Automag III and loose chamber

KotKotofeich

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I'm hoping someone with one will step up - I think there was one sold on the EE recently.

I think mine has a loose chamber. Generally wasn't a problem before (but this is not a gun one shoots often so it's not like I had a lot of rounds through it and I haven't shot factory ammo before either...) but a friend asked to play with it recently so I took it out to shoot...

S&B factory ammo, FTF on second round, primer had a firing pin imprint on it... he finished the magazine and I wanted to see if the FTF round would fire, I put a few more rounds in the mag and the FTF round on top... let the slide go forward... pull the trigger - nothing, wait the few seconds, repeat... well, it fired after a few tries... didn't feel any different except the casing didn't eject... and the primer was gone... and there were some serious signs of overpressure... (case head smooshed)

Well... time for some pictures to tell the tale and why I think there is a problem with the chamber that I never noticed before...

Put a rod in the barrel and hammer out the casing... except the a part of the casing is still in there... (case head separation alright)

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Ok, let's see if I can extract the rest of it _carefullly_ with my field expedient broken case extractor aka a tap - worked well

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Except is that the rest of the bullet jacket still there? Look carefully at the mouth of the case, zoom in...

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Yup (after taking the tap out) - and the remnants of the primer... that were somehow in the case...

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I'm thoroughly impressed with how strong the gun is - no signs of damage whatsoever... I'm very lucky - things could have gone much worse, I know. But none of my past experience led me to expect anything of this sort... But how could this happen? By the looks of the case mouth, could it be jammed past where it's supposed to be in the chamber?

Ok, let's try some plunk tests with this ammo. Most of the time it looks just fine:

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But occasionally

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This shouldn't happen, right? Just on the off chance I pulled out the carbine - nope, can't do that.

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So... here's what I think happened.

Cartridge got picked up from the mag, but instead of the extractor jumping over the rim it pushes it into the chamber because the chamber is just too big, huge out of spec headspace results. 30carb headspaces on the case mouth, right? And in this case (ha!) the cartridge got pushed past that point...
FTF, of course, because the firing pin doesn't quite reach the primer. At this time the bullet is jammed into the rifling - you can see marks on the jacket that got left behind.
I keep cocking the hammer and trying to fire until eventually the primer has enough abuse and goes...
Out of spec headspace + bullet in the rifling - overpressure. The primer is blown, the case is torn in half as it's pushed back to the boltface, but the bullet is still jammed in the rifling so the core gets blown forward with most of the jacket...

If this were a new gun, I'd call this a warranty issue, but for lack of an ouija board, AMT is quite out of reach for any claims :) Anyone with an automag III, could you try the plunk test in yours and see if you have the same issue? If you have factory S&B please use that - i.e. did they just ream _all_ chambers generously and I never saw this before with reloaded ammo? Or is S&B generally small? I can only replicate this with the S&B factory, not with my reloads from a Lee die... I don't have a headspace gauge...

Does anyone know where I can get a spare barrel? :)
 
Have you had the Automag 3 for some time? I would wager it does have something to do with the S&B rounds, Do you have any others you could chamber check with? But also, it could be chalked up to AMT QC as well. I'll be following this with Curiosity! Wish I had an AM3
 
I've never shot anything but my own reloads in it... I asked around and was able to get some old surplus...

So what do you know! No problems whatsoever, and when I measure at the mouth (Mitutoyo dial caliper - quality ;) )

S&B is smaller by .004" compared to surplus. Ouch! (.334 being max spec, I believe, .332 on surplus and .328 on S&B)

So fair warning, NOT ALL FACTORY ammo is SAFE in these pistols!!!

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Undersized chambers are not uncommon with that pistol. It's the opposite of what you are thinking, stiction has the case held while the gun is trying to pull it out. A quick ream and polish is the fix. Sounds like yours is right on the edge with it running fine with certain ammunition.

Edit: I actually skipped the part with your live round deep in the chamber... Not sure why SB would do that but nothing else. I have several cases of that ammo and haven't had any issues. Then again I don't have an Automag.
 
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Based on my checks and what others are reporting S&B is sized 4 thou smaller. Can be a safety issue if the chamber is larger like mine seems to be. I haven't been able to find info on what minimum diameter at the mouth is still in spec? CIP seems to only indicate maximum?

I'll know to avoid the brand, no biggie _for me_ but it's a general problem - who expects to have that kind of issues from factory ammo when there were no issues up till then? I'll see if I can find a 30carb headspace gauge to borrow, but I strongly suspect it's going to be in spec...
 
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