Need Help From the Wildcat Loaders

[hdwhit]

Those who have spent any time on this site will know that the 5.7mm Johnson (a/k/a .22 Spitfire) round has been my "one-arm man" since I was in my twenties.

It is the invention of Col. Melvin Johnson (of Johnson Machine Gun fame) whereby a 30 Carbine case is necked down to either .223 or .224 (as I would later learn, different conversions used different barrels) and loaded accordingly to push a 40 or 45 grain bullet to about 3,000 fps.

When I bought a carbine chambered for 5.7mm Johnson, I got a set of RCBS reloading dies and about a dozen loaded rounds along with the gun. Apparently, the previous owner of the rifle had not bought the RCBS case forming dies and was just shoving .30 Carbine brass into the Full-Length Resizing Die and calling it good.

I DID contact RCBS (before they closed their custom shop) and ordered the Forming Die & Trim Die (specially hardened to allow a file to be used to trim the case to the correct length). I set up the dies according to the instructions received from RCBS and loaded about 100 rounds using the load data available to me (i.e. the former-Pacific Reloading Manual as well as information received from Col. Johnson's son). The result was caseheads smashed into the bolt and brass stretched to the point head separation was imminent after the first firing.

I subsequently cast the barrel and discovered it was what I can best describe as 0.2235; something between .223 and .224.

Please note that I was afraid using a file with the Trim Die to "trim" the case would produce uneven results, so I used the Trim Die only for its step in case forming. I used a Forster Case Trimmer to trim the cases to length as a separate step.

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So, my question to the wildcatters (along with any machinists who may be able to help out) is: "How do I go about adjusting the three dies (Forming, Trim, Resizing) to consistently achieve the proper shoulder formation and case length?" I assume I have to begin with the Forming Die and then back off from there to the Trim Die and finally, the Resizing Die, but is that assumption correct?

Any cogent suggestions would be appreciated.

Thank you.

 

[Blue68f100]

Measure the shoulder position on a fired cartridge. Then when you setup your dies, do not go less than 0.002"-0.003" below spec. What ever it is. The brass is probably being stretched during ejection. I would set the forming die so it would be within 0.003" to 0.005" long then finish with the sizing die.

There are several ways to measure shoulder position, Hornady has a tool that fastens to calipers. A cheap way is to use a spend round that will ride on the shoulder then measure the total length. This will be your target. Size one and check against the measurement. Start long and work down slowly. If you anneal it will make the sizing easier and less stress on the brass.

 

[hdwhit]

Blue68f100 wrote:
...I would set the forming die so it would be within 0.003" to 0.005" long then finish with the sizing die.

Thank you. The order of setting up the dies had me uncertain. I will certainly give this a try.

 

[hdwhit]

Sorry for what amounted to a "drive by" posting, but in the interim I found out I have thyroid cancer, so my attention got diverted.

 

[hdwhit]

Know I need to move the shoulder forward at least 2/1000 inch.

My concern was not determining how much to move the shoulder forward, but the order in which I should adjust the dies given that each die (forming, trim and resizing) plays a part in forming the shoulder and case neck.

 

[Blue68f100]

You are actually moving the shoulder back, during sizing.

The shoulder moves forward during firing. The actual mechanics is on ignition:
The impact drives the brass forward
The neck expands, sealing.
Then the pressure stretches the body of the brass pushing the base back against the bolt face.

You only trim after sizing.

 

[hdwhit]

Blue68f100 wrote:

You are actually moving the shoulder back, during sizing.

In this case, NO.

I am NOT talking about resizing an already formed case.

I am talking about forming a shoulder on a case that didn't previous have a shoulder.

Please re-read the original post.

I am forming a case from brass of a different caliber.

I am not simply trying to "re-set" the shoulder on an existing caliber after firing in the same chamber.

The cartridge I am seeking to form requires that I engage in a three-step process of 1) forming a case shoulder where none had previously existed, 2) further forming the shoulder and trimming to length and 3) finishing the case mouth and resizing it in the resizing die.

This is not a case of "resetting" an existing case shoulder! It is a case of forming a shoulder that did not previously exist! That is why I specifically asked for input from people who have experience loading wildcat cartridges.

