Post by: yorketransport on October 24, 2018, 07:57:05 PM
(https://i.imgur.com/MkT7UxP.jpg?1)
(https://i.imgur.com/lZ2hM38.jpg?1)
I'll wait to hear a couple responses before giving any info on this. Biggerhammer doesn't get to play though. :chuckle:
Post by: bear on October 24, 2018, 08:03:49 PM
Post by: BULLBLASTER on October 24, 2018, 08:05:36 PM
Excessive headspace? Primer pushed out a little and then case slammed back to the bolt face and squashed the primer.
If you hadn’t mentioned fireforming I’d say ya overpressure. But there should be some flow into the ejector.
Post by: Magnum_Willys on October 24, 2018, 08:10:11 PM
Post by: Jolten on October 24, 2018, 08:14:26 PM
Post by: yorketransport on October 24, 2018, 08:23:04 PM
Post by: BULLBLASTER on October 24, 2018, 08:27:38 PM
To confuse everyone a little more, the powder used was Trailboss.......I live in a constant state of confusion.
My new theory is you just suck at fireforming... do it better next time sir.
Mostly because I know nothing about nothing related to fireforming or trailboss and can’t even think of anything that would sound smart. :chuckle:
Post by: yorketransport on October 24, 2018, 08:41:06 PM
To confuse everyone a little more, the powder used was Trailboss.......I live in a constant state of confusion.
My new theory is you just suck at fireforming... do it better next time sir.
You may be on to something here! :chuckle: I'll admit that forming 6.5 Badger brass from the original 338 RUM parent case is a lot easier than forming it from 7 RUM brass. I just have a couple hundred 7 RUM cases left over from a different project and this seemed like a good way to waste them.
I will say that your excessive headspace comment does come into play here. Since I'm headspacing off of a false shoulder, the case does move forward slightly from the firing pin strike, which can cause the primer to back out slightly.
Post by: Reidus on October 24, 2018, 08:41:33 PM
Regardless it take some pressure to make a primer that flat.
Post by: Jonathan_S on October 24, 2018, 08:42:55 PM
Post by: yorketransport on October 24, 2018, 09:01:12 PM
its not cratered like a normal factory gun gets with high pressure but you maybe have a custom action with tighter tolerances so no cratering?
Good observation! This was shot in one of the new ARC Nucleus actions. The clearance between firing pin hole and the firing pin is very tight. Also, the ejector is a mechanical style so an ejector mark would show up as a rectangular mark on the case head.
Now, one more bit of information to confuse everyone. The case head expansion was only .0038" on a new, never fired case.
Post by: bullfisher on October 24, 2018, 09:48:08 PM
Post by: yorketransport on October 24, 2018, 09:59:20 PM
Could have been from not jamming the bullet into the rifling when fire forming. Could be from excessive case growth in the chamber. Either way, that case is getting a run at the bolt face.
Getting closer!
Post by: Fl0und3rz on October 24, 2018, 11:33:48 PM
I’ll bite...
Excessive headspace? Primer pushed out a little and then case slammed back to the bolt face and squashed the primer.
If you hadn’t mentioned fireforming I’d say ya overpressure. But there should be some flow into the ejector.
Maybe not excessive, but the general process seems on target. I would expect to see washed out or flattened headstamp more than is shown.
Post by: RadSav on October 25, 2018, 12:13:06 AM
Guess my response is more a question of intrigue than an answer or solution to anything.
Post by: jasnt on October 25, 2018, 05:28:02 AM
Post by: Yondering on October 25, 2018, 10:31:33 AM
Now, one more bit of information to confuse everyone. The case head expansion was only .0038" on a new, never fired case.
Case head expansion, ejector hole marks, and flat primers can all be a result of excess headspace at reasonable pressure, so it's hard to guess much further with the pictures and detail provided. The same things can also be cause by high pressure, but aren't reliable pressure signs by themselves.
Since you said Trailboss and fireforming with a false shoulder, I'm guessing excess headspace, unless your chamber neck is too tight and actually causing high pressure. The force of the primer igniting is probably defeating your false shoulder, even if headspace is correct when you insert the case in the chamber.
Post by: yorketransport on October 25, 2018, 02:04:28 PM
Could you even fit too much trailboss in that case?
If you compress it enough you could! :chuckle:
So far everyone has cover all the obvious causes, but overlooked a pretty common issue that causes a lot of “unexplained” pressure problems.
Here’s the last hint: I fired 49 other identical loads and this is the only one that came out like this. Charges were all hand weighed, OAL maintained within .003”, necks turned to the same dimensions and it wasn’t caused by any kind of anomaly with the bullet.
