Chamber cast for new barrels?

adamsgt

adamsgt

Jerry Adams
The recent thread on the "click" led me to think about doing a chamber cast of my barrels in order to capture the actual chamber measurements. I've got a couple of barrels in the pipeline and thought about this after reading the aforementioned thread.

So, waste of time or no added value?
 
adamsgt said:
The recent thread on the "click" led me to think about doing a chamber cast of my barrels in order to capture the actual chamber measurements. I've got a couple of barrels in the pipeline and thought about this after reading the aforementioned thread.

So, waste of time or no added value?
Click to expand...

To do correctly chamber casts are a pain, especially for a novice. And, what you are looking at is history. IMO, spend your money on your own reamer, set your dies to that and then go from there.


Edit- Someone like Kiff, PTG, has good standard reamers in stock and probably could ship immediately to your gunsmith.



.
 
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Jerry, I never commented in the thread on the "click", most of us solved this problem years ago by having our reamers dimensioned properly, and then developing a chambering procedure that insured that the reamer did cut to those dimensions.

Personally, I think what you are doing is a waste of time. You can just as easily ascertain the dimentions of the chamber with nothing more than a small hole gage and a set of outside Mic's.

The biggest culprit in that "click" is a chamber that is too tight at the head. You ask..."why would they grind a reamer that small?"

Here is the history. About 12 years ago, a very well known shooter complained that his chambers were too big. So, his gunsmith had a reamer ground that produced the dimensions they wanted.

Since this shooter won a lot, other people ordered this reamer. But, complaints started cropping up that it cut too small, resulting in that dreaded " click" after just a few firings.
It turns out, the real problem was not the first reamer cutting too large, the problem was his gunsmith used a chambering technique that caused, or allowed might be a better word, the reamer to cut large. The combination of his technique and the smaller reamer produced yhe results they wanted.

But, when shooters who were real machinist, and knew how to make a reamer cut the actual size it was ground too used this smaller reamer, the chamber's came out too small.

This is all old history. You still have gunsmiths who are painting by the numbers, and those that know how things work.

Get a reamer that is dimensioned correctly for a 220 Russian web, and find a gunsmith that can cut a chamber without it wallowing all out.
 
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OK, I did buy a reamer and it is at the gunsmith now to do two barrels. After that I'll attempt to do them myself. My thought on the chamber cast was that it would be easy to do the cast before the barrels were mounted on the actions. That way I would have the chamber measurements documented. Plus, I have a couple of pounds of cerrosafe that have been gathering dust for years. I have a Mitutoyo small gauge set so I can go that way also. The reamer I bought from PTG is sized .4414 at the case head.

Oh well, I guess I can use the cerrosafe as a paper weight.
 
adamsgt said:
OK, I did buy a reamer and it is at the gunsmith now to do two barrels. After that I'll attempt to do them myself. My thought on the chamber cast was that it would be easy to do the cast before the barrels were mounted on the actions. That way I would have the chamber measurements documented. Plus, I have a couple of pounds of cerrosafe that have been gathering dust for years. I have a Mitutoyo small gauge set so I can go that way also. The reamer I bought from PTG is sized .4414 at the case head.

Oh well, I guess I can use the cerrosafe as a paper weight.
Click to expand...

Out of the 12 barrels in 6PPC I have, only 2 have chambers corresponding to the diameter stamped in the barrels; this from 4 different gunsmiths, even when the last 4 barrels used the same reamer. Sometimes the difference is quite small, for instance .2622 or 3 instead of the advertised .262.
I use something called 'Liquide de Leibowitz', probably quite similar to cerrosafe but not having tried cerrosafe I can't be sure. It is a dull grey stick that melts over a candle flame in a minute or so, hardens in about 30 seconds. I wait a few minutes before pushing it out gently to measure with a Mitutoyo .0001" micrometer. I have Googled the 'Liquide' but couldn't get any relevant hits. After Googling cerrosafe, my stuff looks suspiciously similar except it didn't come in the form of ingot but of stick, about the same size as a fountain pen.
 
P. Octo said:
....; this from 4 different gunsmiths, even when the last 4 barrels used the same reamer. Sometimes the difference is quite small, for instance .2622 or 3 instead of the advertised .262.