During a typical "resizing" operation the objective is to move the shoulder "back" (i.e. "moving back" meaning decreasing the distance from the case head to the start of the shoulder) so as to allow it to fit into the chamber of the gun that will next fire it.

I am not asking about that process at all.

The shoulder moves forward during firing. The actual mechanics is on ignition:
The impact drives the brass forward
The neck expands, sealing.
Then the pressure stretches the body of the brass pushing the base back against the bolt face.

YES, all of this is true, but it is irrelevant to my question.

As the powder converts to gas and the expanding gasses press against the cartridge walls, the case conforms the case to the chamber walls. In the case of so-called "bottleneck" cartridges this "conforming" causes the case wall between the case head and the shoulder to stretch as it conforms to a chamber longer than the cartridge case.

Again, I am well-familiar with this aspect of shooting.

But, before you tell me to move BACK a case shoulder that is already not sufficiently far forward, you should review the original posting and consider the consequences of "bumping back" a case shoulder that is already so far short of the shoulder in the chamber that firing results in obvious stretching near the case head (imminent separation). All such advice to advise me to move the case neck "forward" (i.e. a greater distance from the case head) would accomplish would be to advise me to invite actual (rather than imminent) head separation that on previously fired brass where head separation was merely imminent and not a reality.

I adjusted my dies according to the instructions received from RCBS and they nevertheless form a shoulder at least 2/1,000 inch short of the shoulder of the chamber. Thus, when - as you elaborated - the pressure within the cartridge moves the shoulder forward (to bring it into contact with the chamber wall), it stretches the case to the point where upon first firing of the case I experience stretching of the case wall near the case head (i.e. incipient head separation) that is nearly enough to cause head separation.

You only trim after sizing.

Yeah.

After 43 years of reloading (zero squibs, zero failures), I will acknowledge that I am aware of the need to trim my brass after sizing.

Thank you.

Hugh

 

[horsey300]

Sorry for what amounted to a "drive by" posting, but in the interim I found out I have thyroid cancer, so my attention got diverted.

Not the best news! Good luck on both of the challenges you've been presented with (this plus the 5.7)!

 

[Blue68f100]

Have you checked to see if the wall thickness of the neck is too thick, causing it to stick during firing. In your case you want the brass to fully float so it will fill the chamber from base forward. You may consider greasing the cartridge before firing it so that every thing will be pushed back against the bolt face then expand out. I believe it's slamfire that does this.

Since your not trimming during the forming die, it may be the reason it's sticking at the neck, causing the stretching in the wrong place. May want to confirm the wall thickness of the brass your using is not to thick contributing to this. But since your already short this does not sound likely. I would not worry about be even during this process. The process is only for forming, indicating that there may/will be some stretching going on.

Did you annealed the brass before forming?

What your finding out may be the reason the original owner let the firing process form the brass.

 

[243winxb]

I adjusted my dies according to the instructions received from RCBS

The RCBS instructions say to have the shell holders make contact with the form & trim dies. This may push the shoulder back to far?

I would start with .020" between shell holder & dies. Make adjustment from there. Trim brass in the trim die or by other means if you like, before fl sizing.

The full length sizing die, when making contact with the shell holder has pushed the shoulder back way to much on sizing for me. (Not rcbs brand, different cartridge)

Apparently, the previous owner of the rifle had not bought the RCBS case forming dies and was just shoving .30 Carbine brass into the Full-Length Resizing Die and calling it good.

Will brass formed this way chamber and fire form?

 

[jmorris]

So, my question to the wildcatters (along with any machinists who may be able to help out) is: "How do I go about adjusting the three dies (Forming, Trim, Resizing) to consistently achieve the proper shoulder formation and case length?" I assume I have to begin with the Forming Die and then back off from there to the Trim Die and finally, the Resizing Die, but is that assumption correct?

If you are taking a larger case than chamber, I would form just enough for the action to close. Trim length would be to specifications for the round and I set resize dies for bolt actions for slight compression upon bolt closing.

If the cases are “under” chamber dimensions the head will need to be installed into the bolt, so the extractor is holding it and a fire form load (Don’t even need a projectile) used to blow the case out to the chamber first. Then use the procedure above.