32 caliber for a Forehand Arms revolver.

[racepres]

I is absolutely easy to put enough fast powder in that small case to create more pressure than is safe so the small case can make more pressure than the long case if that is how the ammo is loaded. The 32 S&W long wadcutter factory ammo is almost always loaded to lower pressures than all the other 32 S&W ammo because that is what the shooters who use it most want, not really the lower pressure but the lower recoil and lower blast because they are shooting at paper targets with precision not how good it might be at killing something.

Regarding the stories about the non-linearity of CUP vs. Psi being caused as you described, it is just a theory. There is very little data on the performance of materials when subjected to impulse loading (short duration high loads). It is clear that such a phenomenon as was suggested is real but it is not documented (or at least I have not been able to find such documentation) that this it actually the case. That you did not really understand it is not a surprise, it is not well understood. There are other theories about that as well but just it is good to know that the pressure might be higher than CUP suggests and using PSI data is probably better.

Tim

Maybe...from a Purely Absolute Safety aspect...But..I am a Believer in "Moment of Impact"
Ruined alot of Transmissions Drag Racing.. even after we learned of M.o.I... A very strong impact, that don't last very long is Sometimes a Good Thing!!!! Relatively!!!! But, There are those who devine to use Big Numbers to Scare Us!!!!

[dtknowles]

Certainly, a structure is more likely to not be damaged by a force that last a extremely short time than the same force for a longer time.

A copper crusher is a structure intended to be damaged and the amount of damage is used to determine the amount of force it was subject too. A huge force for a tiny time might not even show damage. The pressure force on the crusher from something like a small low pressure handgun cartridge is going to be a short duration event in any case. Total duration will be less than a millisecond and the time spent where the pressure is above half the peak pressure less than half a millisecond. The whole event could be considered an Impact.
Tim

[racepres]

Certainly, a structure is more likely to not be damaged by a force that last a extremely short time than the same force for a longer time.

A copper crusher is a structure intended to be damaged and the amount of damage is used to determine the amount of force it was subject too. A huge force for a tiny time might not even show damage. The pressure force on the crusher from something like a small low pressure handgun cartridge is going to be a short duration event in any case. Total duration will be less than a millisecond and the time spent where the pressure is above half the peak pressure less than half a millisecond. The whole event could be considered an Impact.
Tim

I am going to go wayyyy out on this limb now.. If I was looking for a Cylinder that needed to contain extremely high pressure...I would devise a method to place a Measured amount of Pressure In the cylinder...to test it against a Competing Cylinder...and either Place an amount of pressure to Destroy the cylinder...and choose the Cylinder that was Destroyed at the Highest Pressure... or...Place a Strain Gauge on the cylinders to be tested, and decide that the Cylinder that held the most Strain, yet returned to it's original Shape/configuration, was the strongest... IMO the Proper use of a Strain Gauge...
Assuming that A Chiwanese Sewer Pipe, would react the same as High quality, properly heat treated, ordinance steel, is Ludicrous!!
To Then decide that the Same Pressure would make either React Identically...Worser.
Bottom Line ... sorry to say, the assignment of PSI to a Given Strain... while assuming all ordinance steel is Identical...Nah...Simply Cheap... No real idea what is actually being applied... be it assigned the value of PSI or Molecules displaced!!
Not Like A Port that measures what is going on Inside, by Crushing a Known composition pellet... Not Cheap!!!
I cannot imagine a Device that could measure, and Record. Real PSI...
Edit; The reason we are constantly admonished that a given "load" is Not going to be the same in every Firearm... we need to test in Our Own... assuming we can recognize safe from Not Safe.

[Larry Gibson]

racepres

The correct use of either a Transducer, a strain gauge or the C.U.P. system requires the use of "reference ammunition" to get a correlation/correction factor. That factor is then used to adjust for the differences in the test barrel steel, the chamber and bore dimensions and wear. The reference ammunition is of known pressure and then becomes the "standard". Even the best of test fixtures used by different ammunition manufacturers or test facilities will give different pressure measurements with the same ammunition. They do that because each test machine is, in fact, "different" whether a very expensive test fixture or a production firearm.