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Click to expand...

If you got 4 different results using the same reamer and the same gunsmith you need to change gunsmiths. Most 262 reamers cut an actual 2622-2623. I guess the grinder was allowing for wear. This is why I insist most folks don't have a clue to what their chamber neck diameter ACTUALLY is, yet they try to cut the neck walls of the brass to an exact tenth.

All that said, performance doesn't suffer if you have 0.001" or 0.002", or 0.003" actual finished clearance, just don't mix the sizes in the same load lot.
 
My Opinion Again

adamsgt said:
The recent thread on the "click" led me to think about doing a chamber cast of my barrels in order to capture the actual chamber measurements. I've got a couple of barrels in the pipeline and thought about this after reading the aforementioned thread.

So, waste of time or no added value?
Click to expand...


Jerry, chamber casting your new barrels would be a waste of time in my opinion. :p

The best chamber cast is a case that's been fired several times in the chamber with a normal load.

Remove the spent primer and do some measuring.

1. Measure the pressure ring right in front of the extractor groove using a 'tenth' micrometer.

2. Using a good dial caliper, measure the shoulder diameter at the junction of the body and shoulder radius.

3. Using a shoulder measurement 'gizzy' and a dial caliper, determine the headspace measurement.

4. Measure the neck diameter with a 'tenth' mike.


Now you know where you are and will be able to tell if your sizing die is compatible with the chamber. The die should reduce the diameter at the base one to one and a half thousandths, the shoulder by a couple of thousandths and the neck by whatever produces the desired bullet neck tension. Mike Ratigan in his book 'Extreme Rifle Accuracy' suggests a little less squeeze suggesting as little as half a thousandth at the base but I prefer to err on the conservative side and size a little more. I say one to one and a half squeeze and two thousandths is not at all excessive.

Hope this helps and saves some time.

Gene Beggs
 
OK, guys, the cerrosafe stays on the shelf. Sometimes it seems that the more I learn, the less I know. :confused:
 
JerrySharrett said:
If you got 4 different results using the same reamer and the same gunsmith you need to change gunsmiths. Most 262 reamers cut an actual 2622-2623. I guess the grinder was allowing for wear. This is why I insist most folks don't have a clue to what their chamber neck diameter ACTUALLY is, yet they try to cut the neck walls of the brass to an exact tenth.

All that said, performance doesn't suffer if you have 0.001" or 0.002", or 0.003" actual finished clearance, just don't mix the sizes in the same load lot.
Click to expand...

Not the same gunsmith; actually, 2 different gunsmiths with the same reamer gave me the 2 chambers matching the .262 reamer. I agree with you about the clearance, I like to have .002, personally.
Anyway, I have the 2 reliable gunsmiths now: long may they prosper!
 
Gene Beggs said:
Jerry, chamber casting your new barrels would be a waste of time in my opinion. :p

The best chamber cast is a case that's been fired several times in the chamber with a normal load





3. Using a shoulder measurement 'gizzy' and a dial caliper, determine the headspace measurement.




Hope this helps and saves some time.

Gene Beggs
Click to expand...

The very best shoulder measuring gizzy as Gene puts it is the Chuck Mccluer device.
Set it to zero with your headspace gage. Much better than these Hornady and such devices.

http://6mmppc.com/Page_2.html


.
 
adamsgt said:
I also use that device and it is great for setting your sizing die. However, it doesn't measure "headspace". But that's another discussion.
Click to expand...

The "old" classical definition of headspace (HEAD SPACE) was "the distance between the face of the bolt and the base of the cartridge with the cartridge fully seated in the chamber"

No, this device doesn't measure that but if you will zero it on your GO gage it will read the difference over or under.
 
JerrySharrett said:
The "old" classical definition of headspace (HEAD SPACE) was "the distance between the face of the bolt and the base of the cartridge with the cartridge fully seated in the chamber"

No, this device doesn't measure that but if you will zero it on your GO gage it will read the difference over or under.
Click to expand...

Thanks Jerry, I may just have a BR Go gage, I'll have to do a little search.
 
Gene Beggs said:
Jerry, chamber casting your new barrels would be a waste of time in my opinion. :p

The best chamber cast is a case that's been fired several times in the chamber with a normal load.

