Split HMR Casing Neck

[Carson]

I took the HMR out for some target shooting yesterday an put some 70 odd rounds through it. On 3 occasions I experienced a slight hang-fire where the round went off around 1/2 second later than the firing pin striking. Having never experienced this before with my rifle I inspected the ammunition to see if I could spot anything obvious that might be a cause. The 3 rounds that hang-fired and 3 others all had a split down one side of the neck of the casing.

 

By the way, the ammunition in question is Remmington 17Grain Accutip.

 

Here is a pic of the split im talking about

 

Can anyone explain whats going on?

Edited March 9, 2014 by Carson

[pegasus bridge]

I've had loads of split cases, IIRC it's something to do with the annealing (?) process to reduce the neck size of the wmr case.

 

I haven't found though that it made any apparent differences to the performance of the round, I would be returning the batch if it resulted in 3 hang fires in 70 rounds though!

[Fisheruk]

IMO the split is not uncommon. The brass is hard because rimfire cannot be annealed after it it formed. The case expands into the chamber when it is fired, which is normal. This can cause the neck to split as per your pictures. The hang fire is unlikely to be related. Check the firing pin and spring to see if it is striking hard enough. Maybe damp ammo.

I wouldn't worry about the split cases, I've seen hundreds without any problems of accuracy or safety. The hang fire is different and you need to be more careful about that.

[kent]

if the splits were not there before firing then this is not the issue. I should strip the bolt and clean it internally and check the tip for damage. Next move is an inconsistent rim thickness on those rounds. Only after that I should look towards a badly primed batch of ammo, rimfire priming compound is spun wet into the case rim (things can go wrong though its frankly rare).

Odds on its dirt in your bolt IMO

[wymberley]

How old is the ammo?

[dukeboy]

I've never had any split necks that i noticed but did have a few hang fires with remington. never had any problems with hornady and it's the most accurate in my rifle too so just stick with it now

[dadioles]

The ammunition in the photo looks a bit dull and even a bit grubby. It makes me wonder if perhaps it is fairly old and possibly stored in less than ideal conditions (cold and damp?).

 

The split should not, in itself, cause any problems but it might allow the powder to get slightly damp and burn less effectively.

 

I use Hornady and although some of my ammunition does show evidence of splits I have never had any firing problems.

[kent]

The ammunition in the photo looks a bit dull and even a bit grubby. It makes me wonder if perhaps it is fairly old and possibly stored in less than ideal conditions (cold and damp?).

 

The split should not, in itself, cause any problems but it might allow the powder to get slightly damp and burn less effectively.

 

I use Hornady and although some of my ammunition does show evidence of splits I have never had any firing problems.

 

Cracked necks before firing don't exactly help even neck tensions. accuracy is certainly effected, I should never fire one if I knew it was cracked ( in fact I got two cracked necks with some worn out brass I was loading this week - both dismantled and binned)