I have a question concerning case expansion. I take my fully fire formed cases, measured from the datum, and bump the shoulder back .003. I then load a lighter load and after firing I am only reading a .0005 to .0015 increase in length, measured at the shoulder. Could a person assume they are not anywhere near a high or over pressure situation? This may be an elementary question but I wanted some reloaders input just to satisfy. Thanks guys
Undserstanding case pressure
- Thread starter amtx2019
- Start date
Just a guess here but I would say that is your spring back. It would help to have more information before anyone recommends increasing your charge.
Caliber? Load data? Bullet? Brass? Number of firings on brass? Velocity? Do you anneal? Was your initial measurement taken on once fired brass? How much did it grow from first firing to setting your die? Are you using the same brand of brass from when you set up the die?
Just some random questions to help those more in the know answer your question better..
SHM
Caliber? Load data? Bullet? Brass? Number of firings on brass? Velocity? Do you anneal? Was your initial measurement taken on once fired brass? How much did it grow from first firing to setting your die? Are you using the same brand of brass from when you set up the die?
Just some random questions to help those more in the know answer your question better..
SHM
Not enough pressure to stretch the head back against the bolt face . The theory is the firing pin pushes the case fully forward , the case expands sealing the chamber holding the case forward resulting in a small gap between the case head and the bolt face . In your case that should be .003 . If your case only grew .0015 that means there was still a gap at the case head and bolt face area of .0015 , if that’s the case your primer should’ve popped out that much . Check and see if your primers are sitting slightly higher than your case head .
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I should have given more information but did not want to start any long debates on what I was doing. I'll try and explain the best I can. I am loading for my 308 Win. With my method of hunting I started playing with some reduced loads for less recoil and muzzle blast. I tried several published powders and load configurations and was not satisfied until I ran across some data using IMR4198. The 4198 yielded good accuracy but I was not happy with the problem of my cases getting shorter after firing. I have read where this is common with very reduced loads. My equipment consists of:
18in. Criterion 12 twist 308 Win.
Lapua brass
Federal 210 M primers
IMR4198 powder
125 grain Nosler ballistic tip bullets 2.807 OAL
My initial testing was with new lapua brass measureing 1.622 at the shoulder.
My initial loads were 32.5 IMR4198 which yeilded an avg of 2475 fps with no case stretch.
I went with .5 grain increments to 34.5 grains which yeilded 2660 fps and I was gaining .005 to .0015 case stretch measured at the shoulder with no case head swelling or any other signs of pressure. This load IS pushing the primer slightly but not as bad as the lighter loads. The IMR burns much cleaner than the IMR 4895 I tested and has a light recoil and low muzzle blast which is what I wanted. From the information I can find this should not be near a max load with IMR 4198 even though it is not really recomended powder. I was wanting to purchase QUICK LOAD until this virus thing cut into my cash flow as I am sure it has dinged some others hobbies too! I do appreciate any help I can get.
18in. Criterion 12 twist 308 Win.
Lapua brass
Federal 210 M primers
IMR4198 powder
125 grain Nosler ballistic tip bullets 2.807 OAL
My initial testing was with new lapua brass measureing 1.622 at the shoulder.
My initial loads were 32.5 IMR4198 which yeilded an avg of 2475 fps with no case stretch.
I went with .5 grain increments to 34.5 grains which yeilded 2660 fps and I was gaining .005 to .0015 case stretch measured at the shoulder with no case head swelling or any other signs of pressure. This load IS pushing the primer slightly but not as bad as the lighter loads. The IMR burns much cleaner than the IMR 4895 I tested and has a light recoil and low muzzle blast which is what I wanted. From the information I can find this should not be near a max load with IMR 4198 even though it is not really recomended powder. I was wanting to purchase QUICK LOAD until this virus thing cut into my cash flow as I am sure it has dinged some others hobbies too! I do appreciate any help I can get.
Don't try to guess pressure.
A problem pressure FOR YOU will show up as a problem FOR YOU.
Conversely, if there is no problem, then regardless of pressure, it's not a problem.
With this, you can accept that a problem pressure (for you) isn't what you read in manuals. It's what it ends up being. So creep into it carefully, stopping at problems, regardless of what you read. The golden rule.
So for example, you're not seeing any primer blow-by, case head wiping, case cracks, difficult bolt turn, or difficult extraction, and measured velocities are in alignment with books. Cool so far, but,, primer pockets are loosening by 3rd reload cycle? Is that a problem for you? It would be for me, and I would resolve it before continuing. But it might not be a problem for you.
One thing I do early on is test for what I call 'MyMax' load.
With new cases, which I've probably culled due to thickness variance or something, I'll run incremental powder loads upwards while measuring the case web-line with a mic. The web-line is visible to the eye and is simply the widest dimension of fired cases. It's not a set datum(set distance from case head), but whatever your breech support produces.
Barring any early 'problems' I'll see this dimension rise to plateau. I keep going up, and eventually there will be a step change of another 0.0005". That's MyMax, which I log.
