Just Right Carbine explosion

OOB? Short chamber holding the bolt open maybe?

Anything remain in the chamber and/or barrel now?

Short chamber is a possibility but not probable. More likely improper headspace when installing the barrel that allows the extractor to hold the round against the breechface but when the bolt is fully forward the round is not completely chambered.

Ah, #4 would do it.

Setback can cause destruction for sure. Speer has wrote about some combinations that seated just .030” deeper more than doubled pressures.



CCI aluminum cases are ones I avoid too.

Nice photos. Two questions.
Is this factory ammunition? It looks like it was Remington factory ammo.
Is something missing from the bolt face?

The photo of the case in the stuck chamber shows it is probably seated correctly and the bolt was closed when fired. Note the interior & exterior case taper in relation to the end of the barrel/chamber and the extractor mark on the side of the case. Also, the top of the case head blew out, the bottom of the case head directed gasses down the feed ramp towards the nose of the next bullet in the mag setting it back.

The photo of the receiver shows there is no gas port. If there is no gas port, that is strike one.
The photo of the bolt face shows the the case head is not supported on the top of the case, by design (if something’s not missing). Strike 2.
The photo of the set back round shows gasses pushed it back. That was strike three for your third round fired.

Your first round may have set back and compromised (crack) the case on the second round which may be why it was smokey - insufficient pressure. The second round set back the third round. And the third round set back the fourth, sitting in the mag when the gun came apart.

Thank goodness you weren’t seriously hurt.

View attachment 948238 View attachment 948239 View attachment 948240

Glad to hear you're OK. Even more glad to hear a good lesson was learned. Kudos to you.

MySuomi said:

I was wondering if some how the bullet was getting pushed into the casing

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take a "good" round and try to push the bullet down into the case. use a table or counter top and push with your hand. you may have some bad rounds.

luck,

murf

Check the barrel closely for a bulge. is it possible that the two shots that didn't sound right were squibs and the third shot cleared the obstructions (with great pressure).

The round looks fully seated, and out of battery isn't nearly as catastrophic on a blow-back action vs a locked breach.

Given that the first two rounds sounded weird, SOMETHING was already up. I'd wager that they were either squibs or severly underloaded. One or both of them likely lodged in the barrel. When the third (full power) round went off it likely pushed the barrel clean but with enough back-pressure to rupture the case.

As Jerry M said, I'd check carefully for a bulge in the barrel. If there are none I'd personally try again with a single round, make sure it sounds ok and remove the upper afterwards to ensure that it cleared the barrel.

Sounded funny = (usually) squib-ish load.

Had something like happen in an Uzi. Round sounded funny, fired next shot before realizing it. BOOM! Bulged the barrel and nothing more thankfully.

Seen 38 spcl 110gr projectiles lodged in the forcing cone by just a primer.
Then the idiot decided to shoot it out, and cracked & bulged the barrel and frame.

Another thing to look at is headspace as others have mentioned. The headspace for that round is based on OAL for the cartridge. Double check your barrel marking to make sure they didn’t give you a 10mm by mistake or anything else funny. It sounds to me like there was something wrong from the get go indicating that the condition never changed. My suspicion is the relationship between the bolt snd barrel.

I still believe headspace is the problem. Did they give you instructions for headspacing the barrel when you did the caliber change?

Squib round on the first shot? By sounded funny do you mean it sounded weak?

My monies on a headspace problem and the fact the gun will fire in that condition. Aren’t these short, mouth head spaced cartridges like 9s and 40s big on case bulging at the base any way?

At any rate if it don’t sound right it usually I ain’t. A prudent shooter stops right there.

Just a question about the conversion kit. Did the mfg include a new recoil spring? The cases may be blowing out due to the bolt moving early.

Blow back action opened to soon, will show high pressure signs as the round is still in the process of firing. Brass not supported. 35,000 PSI got loose. Blow back actions at this PSI, not a great idea. Imo.

The added smoke and odd sound on firing goes with the action opening too soon. Brass not stuck in barrel, shows no over pressure factory ammo as cause.

Out of Battery firing- The disconnector should keep the gun from firing if the round is not full chambered.

The round that kaboomed was not fully in the chamber , at peak pressure, for some reason?

https://www.thehighroad.org/index.php?threads/hipoint-40s-w-carbine-kaboom.773546/

Headspace - "Readjusted (set deeper)"
Chamber - "burr in chamber"

Trigger - "Shortened disconnect"

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you're so lucky you didn't have a squib load stuck in your barrel. if something isn't right or feels really odd, firing again is a wicked mistake, unless someone is shooting back at you and it is the lesser of 2 evils.

Did the funny sounding rounds work the guns action?

I have a few of the TNW's which from the outside look like the same rifle. Did the conversion just include a new bolt head? If so did it say anything about the buffer spring? It sure looks to me like as others mentioned the action is opening too soon. So not enough weight between the bolt, and the buffer spring combo. This is assuming the JR is the same internally as the TNW's. I can shoot 9mm, .45, and 10mm through mine with just different bolt heads but I have never seen the internals on the JR to see if they work the same. ??