A puzzler for y’all...
- Thread starter Dkcampbl
- Start date
I get donuts after one firing changing the shoulder angle from 20 to 31 degrees with a .003” crush fit at the NS junction.
Guys in this thread are suggesting that- expanding brass uses energy that takes an over pressure load and drops it to safe levels while in the smaller (pre-fired) case, but when the load is used again in the expanded (fire-formed) case the over pressure condition exists, because the energy that was being used to expand brass is now directed down the barrel. That’s not what’s happening.
If that were true, then:
There are only a few things that will cause this type of pressure: wet oily ammo / chamber, seating depth issue, and necks that are too tight. His necks are tightish and the very beginning of these donuts are enough to cause him problems. The other problems have been eliminated.
No, but an AI chamber is just a larger example of the same principle.
Take your favorite 6BR or 30-06 load and fire it your SAAMI chamber, 2900. Now take the same ammo and fire it in an AI chamber, 2890, not 2675.
Whether AI or not you are always fire-forming.
Take your favorite 6BR or 30-06 load and fire it your SAAMI chamber, 2900. Now take the same ammo and fire it in an AI chamber, 2890, not 2675.
Whether AI or not you are always fire-forming.
Take a loaded round and place a bullet at the tip of the loaded round. Does the bearing surface go past the neck shoulder junction? I agree the a donut forming after one firing is rare.
Now that was a good question I hadn’t thought about. The bearing surface of the bullet never reaches the shoulder jct. By my caliper it is .110 from it. No way a donut in the shoulder area is causing this.
That’s not what I was suggesting. I was saying that the direction of spring back and the large degree of expansion allow a virgin case to behave differently from a 1x fired case.
The OP does not have an AI chamber, but his case is undersized in his factory chamber. That is why it behaves like there is no high pressure when there is high pressure. And it manifests itself once the case is minimally sized and reloaded.
How do either of you know that?
Inside neck ream or turn the neck on one case and see if the problem goes away,
. Humor me.You can drop the charge weight til velocity is in check, if I’m right accuracy won’t return.
It partially fills the chamber, and if you run the same load in the mostly fire-formed brass velocity goes down not up. Because it’s now a bigger case.
So your saying that the velocity of using a non-ai round in an ai chamber is higher than using an actual ai round in an ai chamber?
Sounds like you thought the donut would be formed or forming at the shoulder/neck junction correct? I suppose it could be happening but the bearing surface of the bullet isn’t close enough to that area to be influenced by a donut if it was there. I inspected the neck id and od pretty closely and both are smooth as can be. Either way I’m not set up at this time to do neck reaming anyway.How do either of you know that?
Inside neck ream or turn the neck on one case and see if the problem goes away,
You can drop the charge weight til velocity is in check, if I’m right accuracy won’t return.
No, under zero on Whidden's gauge. I don't use it to check anything but shoulder bump, so I have to confess that I have no idea what the zero represents. Corrected my post for clarity. For reference, my AXMC barrel, chambered by Shawn at Hawk Hill, brings it to about +.002, so it is growing a good bit on the first firing.
Y’all aren’t talking about the same thing. You stick a 223 in a 223ai and it will be slightly slower than if you shot it in a normal 223. But you eject ackley brass for your efforts which you can then reload hotter for the subsequent firings to take advantage of the now larger case volume.
I understood it to mean that if you fire a 223 load in a 223 case in an AI chamber it will be faster than a 223 load in an AI fire formed case.
Yes, you’re both right for the same reason a very mild variation in pressure. But we are talking about 10-20 fps here not 200.
There are only a handful of things that can create this kind of pressure.
There are only a handful of things that can create this kind of pressure.
Why is that? Brass does not quench harden. Once it reaches your required annealing temps it shouldn’t matter how quickly it cools. That and I’ve got a limited amount of room, pretty handy to just drop hot stuff in a bucket of water.
DK, in my 300 NM my new lapua brass grew .014" after first firing. With no annealing, a Hornady Match FL and a .334 bushing, I bumped back .001 . 1x velocity was the same as new which surprised me a bit but I had abut 50 down the pipe by then so made sense. This is all with H1000 and 230 Hybrids. On road and don't have my notes but I saw above that you're seating depth wasn't even pushing deep enough to get to shoulder base and think I came to same conclusion. I'm convinced that .342 loaded neck is an issue for your chamber. Not sure if I have any wisdom from there. If it were me I would start varying my prep routine one step at a time to see if I find something. Different set of dies, etc. Good luck
You don’t want to wait 10 minutes for it to cool (less with a fan) but you want to wait an hour for it to dry, despite the fact you know quenching does nothing except get the brass wet?
It doesn’t and I doubt anyone actually cares at all but I get the sense that he was just trying to be helpful and save you a few hours or days.
I typically just do a quick dip in an old butter dish of water then throw them on a towel as I go. They are dry the outside then into the walnut or corncob media for 30 min. Dry as can be and clean after that.
Too durn much going on too get the annealed rnds shot today and on the road in the am till next weekend. May be home in time give them a try Fri evening. Thanks for all the comments everybody.
Too durn much going on too get the annealed rnds shot today and on the road in the am till next weekend. May be home in time give them a try Fri evening. Thanks for all the comments everybody.
You might try a Wilson case gauge and see where the case head is in relation to SAAMI specs, taking a reading with the new brass and your once fired, sized brass. If the shoulder is bumped back too far, you'll have excessive headspace, extruded and blown primers. If this is the case, the sized case head will be deeper into the gauge. You need a dial indicator and an adapter, like Mike Bellm sells on his T/C website. Headspace may be different with each brand and batch of brass.
I'd be scratching my head, too.........as I got on my keyboard to order more Lapua brass! With that kind of accuracy, I'd stick with what works, even if you lose the cost-efficiency of reloading.
Are you annealing your once-fired Lapua brass before trimming and reloading? All new Lapua comes freshly annealed, doesn't it? Mine appears to.
I think if you ask any of the bench rest shooters , guys that shoot any of the 6 mil variety's will tell you that fire forming usually gives the best groups and it takes testing to get back to those groups again. New brass has less volume internally, once fired it has a larger volume . Therefore pressure is different and velocity, just refine the load and keep testing
My experience with the same brass/bullet and .014" expansion on 0x brass is that it doesn't. My wildcats show the same. DK's original velocity numbers were inline with numbers for that weight of RL50. IMHO, that velocities increased drastically with the same powder weight and that he can still duplicate his original results with virgin brass shows that his reloads aren't playing nice with his chamber. I've been down that road before. Its frustrating.
How do you get 15-20k psi? If I’m loaded to the edge of pressure and then go .02 grains more and get pressure signs does that mean I’m 15-20k psi over?
I was just guessing how many PSI it takes to drive his projectile from 2975 to 3200.
Exactly. Anyone who has formed many cases knows that his chamber dimension isn’t the problem. It sure seems to be his neck... Unfortunately, that has already definitively been ruled out.
did you use more powder than you did the first time , was the temperature hotter on this go around , powder temperature sensitive , your wife / girlfriend cursed you , kids trying to bump you off for an insurance payday ? 
Id go black magic someone has it in for you .
Id go black magic someone has it in for you .
