Brass separation question

[rdb8847]

Experiencing case separation that I dont fully understand. 223 bolt gun. Running 24 grains of Varget with a 77 grain Sierra HPBT with cannelure seating at 2.260. Using CCI #41 primers and CCI 400. Both show signs of fracturing and some have actually separated completely. First reload on FC brass. Can a bad sizing die contribute to this condition? Had it happen it 2 different 223 bolt guns. Brass new factory Federal TAC (red box) and fired in my AR. No signs of ejector marks or bolt lift problems. Primers do show a slight bit of cratering but no blown primers

Thinking either my AR chamber or sizing die is weaking this area where the separation is occurring.

Any help is greatly appreciated

 

[gdbleb]

Where is the case separation happening? Above the web?
How much shoulder setback are you performing on the resize? It may be too much.

Are you equipped to measure cases base-to-shoulder?
Measure base to shoulder for 1) factory-loaded case 2) fired case fired in your AR 3) resized case 4) factory round fired in your bolt gun.

We need to compare these measurements in terms of thousandths of an inch difference.
You don't care about the absolute measurement.

 

[358WCF]

In my experience the ONLY thing that causes case separation is excessive headspace caused by either an improperly adjusted sizing die &/or a long chamber with short virgin brass.

Unsure where on the web I got this pic from, but it's a good visual. Sometimes the separation happens on the initial firing.

 

[Straightshooter1]

1st thing I'd check is for proper head space and then along with that whether the amount of shoulder set back isn't too much.

 

[markm87]

When I first started loading bolt gun ammo, I wrecked several pieces of LaPua .308 brass by using a case gauge to set my sizing die instead of the chamber. I just set the die to match SAAMI/Factory ammo, and watched the brass fail.

 

[Coyotefurharvester]

Hodgdon shows 23.7 compressed load. I load AR ammo below bolt gun levels. So a hot load through a AR chamber 223,Wyde or 556? Then sized and shot in a bolt gun, firing results in case separating. Have you fired same load(new brass) in bolt gun first and reloaded and shot again without separation in same rifle? Probably more than one factor contributing to the brass malfunction, keep in mind any case/primer failure can be dangerous to firearm or shooters/near by. Die adjustment,load, firearm.

 

[rdb8847]

pic added to original post

 

[rdb8847]

Hodgdon shows 23.7 compressed load. I load AR ammo below bolt gun levels. So a hot load through a AR chamber 223,Wyde or 556? Then sized and shot in a bolt gun, firing results in case separating. Have you fired same load(new brass) in bolt gun first and reloaded and shot again without separation in same rifle? Probably more than one factor contributing to the brass malfunction, keep in mind any case/primer failure can be dangerous to firearm or shooters/near by. Die adjustment,load, firearm.

I have not tried any virgin brass since I have plenty of once fired .556 brass from my AR shooting activities

 

[Bronsin]

It was fired in the AR first?

 

[rdb8847]

Where is the case separation happening? Above the web?
How much shoulder setback are you performing on the resize? It may be too much.

Are you equipped to measure cases base-to-shoulder?
Measure base to shoulder for 1) factory-loaded case 2) fired case fired in your AR 3) resized case 4) factory round fired in your bolt gun.

We need to compare these measurements in terms of thousandths of an inch difference.
You don't care about the absolute measurement.

What tools do I need to measure base to shoulder? I have a case gauge, mics, calipers.....

 

[rdb8847]

It was fired in the AR first?

correct

 

[Bronsin]

Yeah, I wouldn't do that. The headspace will be different, and the real problem is that unless you are using a stiffer buffer spring and a carrier weight system, the AR will really stretch brass out when fired. That creates a thin spot in the brass. Then, if you push the shoulder back too far, it will get really stretched again, and in your case it will separate.

Hornady makes an inexpensive headspace gage for your calipers. Use from new brass, load a mild charge and fireform your brass. Then measure the headspace to set up your FL die to push the shoulder back about .002. It should be good to go then.

 

[Coyotefurharvester]

Give us your method of setting up the sizing die for AR, then die adjustment for AR fired brass to be used in the bolt rifles. Does the fired brass(AR) chamber easily in the bolt guns WITHOUT sizing?

 

[358WCF]

What tools do I need to measure base to shoulder? I have a case gauge, mics, calipers.....

 

[GLShooter]

When I first started loading bolt gun ammo, I wrecked several pieces of LaPua .308 brass by using a case gauge to set my sizing die instead of the chamber. I just set the die to match SAAMI/Factory ammo, and watched the brass fail.

And that's exactly why I feel case gauges are the spawn of the devil.

Greg

 

[rdb8847]

Give us your method of setting up the sizing die for AR, then die adjustment for AR fired brass to be used in the bolt rifles. Does the fired brass(AR) chamber easily in the bolt guns WITHOUT sizing?

I have never tried to chamber an empty from my AR without re-sizing. I use a standard Redding sizing die and just do a full length sizing operation (with a very slight cam over). I dropped my first few sized cases in my case gauge and they dropped in so went to trimming, deburr, clean primer pockets, tumble to remove and lube. Prime and throw powder (weigh each charge on beam and verify on electronic scale), seat bullet. No crimping die used.

My AR is a Wylde chamber and perhaps I am causing a pre-fracture by oversizing an already stretched case as mentioned. I will get some virgin brass and give it a try.

Thanks for the great replies.

 

[fkimble@charter.net]

You can use your case guage and your mic or calipers. You will need to measure protrusion or recession of a couple factory cases. then measure same cases after firing in each gun. You won't get typical headspace numbers but you will get the change (growth) of the case from new to firing. Then resize them and measure again, this is the amount you are resizing them. This number should be no more than .003. Also it will tell you the relative size difference in your two chambers.

Frank

 

[L.Sherm]

Fed brass is real soft so if it stretch alot first go round id be thinking about new brass for your bolt gun.

 

[rdb8847]

Thank you all

 

[Coyotefurharvester]

Review carefully the instructions for setting up fl Redding sizing die, often I can size brass to fit ammo checking Gage and firearm Without cam over, or even touching shell holder with die.