Making a chamber casting

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  • Last Post 16 September 2020
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max503 posted this 13 September 2020

OK.  I got some cerrosafe alloy.  Plugged my 357 Contender barrel with a cloth patch then clamped the barrel vertically.  I melted the alloy in a cutoff soda can with a heat gun and poured it in the chamber.  

After hardening I could not get the casting out.  After busting a couple hardwood dowels trying to "coerce" it out I took my soldering iron and melted most of the plug out.  I did get the forward end of the plug out and was able to measure the bore diameter.  Unless I'm wrong, it measured .356"  

I might have had the plug too far in barrel.  There was at least an inch of rifling on the cast, certainly more.  Maybe closer to two.  (It's in the basement as I type this).  Maybe that's the reason the casting didn't want to let-loose?  

I will try this again.  I've always wanted to make chamber casts but never got around to doing it.  It seemed difficult or something.  But now I've broken the ice and I hope I have better luck next time.  I have other guns I want to try this with.  Hoping to get some tips here on how to be more successful.  My brother gave me the cerrosafe as a gift. 

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Glaciers posted this 13 September 2020

I will follow this one as I have cerrosafe just for chamber casts.  I hate pounding on guns, so I thought a casting would be the way to go, still do.  I know you need to take your measurements at a certain time, within 60 minutes or something because the casting will keep changing.  

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Tom G posted this 13 September 2020

Max,   I've done a lot of chamber casts with cerrosafe and never had one stick unless it flowed out into the locking lug recesses.  It sounds like you made it way too long and when you tried to extract it it was locked into the rifling. Since the rifling twists, the casting has to twist or shear off the groove part of the casting when you try to remove it. This can cause a lot of friction as you found. If my memory serves correctly, you can use a little light oil in the chamber to help release. "Light" being the operative word here. 

So, keep it short and no longer than needed. If you want to measure the groove dia. just use a soft lead slug. You can get a nice casting of the throat if you place the plug just forward of the end of the taper in the throat. 

The neat thing about cerrosafe is that it shrinks on cooling and then expands to the dimension of the hole and should be measured exactly one hour later to get a good reading.  In the last one I did a few weeks , I used an industrial strength heat gun to heat the metal. It worked fine.  You could also heat the barrel if the casting is stuck in there and get it to melt without hurting anything if you are careful.  . 

Tom G

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max503 posted this 13 September 2020

Yea.  Looks like I got into the rifling just a bit. tongue-out

What's the best way to make the plug?  I used a wad of cloth. Had a hard time positioning it just right.

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Lee Wiggins posted this 13 September 2020

Max,

   I push a gas check into the breach end of the barrel past the throat a little. I use a brass rod with the diameter turned on the end for a gas check fit ( just like the base of a bullet. After poring the cast the brass rod is used from the muzzle to tap out the chamber cast.

Trust me on this, do not use a steel cleaning rod .

Lee Wiggins

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Tom G posted this 13 September 2020

The easiest way is to take a cleaning rod and jag of the proper caliber for the barrel and place a tight fitting cleaning patch on it. Run it into the barrel and stop it just short of what you wan't to measure. Then when the casting cools where you can handle it comfortably, pop it out using the cleaning rod and pick the patch off the casting. it will be stuck on the casting but can come off easily. 

What you get when you include the riled part of the barrel is the same as having a bolt screwed into a threaded hole. if you try to drive the bolt out without turning it, it goes pretty hard. The barrel part of the casting acted like a bolt in a threaded hole ( the barrel).  When you pounded on it, the soft casting material slugged up and got even tighter, making it worse.  The easiest way to get it back out ( if it's stuck) is to melt it out, not pound it out . You didn't say how long you waited  before you tried to knock it out. If you wait very long, it will swell up and get tighter. So extract the casting soon after the barrel cools to the touch and keep the rifled part short. The casting is very soft so knock it out with minimum force onto a padded cloth to keep from bending it or putting dings in it. 

If you can find a cheap tin cup, they work well for melting and storing the cerrosafe. A pop can is pretty flimsy and has no handle. I just drop the casting into the cup and leave it like that till I need it again. 

When measuring, use a known accurate micrometer if you really want to get a good reading. I don't use indicating calipers as they are seldom accurate within a thou. unless you buy a good set and pay lots of money for them. You can check the accuracy of your mikes or caliper on a standard that comes with good mikes. Or, I have a set of Jo blocks and use them to check my measuring tools with. I have a set of Mititoyo  digital one inch mikes.  They read out to plus or minus 5 millionths of an inch. When they are that sensitive, you can see them change over time as the temperature of the mikes change. It's a simple matter to just hit the re zero button and be accurate again. Indicating calipers are large and can change a whole lot more just from temperature changes. So don't rely on them if you want to measure down into the .0001" range. 

Once you do a couple of casting you will find that it is pretty quick and easy if you do it correctly.  Keep us posted on how it works out for you.  

Tom G. 

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Bud Hyett posted this 13 September 2020

Setting the plug distance to get the leade is a problem. I use the following procedure. A wood dowel slightly smaller than bore diameter (e.g., for .30 caliber, 5/16 diameter slightly reduced with a dremel tool) set in a fired case like a plugged case for breech seating. 

  • Set the dowel in a fired case with about 1/16 inch sticking out.
  • Insert case in chamber.
  • Push a cleaning rod in to hit the dowel.
  • Mark the spot on cleaning rod.
  • Check the chamber drawing, add the length from the case to the front edge of the leade to a second mark on the cleaning rod plus 1/4  inch.
  • Push the tight cloth plug on the jag to the second tape mark on the cleaning rod.
  • Prepare your Cerrosafe and chamber cast
  • Let cool
  • Gently tap to push the Cerrosafe out.