MyMax is the point where FL sizing would be REQUIRED to continue use of the case (from that single shot). It has nothing to do with a particular pressure, but experience tells me this point will lead to actual pressure problems. MyMax and YourMax would likely be different.
That plateau is the case expanding normally to chamber wall and springing back. The step change upward means the chamber is expanding enough to allow additional yielding of the case. Then soon, the chamber will be springing back against the case, leaving an interference fit, and popping extraction.
It's a step change because chamber expansion is not as linear as brass expansion. It takes at least a certain pressure level to even cause it (enough for this test).
And I'm not suggesting that FL sizing is the problem, just that such a requirement, so early, is too much for viable long term use of the brass. Maybe pockets will be opening faster, etc.. This, because brass wants to go where it's been, and it will,, nothing you can do about it (except annealing).
I throw away the cases used for this.
I don't know what SAAMI uses for their standard of Max. But per QuickLoad(velocity calibrated to my powders), I have consistently seen MyMax very near listed SAAMI Max. For me, just above SAAMI, within ~2-5Kpsi. As to what pressure really is? Don't know, don't care.
A problem pressure FOR YOU will show up as a problem FOR YOU.
Conversely, if there is no problem, then regardless of pressure, it's not a problem.
With this, you can accept that a problem pressure (for you) isn't what you read in manuals. It's what it ends up being. So creep into it carefully, stopping at problems, regardless of what you read. The golden rule.
So for example, you're not seeing any primer blow-by, case head wiping, case cracks, difficult bolt turn, or difficult extraction, and measured velocities are in alignment with books. Cool so far, but,, primer pockets are loosening by 3rd reload cycle? Is that a problem for you? It would be for me, and I would resolve it before continuing. But it might not be a problem for you.
One thing I do early on is test for what I call 'MyMax' load.
With new cases, which I've probably culled due to thickness variance or something, I'll run incremental powder loads upwards while measuring the case web-line with a mic. The web-line is visible to the eye and is simply the widest dimension of fired cases. It's not a set datum(set distance from case head), but whatever your breech support produces.
Barring any early 'problems' I'll see this dimension rise to plateau. I keep going up, and eventually there will be a step change of another 0.0005". That's MyMax, which I log.
MyMax is the point where FL sizing would be REQUIRED to continue use of the case (from that single shot). It has nothing to do with a particular pressure, but experience tells me this point will lead to actual pressure problems. MyMax and YourMax would likely be different.
That plateau is the case expanding normally to chamber wall and springing back. The step change upward means the chamber is expanding enough to allow additional yielding of the case. Then soon, the chamber will be springing back against the case, leaving an interference fit, and popping extraction.
It's a step change because chamber expansion is not as linear as brass expansion. It takes at least a certain pressure level to even cause it (enough for this test).
And I'm not suggesting that FL sizing is the problem, just that such a requirement, so early, is too much for viable long term use of the brass. Maybe pockets will be opening faster, etc.. This, because brass wants to go where it's been, and it will,, nothing you can do about it (except annealing).
I throw away the cases used for this.
I don't know what SAAMI uses for their standard of Max. But per QuickLoad(velocity calibrated to my powders), I have consistently seen MyMax very near listed SAAMI Max. For me, just above SAAMI, within ~2-5Kpsi. As to what pressure really is? Don't know, don't care.
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There are no high pressure problems here . Maybe not even a problem. The “issue” is low pressure, and the case not stretching/blowing back out to fully fire formed dimensions .
The fact he is trying to use reduced loads and his primers are popping out/back from fully seated is a classic sign of low pressure loads . There is enough pressure to expand the case and seal the chamber but not enough to push the case head back against the bolt face . Resulting in the primer being pushed out of the pocket the same distance the gap is between the case head and bolt face .
The fact he is trying to use reduced loads and his primers are popping out/back from fully seated is a classic sign of low pressure loads . There is enough pressure to expand the case and seal the chamber but not enough to push the case head back against the bolt face . Resulting in the primer being pushed out of the pocket the same distance the gap is between the case head and bolt face .
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My 30-30 at the max pressure of 38,000 cup or 42,000 psi always has the fired primers protruding, and like metal God said above its a sign of low pressure.
You will see the same thing with a workup load starting at the suggested starting load and working up. As the load and pressure increases the primers slowly became flush with the base of the case as the case stretches to meet the bolt face.
In most reloading manuals there are warnings about using cases fired with reduced loads again with high power loads. Meaning the shoulder can be set back far enough to cause a case head separation with the high pressure loads.
amtx2019
What you need is a good M1 Garand to fire your .308 cases and not worry about cartridge headspace.
Look at the center case in the photo below and primer protrusion vs actual headspace.
You will see the same thing with a workup load starting at the suggested starting load and working up. As the load and pressure increases the primers slowly became flush with the base of the case as the case stretches to meet the bolt face.
In most reloading manuals there are warnings about using cases fired with reduced loads again with high power loads. Meaning the shoulder can be set back far enough to cause a case head separation with the high pressure loads.
amtx2019
What you need is a good M1 Garand to fire your .308 cases and not worry about cartridge headspace.
