Interesting 6mm Creedmoor reloading session

[Poper]

I built my 6mm Creedmoor on my old Remington 788. Now the barrel is a 25" Lilja with a recessed target crown, the trigger is Timney, scope is Swarovski 5-25x50, and stock is a fancy grade walnut unit from Boyds with pillar and glass bedding. After 400+/- rounds the barrel seemed to be well settled in/broke in and it began shooting groups more consistently. I have one load with 105 grain Bergers that consistently prints 5 round groups in the 0.304" - 0.373" range. That is when I concentrate on my shooting fundamentals.
Anyway, back to the Interesting reloading session: I was sizing brass fresh out of the tumbler and as I picked up the third case I noticed an insipient case head separation crack. I started looking closer and all but two of this batch of thirty either displayed the crack, beginnings of a crack or the shiny signs of an impending crack/separation. All but two of the signaling cases showed these signs AFTER sizing and the two that that didn't had their crack before sizing. These are Lapua small primer pocket cases that have been fired six times with only one firing at manual specified maximum charge, None of the loads fired ever showed an indication of excessive pressure; ie: loose primer, sticky bolt turn, etc.
This particular session I was intending to load both these thirty Lapua cases and an additional thirty Federal cases. The federal cases are large primer cases and have four firings. They, too are exhibiting similar signs and I also had two cases with cracks that can be felt with a fingernail before sizing.
My routine is that anytime I touch a case in the course of the reloading procedure, I give it a quick inspection looking for leaking primer, dents, cracks, split necks or anything that appears out of the ordinary. Though I expect cases to wear out, I thought four to six firings to a case was a little light. I know I have 6.5x55 cases that have nine or ten firings and .270 Win. cases that have more than that. I guess I would like to know if you other guys that are loading 6MM Creedmoor are finding similar case life? And what brand of 6MM Creedmoor cases do you prefer?

Oh, just for grins and giggles I ran a fired .308 Win. case (RP) through the sizing die in a single pass and it came through just fine. Had to trim .052" off the neck to meet the 6MM Creedmoor trim-to-length of 1.910" is all. As I no longer have a .308 and I have LOTS of .308 brass.....

 

[horsey300]

I built my 6mm Creedmoor on my old Remington 788. Now the barrel is a 25" Lilja with a recessed target crown, the trigger is Timney, scope is Swarovski 5-25x50, and stock is a fancy grade walnut unit from Boyds with pillar and glass bedding. After 400+/- rounds the barrel seemed to be well settled in/broke in and it began shooting groups more consistently. I have one load with 105 grain Bergers that consistently prints 5 round groups in the 0.304" - 0.373" range. That is when I concentrate on my shooting fundamentals.
Anyway, back to the Interesting reloading session: I was sizing brass fresh out of the tumbler and as I picked up the third case I noticed an insipient case head separation crack. I started looking closer and all but two of this batch of thirty either displayed the crack, beginnings of a crack or the shiny signs of an impending crack/separation. All but two of the signaling cases showed these signs AFTER sizing and the two that that didn't had their crack before sizing. These are Lapua small primer pocket cases that have been fired six times with only one firing at manual specified maximum charge, None of the loads fired ever showed an indication of excessive pressure; ie: loose primer, sticky bolt turn, etc.
This particular session I was intending to load both these thirty Lapua cases and an additional thirty Federal cases. The federal cases are large primer cases and have four firings. They, too are exhibiting similar signs and I also had two cases with cracks that can be felt with a fingernail before sizing.
My routine is that anytime I touch a case in the course of the reloading procedure, I give it a quick inspection looking for leaking primer, dents, cracks, split necks or anything that appears out of the ordinary. Though I expect cases to wear out, I thought four to six firings to a case was a little light. I know I have 6.5x55 cases that have nine or ten firings and .270 Win. cases that have more than that. I guess I would like to know if you other guys that are loading 6MM Creedmoor are finding similar case life? And what brand of 6MM Creedmoor cases do you prefer?