Sometimes I am a little short and need to do this again.

The chamber drawings for many cartridges are in the back of the NRA Reloading Book or on the Web. 

SAAMI Technical Drawings

I use a cleaning rod extensively wrapped in Teflon tape for some calibers, a brass rod where I have one that fits tightly.

I know this is a lot of busy work. However, my first two tries with Cerrosafe ended with me setting the rifle upside down in a rifle vise and watching candles provide enough heat to slowly drip the Cerrosafe out. This can be long and involved sometimes. 

Country boy from Illinois, living in the magical Pacific Northwest

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Tom G posted this 13 September 2020

I really like Lee's way using a gas check. I never would have thunk of that myself. Tom G

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Larry Gibson posted this 13 September 2020

From Cerrosafe instructions;

The barrel and chamber must be clean and dry. Insert a tight-fitting cotton cleaning patch on a jag into the bore from the muzzle to serve as a “dam” for the Cerrosafe. Position the cleaning patch about 1⁄2"to 1"into the bore, ahead of the throat of the chamber. Heat the barrel at the chamber just to the point where it is uncomfortable to hold with your bare hand.     Heat the Cerrosafe as directed above and carefully pour the Cerrosafe into the chamber until it shows a slight mound at the rear of the chamber. Excess Cerrosafe at the rear of the chamber can sometimes prevent removal of the chamber cast. If this happens, melt the Cerrosafe in the chamber with a propane torch on the barrel and pour the Cerrosafe back into the ladle.     After the Cerrosafe has solidified, the chamber cast can be pushed out of the chamber. We recommend using a nylon covered steel cleaning rod with a brass jag tip onit.Pushoutthe Cerrosafe chamber cast within one-half hour after casting.

If more than one hour elapses after casting before attempting to remove the chamber cast, the Cerrosafe will start to expand and will have to be remelted and allowed to cool in the chamber to remove it

LMG

Concealment is not cover.........

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max503 posted this 14 September 2020

Using an infrared thermometer, what temperature should your chamber be preheated to?  

 

Those instructions say to go 1/2 to 1" into the rifling.  Isn't that why mine stuck and had to be melted out?

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Larry Gibson posted this 14 September 2020

"Heat the barrel at the chamber just to the point where it is uncomfortable to hold with your bare hand."  

Heat one up as stated then measure and let us know.  Or, if you've measured a barrel when shooting to that level and measured it then that should be the same.

LMG

Concealment is not cover.........

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Bud Hyett posted this 14 September 2020

In spite of my earlier reply with details, this is as much an art as a science. You may take several tries to get your correct procedure. 

Country boy from Illinois, living in the magical Pacific Northwest

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John Alexander posted this 14 September 2020

I have never had occasion to make a cast of the whole chamber but have often wanted to know what the groove diameter, throat and, space at end of neck measured.  I have done it with Cerrosafe and by expanding a soft lead slug.

It has always seemed to me that expanding a slug is a better method.  Simpler, quicker, and more reliable since  the lead doesn't expand or contract after it is out.  If you want to keep the slugs for future reference they will stay the same dimensions.

Select a fired case. Shorten the case neck a bit and pour full of lead, any alloy -- probably a good idea to double check to see that it really is a spent primer.

Chamber the filled case

Drop a soft slug (the softer the better) down the muzzle.  A long cast bullet that has been reduced in diameter by rolling it between two pieces of steel so it will easily slide down the barrel works well.

Get a steel rod as close to bore diameter as Your hardware carries and shorten till it only protrudes from the muzzle a bit when the other end is on filled case.   Makes sure rod is smooth and the end that contacts slug has edges slightly rounded so no chance of scratching the bore.

Tap lightly with a heavy hammer.  It doesn't take much till the sound will change indicating that the slug is fully filled out. Under do the tapping a couple of times and check slug to get the hang of it the first time.

John

 

 

 

 

 

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Geargnasher posted this 15 September 2020

^^^^^^^ this is essentially how I do it. The impact impressions last indefinitely and are labeled and kept with reloading dies as a reference.

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RicinYakima posted this 15 September 2020

I do the same and gave my cerrosafe to my buddy.

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Ken Campbell Iowa posted this 15 September 2020

little detail ... with the lead upset, i use a hundred light taps rather than beating the crap out of the bolt lugs with 3 or 4 mighty whacks. ... besides, lead moves slowly,  patience is rewarded ...  

  also i hold the barrel of the gun when tapping, not resting the stock butt on the floor ... saves stress on the bedding.

btw, i " bit the bullet " years ago and bot 25 pounds of lead swaging wire ... 1/4 inch ... a little guilty sin of mine to get soft wire for upsetting images ...

ken

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John Alexander posted this 15 September 2020

Ken is right. Deformation of lead is time dependent.  That's the reason that a heavy hammer with slow light taps is better than a light hammer and higher speed strokes.

John 

 

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Geargnasher posted this 16 September 2020

Ken is right. Deformation of lead is time dependent.  That's the reason that a heavy hammer with slow light taps is better than a light hammer and higher speed strokes.

John 

 

Quite true. I use a 2# swing press, with the back gear engaged. Electrical tape spiraled around a section of O-1 drill rod makes a fine punch, just chamfer and polish the end so it cannot nick the lands.

I am baffled by those who are concerned about damaging their bedding or breech mechanisms with a few hammer whacks against a soft lead slug supported by a lead-filled cartridge case. How do tens of thousands of pounds of force per square inch, applied to the locking lugs, action, and recoil surfaces at over 20,000 fps velocity, compare to your hammer?

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