Post by: BULLBLASTER on October 25, 2018, 02:06:54 PM
Was it all wet?Could you even fit too much trailboss in that case?
If you compress it enough you could! :chuckle:
So far everyone has cover all the obvious causes, but overlooked a pretty common issue that causes a lot of “unexplained” pressure problems.
Here’s the last hint: I fired 49 other identical loads and this is the only one that came out like this. Charges were all hand weighed, OAL maintained within .003”, necks turned to the same dimensions and it wasn’t caused by any kind of anomaly with the bullet.
Or maybe you just punched the trigger way harder on that one?
Post by: yorketransport on October 25, 2018, 02:42:34 PM
Was it all wet?
Or maybe you just punched the trigger way harder on that one?
I’m going to call that a win! :tup:
I didn’t wipe all the lube off of that case. The chamber pressure was likely only between 35-40K psi, but the case couldn’t grip the chamber walls because of the lube. This causes the case to “slip” towards the bolt face faster, causing the primer to get smashed between the bolt face and the case head, giving the lip on the spent primer.
Normally a mistake like this would cause very heavy bolt lift and a potentially dangerous situation which could damage the action. Since these were such low pressure loads (that’s why I use TrailBoss) even the elevated bolt thrust caused by my mistake was less than what would have been caused by a full pressure load.
I just thought this would be a good example of why primers make poor pressure indicators. I cringe every time I hear somebody suggest that a load is safe just because the primers or bolt lift seem “normal”. Likewise, sometimes a primer says the pressure is too high when really there’s something else going on.
Post by: BULLBLASTER on October 25, 2018, 03:05:04 PM
When I’m developing loads for my hunting rifles I like to test wet rounds. Even water on a case will increase the pressure or apparent pressure symptoms.
Post by: Yondering on October 25, 2018, 03:33:33 PM
I didn’t wipe all the lube off of that case. The chamber pressure was likely only between 35-40K psi, but the case couldn’t grip the chamber walls because of the lube. This causes the case to “slip” towards the bolt face faster, causing the primer to get smashed between the bolt face and the case head, giving the lip on the spent primer.
I don't think that's quite the whole story; if headspace was tight and stayed that way the case wouldn't "slip towards the bolt face". Lube on the case can allow the primer to force the case forward more (i.e. sizing it in the chamber, case lube makes that easier), causing the effect of temporary excess headspace. That is what I described in my post above too, but of course lube can sometimes make the problem worse.
On the other hand, sometimes lube has no effect at all, as I've found a number of times, like in a recent batch of fireforming Grendel brass.
Note that it's primer ignition that I'm saying set your case forward, not impact from the firing pin. It's fairly easy to test the effect of each, and I haven't seen firing pin impact set headspace back significantly.
As a somewhat related observation - I've measured as much as .007" headspace increase in some rounds just from dropping a bolt closed in an AR action, without firing the round. I suspect that primer ignition can produce more force to push a case forward than dropping the bolt...
Post by: yorketransport on October 25, 2018, 07:01:29 PM
I didn’t wipe all the lube off of that case. The chamber pressure was likely only between 35-40K psi, but the case couldn’t grip the chamber walls because of the lube. This causes the case to “slip” towards the bolt face faster, causing the primer to get smashed between the bolt face and the case head, giving the lip on the spent primer.
I don't think that's quite the whole story; if headspace was tight and stayed that way the case wouldn't "slip towards the bolt face". Lube on the case can allow the primer to force the case forward more (i.e. sizing it in the chamber, case lube makes that easier), causing the effect of temporary excess headspace. That is what I described in my post above too, but of course lube can sometimes make the problem worse.
On the other hand, sometimes lube has no effect at all, as I've found a number of times, like in a recent batch of fireforming Grendel brass.
Note that it's primer ignition that I'm saying set your case forward, not impact from the firing pin. It's fairly easy to test the effect of each, and I haven't seen firing pin impact set headspace back significantly.
As a somewhat related observation - I've measured as much as .007" headspace increase in some rounds just from dropping a bolt closed in an AR action, without firing the round. I suspect that primer ignition can produce more force to push a case forward than dropping the bolt...
Saying that the case slips faster was an incredibly simplified version of what's happening. Cases always move forward to some degree on ignition regardless of headgap (it's not technically headspace when referring to the gap between case head and the bolt face). How quickly they expand to fill the chamber again has a lot to do with peak pressures, friction on the case walls (affected by lube or water in the chamber) and malleability of the brass regardless of headgap.
