17 rimfire question

[Shoot44]

While shooting in the woods at our usual place, we found a bunch of what was obviously 17 caliber rimfire brass. But it looked/looks very strange. Instead of the nice clean 'shoulder' usually found, this had a sort of 'rounded out' form in that area. The picture shows the two cases; one from my Savage bolt action, which looks normal, and the other we found on the ground.

Upon discussing it, we sort of decided that it must have happened when someone shot 17 HM2 ammo in a gun chambered for the much longer 17HMR round. OK, that made sense. . . . at that point.

But, when I got home, I compared one of the cases with some fired 17 HMR brass. As you can see, they are the same length. So our 'theory' cannot be correct. They must be cases from the HMR round.

The question now is how DID these cases get that shape???

Is it possible that this is what happens when 17HMR ammo is fired in an autoloader? Is this, perhaps, why we've now been warned to NOT do this? Could the action be 'opening up' way too soon, and the cases thus have their shoulders 'blown out' like this???

Expert advice requested....

 

[9x19]

None of my brass looks like that when fired from a 10/22M with a 96/17 barrel.

 

[mike7mm08]

My guess is a 17 hmr fired in a 22 mag chamber. If you have an issue with a semiauto 17HMR the case will blow. That case you found had to be in the chamber until the pressure spiked completely to get a perfect fireform. The other possibility is the case was fired in a 5mm rimfire. Another note on the semi auto warning. The general consensus is it is a hot ammo issue. Several people have found numerous batches of ammo way hotter than they should be. Lots of info of the 17HMR "problem" over at rimfire central.

 

[Shoot44]

My guess is a 17 hmr fired in a 22 mag chamber. If you have an issue with a semiauto 17HMR the case will blow. That case you found had to be in the chamber until the pressure spiked completely to get a perfect fireform. The other possibility is the case was fired in a 5mm rimfire. Another note on the semi auto warning. The general consensus is it is a hot ammo issue. Several people have found numerous batches of ammo way hotter than they should be. Lots of info of the 17HMR "problem" over at rimfire central.

Yeah, that may be a possibility. But the target that they had shot at had some fairly good groups in it. I doubt that a 17 caliber bullet fired in a 22 caliber barrel/chamber would shoot very accurately. . . .?

 

[Snake45]

It's a .17 HMR Ackley Improved. :lol:

 

[Shoot44]

It's a .17 HMR Ackley Improved. :lol:

:lol:

 

[Waldo Pepper]

The 5N7x28 FN round looks pretty much like that after fired, but the gun fires in a chamber that shaped slightly different then the round. It sort of a out of battery firing on the FN and I suspect a 17HMR auto rifle or possibly a Accelerator 17HMR pistol. A bottleneck cartridge will look like that if fired out of battery slightly, if out of batter too far it will swell at base and possibly blow off lower section of case.