Cracked .17 HMR cases

[David Grove]

To the group:

Has anyone had any problems with cracked casings in their .17 HMR ammo? (see attached pic) Today I was shooting Winchester .17 HMR ammo out of my bolt action Savage .17 and noticed that every 10 rounds or so one of the empty shells wouldn't eject. I had to use the tip of a knife to pry each non-ejected shell of the chamber. I couldn't figure out why the spent shells were getting stuck and then I noticed the cracks. I probably had 15 rounds do this today. I looked online and it looks like some other people have had these problems. I am not the most knowledgeable about guns so my questions are:

• Is this dangerous?
  
• Does this affect accuracy (does gas escape out the side of the shell reducing bullet velocity?)
• Will this harm the gun?
• Should I call Winchester and make a big stink?

Any advice would be much appreciated.

Thanks,

Dave

[Eric Blomquist]

This could be caused by a number of things, including a brittle batch of brass, a mis-match in specs as between the OD of the round and the chamber, or excess pressure.  I'm guessing it's not the latter because you're using factory rounds.  More likely, in my estimation, it's a design flaw.

 

Normally, on ignition of the charge, the brass cartridge casing will flow and expand to the dimensions of the chamber.  This is why, when reloading, one must re-size the brass as one of the first steps.  I have seen cases fail in this way after being reloaded a number of times.  In this case, it's a rimfire round direct from the factory, so fatigue isn't an issue.  It's either too thin for the pressure, the brass is too brittle, or the dimensions of the brass and chamber leave too much room for the case to expand without rupturing.

 

The .17 HMR is a necked-down .22 WMR/.22 Win Mag, which itself is a very hot round, comparable to a .38 Spl in muzzle energy.  The .17 HMR generates over 240 ft-lbs. of muzzle energy and a muzzle velocity of 2350-2550fps.  A .223 Remington and a .308 Winchester have about the same muzzle velocities, for example.  My guess is that the casing on such a small cartridge is relatively thin and consequently prone to failure at the pressures the cartridge generates.

 

This shouldn't harm the gun and how dangerous it is depends on the gun's design.  Absent another outlet, gasses can blow back along the bolt rails and unless deflected by a flange at the rear of the bolt, hit the shooter in the face in the worst case.  This will affect accuracy to the extent accuracy depends on consistency, because if there is less pressure pushing the bulllet when a casing fails, its velocity will be lower and its trajectory less flat.

 

I would keep statistics on the number of failures with this batch of ammo, then experiment with another brand and compare the failure rate with it.

 

Bigger picture, this illustrates a lesson I learned long ago, which is to abjure arcane calibers in favor of more common ones.  The arcane calibers can be intellectually interesting and a gas to shoot.  On the other hand, they may not be ready for prime time, and ammunition is expensive, hard to find, and liable to being discontinued.  So, for example, does one really need a .30-338 instead of a .308 Win, .30-'06 Spfld, .300 Win Mag,  or .338 Win Mag?  Probably not.  The chief exceptions to this rule are if one reloads the caliber or if it has a genuine reason to exist.  A classic example of the latter is the .280 Remington, the new name for a 7mm-'06 wildcat.  7mm is the most common bullet size and has particularly efficient ballistic characteristics, and the .30-'06 casing is common and well-tested.  In this case, one could probably get a bolt action .223 Remington and get near-identical performance to the .17 HMR, with far cheaper and more plentiful ammo.  It may not be as cool, though.

 

Hope that helps.

 

-Eric

--
You received this message because you are subscribed to the Google Groups "Bull Moose Hunting Society of Northern California" group.
To unsubscribe from this group and stop receiving emails from it, send an email to bullmoose+...@googlegroups.com.
To post to this group, send email to bull...@googlegroups.com.
Visit this group at http://groups.google.com/group/bullmoose.
For more options, visit https://groups.google.com/groups/opt_out.