Serious over-pressure from annealing?

[hboothe]

Hey, all, I'm having a problem with some rounds I loaded for a 224 Valkyrie in an AR-15 platform and I'm wondering if annealing the cases has something to do with it.

I am loading 60gr Nosler BT Varmint bullets in used brass over 29.2gr CFE-223, CCI #41 primers. I use these for hunting, switching from the factory Federal cartridges, and I go through 20 or so each week. I had worked up the load from down around 28gr powder, shooting over a chronograph, finding which amount of powder would get me the velocity I wanted and looking for pressure signs (specifically: flattened primers, extractor/ejector extrusion, ejector swipe). I found that 29.2gr of CFE-223 gave me a slightly flattened primer, good velocity (similar to the Federal factory stuff), and no other signs of over-pressure.

I got good groups from the test batch and decided to load up 50. Considering that this is a hunting rifle and also an AR-15, I always full-length resize my cases. Furthermore, considering that I do not sort, organize, and log "rounds fired", some of these may be on their 3rd or 4th or 2nd or whatever trip through the rifle...so I thought annealing the cases might be a neat idea. So, I annealed them. I loaded them with the same load/components I'd used in the workup. And they are dangerously over-pressured! Jeez, I shot 3 of them, 2 before I noticed the problem and 1 afterwards to "be sure", and all three: blew the primer out and expanded the case head. I mean, I can see where the chamber ends support for the case, and the primers can be put back in by just dropping them in. Wow!

I pulled 5 of cartridges randomly and weighed the powder charges, in case I made a dumb mistake in the loading, but, no, 29.1 and 29.2 grains for each. I had the correct powder and primer and seating depth. I noticed the seating effort was seriously reduced when I loaded the annealed cases (I used a light crimp with a Lee FCD like usual for the AR-15), and, of course, pulling them apart is easy, too. I had stuck a bullet in a naked case in the reloading process to compare bullet seating effort and, when I pulled it apart, I noticed that the effort was significantly higher to remove the bullet from the case.

So, my question then is: what happened? My best guess is that the reduced neck tension allows the bullet to slide forward either with the primer discharge or otherwise dramatically earlier on in the powder burn and, therefore, is jamming on the lands and causing a serious spike in chamber pressure.

I'd like to see what insight/thoughts you folks might have. Also, if it is just the neck tension causing the change (in this case, from annealing), then this might serve as a warning to others.

Thanks for your time.

--HC

 

[Crosshair1]

I would think that the reduced neck tension is allowing the bullets seat deeper in the case at some stage of the cycling process.
I would load a factor round followed by a handload, fire the factory but remove the handload unfired from the chamber and check dimensions.

 

[T-shooter]

It possible that the bullet slides forward. Measure a few, chamber them with the bolt slamming home hard, carefully eject them and measure the lengths. You could be getting bullet setback which will also increase the pressure. Sounds like they may have been over annealed and softened too much. Hopefully you watched the heat and didn't get the case hot too far down. The heat ring on the3 cases shouldn't go any farther down the case than this. (The black mark is a 450° heat crayon used to test it). A soft case would probably show all the signs of overpressure even though the charge and pressure are ok because the metal has lost some of it's strength. Anyway, this is a very dangerous situation and I would advise not firing any more of those cases. If you have a chronograph, the velocity would probably indicate higher pressure with increased velocity. Still, I wouldn't use them. Better to be safe than worry about the cost of some cases.

 

[hboothe]

I would think that the reduced neck tension is allowing the bullets seat deeper in the case at some stage of the cycling process.
I would load a factor round followed by a handload, fire the factory but remove the handload unfired from the chamber and check dimensions.

Thanks for the reply. I believe I did as you suggested: I loaded a factory round, discharged it with one of the offending cartridges next up in the mag, and then checked the length after extracting the offending cartridge from the chamber. With a Hornady comparator and digital caliper: 1.808" before being placed in the magazine, 1.811" after being stripped from the magazine and chambered. My rifle got dusty last night hunting (it was in the back of the side by side) and marginally gassed apparently; it took three factory rounds and an adjustment of the gas block before it stripped the reload off the magazine. I checked the cartridge length each time to be sure it had not moved and it had not. So, the act of being stripped and chambered made it grow by 0.003" but recoil from the rifle did not impact its measured length.

Thanks again.

--HC

 

[fyrewall]

Did the case heads also get annealed & softened? I toast my brass with a ring flame tip with the heads under 1/2 of water. Propane has flame temps over 2000 degrees F and brass is a good heat conductor. Whatever, toss those annealed cases.

 

[Rdlningcltchdmpr]

Hey, all, I'm having a problem with some rounds I loaded for a 224 Valkyrie in an AR-15 platform and I'm wondering if annealing the cases has something to do with it.

