Case Separation

[techdiver]

Last Wednesday I had a case separate about half way up the case. It left the top half of the case in the barrel. I was able to remove the case using a chamber brush. I had been noticing a faint circle around some of my cases but the circle was smooth inside and out. The batch had been fired 16 times so I threw out the entire batch. I am loading tonight and found three cases with the ring and I could feel the outside ring with my fingernail and the ring inside the case with a paperclip. This batch had been fired four times. Any idea what might be causing this.

Remington 700 SPS Tactical chambered in .223
Lapua brass and 69 grain SMKs
CCI 400
24 grains of Varget
Chrony has shown velocities around 2750 fps.
About 1,200 rounds fired through the barrel.

 

[Ljutic SS]

Are you neck sizing or full length resizing with each reload?

 

[techdiver]

FL with Redding S Bushing die.

 

[HodgdonExtreme]

Sure sounds like you're sizing your cases too much.

How many thousandths of an inch are you bumping your shoulders back?

 

[hk dave]

16 times? Wow

 

[Twitch2120]

Sounds like a roomy chamber and you are making tiny brass

 

[roggom]

Yes, a bump gauge should be your next buy. The Hornady kit allows you to check pretty much any case you load for.

Hornady Manufacturing Company :: Reloading :: Metallic Reloading :: Tools & Gauges :: Lock-N-Load Gauges-Formerly Stoney Point :: Headspace Gauges :: Headspace Gauge Kits :: Lock-N-Load® Headspace Kit With Body 1 Each

 

[LRJammer]

16 times? Wow

Agreed. About twice as many loads as I ever attempt to get out of brass. Wonder how many times they have had to be trimmed.

 

[techdiver]

Case Separation

Agreed. About twice as many loads as I ever attempt to get out of brass. Wonder how many times they have had to be trimmed.

16 times was a bit too much. I am bumping back about .002". My primers indicate 'possible' over-pressure but I don't know where it is coming from since the measured velocity of 1,750 is not high.

 

[techdiver]

Photo of ring and primer.

 

[dabibbee]

I have the same firearm and have experienced the same issue with case separation. All of the answers are correct, the main problem is that your neck die is bumping back the shoulder too far.
This condition shortens the brass too much then it is expanded again when firing. I have also had the case separate in a FL sizing die, same reason. I solved the issue with a Lyman headspace gauge.
Adjust your die in the press until it is between the go/ no go region. As a side note, my Remington brass only lasted 10 reloads.

 

[techdiver]

I didn't think pushing the shoulder back .002" was a problem. On the current batch I am trimming to 1.760" brass OAL which on my Wilson go/no go gauge shows between low and high markers. I haven't tested any of my changes so I will have to wait until Wednesday when I go to the range. On Monday I will have a new Forster bushing die so I will do a batch with this die. I have also changed my seating die to seat the bullet .025" deeper. Seating the bullet too far into the lands could cause too much pressure? My current COAL is 2.30". The bolt closes without excessive pressure required. I realize making multiple changes is a sure way not to know what the problem was but I can't spend weeks making these changes while another case separation changes my face.

 

[techdiver]

I didn't think pushing the shoulder back .002" was a problem. On the current batch I am trimming to 1.760" brass OAL which on my Wilson go/no go gauge shows between low and high markers. I haven't tested any of my changes so I will have to wait until Wednesday when I go to the range. On Monday I will have a new Forster bushing die so I will do a batch with this die. I have also changed my seating die to seat the bullet .025" deeper. Seating the bullet too far into the lands could cause too much pressure? My current COAL is 2.30". The bolt closes without excessive pressure required. I realize making multiple changes is a sure way not to know what the problem was but I can't spend weeks making these changes while another case separation changes my face.

I forgot to mention that the rings are now showing on Lapua brass fired 4 times.

 

[bas402]

To many cycles, brass does not last forever regardless of mild loads or not and double check that bump back I bet you will find you are bumping back more on some and it doesn't take much on repeated cycles. I only go as minimum as possible which usually .0015" max. I check this on every cycles maybe your dies have changed? and i anneal every cycle. My suggestion is start with a new lot of virgin brass and track measurements on each cycle

 

[bas402]

I can see you are a reloading master so I will bow out as I know you will have the Op's problem resolved in your next post, sorry for the intrusion.

You might have missed that the op had phenomenal success with up to 18xs.. But now is having issues on only the 4th firing!

Also he is bumping only .002o and your thinking he'll get better results by somehow managing to only bump .0015? Hell it is not only hard to actually measure brass at the .000(4th place) but it will differ in spring rate even after annealing.

So I think - he is looking for help on why a proven process that was accurate mild and provided longevity now is neither..




Jt

Sent from my iPad using Tapatalk HD

 

[LawnMM]

So I think - he is looking for help on why a proven process that was accurate mild and provided longevity now is neither..




Jt

Sent from my iPad using Tapatalk HD

Have we established that it really is only a 0.002 bump, measured with a gauge? If that's the case then something else is different, different brass, different lot of powder, etc. I'm betting that he's bumping more than he thinks.

Brass wearing out, especially Lapua, in four firings is going to be caused by over working the brass. It wouldn't surprise me if he had the head separation and is now mistaking the die marks as another separation coming.

I saw he was using the paper clip, if he feels a ridge inside the case after four firings either his dies aren't set right or he's running very high pressure.

How are the charge weights measured?

 

[M40_A1]

It wouldn't surprise me if he had the head separation and is now mistaking the die marks as another separation coming.

My thought, exactly.

 

[techdiver]

Case Separation

Have we established that it really is only a 0.002 bump, measured with a gauge? If that's the case then something else is different, different brass, different lot of powder, etc. I'm betting that he's bumping more than he thinks.

Brass wearing out, especially Lapua, in four firings is going to be caused by over working the brass. It wouldn't surprise me if he had the head separation and is now mistaking the die marks as another separation coming.

I saw he was using the paper clip, if he feels a ridge inside the case after four firings either his dies aren't set right or he's running very high pressure.

How are the charge weights measured?

Bump is measured with a Sinclair Comparator. I only use Lapua brass although that doesn't guarantee the brass is identical--same batch. I am only using Varget through this whole process. Actually the same can. The separation occurred half way between the head and the shoulder. Die marks don't usually turn into rings that can be felt. I now have three such cases out of a batch of 50. They didn't separate but they are on the way. The sizing die is a Redding bushing die and I have reset it to make sure that is not the problem. I am using 24 grains of Varget behind a 69 SMK. Chrony shows velocity averaging 2,750 fps. Doesn't sound high pressure to me. Charge weights are measured with an RCBS 10-10 and re-checked with an RCBS 5-0-5.

 

[techdiver]

Not to derail the thread-- but really? I pointed out "you might have missed", and I was pointing out that to be helpful. Seems no reason for frustration or an apology -

Anyway, back to the op's issue------I am staying tuned as I know somebody is going to find the answer..


Jt

Sent from my iPad using Tapatalk HD

Just in case I have used my Redding S bushing dive for 25 cases I am processing and a new Forster bushing die for the second 25. Should eliminate the effects of a particular die.

 

[techdiver]

I owe everyone an apology for wasting your time. I did measure the shoulder bump for a batch I loaded today and one I loaded a few days ago. No problem. I just remembered I had a batch from two weeks ago and so I measured the bump. The numbers were all over the place and would certainly cause the rings and case separation. I had changed sizing dies and made a mistake in setting up the die. Sorry for the trouble.