Remove the spent primer and do some measuring.

1. Measure the pressure ring right in front of the extractor groove using a 'tenth' micrometer.

2. Using a good dial caliper, measure the shoulder diameter at the junction of the body and shoulder radius.

3. Using a shoulder measurement 'gizzy' and a dial caliper, determine the headspace measurement.

4. Measure the neck diameter with a 'tenth' mike.

Gene Beggs
Click to expand...
I'm curious about using this method to measure the neck diameter. Is it accurate? Does one add something for brass spring-back? Like .0005 or so? I'm asking because I set up some PPC brass long ago based on my gunsmith's numbers and it seems like the loaded rounds are a bit tight. The neck with bullet seated may have less than .001 clearance.
 
feffer said:
I'm curious about using this method to measure the neck diameter. Is it accurate? Does one add something for brass spring-back? Like .0005 or so? I'm asking because I set up some PPC brass long ago based on my gunsmith's numbers and it seems like the loaded rounds are a bit tight. The neck with bullet seated may have less than .001 clearance.
Click to expand...

I have never been able to predict the amount of springback and I am not aware of anyone else that has. Too many factors enter into what controls that element of tTHAT piece of brass. Springback is the result of a mechanical process called "work hardening or "cold working". Even within a particular lot of cartridges there will be variations based on;

1) how many times THAT particular cartridge has been cycled (shot and resized),

2) how much (movement) THAT particular cartridge has been subjected to in the resizing process.

3) how violently (hot) THAT cartridge has been subjected to and a few other factors, but these 3 are the main ones that effect materials that react to cold working.

Some of the top shooters, now, are shooting loads with such high pressures today they only use that lot of cartridges for one or two aggregates.

Lets say you take 15 pieces of brass out of the big blue box and place them in a MTM or Masto box. Notice that you do not shoot all of them an equal amount or shoot them all with the same pressure load. See the issue?

As to annealing, forget it. Most shooters know too little about metallurgy to get any more consistent product than they started with. And, over annealing can cause more problems that not annealing at all.

In times past in big bore silhouette we would use a bullet melt pot and hold the cartridge by its base while dipping the neck into the melt until we felt the base getting warm, then drop it in a bucket of water. This probably works as well as any of the aftermarket machinery sold today to anneal brass.

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adamsgt said:
So, that should be .4406? Is that on the line from .4310 to .4414?
Click to expand...

Dave always places a dimension diameter .200 down fro the bolt face. My print is .4404 at that spot.

Back when we did all of this, (some 8-10 years ago), we went to great pains to arrive at the ideal size for those that know how to chamber a barrel and make the reamer cut what it is actually sized to cut.
 
An interruption at best....

A few years ago, 40 some odd years, I had some kind of fancy varmint rifle...I think a Remington but can't remember. I decided I would make a chamber casting out of melted sulphur. Looking back, I don't know what I would have done with the casting but it looked like a fun thing to do. As it turned out, it wasn't fun. Might have been a little fun had I not become distracted and poured the darn thing full. Hardened sulphur is extremely difficult to get out of a hole...especially if the hole can't be damaged. Thankfully, I plugged the barrel at the chamber end and all I had to do was get the brick hard sulphur out of the chamber end. As I remember, I poured sulphur up to and maybe over the locking lugs.

Trying to get the darn stuff out, I was using a loaded round as a guage of progress (don't know why exactly). I didn't want to goof up the stock so I removed it, and with it came the trigger guard. Somewhere along the line, the bolt closed and I shot the sewing machine. I was glad for a moment that it wasn't my wife but before long...well, I guess I'm glad it wasn't my wife. This took about two days to get the rifle to shoot and another day to get it ready to trade. I picked little pieces of sulphur out of there for a long time.

Soooo, if you cast with sulphur (or anything else for that matter) - remove the barrel. If you can't remove the barrel, don't do it.
 
Wilbur said:
A few years ago, 40 some odd years, I had some kind of fancy varmint rifle...I ......


Soooo, if you cast with sulphur (or anything else for that matter) - remove the barrel. If you can't remove the barrel, don't do it.
Click to expand...


CCBW, please don't take this personally but I've always heard "The good Lord takes care of fools and idiots"!!
 
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