I am loading 60gr Nosler BT Varmint bullets in used brass over 29.2gr CFE-223, CCI #41 primers. I use these for hunting, switching from the factory Federal cartridges, and I go through 20 or so each week. I had worked up the load from down around 28gr powder, shooting over a chronograph, finding which amount of powder would get me the velocity I wanted and looking for pressure signs (specifically: flattened primers, extractor/ejector extrusion, ejector swipe). I found that 29.2gr of CFE-223 gave me a slightly flattened primer, good velocity (similar to the Federal factory stuff), and no other signs of over-pressure.

I got good groups from the test batch and decided to load up 50. Considering that this is a hunting rifle and also an AR-15, I always full-length resize my cases. Furthermore, considering that I do not sort, organize, and log "rounds fired", some of these may be on their 3rd or 4th or 2nd or whatever trip through the rifle...so I thought annealing the cases might be a neat idea. So, I annealed them. I loaded them with the same load/components I'd used in the workup. And they are dangerously over-pressured! Jeez, I shot 3 of them, 2 before I noticed the problem and 1 afterwards to "be sure", and all three: blew the primer out and expanded the case head. I mean, I can see where the chamber ends support for the case, and the primers can be put back in by just dropping them in. Wow!

I pulled 5 of cartridges randomly and weighed the powder charges, in case I made a dumb mistake in the loading, but, no, 29.1 and 29.2 grains for each. I had the correct powder and primer and seating depth. I noticed the seating effort was seriously reduced when I loaded the annealed cases (I used a light crimp with a Lee FCD like usual for the AR-15), and, of course, pulling them apart is easy, too. I had stuck a bullet in a naked case in the reloading process to compare bullet seating effort and, when I pulled it apart, I noticed that the effort was significantly higher to remove the bullet from the case.

So, my question then is: what happened? My best guess is that the reduced neck tension allows the bullet to slide forward either with the primer discharge or otherwise dramatically earlier on in the powder burn and, therefore, is jamming on the lands and causing a serious spike in chamber pressure.

I'd like to see what insight/thoughts you folks might have. Also, if it is just the neck tension causing the change (in this case, from annealing), then this might serve as a warning to others.

Thanks for your time.

--HC

When an ar strips a cartridge and sends it into the chamber it smash's into the feedramp very hard. Probably pushing bullet back into the case- way way into the case.

 

[mauser284]

No. Annealing can not create an over pressure. Annealing of copper alloys softens them. Soft brass is less likely to tear. Copper alloys work harden so they are striking the chamber every time you fire them just like they are being hammered from the inside out. All metals have some level of elastic modulus. So you can deform them a specific amount and they will spring back or rebound. Go beyond that and you get stretch that does not return.Go past that and you get a rupture. If you do not break it then it can be reformed many times and re-anneals and reworked over and over. If not for the thinning and stretching you could keep using the same brass forever if you stayed on top of hardness and reforming. That is why the more gentle low pressure cartridges can be reloaded far more times than insane high pressure beasts. I am greatly over simplifying things to keep it simple. I make trumpets which are all made from various copper alloys cartridge brass/ordnance brass 70/30, Gold Brass 80/20, 85/15, Bronze 80%+Copper/No Zink remainder tin, Copper 95%, Gliding Metal think Greek Mauser silver looking jacket also called German Silver, Muntz Metal, Modern Nickle Silver contains no silver it is 10% or 30% Nickle and the rest is copper, zink, tin etc.....So I draw and hammer copper alloys weekly.

Generally assuming your cases are uniform and sorted and all the same brand over pressure is normally over loaded brass, bullet seating depth into the case, and how close you are to the rifling.....Chasing the lands can create insane over pressure in what is other wise a safe load. So reheck the powder charge, seating depth and the actual chamber on the rifle!

 

[hboothe]

It possible that the bullet slides forward. Measure a few, chamber them with the bolt slamming home hard, carefully eject them and measure the lengths. You could be getting bullet setback which will also increase the pressure. Sounds like they may have been over annealed and softened too much. Hopefully you watched the heat and didn't get the case hot too far down. The heat ring on the3 cases shouldn't go any farther down the case than this. (The black mark is a 450° heat crayon used to test it). A soft case would probably show all the signs of overpressure even though the charge and pressure are ok because the metal has lost some of it's strength. Anyway, this is a very dangerous situation and I would advise not firing any more of those cases. If you have a chronograph, the velocity would probably indicate higher pressure with increased velocity. Still, I wouldn't use them. Better to be safe than worry about the cost of some cases.
View attachment 1111781

Thanks for the reply. I just tested one case getting stripped and chambered and it actually got 0.003" shorter in the process. After reading your post I randomly grabbed 3 of the remaining as-yet still-assembled units and cycled them through the rifle from the magazine, allowing the BCG to fly forward from full rearward to battery unimpeded. All three cartridges measured 1.808" before. After: 1.8065, 1.8075, 1.811". Not a huge difference but I don't have my measurement for the "contact" length with this bullet at hand.