Look at the center case in the photo below and primer protrusion vs actual headspace.
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That's an interesting concept Mikecr. I have used the case head measurement when running known higher pressure loads to keep track of things but not for establishing maximum loads. Will keep that process in mind. Metal God and Uncle Ed, I think you both are exactly right on what I am seeing in my loads. I was worried about the lighter loads shortening my cases and getting some mixed in with my hotter loads causing case head separation. That's one reason I juiced them up a little to get some case stretching. With minimal case stretch I can maybe get a few firings by just running them through my collet neck sizer before I have to full length and push the shoulder back. I am happy with the accuracy of the reduced load and plan on trying some 135 grain bullets. I like how you "fire formed" your 45-70 brass!! lol It's hell to be humane!!
No , No sorry I'm not upset at all . I wrote a long reply and realized it was not really needed so just deleted it but you can't completely delete a post . you must put something in it's place so I added "never mind" I probably should have just wrote deleted instead .
Sorry for the confusion
MG
Sorry for the confusion
MG
I know you said you don't prefer 4895 but I also was searching for a reduced load for my 308 Tikka which due to it's light weight kicks like a mule on steroids.
I also choose Nosler 125 grain BT's which is a big game bullet, not a varmint bullet. Excellent bullet for deer size game.
I select H 4895 since it's a well established powder used for reduced load. I worked up a load of 40.0 grains in Rem Cases, Federal 210 primers. Recoil is mild even in this light rifle. Clocked at about 2,600 f/s. No problems with case expansion or primer blow back in my rifle with this load. Excellent accuracy for a light weight sporter, 5/8" groups at 100 yards. Since 99% of my shot opportunities at deer where I hunt are under 200 yards this load is more than adequate.
I also choose Nosler 125 grain BT's which is a big game bullet, not a varmint bullet. Excellent bullet for deer size game.
I select H 4895 since it's a well established powder used for reduced load. I worked up a load of 40.0 grains in Rem Cases, Federal 210 primers. Recoil is mild even in this light rifle. Clocked at about 2,600 f/s. No problems with case expansion or primer blow back in my rifle with this load. Excellent accuracy for a light weight sporter, 5/8" groups at 100 yards. Since 99% of my shot opportunities at deer where I hunt are under 200 yards this load is more than adequate.
I understand MG and Thanks! I had fair luck with the H4895 but found it a little dirtier and had better accuracy with the IMR 4198. I may revisit the H4895 just to give it a try again. I enjoy the reduced recoil and reduced powder consumption of those reduced loads. I think the 125 ballistic tip is a good bullet choice and I will be trying the Wilson Combat 135 grain HAMR bonded bullet also which should be a great lower velocity performer. Thanks for the reply
dcali
Bullet Maker
You can shoot reasonably stout loads and get away with neck sizing for at least a few firings.
Generally bolt action rifles are designed to fail at the brass, rather than some structural part of the firearm itself (barrel, action ring, bolt lugs, etc). Even the strongest brass will unless something else is wrong. But we don’t want anything failing. You want the high pressure, high temperature brass going safely down the barrel.
As as been discussed above, the exact pressure at which that becomes a problem varies. And it escalates. You might get a little sticking in the chamber, ejector wipes, primer blow by (and bolt face etching), then a lot of sticking, then ballooned caseheads, or separation. Not necessarily in that order. There are lots of ways to fail brass, and in my opinion it’s not wise to push any of them. Use a pressure that will give you acceptable life and prevent any failure modes that are problematic. For me, that means getting 8+ firings before the primer pockets start to loosen up with no other functional issues. That’s usually around book (Or QuickLOAD) max. As always, be smart and start low. It only takes a few rounds to work up and check for signs along the way.
Generally bolt action rifles are designed to fail at the brass, rather than some structural part of the firearm itself (barrel, action ring, bolt lugs, etc). Even the strongest brass will unless something else is wrong. But we don’t want anything failing. You want the high pressure, high temperature brass going safely down the barrel.
As as been discussed above, the exact pressure at which that becomes a problem varies. And it escalates. You might get a little sticking in the chamber, ejector wipes, primer blow by (and bolt face etching), then a lot of sticking, then ballooned caseheads, or separation. Not necessarily in that order. There are lots of ways to fail brass, and in my opinion it’s not wise to push any of them. Use a pressure that will give you acceptable life and prevent any failure modes that are problematic. For me, that means getting 8+ firings before the primer pockets start to loosen up with no other functional issues. That’s usually around book (Or QuickLOAD) max. As always, be smart and start low. It only takes a few rounds to work up and check for signs along the way.
Good advice damoncali! I try and avoid loading max velocity/pressure loads and I do look my brass over after a range session just to satisfy my curiosity. I have no need for real hot loads for my hunting situation. I do want the best life for my brass as possible. I have started keeping better track of number of firings on my brass. I don't neck turn or anneal at this time. I tried some "torch and socket" annealing once and was not at all satisfied and decided not to try again until I could get a proper annealing machine. Not sure if it will pay for itself in the long run.
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