Oh, just for sh*ts and giggles I ran a fired .308 Win. case (RP) through the sizing die in a single pass and it came through just fine. Had to trim .052" off the neck to meet the 6MM Creedmoor trim-to-length of 1.910" is all. As I no longer have a .308 and I have LOTS of .308 brass.....

Just out of curiosity, what are the odds of an overly generous chamber?

 

[horsemen61]

Just out of curiosity, what are the odds of an overly generous chamber?

That’s my guess right now but being a custom barrel it shouldn’t be that way I wonder what the load is? @Poper can you share it please

 

[hunt127588]

Measure your case shoulders both after firing and after sizing and see how much you are pushing the shoulders back. You shouldn't be pushing the shoulder back any more than .002. Ideally, I try to push my shoulders back about .0015. You may be over sizing the case causing premature stretching upon each firing.

 

[Howa 9700]

Measure your case shoulders both after firing and after sizing and see how much you are pushing the shoulders back. You shouldn't be pushing the shoulder back any more than .002. Ideally, I try to push my shoulders back about .0015. You may be over sizing the case causing premature stretching upon each firing.

X2

Who cut the chamber in the new barrel? What was your die setup? Followed the normal setup instructions, or set dies to your chamber?

I am loading for a 6mm Rem and 6mm CM. The 6mm Rem was a factory rifle and factory ammo fired in it blows out the shoulder a full 0.006 thousands. "Blows the shoulder out" may not be entirely right, as the movement of the brass is not at the shoulder, it stretches at the base, just above the webbing. Then when it gets resized, it does not push the brass back where it came from, it forces the shoulder in........and since the it has to go somewhere, it oozes out at the case mouth. Cases that have to be trimmed all the time are being worked pretty hard. When I was sizing these cases as per instructions on the die, I was having to trim them. But once I figured out what was going on, I figured out how to strip the bolt so I could set the dies to move shoulders back far enough the bolt would drop easy. That translates to the 0.002 to 0.0015 setback. They still chamber like a fully sized or factory round would, but the excessive movement of the cases went away. What they won't do is chamber in just about any other 6mm Rem. They are sized for this rifle only.

The 6 CM is a custom job. Smith what cut that chamber only went 0.002 over SAMMI min, so cases fired in that chamber are barely, just barely expanded enough if you set the dies as per instructions.......it is barely able to resize the cases enough for the stripped bolt to close. I asked the smith and he said they do it that way on purpose. And reason is to extend case life. He said to expect at least 10 loadings.....or more.

 

[Poper]

That’s my guess right now but being a custom barrel it shouldn’t be that way I wonder what the load is? @Poper can you share it please

These are test loads starting at the Manual starting load and progressing to Manual maximum in .5 gr. increments. No signs of excessive pressure.
Chamber is not oversized. Barrel came unchambered and was cut, chamber reamed, crowned and all of the associated gunsmithing done by a very reputable and well known gunsmith in the Phoenix Metro area.

I am curious if other people loading for their 6mm Creedmoor are experiencing similar case life. If not, are they using the same case manufacturers?
My next round of loads will be using new, unfired Nosler brass.

 

[Poper]

X2

Who cut the chamber in the new barrel? What was your die setup? Followed the normal setup instructions, or set dies to your chamber?

I am loading for a 6mm Rem and 6mm CM. The 6mm Rem was a factory rifle and factory ammo fired in it blows out the shoulder a full 0.006 thousands. "Blows the shoulder out" may not be entirely right, as the movement of the brass is not at the shoulder, it stretches at the base, just above the webbing. Then when it gets resized, it does not push the brass back where it came from, it forces the shoulder in........and since the it has to go somewhere, it oozes out at the case mouth. Cases that have to be trimmed all the time are being worked pretty hard. When I was sizing these cases as per instructions on the die, I was having to trim them. But once I figured out what was going on, I figured out how to strip the bolt so I could set the dies to move shoulders back far enough the bolt would drop easy. That translates to the 0.002 to 0.0015 setback. They still chamber like a fully sized or factory round would, but the excessive movement of the cases went away. What they won't do is chamber in just about any other 6mm Rem. They are sized for this rifle only.

