Cimarron Short Deluxe 1873 .357 Mag bulging/breaking cases.

[Capn Beeb]

Hey y'all, my Cimarron '73 developed a bit of a problem recently in that .357 Magnums shot through it will result in bulging cases, and in the case of Sellier & Bellot, full on case head separation.

Here's the remains of the S&B brass:



And here's a piece of Federal brass, where you can see it bulged in the same spot the S&B brass separated:



Searching around and talking to other folks has suggested a few things:

1) Barrel is backing out, impacting headspace. This is being considered unlikely as the barrel is threaded into the receiver and the gun still shoots true with both .38 Specials and .357 Magnums, and the sights aren't canted at all.

2) Compromised/damaged chamber. This would make sense if the brass was breaking in a single point, rather than a consistent complete circle. I've inspected the chamber the best I can, and I see no irregularities in the metal.

3) Compromised headspace brought on by the toggle links not squaring up. This is kinda what I'm leaning to as I removed the links a few months back for cleaning, and it would certainly explain my foggy memory as I've been wondering just how long this problem has been going on as I simply can't recall

For what it's worth, the gun is short stroked with Pioneer Gun Works' super short stroke kit. Hopefully y'all can shed some light on this, cause I absolutely love the rifle and while I don't shoot Magnums out of it regularly, they're a hoot.

[greyhawk]

Those are all the signs of
1) a HOT load
2) Sloppy chamber
3) excessive headspace
pretty much take your pick but the load is too much for the gun irts being fired in in the condition it is in right now - I dont care what the books say you have concrete evidence in your fingers
How many times those shells been loaded ?
I am guessing here but me thinks a short stroke 73 is not as strong in the action as a full throw system - ? geometry - the closed links have less ability to resist bolt backthrust ?
heres a newsflash - if ya keep blowin up cases - sooner or later (likely sooner) you are headed for a very unhealthy outcome - proly break the gun - could end up wearin a piece of it (bolt in eye socket perhaps)

I would
1) tone the load down
2) check headspace 
3) if two is a problem - yank the short stroke kit OUT and put the gun back how it was.

Are you handloading these ? whats the charge? 

[August]

I've been told that recent Uberti's have headspace issues.  Seems like a gunsmith familiar with the '73 is in order.

[Capn Beeb]

Those are all the signs of
1) a HOT load
2) Sloppy chamber
3) excessive headspace
pretty much take your pick but the load is too much for the gun irts being fired in in the condition it is in right now - I dont care what the books say you have concrete evidence in your fingers
How many times those shells been loaded ?
I am guessing here but me thinks a short stroke 73 is not as strong in the action as a full throw system - ? geometry - the closed links have less ability to resist bolt backthrust ?
heres a newsflash - if ya keep blowin up cases - sooner or later (likely sooner) you are headed for a very unhealthy outcome - proly break the gun - could end up wearin a piece of it (bolt in eye socket perhaps)

I would
1) tone the load down
2) check headspace  
3) if two is a problem - yank the short stroke kit OUT and put the gun back how it was.

Are you handloading these ? whats the charge?  

Sorry, should've specified that this is factory ammo rather than handloads. It's this stuff specifically:

Federal American Eagle 158gr JSP
https://www.midwayusa.com/product/1001550710/federal-american-eagle-ammunition-357-magnum-158-grain-jacketed-soft-point

Sellier & Bellot 158gr JSP
https://www.midwayusa.com/product/712744/sellier-and-bellot-ammunition-357-magnum-158-grain-full-metal-jacket-box-of-50

I feel you're on to something with the ammo just being too hot for the gun as I tried some of Magtech's cowboy ammo in .357 Mag today and had zero problems. No bulging or ruptured brass, no problems extracting or ejecting, just smooth sailing all the way. The Federal and S&B ammo on the other hand are putting out far higher levels of muzzle energy, upwards to a 150 ft-lbs difference, so I'm thinking the ammo is just way too hot for the gun.  I've also fired off an email to Pioneer Gunworks for their take on the idea that the short throw links might sacrifice structural rigidity in favor of speed.

What a shame it is having to buy and eventually load cowboy rated ammo for a cowboy gun

[Roscoe]

If there was only one case head separation, there may not be any problem with the gun. Bulging should not be surprising in high pressure ammo and a generous, easy running chamber. Becoming a reloader would solve many things.

[Baltimore Ed]

It's a dedicated short stroke CAS rifle, get some Black Hills CAS ammo. If you want a hunting .357 get a Marlin but ultimately if you intend to compete in cas you'll need to reload and  build your own ammo which creates an entire new world of potential ammo problems and solutions. Not to scare you off but there is a complete set of Funk and Wagnals Encyclopedia worth of experience and knowledge on this forum. Ask and someone will know the answer. My personal thinking is that Greyhawk is correct. Too hot a load and too much headspace from the ss kit. It doesn't take much when you're messing with the toggles to affect the headspace in a 73 or 76. Good luck, have fun and stay safe.
PS: from my experience, milder loads are generally more accurate than hot ones.

[dusty texian]

Greyhawk has very good advice , the problem could be 1. 2. and 3 that he mentioned . If it were mine I'd check headspace , then a chamber cast , before shooting this rifle .    .357 Mag. in a 73 style toggle link action / not a good idea . Just my opinion . ,,,DT

[Coffinmaker]

Yelling "TA DA" as he leaps into the fray  

First step.  You need a rifle mechanic with feeler gauges that go around the the extractor and check the head space.  I don't care what ammo you use, you need to look at your head space.  Check the space between the Case Head and Bolt Face with the action tightly closed.  Optimum head space is .004   However, toggle link rifle will run with head space clear out to .010   I DO NOT recommend that.

If your head space is out of spec, Joe Alves at Pioneer Gunworks can and will exchange your Short Stroke links for longer links.  Pioneer links always close up to align in parallel.

It also appears you have a slightly mis-cut chamber.  Ammo loaded to full 357 Mag pressure can and will expand cases to fill the chamber voids.  Even with correct head space, you may well have to shoot lighter loads to keep case expansion down.  With a correct chamber, 357 ammunition WILL NOT over stress a Uberti '73

AW KRAP!!  I just re-read this here post and realized I really screwed up.  First paragraph where I suggest checking the head space, the head space should be checked between the cartridge case Head and the Breach Face of the Bolt.  That is why you need a feeler gauge adapted (re shaped) to go around the extractor.  OOPS.  My Bad.   

Or a nice set of tapered feeler gauges.   

So I fix'd the original paragraph.  So if you read this before and thought I had really lost it ................. 

[RRio]

Yelling "TA DA" as he leaps into the fray 

AW KRAP!!  I just re-read this here post and realized I really screwed up.  First paragraph where I suggest checking the head space, the head space should be checked between the cartridge case Head and the Breach Face of the Bolt.  That is why you need a feeler gauge adapted (re shaped) to go around the extractor.  OOPS.  My Bad.   

Or a nice set of tapered feeler gauges.   

So I fix'd the original paragraph.  So if you read this before and thought I had really lost it ................. 

AAWWW   Don't be so hard on yourself, Coffinmaker. We knew what ya meant.