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Old May 28, 2018, 05:17 PM   #51
Unclenick
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How about the head diameters?

If the primers were rounded, this is starting to sound stranger than expected.

Can you take and post photos of the cracks and the case heads? Before and after, ideally. After cleaning and before resizing, then again after resizing.

Also, you said it's not happening with commercial loads. Something odd is certainly going on here.
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Old May 28, 2018, 05:51 PM   #52
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I can't figure out how to post photos here
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Old May 28, 2018, 05:53 PM   #53
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How much did you reduce the OAL??
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Old May 28, 2018, 05:55 PM   #54
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I use this for posting images:

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Old May 28, 2018, 06:11 PM   #55
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How much did you reduce the OAL??


From 3.365-3.341
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Old May 28, 2018, 06:21 PM   #56
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[/IMG]



Before sizing
top is 50 grains of Aa4064 1st firing norma brass
Second is 55 grains of imr 3540 1st firing norma brass
Third is RP brass 2nd firing 1st firing factory in my rifle second firing 50 frains of AA4064

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Old May 28, 2018, 06:50 PM   #57
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Old May 28, 2018, 06:53 PM   #58
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Old May 28, 2018, 08:07 PM   #59
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Assuming that you have measured your chamber and know the distance from the bolt face to the lands, with the bullet seated at 3.341", how far off the lands does that put it??

The reason I am asking is explained in Unclenick's post #49.

Also, you understand that almost all bullets have manufacturing tolerances that create different distances from bullet base to ogive, and seating with an OAL (to the point of the bullet) instead of CBTO (cartridge base to ogive), all your cartridges can have the same OAL but the CBTO can vary as much as 0.005" more or less.

I am stating this as I have learned from experience (normally known as the hard way) that the symptoms you are having CAN be created by seating with too little bullet jump to the lands.

I start load development generally with a 0.020" jump and sometimes 0.030".

The most accurate rifle that I have developed loads for has a 0.204" jump to the lands. that is not a typo. It is a hunting rifle and will put 10 holes into 3/8" consistently.

A 0.003" case head expansion is not a good thing. The case head is not normally supported by the chamber.
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Old May 28, 2018, 08:23 PM   #60
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I used a modified case and a bullet to determine where my lands are and backed off .003 I very well could have made a mistake. Is there a better way or a tool to help determine where the lands are.
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Old May 28, 2018, 08:34 PM   #61
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You'll find bullet ogive tolerances ~ +/- 0.005"
So get out to 10-thou or more to ensure you're not half in/half out.

That said, what tests lead you to reduce clearance to that dimension ?
more often than not, some larger jump actually improves accuracy/precision.




BTW: There isn't even a hint of excess pressure on that 0.469" case head -- not even a "smidgen."
Something else is at work here.
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Old May 29, 2018, 09:33 AM   #62
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I used a modified case and a bullet to determine where my lands are and backed off .003 I very well could have made a mistake. Is there a better way or a tool to help determine where the lands are.
Yes there is: I use transfers, I transfer the dimension of the chamber to the seating die. I am the fan of the running start, I want my bullet to have that jump. And I want to know how far the bullets has to run to hit the rifling; if my bullets have that jump I want to know how far.

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Old May 29, 2018, 09:40 AM   #63
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First I would determine the length of the chamber from the shoulder/datum to the bolt face. For reloaders and smiths determining the length of the chamber from the shoulder/datum to the bolt face should be simple procedure.

After all of these years I am convinced it is neither understood or simple.

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Old May 29, 2018, 11:14 AM   #64
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Jwilson904,

Where you are measuring the case head diameter is very close to what is normally called the pressure ring (where your splits are occurring). I can't tell from the end-wise photo of the measurement exactly where you are picking it up. 0.003" of expansion is within SAAMI standard chamber dimensions for 30-06 at that point where the split is occurring and a fraction behind it. (Chambers are always wider than cartridges so they will feed properly.) To measure head expansion, try picking it up just barely in front of the extractor groove relief angle or across the bottom flats in the extractor groove, but definitely well clear of where your cracks are appearing.

I still get back to commercial ammunition not causing the split. Even though your rounded primer suggests excess pressure is impossible, sometimes odd things happen, so, just-in-case, let's check a few other basics:

Make sure your sizing die has "30-06" stamped on the side of it and not something else.

