Case head separation.

[Bigeclipse]

I thought he got the separations once it was reloaded the first time. Am I mistaken?

There is a post early on where he said he was getting ejector marks on factory loaded ammo.

this is what he said: "At the time I don't have access to a go nogo. Yes it's .1 over max from hornadys data. I have since backed it off trying to find a safer pressure load. The stuff from the factory is up in pressure as well. Most of it leaves a pretty good ejector mark and a flat primer. Now my new load is 77.5 of retumbo."

 

[Mram10us]

There is a post early on where he said he was getting ejector marks on factory loaded ammo.

this is what he said: "At the time I don't have access to a go nogo. Yes it's .1 over max from hornadys data. I have since backed it off trying to find a safer pressure load. The stuff from the factory is up in pressure as well. Most of it leaves a pretty good ejector mark and a flat primer. Now my new load is 77.5 of retumbo."

Thank you. Totally missed that. Back to the nogo gauge. Is the OP even here anymore?

 

[sturner]

As did I

 

[JAYgs8163]

The parent case was the 375 H&H cartridge. It was designed to chamber 100% by head spacing off the belt because it was for dangerous game. On my 7mm RM, the shoulder would move as much as .016 if I remember my measurements correctly. It's just designed into it.
Old technology.
Never separated one though.

So resize the brass then and trim to length?

 

[Bob Wright]

So resize the brass then and trim to length?

So, measure 10 or more fire formed cases. If within .002 or less record the average. This is your baseline for setting your dies for full length sizing. If these all chamber well you may leave them without bumping the shoulder this time. Setting your dies to bump additional .001 is fine just to set and lock your ring for the entire lot.
Then trim to the over all length in your manual. That's my process.

 

[maximini14 223]

I would be concerned about excessive headspace if brass is cracking after only 2 shots. Are you neck sizing only?

 

[Vol1975]

So I just got my 300 prc built a few weeks ago and have been shooting factory hornady match 225s. I wasn't getting the accuracy I wanted so I got a die and started doing some work up. I found a load my gun really liked at 79 grains of retumbo I set oal to the same as the factory stuff. Shot a 3 shot at .20 on center. However when I loaded it a second time testing the speed I got a case head separation. The brass has only been good for 2 firings. Just wondering if anyone has had any issues like this. Maybe a bad batch of brass?

ADG is now taking back orders on 300 prc brass

 

[Grizzhunt]

ADG is now taking back orders on 300 prc brass

Yep I'm on the list just waiting for a response. I called them a week or two ago and the guy said it would be sometime next month.

 

[DJ Fergus]

I

So I just got my 300 prc built a few weeks ago and have been shooting factory hornady match 225s. I wasn't getting the accuracy I wanted so I got a die and started doing some work up. I found a load my gun really liked at 79 grains of retumbo I set oal to the same as the factory stuff. Shot a 3 shot at .20 on center. However when I loaded it a second time testing the speed I got a case head separation. The brass has only been good for 2 firings. Just wondering if anyone has had any issues like this. Maybe a bad batch of brass?

You probably have excessive head space and/or you are full length sizing the case way back down creating even more headspace and with a near max load with that situation, you have stretched at the head in just two firings to thin the brass enough for separation. If its an oversized chamber diameter near the case head, this will add even more stretch. If it was a factory built rifle with a big sloppy chamber, I would neck size only,(yeah I know the cool guys no longer neck size only). Being that it's a custom built rifle, you probably don't want to remedy something that you paid big bucks for but instead have a correctly sized chamber.

 

[cajun]

Get a Hornady headspace gauge set. Had the same issues. Die was setting the shoulder back 12 thou bottomed out.

 

[Lee Goodwin]

After asking some gurus it seems as though setting the shoulder back too far, hot loads and over worked, multiple reloaded brass ...was just too much to ask of the brass.

 

[DJ Fergus]

Get a Hornady headspace gauge set. Had the same issues. Die was setting the shoulder back 12 thou bottomed out.

Cajun is correct, measure virgin case, then measure fired case, then measure sized case and the answer will be clear as day.

 

[Grizzhunt]

It's all been worked out. I bought a comparator gauge and reset my die. I haven't fired the newer brass I have more than once yet. I honestly don't plan to either. ADG will have brass put next month so I'm waiting for that, also I used the last of my retumbo so I'm going to make a brand new load with the ADG brass and h1000.

 

[cajun]

It's not uncommon with new brass and a long chamber to see .010 growth on the first firing. It's not ideal but as long as you bump it .002 or so on subsequent firings you should be ok.