I am not saying this defensively or to say I know it all, just saying: I've read a lot about annealing brass and what not to do (Annealeez has some good information on their site, and I tried to avoid the general Internet-commando posts regarding the process). I knew to stay away from the case head and my heat color ring ends around the area shown in your picture. That's not to say I didn't screw something up or that I don't screw stuff up, just saying I didn't just jump in and throw the cases in a kiln for a day.

Reading your reply and the other one I've received so far gives me an idea: I'll crimp the heck out of one cartridge and see if it makes a mess of the case like the others.

Okay, done. So, crimping the snot out of the bullet and then firing one round got me: no ring around the case head area on the body like I had before, but the primer still blew, the extractor bent and started to rip the rim, and a small ejector mark. Increasing the bullet-removal force required seems to impact the peak pressure in the chamber.

--HC

 

[hboothe]

When an ar strips a cartridge and sends it into the chamber it smash's into the feedramp very hard. Probably pushing bullet back into the case- way way into the case.

Thanks for the reply. That's a valid point but, unfortunately, not what seems to be happening here. In response to a couple of (slightly) earlier posts, I've strip fed several of the cartridges from the magazine into the chamber and done measurements before and after and the differences have been very small: from +0.003" to -0.0015" (1.5 thousandths, not 15 thousandths).

--HC

 

[hboothe]

No. Annealing can not create an over pressure. Annealing of copper alloys softens them. Soft brass is less likely to tear. Copper alloys work harden so they are striking the chamber every time you fire them just like they are being hammered from the inside out. All metals have some level of elastic modulus. So you can deform them a specific amount and they will spring back or rebound. Go beyond that and you get stretch that does not return.Go past that and you get a rupture. If you do not break it then it can be reformed many times and re-anneals and reworked over and over. If not for the thinning and stretching you could keep using the same brass forever if you stayed on top of hardness and reforming. That is why the more gentle low pressure cartridges can be reloaded far more times than insane high pressure beasts. I am greatly over simplifying things to keep it simple. I make trumpets which are all made from various copper alloys cartridge brass/ordnance brass 70/30, Gold Brass 80/20, 85/15, Bronze 80%+Copper/No Zink remainder tin, Copper 95%, Gliding Metal think Greek Mauser silver looking jacket also called German Silver, Muntz Metal, Modern Nickle Silver contains no silver it is 10% or 30% Nickle and the rest is copper, zink, tin etc.....So I draw and hammer copper alloys weekly.

Generally assuming your cases are uniform and sorted and all the same brand over pressure is normally over loaded brass, bullet seating depth into the case, and how close you are to the rifling.....Chasing the lands can create insane over pressure in what is other wise a safe load. So reheck the powder charge, seating depth and the actual chamber on the rifle!

Thanks for the reply. While not a metallurgist, I am familiar with elastic and plastic deformation and repetitive forays into plastic deformation causing stress fatigue failures. My concern here, regarding the annealing causing, or not causing, over-pressure is that the annealed cases have considerably less grip on the bullets than the un-annealed cases in which the load was developed. If the "loose bite" allowed the primer ignition to shove the bullet into the lands before much powder ignition occurred, it might be allowing the bullet to, for a microsecond, be a bore obstruction and cause a significant chamber pressure spike. After forensic analysis of a random sampling of the un-fired cartridges shows them to be loaded with the correct amount of powder and since I only load one powder for this cartridge and only use one primer for this cartridge and am using the same box of bullets for this cartridge as in the work-up loads, the only difference I can discern is that the annealing reduced (significantly) the case's grip on the bullet.

--HC

 

[243winxb]

Check chamber length and brass trim length. Long brass, short chamber, bullet crimped by chamber on loading.

Not keeping brass sorted by times fired is something to watch. I would not mix.

It may take up to 5 firings for primer pockers to expand. Your load seems to be maximum?

 

[MikeMcCasland]

I'm sure the answer to this is no, but I'll ask anyway...Not trying to imply anything by it.

New lot of powder, or bullets? Any chance you cleaned the barrel, and maybe left the chamber a little wet?

Where I'm getting at is that annealing shouldn't cause that, so I'd be looking elsewhere.

 

[rebeltex]

Over-annealed case = too soft brass.
Too soft to handle the pressure you have.
You may actually not be over pressure for good brass but that soft brass wants to run somewhere when fired.

 

[fyrewall]

Did the case heads also get annealed & softened? I toast my brass with a ring flame tip with the heads under 1/2 of water. Propane has flame temps over 2000 degrees F and brass is a good heat conductor. Whatever, toss those annealed cases.