The 6 CM is a custom job. Smith what cut that chamber only went 0.002 over SAMMI min, so cases fired in that chamber are barely, just barely expanded enough if you set the dies as per instructions.......it is barely able to resize the cases enough for the stripped bolt to close. I asked the smith and he said they do it that way on purpose. And reason is to extend case life. He said to expect at least 10 loadings.....or more.

I normally set my FL sizing die to set the shoulder back .003" using the RCBS Precision Mic tool. I do not reset the die every time and use Forester lock rings on my dies. Dies are Redding Competition Body/Neck bushing and micrometer seating dies. Neck tension is .003".

I do have a RCBS neck sizing die. I am thinking I will neck size the Nosler cases and FL size them every 3rd or 4th firing. Might be able to extend case life that way, too.

 

[Silverstater]

I built my 6mm Creedmoor on my old Remington 788. Now the barrel is a 25" Lilja with a recessed target crown, the trigger is Timney, scope is Swarovski 5-25x50, and stock is a fancy grade walnut unit from Boyds with pillar and glass bedding. After 400+/- rounds the barrel seemed to be well settled in/broke in and it began shooting groups more consistently. I have one load with 105 grain Bergers that consistently prints 5 round groups in the 0.304" - 0.373" range. That is when I concentrate on my shooting fundamentals.
Anyway, back to the Interesting reloading session: I was sizing brass fresh out of the tumbler and as I picked up the third case I noticed an insipient case head separation crack. I started looking closer and all but two of this batch of thirty either displayed the crack, beginnings of a crack or the shiny signs of an impending crack/separation. All but two of the signaling cases showed these signs AFTER sizing and the two that that didn't had their crack before sizing. These are Lapua small primer pocket cases that have been fired six times with only one firing at manual specified maximum charge, None of the loads fired ever showed an indication of excessive pressure; ie: loose primer, sticky bolt turn, etc.
This particular session I was intending to load both these thirty Lapua cases and an additional thirty Federal cases. The federal cases are large primer cases and have four firings. They, too are exhibiting similar signs and I also had two cases with cracks that can be felt with a fingernail before sizing.
My routine is that anytime I touch a case in the course of the reloading procedure, I give it a quick inspection looking for leaking primer, dents, cracks, split necks or anything that appears out of the ordinary. Though I expect cases to wear out, I thought four to six firings to a case was a little light. I know I have 6.5x55 cases that have nine or ten firings and .270 Win. cases that have more than that. I guess I would like to know if you other guys that are loading 6MM Creedmoor are finding similar case life? And what brand of 6MM Creedmoor cases do you prefer?

Oh, just for sh*ts and giggles I ran a fired .308 Win. case (RP) through the sizing die in a single pass and it came through just fine. Had to trim .052" off the neck to meet the 6MM Creedmoor trim-to-length of 1.910" is all. As I no longer have a .308 and I have LOTS of .308 brass.....

Poper, I too shoot a couple 6 Creedmoor's with Lapua SR brass. I have 6 firings on one of them with no signs similar to what you are finding. I bump my shoulders back .002" each loading. Also anneal each loading. My loads are reasonably moderate. 108 Berger BT's at 3050'/ sec. with 26" Bartlein chambered by ALTUS. I have 1700 rounds on this barrel and still shooting well. I will be monitoring my brass closely after becoming aware of your problem but have not had any issues at this time. Fingers crossed. If I can share anything to help you feel free to PM me.

 

[Howa 9700]

Before going to neck sizing, I'd reset the sizing dies to apply just enough shoulder bump to get a stripped down bolt to close on a sized case. That might be half or less than you are sizing now.

 

[Varminterror]

Though I expect cases to wear out, I thought four to six firings to a case was a little light.

It is.

I put a lot of use on my 6 creeds, I have 20 firings on some of my brass, even some of that is Hornady, and some have been pressed to 3180fps with 105’s for most of their life.

The only way that happens if you have excessive room for case stretch during firing, then resizing back to an undersized state. The odds of a bad batch of brass is remarkably low. But 4-6 firings is abysmally poor case life, and far lower than you should be experiencing in 6 creed.