy was to depend on that reading without subtracting some unknown percentage for each diameter of boolit and using the rule of thumb of shooting a throat size or larger then throat size boolit, he will be trying to shoot a .4789 to .480 boolit, or even larger. A .476 boolit will shoot fine and a .477 one would be better, even .478 will shoot if it is not too long to chamber. A longer boolit that has to enter the throat is best served with .476 to .4765. My bore is .475. I don't see any difference in accuracy between a .476 to .478 boolit, both shoot better then I can hold.
So you see that using Cerro-safe without thinking can cause a great deal of headaches. Let alone thinking that no mold is made for those strange sizes.
I learned long ago to not believe the size. The stuff is more useful for seeing chamber configuration, throat length relative to rifling start and if the chamber is in line.
A mold maker has to know more then all of us and can determine the size needed for the gun by using a Cerro-Safe casting. Don't believe for a second that he is using the actual size of the casting. He would not be in business long making molds for boolits that won't chamber.
You can have more leeway with a rifle with generous throats and can shoot a much larger boolit as long as the bore size portion will enter the bore. For instance, my BPCR has a little over a .459 groove to groove but a .450 bore. As long as the nose is between .450 to .4505 and even .451 with help, I can shoot a .464 boolit. My chamber and throat is large enough.
I wasn't trying to flame anyone and don't mind if anyone is critical. I am just trying to pass on what my experience has been. As Ripley says "believe it or not."

[brshooter]

If you really want to find out an ID, you might want to try Deltronic Pins. I use a set for my 6mm barrels to determine the right pilot for the chamber reamers. I have a TP25 set, 0.2365". There are 12 pins smaller and 12 larger in 0.0001 increments. Total range on my set is 0.2353" - 0.2377. They unconditionally guarantee each gage pin to be within a size tolerance of + 0.00040, minus nothing, surface finish ~ one microinch with both ends concentric to one another at a temp of 68 degrees +/- one tenth of a degree. The gage pins are 2.5" overall with under cut of 0.5" in the middle. A very nice way to exactly find out the ID but pricy. Most holes will surpise you as they are not round at all. These pin gages will show it. I forgot where I bought mine but you can do a Goggle search for Deltronic Gage Pins. Jon

[44man]

You said the magic word, pricey! And to get them to cover all calibers---WOW. I done be retired!

[leftiye]

Enco has a set of pin gages; .251" to.500 " by thousandths (.250 of 'em) with either plus tolerance, or negative tolerance of.0002" for about $67. Z standard. They have both smaller and bigger sizes of pin gages in sets which cost somewhat less.

[44man]

Thanks, I get my tool steel and cutters from Enco. Have to see if there is money for those gages.