Case head seperation?

[Bbowl1]

6.5 grendel
Alexander arms 24" upper

28.0 XBR
123gr amax
AA brass 4x fired
Primers flat, but no more so than factory hornady match
Shiny extractor marks

Chronod consistently at 2600fps. SD is usually around 10fps

I hadn't noticed the extractor marks before.

Signs point to over pressure, I know. Data, my fps and others results don't though


All I can think of is I know I haven't been bumping neck back far enough when FL sizing. Hornady die set. I say that because 1/50 or so every cycle through this brass I get one that doesn't chamber all the way.

I guess my question is. Should I bump back farther? Cut my load back?

I use hornady comparator and I am bumping .004. I also check with a Wilson chamber gage. Some still sneak through.

 

[rrflyer]

Don't know anything about that cartridge but

case head seperation usually occurs when you bump the shoulder back to much/to many times.

I usually bump mine back .002 for my bolt guns.


4x firings may not be out of line with as much as your moving the shoulder.

 

[sawgunner2001]

Case head seperation?

I've been fortunate enough to have not yet had a case head separation, so my experience here is limited. However, don't case head separations usually occur closer to the shoulder than the ring displaying on your casings? Halfway between the shiny brass ring and the sharpie mark is where I've seen others have CHS's. I'm not 100% sold that the mark displayed on your brass is an imminent CHS. Maybe that's the bottom of your sizing die?

Again, my actual experience in this subject matter is limited, so take what I wrote above with a grain of salt.

 

[Bbowl1]

That is a good point. I got a batch of hornady brass and was using it with my old 308 bolt gun. I had real seperation with that (gas escaping through the ring). It was closer to the neck than this ring. Not half way to the sharpie mark. Maybe 25%. Of course in relation to the 308 case.

I only do .001 with bolt gun. Never an issue with my new .308

.004 is standard for a semi and... It apparently isn't quite enough with this chamber as I have had a few fail to chamber all the way. Then I get a click instead of boom and a really hard extract.

Was I smart enough to save those rounds to measure? No. If they are fire chambered no problem. So many more may actually have an issue. It's the manually chambered (drop bolt on) ones that doesn't get it chambered.

I do check the first few cases every time now to make sure they chamber properly after siIng. Then again after I load a few. I only do a very very light crimp but just making sure.

 

[Bbowl1]

With my old .308 bolt I was full length small base sizing. That is what I blamed the separations on. Reason was difficult unlocks after fired no matter what I did with the lee 308 FL die I was using. My gunsmith recommended I try the SB as he saw no issue with the rifle.

 

[milo 2.0]

I don't believe that is chs, which starts from the inside of the case-out. I'd say it's an oversized chamber, and when sizing, the bottom of the die is leaving the mark. I've tried to read all the posts, not sure if you're using a small base die or not?
Measure fired cases before sizing, then check a manual or reamer specs to see if the base diameter is greater than it should be.
Your mark or line is clearly felt with your finger, chs, you can't feel, but you may see. You have issues.

Easy fix would be your die being out of spec, reducing the diameter too much, but don't bank on this.

Check this thread out where I tell JGorski to polish his die, and reference his pic of the die, his die could easily do the same thing a s what your experiencing.

http://www.snipershide.com/shooting/snipers-hide-reloading/228149-polishing-dies.html

 

[Pinecone]

How about overgassed?

Bolt opening before the pressures have dropped enough for the case to release from the chamber wall.

 

[sawgunner2001]

I would suggest a paperclip test to tell for sure. Or split a case open with a Dremel and have a look-see.

 

[former naval person]

AAs Sawgunner says...split a case open and find out for sure.

 

[mdmp5]

Never seen a belted grendel case before. But seriously, those cases don't look safe to use. Maybe 2-3 firings max left before they most likely will bust on you. You have it backwards; you are reasoning that you are not bumping the shoulder enough, which is the cause. In actuality, you most likely are bumping too much, which causes the brass to stretch backwards more during a cycle, weakening the walls of the case. Bump as little as you can get away with. Try using a case gauge after sizing.

 

[Bbowl1]

Never seen a belted grendel case before. But seriously, those cases don't look safe to use. Maybe 2-3 firings max left before they most likely will bust on you. You have it backwards; you are reasoning that you are not bumping the shoulder enough, which is the cause. In actuality, you most likely are bumping too much, which causes the brass to stretch backwards more during a cycle, weakening the walls of the case. Bump as little as you can get away with. Try using a case gauge after sizing.

Like I said though, I am doing .004 and still getting some that fail to chamber/undersized.

 

[Bbowl1]

I would suggest a paperclip test to tell for sure. Or split a case open with a Dremel and have a look-see.

I did scrape the inside with an angled pic. I know what to feel for from my previous .308 issues. Nothing on the inside can be felt.

 

[milo 2.0]

Like I posted last night, it's not CHS. You need to get a new piece of brass, load and fire it, then measure around the base of the case. If it's greater than .437, your chamber if fubar'd. If it's under that, get ahold some tool to measure your die opening, to determine how much it's crunching the case.
Either way, IMHO your brass is getting unsafe to load.

 

[longshooter]

I would check the chamber to ensure that there is no corresponding flaw engraved in the same area.

Also, check to make sure you are not seating into the rifling.

 

[Bbowl1]

Like I posted last night, it's not CHS. You need to get a new piece of brass, load and fire it, then measure around the base of the case. If it's greater than .437, your chamber if fubar'd. If it's under that, get ahold some tool to measure your die opening, to determine how much it's crunching the case.
Either way, IMHO your brass is getting unsafe to load.

Depending on how hard I tighten the caliper and exactly where I measure from it ranges from .435-.437. The die opening is .439-.440

Also, the upper only has about 500-600 through it

 

[milo 2.0]

OK, by your measurements, the die wont size the brass at all????

 

[joey fox]

Use the pic and check your chamber and reloading die for a ring