Long crack in .308 necks, why?

[fenwick253]

I went shooting the other day and didn't shoot all of my reloaded ammo. I came home to notice 14 case necks were cracked on unfired ammo. In the photos, the brass is on its third cycle and I thoroughly checked and inspected all brass prior to reloading. The cracks are huge, there is no way I would have missed it 14 times. I have a safe load so I have no clue as to how it cracked. I weigh all of my powder so there are no accidental hot loads. I know when I was shooting it was snowing (~30degF) and ammo was at my car’s interior temp (~70degF). Could it be moisture or temperature fluctuation? Defective brass? I have no clue otherwise. Anyone see this before?

Recipe
.308Win Hornady Case
Fed Match Primer 210M
.30cal .308dia SMK 168gn
42gn Reloder-15

 

[ChrisGarrett]

Re: Long crack in .308 necks, why?

I'm guessing a so-so annealing job out of the factory and they cracked when you seated the bullet. Basically they're work hardened and can't stretch around the bullet.

It happens.

What sizing die are you using, what diameter do the case necks come out of the chamber at, what diameter does your sizing die size the necks down to...specifically?

You might be exacerbating the issue.


Chris

 

[flashhole]

Re: Long crack in .308 necks, why?

I agree with Chris' assertion. I would anneal the cases before trying to do any more loading.

 

[fenwick253]

Re: Long crack in .308 necks, why?

I'm using RCBS full-length resizing dies.

Shot:
0.340 OD/ 0.319 ID

Resized:
0.330 OD/ 0.309 ID

I don't think the 0.308 bullet dia is doing much in the neck stretching department.

 

[ChrisGarrett]

Re: Long crack in .308 necks, why?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: fenwick253</div><div class="ubbcode-body">I'm using RCBS full-length resizing dies.

Shot:
0.340 OD/ 0.319 ID

Resized:
0.330 OD/ 0.309 ID

I don't think the 0.308 bullet dia is doing much in the neck stretching department. </div></div>

You're sizing down to an O.D. of .330". Nominal bullet diameters are .308". Many of us live with .001"-.003" of neck tension, so that would be an O.D. of .335"ish.

Even with the freak batches of thin walled Winchester cases that I've come across, where I really 'needed' a .331" bushing and not the .332" bushing I used, I've never needed to size down past .334" as a rule, with multiple brands of brass that I shoot.

Your RCBS is imparting too much movement (tension) on your brass, IMO and going from .340" to .330", without a step down (bushing,) is indeed, as I surmised, work hardening your brass unnecessarily.

Either live with the necks splitting, or saddle up cowboy and git yerself some bushing dies of one make, or another. You can try annealing to soften the necks up, as this might be a cheaper way to go, but moving back down to .330" is a lot of sizing for 'most' brands of .308" brass.

Chris

 

[Jackalope33B]

Re: Long crack in .308 necks, why?

Im new to the game as well. Here is a thread I started about Redding S Dies and .308
http://snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=3256638

 

[FLIGHT762]

Re: Long crack in .308 necks, why?

I've used RCBS F/L 308 dies for years with many reloads and haven't had multiple stress case neck cracks you show in your photos. I think you may have a bad batch of brass that didn't get annealed properly. Having 14 case necks stress crack, there's something going on with that particular brass, it doesn't look as though you neck turned the brass, did you?

I would suggest you try another brand of brass.

Even though you F/L die is sizing .010" or so in one pass, you shouldn't be getting these stress cracks after 3 firings in so many cases.

 

[X-fan]

Re: Long crack in .308 necks, why?

RCBS tends to size the bejezuz out of brass..You will need to anneal that run of brass no matter what die you use.
Not hard to do, just do your homework.

I agree with CG.
Bushing dies at about 0.335 or (my preference) a plain (cheaper too) Forster sizer custom ground to 0.335.

 

[fenwick253]

Re: Long crack in .308 necks, why?

Thanks for the input guys. Flight, I haven't needed to trim those cases yet, but I do agree with trimming the entire cycle for consistency. Perhaps I need to look into some new bushing dies. I do agree with Chris that the large amount of neck sizing could lead to work hardening. I'm just surprised that after 2 cycles, the cases would crack on the third since it is not exactly "cheap" brass.

 

[boltgunluvr]

Re: Long crack in .308 necks, why?

WOW. I use inexpensive Win brass, neck size with Lee collet die (bolt gun) and have never had this happen. Damn....thats gotta be disappointing. I will say I've seen Rem brass do this.