Wimpy neck tension would not be the cause for your angst. Upon primer explosion the primer is jammed into the rifling (leade) and the entire powder charge is like an uncompressible liquid plastered forward with bullet immediately prior to powder combustion. Wimpy neck tension or tight (short of welding the bullet in place) this would happen no matter what. Are your bullets in place after shoving the loaded rounds into the magazine and COAL unchanged after stripping a loaded round from magazine into chamber? I did see some reference to crimping.

My suggestion would be to look at annealing for making those brass heads sort of soft (annealing). The real big question - were the cartridge brass heads protected from the 2000 plus degree heat blast of the propane torch (assuming propane was used)?

Annealing, crystal size, work hardening, tough hard springy brass heads, primer pockets, signs of annealing by colors just below shoulder to mouth all good stuff to know about - "forensic analysis", has always scared me real bad no matter what, legions of lawyers, court testimony, depositions, pressure…. Should I be compelled to perform any "forensic analysis" on my ammo production factory loaded ammo would be the only option.

Take care and make good ammo!

 

[T-shooter]

Thanks for the reply. While not a metallurgist, I am familiar with elastic and plastic deformation and repetitive forays into plastic deformation causing stress fatigue failures. My concern here, regarding the annealing causing, or not causing, over-pressure is that the annealed cases have considerably less grip on the bullets than the un-annealed cases in which the load was developed. If the "loose bite" allowed the primer ignition to shove the bullet into the lands before much powder ignition occurred, it might be allowing the bullet to, for a microsecond, be a bore obstruction and cause a significant chamber pressure spike. After forensic analysis of a random sampling of the un-fired cartridges shows them to be loaded with the correct amount of powder and since I only load one powder for this cartridge and only use one primer for this cartridge and am using the same box of bullets for this cartridge as in the work-up loads, the only difference I can discern is that the annealing reduced (significantly) the case's grip on the bullet.

--HC

Do you have any un-annealed cases of the same brand to re-test the load in again? A loose grip on the bullet wouldn't be a problem unless it allows the bullet to move when the round if chambered hard. .001" or .002" shouldn't matter at all. Something else that comes to mind is the temperature. If you developed the load in 35° air and it's 85° now, that could make a substantial increase in pressure depending upon the powder you are using. When I was learning to anneal I under and over heated brass as a test. Properly annealed, my .308 necks can be pinched slightly with pliers and spring back. I' talking about using a magnifying glass and pinching them maybe .005", enough to see movement. Much more than that and the deformation remains. When overcooked, the brass is basically dead and won't return at all and will have next to no neck tension. I've seen them to the point I can flatten the neck quite a bit with my thumb and finger.

A stupid mistake I made once was washing the cases and then tumbling them in walnut media. I was sure they were dry. I fired a few and got noticeable pressure signs and loose primers (one fell out) when the same exact loads were fine before, even reusing the same cases. I broke down the other rounds and found the problem. Evidently several of the cases were not completely dry and had clumps of wet tumbling media in the cases along with some of the powder sticking together. The reduced the case capacity and increased pressure. Also the steam from the moisture may have made it worse.

Be careful of overpressure, back the loads down until you find the problem.

 

[Metal God]

Tshooter may have something with the temp issue . I’ve found CFE-223 to be unstable temp wise . I’ve not seen what’s going on with your loads using the powder but have had very inconsistent velocities with large ambient temperature swings .

 

[rogn]

If you are not logging the firing of cases, are you checking case length before each reload. Could the annealing allowed the cases to stretch a bit in the neck during the neck expansion of the resizing process? A case thats only a few thousandths over long will give you exactly what youre describing.

 

[243winxb]

Modulus of elasticity- Cartridge Brass-

Material is 70 copper/30 zinc with trace amounts of lead & iron , called C26000. Material starts to yield at 15,000 PSI when soft (annealed), and 63,000 PSI when hard.

Material yields, but continues to get stronger up to 47,000 PSI when soft, and 76,000 PSI when work hardened.

Modulus of Elasticity is 16,000,000 PSI. This means to pull a 1.000 inch long strip to 1.001 inch long induces a 16,000 PSI stress.
So if you pull a 1.000 inch strip to 1.005 inch long, you get about 76,000 PSI, which is the max obtainable.

If the neck and shoulder were made bright red, over done, the heat to the case head should not be high enough to do harm?? Imo. Case head may have gotten some stress relieving at around 400F??
.

I gave up on annealing with a hand held torch. The process needs special equipment. Imo.

 

[J F Johannes]

Might be a little much on the powder for an AR-15. Hodgden's site has this:

 

[MikeMcCasland]

Might be a little much on the powder for an AR-15. Hodgden's site has this:

View attachment 1111859

I believe that's .223 data; he's shooting a .224 Valk. He's on the upper end of their charge weights, but nothing crazy.