5.7 mm Johnson Die Issue (not 5.7x28)

[hdwhit]

Please excuse the length of this post.

I have been attempting to work out a process and a load for the 5.7mm Johnson round (a/k/a 22 Spitfire). The round was developed by Col. Melvin Johnson - of Johnson machine gun fame. A similar round called the 22 Carbine also exists. In either case, this is a 30 Carbine case necked down to accept a .224 bullet.

I acquired the rifle in about 1983. The rifle came with reloading dies, but not case forming dies. In 1985, I met a handloader who was getting rid of his 5.7mm components because he couldn't make the thing work.

I have been in correspondence with Col. Johnson's son regarding what was done at the Johnson plant while it was still in operation. Those conversations have not been as helpful as I hoped.

About 1993, I bought a set of case forming dies from RCBS' custom shop. I set up the dies according to the instructions included with the dies.

The problem is that cases which come out of the dies evidence imminent head separation on first firing. That tells me I have my dies adjusted incorrectly. The so-called forming die sets the begiing of the case shoulder. The so-called trim die further refines the shoulder and provides an opportunity to use a file to trim the die to length. I skip the file and just use a Forster trimmer to trim the cases. The final step in case formation is the sizing die.

There are no comparators or other tools that I am aware of for this cartridge. If you know of any, please let me know.

It seems to me obvious that the neck is being formed too low on the case. Assuming this is correct, how do I adjust all three dies (forming, trim and sizing) to hit the shoulder at the same place at each step in the process?

Thank you in advance for any assistance.

 

[LoonWulf]

Im not intimately familiar with the round, or turning straight walls into bottle necks, but heres what i would do.

If the "forming" die can size the cases enough for the rifle to chamber them, do that, but do only as far as is needed to chamber without forcing it. Then adjust your "trim" die so that it dosent bump the should back any father.
If you HAVE to use the "trim" die to form a shoulder that will chamber in the rifle, run the case thru the forming die, then very slowly bump the shoulder with the "trim" die. Stop as soon as the bolt will close without having to force it. That SHOULD have made it so that some portion of the case shoulder is in contact with the chamber shoulder. One thing to note is that youll need to make sure that every case will fully chamber and the bolt will close completely, but not be loose.
This is actually similar to how i form belted magnum brass for its first firing. It keeps case stretching to a minimum.

If your still getting excessive stretch on the first firing after careful sizing, then you may need to look at a mechanical issue with the rifle, such as the bolt unlocking too soon.

 

[Engineer1911]

Back in ~1980 I bought a TC in 30 Herrett. Cut the case neck off, reform new neck and shoulder, new case OAL = 1.750" (from memory). The advice / process described by LoonWulf is what I successfully followed. Form, chamber to test bolt lock-up, adjust dies as required. It is possible that the trim dies sets the shoulder back too far to achieve correct case length. Use your Forester trimmer instead of the file.

 

[FROGO207]

First thing to do is make a chamber cast with Cerro safe to see just what you actually have to work with. Then on to the brass prep. Start with 10 brass to get things in order before doing them all. I would first anneal the necks to soften the brass there before forming ( use a pan of water to keep the web from overheating due to short case length). Slowly form a case to match the chamber cast and trim as needed to make sure it will not be too long to pinch at the end of chamber. Then measure the ID of the brass. I bet you are dealing with tight brass and bullet fitment expanding the neck and pinching it. Get the tools to ream the inside neck so that you have the .001 or even .002 undersized ID needed for good bullet tension. Alternatively you could run the formed brass through the regular sizing die to expand the neck for correct ID and turn the outside neck down to a manageable thickness per what you have on your chamber cast. After this is done is the time to find a propellant of the correct speed and worry about recoil spring tension and locking speeds IMHO.

ETA: get the H2O capacity of a formed case and use the pressure and vel of the 30 carbine round to find the best propellant with the size and weight of projectile you want. One of the guys with Quickload will run the numbers for you I bet.

 

[Demi-human]

First thing to do is make a chamber cast with Cerro safe to see just what you actually have to work with.

Start with 10 brass to get things in order before doing them all.

I learned this the hard way...

There are no comparators or other tools that I am aware of for this cartridge.

You don't need one, you have the barrel in question in possession. It only need fit your rifle, not all of them.

The problem is that cases which come out of the dies

One of these dies is not like the others. Only one could be the culprit. A Hornady Ogive Comparator for one's caliper can be used to gauge sizing as well, using a larger diameter insert.
https://ads.midwayusa.com/product/3...ullet-comparator-complete-set-with-14-inserts

 

[edwardware]

You're making this too complicated. Lube a dozen unformed cases, back out all the dies a half turn, and take a single case through the forming process. Chances are good the case won't chamber; that's good (if it will, back off another half turn with a fresh case). Now turn the final (sizing) die in 1/10 turn at a time, resizing each step, until the case chambers with reasonable feel; if you have lube wrinkles in this case that's ok, you're just setting shoulder location.

Now that final sizing is set, turn in the first and second forming dies if necessary. Note that most lube wrinkles can be fixed by meticulously NOT lubing the future shoulder location.

 

[WestKentucky]

Forming any bottleneck isn’t a big deal, it’s just time and labor consuming. If you have a true set of forming dies you should be equipped to tackle the task. If you are having case head separation on the first fire it sounds like you are setting the shoulders too far back when you form. Back off your forming dies a bunch and then slowly but surely take them further down until the cases barely fit.

First shot should be a pretty light load to finish the forming process to match your chamber. After that first shot, carefully check your brass to see what problems might be there. There shouldn’t be any issues at that point, but you never know.

Can you take pictures of your cases after each step and pull some quick dimensions of the parts that are being worked? I would like to see both the process and the problem.