Weigh your bullets to be sure heavier ones weren't put in the box by mistake. I've seen wrong bullets come in a box before.

Checked the diameter of the bullets to be sure they are actually .308 and not 8 mm (0.324").

Checked that the trim length of your cases does not exceed 2.494"?

Measure your handload's case neck OD just below the mouth. It should not exceed .334" with the bullet seated.

Let's get a stretch number just to confirm your gunsmith's finding. If you don't have a case comparator, use the method illustrated below for a .308 to compare an unfired new case to a fired one to see how much growth you've got at the shoulder. Note that the Lowe's spacer shown tends to be oversized, which is fine for .308 with it's wider shoulder that has a 0.400" datum diameter. You should take a case to the store with you and find a spacer that lands roughly in the middle of the shoulder. 0.375" is ideal, but this is a comparison, not an absolute measurement, so anything approximate is good enough. Let's also get a reading on a case you fired from commercial ammo and then resized.



The bottom line here is that the case is stretching the brass too thinly at the pressure ring, so it stretches until it cannot contain pressure and it cracks. Unless the case gets scored over the pressure ring, there is no other mechanism for causing the crack that I am aware of. Excess pressure will stretch the whole chamber so that even though the headspace is good (bolt closes on a GO gauge but not on a NO-GO gauge) the case still stretches too much. If the case is too short for the chamber (excess headspace) that will cause the stretching. We just need to figure out what mechanism is causing it.

If you know someone else who reloads and has some different powders and bullets, let's put together a very standard load of the type used in match shooting with the Garand. A 150-grain FMJ bullet or match bullet over 49 grains of IMR4895. A 168-grain match bullet over 47.5 grains of IMR4895 or 48 grains of IMR4064. QuickLOAD's database thinks you would need about 1.4 grains more Accurate 4064 to match pressure with IMR4064, but your components are suspect until we figure it out. You might also load the rounds on his equipment, if possible, to eliminate your dies and the like.
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Old May 29, 2018, 11:46 AM   #65
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My head is getting screwed up. Nothing can be this difficult to figure. Something I didn't see anywhere is the starting load! If the guy started to hot, that could be a problem. I didn't notice any mention of extractor mark on the case's. Wasn't hard bolt lift mentioned? If those crack's had been along the body of the case and not around the head, I think that may well have been caused by to large a chamber, although I have ever seen one or heard of one before. Looking at the marks on the case's, it would immediately say to me, sloppy chamber or head space problem. Myself I would simply partial re-size a few at the first loading and see what happens. Bear in mind at that first sizing do not bump the shoulder stay away form it at min an eight inch. You need to give the case room to expand. I'd also make sure the case length is not to long and getting into the lands, that jumps pressure! Didn't see a photo of the face of the case head. Ejector mark on there could well mean pressure when combined with a bit sticky bolt. I am suspecting this whole thing is going to boil down to a reloading problem. Clue being there is no sign at all of anything wrong when first fired with factory case's. I have seen that separation ring start on magnum's and a rimmed case. It never showed itself until the case had been fire a few time's. Now I have never felt the need to cast a chamber but if the body dia was excessive, wouldn't a casting measure it? And if that was it, why a separation start around the case head rather than down the side of the case? Interesting to know, is this a new rifle with first reloads doing this? Is the die set up to size a case in another rifle if this is a new rifle? I have 2 243's and the loads in one will not chamber in the other but, the loads from the other will chamber in the one. I suspect that using the load that will fit in both chamber's could cause a problem.
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Old May 29, 2018, 01:27 PM   #66
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Norma cases have not been resized. I will check and make sure the cases are not to long and trim if nessesary. Also I will go thru UNicks list and check all componets. I do have a head space comparator tool and am only mooving the shoulder back .003 inches. On factory rimington brass sometimes the case cracks on the second firing but no sighns of cracking on the first firing.

Also I ordered a Hornady OAL guage ,bullet comparator and a modified case in 30-06.