The force from a primer going off is very significant. Try taking a fired case and popping the primer out without resizing the brass. Now throw something like a Federal 215 primer in there and fire it in the gun. Even an unsized case that's fit to the chamber will be pushed far enough forward to "crush" the shoulder and cause excessive headgap causing the primer to back out. Brass is really soft and the impact of a 19# firing pin spring followed by the force of a primer going off is more than enough to deform the case. Now take that and compound it even more by making dramatic changes in the case geometry when forming a wildcat and changing case taper, shoulder position and shoulder angle all in one shot and that relatively unsupported case doesn't stand a chance against the firing pin and primer.
Forming 6.5 Badger cases from 7 RUM brass requires at least 4 sizing operations plus fire forming with a crush fit in the chamber to make each case. Messing up one of those sizing operations or getting the crush fit in the chamber wrong results in case separation 1/2" from the case head every time; that's the result of improper headspace (headgap). In this situation (not all) it's lubrication on the exterior of the case that's causing the flattened primers even at low pressures.
Post by: Yondering on October 26, 2018, 11:20:15 AM
Post by: yorketransport on October 26, 2018, 12:22:26 PM
It sounds like you're trying to correct or disagree with me, but you're saying the same things I did. What am I missing? :dunno:
Maybe I miss read your post. I thought you were saying that the oil was allowing the case to be pushed forward under the force of the primer. The oil in the chamber isn’t affecting the forward movement of the brass, it’s affecting the rearward movement.
The primer gets flattened out because of the increased bolt thrust caused by oil in the chamber, not headspace.
Post by: Yondering on October 26, 2018, 03:45:42 PM
The primer gets flattened out because of the increased bolt thrust caused by oil in the chamber, not headspace.
That is incorrect; I thought we were on the same page there but I guess not. High bolt thrust does not cause flattened primers. Flattened primers in a case like this (when pressure is reasonable) are generally a direct result of excess headspace, regardless whether that headspace was caused by sizing or during firing. If headspace is correct and it doesn't change during firing, you won't get flattened primers irregardless of whether there's oil present or not.
The only affect the case lube has on the primer flattening is allowing the case to be pushed forward more, creating temporary excess headspace. Case lube absolutely allows the case to be pushed forward more by primer force; that's pretty easy to test for yourself as you described above.
The lube can also help prevent case head separation, and bolt thrust could theoretically be increased by up to the total tensile strength of the case walls, but that's only a small percentage of total bolt thrust and is not related to primer flattening.
Primer flattening from headpace is caused by the primer protruding from the case a little bit during ignition and being unsupported at the rear. In this position, it starts to balloon out larger than the primer pocket, and when the case is forced back against the bolt by pressure, the primer gets jammed back into the pocket.
Post by: yorketransport on October 26, 2018, 07:39:08 PM
The primer gets flattened out because of the increased bolt thrust caused by oil in the chamber, not headspace.
That is incorrect; I thought we were on the same page there but I guess not. High bolt thrust does not cause flattened primers. Flattened primers in a case like this (when pressure is reasonable) are generally a direct result of excess headspace, regardless whether that headspace was caused by sizing or during firing. If headspace is correct and it doesn't change during firing, you won't get flattened primers irregardless of whether there's oil present or not.
The only affect the case lube has on the primer flattening is allowing the case to be pushed forward more, creating temporary excess headspace. Case lube absolutely allows the case to be pushed forward more by primer force; that's pretty easy to test for yourself as you described above.
The lube can also help prevent case head separation, and bolt thrust could theoretically be increased by up to the total tensile strength of the case walls, but that's only a small percentage of total bolt thrust and is not related to primer flattening.
Primer flattening from headpace is caused by the primer protruding from the case a little bit during ignition and being unsupported at the rear. In this position, it starts to balloon out larger than the primer pocket, and when the case is forced back against the bolt by pressure, the primer gets jammed back into the pocket.
We'll agree to disagree on this one. I know folks who're on both sides of the "lubed case" debate and the effects it has on brass. My observations over the years when loading for standard chamberings as well as forming and loading for a wide variety of wildcats don't line up with your experience. My experience does coincide with the experience of many highly regarded smiths and shooters. Of course the same can be said about those who're on your side of the issue as well. I've know very experienced shooters and smiths who follow your line of thinking.
I guess the best thing to do here would be to do some testing! We can set up some standardized procedures in which we'll test 10 cases with no oil, 10 cases with oil in the neck/shoulder area, and then 10 cases with oil on the case body only. All the brass would need to be sized the same to give a consistent crush fit in the chamber. We can collect and compare data, crunch numbers and accept the fact that nothing's been proven either way! :tup:
Post by: Yondering on October 26, 2018, 08:33:07 PM
Post by: argie1891 on November 06, 2018, 01:12:12 AM