The type of steel and the quality of the steel of the barrel obly contain the pressure, they have no bearing on the pressure created by the cartridge.

Consider a test fixture is simply a firearm also. Thus, what the test fixture measures the pressure at will most likely be a different pressure than the same ammunition would produce in a regular firearm. Basically it is due to the variability of "test" conditions. That is the reason for the "admonishment". Also, even with the same ammunition (same lot) the shot to shot variation of the pressure is much larger than most would think. Even with small ES/SDs of velocity there can be a large shot to shot pressure variation. If the data tells you a specific load gives a certain psi/C.U.P. that is just the average that was obtained. That average means half of the shots were a higher pressure and half of the shots were a lower pressure. The data most often does not, if ever, tell you what theat +/- variation was. If you have a 308W load that supposedly give 60,000 psi half of the shots could very well have been in the 60 to 63,000 psi range, or perhaps even more in your particular rifle.

The use of a transducer and/or strain gauge has proven to be the best and most consistent methods of measuring the pressure of cartridges.

[racepres]

Thanks for that Larry...
of course, my feeble mind must wonder who tested the reference ammo...and How??
But...I know I am throwing rocks here...
My "take" on the whole thing is that I do Not see any reason why the term PSI was Used to represent "strain"
Easy and Cheap, I Understand..... PSI??? Not so Much
and my reference to Quality of the Steel... well...just throwing Crap in the Shoot..
Apologies....As I still believe the Copper Crusher to be Accurate no Matter the "steel" and a Real World test IMO
Not easy, and Not economical...Certainly...tho Making Quality Firearms was Not Either..
I will leave this Lay... and again...Not attacking anything nor anyone... Just cannot wrap my feeble mind around SAAMI...nor their Methods...

[rebelrider.mike]

Well, look what showed up a few weeks early:

I'm looking forward to casting some practice bullets.

My next purchase is a bit out of order, but I've read that 32 S&W dies are hard to find. I found one, so I bought it. The rest of the equipment is pretty generic so I'm not worried about finding them. I might get the brass cases next just in case the company decides to discontinue them.

[rebelrider.mike]

The brass cartridges are here:


Everything seems to fit and move perfectly.


I'm still waiting for the die press to arrive. Next week hopefully.

[rebelrider.mike]

I did some bullet casting yesterday.


I don't have a melting pot yet, so I used a torch and an iron ladle. I thought to pre-heat the mold, but I don't think I got it hot enough. Lots of little gaps in the bullets. Also, the diameter isn't consistent. It ranges from 0.3145" to 0.3255".

Also, I don't know the purity of the lead I'm using. Just some scrap stuff I found to practice with. I've read that adding tin not only changes the hardness, but also reduces surface tension of liquid lead so it fills all the spaces in the mold better.

I slugged the bore with one of them and got the same results as I did with the slugs I made before I had the mold. The riffled diameter varies between 0.3135" and 0.3155".


I was mostly just curious as to what the bullet would like after going through the bore.

[rebelrider.mike]

The press has arrived. I made a thing for it out of scrap wood so I don't have to drill holes in my bench.


It all worked well, and I made 4 dummy rounds out of my 4 remaining practice bullets. And they still fit in the chambers.


Just for fun I got my feeler gauges out again and measured the gap between the chamber and bore with the trigger pulled all the way back. I got 0.004". I wonder if it stays that small though when the gun is actually fired.

Things I still need to sort out:

• Melting lead
• Mold temperature
• Scrap lead hardness or alloy
• Primers
• Powder
• Bullet lube

I'm tempted to get a cheaper melting pot, but they all seem kind of dodgy, and the ones made by Lee have pretty good reviews. Plus Lee sells replacement parts for their stuff, which I appreciate.

[Wayne Smith]

I'm still using a 20lb pot on a camp stove. It works and it's cheap. You just need a good ladle.

[racepres]

I'm tempted to get a cheaper melting pot, but they all seem kind of dodgy, and the ones made by Lee have pretty good reviews. Plus Lee sells replacement parts for their stuff, which I appreciate.

I have been using the least expensive Lee Pot with a Ladle, since the '80's... Not exclusively anymore...but, it is still viable, and great for very small runs! FWIW