I am almost certain it is not head space. Right now it could be trim length,bullets into rifling,incorect bullets (diameter/weight)
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Old May 29, 2018, 02:00 PM   #67
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Did the smith charge you for a new extractor?
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Old May 29, 2018, 03:21 PM   #68
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While trim length is a needed check, new brass at worst would be at maximum.
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Old May 29, 2018, 04:30 PM   #69
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No new extractor. I watched him check it and he didn't charge me anything.
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Old May 29, 2018, 05:00 PM   #70
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Sizeing die -30-06 H5 (lee)
New norma case length 2.483
Bullet weights 165 grains (on rcbs beam scale)
Bullet measures .307
Case neck with bullet seated = .333
New norma case shoulder measures 4.042 (measures with hornady comparator and correct bushing)
Fired norma case shoulder measures 4.045
Factory remigton unfired case shoulder measures 4.042
Factory remington fired case shoulder measures 4.044 (fired with factory load)
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Old May 29, 2018, 05:30 PM   #71
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Quote:
Originally Posted by Don Fischer View Post
My head is getting screwed up. Nothing can be this difficult to figure. Something I didn't see anywhere is the starting load! If the guy started to hot, that could be a problem. I didn't notice any mention of extractor mark on the case's. Wasn't hard bolt lift mentioned? If those crack's had been along the body of the case and not around the head, I think that may well have been caused by to large a chamber, although I have ever seen one or heard of one before. Looking at the marks on the case's, it would immediately say to me, sloppy chamber or head space problem. Myself I would simply partial re-size a few at the first loading and see what happens. Bear in mind at that first sizing do not bump the shoulder stay away form it at min an eight inch. You need to give the case room to expand. I'd also make sure the case length is not to long and getting into the lands, that jumps pressure! Didn't see a photo of the face of the case head. Ejector mark on there could well mean pressure when combined with a bit sticky bolt. I am suspecting this whole thing is going to boil down to a reloading problem. Clue being there is no sign at all of anything wrong when first fired with factory case's. I have seen that separation ring start on magnum's and a rimmed case. It never showed itself until the case had been fire a few time's. Now I have never felt the need to cast a chamber but if the body dia was excessive, wouldn't a casting measure it? And if that was it, why a separation start around the case head rather than down the side of the case? Interesting to know, is this a new rifle with first reloads doing this? Is the die set up to size a case in another rifle if this is a new rifle? I have 2 243's and the loads in one will not chamber in the other but, the loads from the other will chamber in the one. I suspect that using the load that will fit in both chamber's could cause a problem.
Not a new rifle have owned it since new around 95 or so. Started reloading for it about 3 years ago. Have shot quite a few of these loads with once fired remington case. 3 of them the case has failed. I bought new Norma cases because I figured the brass was crappy. 1 st firings on the unsized Norma cases show a hair line crack at the same place the Remington cases failed on the second firing.

It has to be something I am doing wrong at this point the only thing I can see it being is jamming the bullets into the lands.
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Old May 30, 2018, 07:30 AM   #72
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Is a micrometer to measure round objects.
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Old May 30, 2018, 09:53 AM   #73
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wouldn't a casting measure it? And if that was it,
That would depend on the ability of the caster.

Again; I believe you should learn to measure the length of the chamber from the shoulder/datum to the bolt face and I believe you should learn to measure the length of the case from the shoulder/datum to the case head.

I am the fan of cutting down on all that case travel.

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Old May 30, 2018, 01:12 PM   #74
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Missed something, somewhere...
You've owned the rifle for 20 something years...just getting around to shooting it? Or did this issue just suddenly manifest itself?

Did the smith check longitudinal clearance on the bolt nose recess?
I'm thinking that if this were cut too deeply (much more than fifteen thousandths clearance or so) you'd have too much unsupported casehead hanging out there resulting in separations despite correct headspace.
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Old May 30, 2018, 02:31 PM   #75
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Did the smith check longitudinal clearance on the bolt nose recess?
I'm thinking that if this were cut too deeply (much more than fifteen thousandths clearance or so) you'd have too much unsupported casehead hanging out there resulting in separations despite correct headspace.
Case head protrusion/unsupported case head; I would think there is more of a chance to expect Catastrophic failure than case head separation.

The 98 Mauser has close to .110 + head space case head protrusion from the chamber. The 03 and 03A3 has .090" case head protrusion from the bottom of the extractor cut to the case head. There are claims the 03 and 03A3 could have .175"; I do not believe the .175" claim, I have measure case head thickness from the cup above the web to the case head on more than a few military cases and found them to be thin on the case head and thick on the case body.

If there was any truth to the .175" thing the case would only have .025" case head support with military cases from 1940 to the end of manufacturing.

F. Guffey

While measuring I was impressed with R-P cases; case head thickness on the P-P cases was .260", that means the case head was thick and the case body was thin.
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