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A puzzler for y’all...
- Thread starter Dkcampbl
- Start date
OK, annealed, loaded and chronoed 5, 1x fired rnds this morning. Everything same, same as 0x fired brass.
- avg FPS on 0x fired brass 2975fps, don’t remember exactly but es was very low, no pressure signs, accuracy superb.
- Avg FPS on 1x fired brass 3100, es of 25 with cratered flattened primers, slightly sticky bolt, no ejector marks this time.
Didn’t try for accuracy but I have little doubt it wasn’t. Damned interesting, I’m maybe becoming a believer in the “new brass stretching absorbs a bunch of pressure” theory. Like I said though been doing this for 50yrs and this is a new one for me....
- avg FPS on 0x fired brass 2975fps, don’t remember exactly but es was very low, no pressure signs, accuracy superb.
- Avg FPS on 1x fired brass 3100, es of 25 with cratered flattened primers, slightly sticky bolt, no ejector marks this time.
Didn’t try for accuracy but I have little doubt it wasn’t. Damned interesting, I’m maybe becoming a believer in the “new brass stretching absorbs a bunch of pressure” theory. Like I said though been doing this for 50yrs and this is a new one for me....
Have you tried 1x NOT annealed? Maybe annealing is making it super soft and allowing it to blow the brass out and cause pressure.... or maybe something else the annealing is causing. I’d try it without for sure just to rule it out.
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This was brass id already fl sized (no expander ball) shoulder bumped back .001”-.002” from fired size and primed. Punched primers, then annealed then ran carb expander thru before loading. Should be like .001”-.002” neck tension. I’m pretty satisfied neck tension nor chamber fit is an issue.
Well then do a ladder at .050” off and another at .100” off and see if you can find a flat spot where you don’t have pressure issues.
Moving the bullet away from the lands will lower start pressure.
Yea I figure I’ll be reducing the charge on fired brass just really stumped on what’s causing this. The aggravating part is I have a killer load for new brass but it goes too shit on fire-formed brass. Buying new Lapua brass or starting over to work up a new load nowadays ain’t for the faint of heart.
I once got some 185gr Juggs for my 308. I seated them .020” off the lands on top of 42.2grs of Varget in Lapua brass and got heavy bolt lift and blown primers in my TRG-22. Everyone here was stumped. No way this could be such a hot load. But yet it did what it did. Pretty popular combo at the time. Some loads are just temperamental.
My theory is his chamber is tight enough that a little bit of a donut or thick brass is stopping the bullet from releasing clean. The bullet isn’t releasing at the same point or pressure as it does with new brass, probably during the primer ignition when the powder is plasticized. With new brass the bullet probably unseats and jams into the rifling, which makes the entirety of the combustion chamber larger. Once fired brass is either thicker or scuffed (STM) enough that the bullet doesn’t release during the primer strike, which in turn makes the combustion chamber, overall at that point in combustion, smaller. This moves the pressure curve up more quickly and causes problems. This is why @orkan was asking about stainless tumbling media (STM). It has caused issues like this by peening the inside of necks.
Yes, they do. The thickness is the same, but the volume is different. When you swedge .015” thick brass from .400” to .338” it’s no longer .015” thick.
He’s using a factory case. Factory cases are designed so that the shoulder material is the same thickness as neck material. That way when the shoulder flows into the neck, the same thickness is preserved.
If you alter the neck thickness by turning or expanding to another caliber, then doughnuts will form when the shoulder flows into the neck. Absent that, doughnuts don’t form.
I have reloaded Lapua brass in several calibers and have used Lapua brass as a parent case to form other calibers and know how it is constructed and how it behaves when brass flows.
If doughnuts don’t form in 308 and 6.5, then why would they form in 300NM?
If you alter the neck thickness by turning or expanding to another caliber, then doughnuts will form when the shoulder flows into the neck. Absent that, doughnuts don’t form.
I have reloaded Lapua brass in several calibers and have used Lapua brass as a parent case to form other calibers and know how it is constructed and how it behaves when brass flows.
If doughnuts don’t form in 308 and 6.5, then why would they form in 300NM?
This thread seems relevant. 300 NM, pressure issues, donut forming on first firing of factory cases:
www.snipershide.com
Doughnuts on 300 Norma Brass - 1st firing!
I’ve been having nothing but fits over the last 6 months of reloading for my 300 Norma Mag. Everything on the rifle is as it should be - headspace checks out perfect, barrel is a 28” bartlein heavy Palma on a Defiance Deviant. I started off trying new Norma brass with H1000 and 230 Bergers. The...
www.snipershide.com
And it was not resolved. And the OP in this thread is using Lapua brass, not Norma or Hornady. But you would think that Norma would know how to make brass for their own round, LOL.
Taking the new fired out of the equation, is the 1X fired a normal load and velocity?
Sooner or later he'll be out of new brass to compare and will have to work up a load for 1X. Then he'll either find a load that doesnt exhibit pressure or begin to diagnose why hes reaching pressure before desired velocity.
If I was OP I would invest in some more tools to help diagnose and perform QC. Ball and/or a blade mic and some pin guages. Maybe even a bore scope.
Sooner or later he'll be out of new brass to compare and will have to work up a load for 1X. Then he'll either find a load that doesnt exhibit pressure or begin to diagnose why hes reaching pressure before desired velocity.
If I was OP I would invest in some more tools to help diagnose and perform QC. Ball and/or a blade mic and some pin guages. Maybe even a bore scope.
I already explained it. What don’t you get? Even though the brass is the same thickness, the case is a funnel, and when the brass flows into the neck it gets thicker. The volume of brass coming out of the shoulder is greater so the neck gets thicker.
Why don’t they form in .308 or 6.5? Because the torch is loaded with 42 grains of powder not 96. The brass is exposed to less pressure and less heat for less time.
I’m done here. I’ve tried to help, keep us updated OP. @918v you’ve built a whole concept based around your previous experience, and you’re wrong.
Interesting that peoples conviction is so strong given such limited information.
You mentioned there is a slight taper in the neck diameter from the case mouth to the shoulder. Can you measure the loaded neck dia near the shoulder with a micrometer?
we should have frank set up 2-3 forms that have to be filled out when asking a question/help
if there isnt the requisite information filled out, it should not be posted
measurements, specific pictures etc
too much guessing and wives tales thrown around with no data backing any of them up to really help someone
if there isnt the requisite information filled out, it should not be posted
measurements, specific pictures etc
too much guessing and wives tales thrown around with no data backing any of them up to really help someone
Measured with mic.
Fired reloaded rnd - at mouth .3381”, parallel too .100 above neck jct, taper starts .3390 at jct.
New loaded brass - mouth .3397”, has same slight .001” taper starting at same point on neck.
With where my seated bullet sits even if there was a donut at the neck jct it is having zero impact.
Fired reloaded rnd - at mouth .3381”, parallel too .100 above neck jct, taper starts .3390 at jct.
New loaded brass - mouth .3397”, has same slight .001” taper starting at same point on neck.
With where my seated bullet sits even if there was a donut at the neck jct it is having zero impact.
Someone posted a link to a thread where another shooter was having the exact same problem with the exact same case. The problem was the necks getting thicker or donuts. Neck turning solved the problem, but it immediately returned. The necks were too thick, or the chamber was too tight, however a guy wants to think about it.
I read many threads calling the 6x47 Lapua finicky. It made no sense to me, so I had one made anyway. Well, I found out why. The “no turn” neck reamer left only 1 or maybe 2 thousandths of clearance. I know the history of how that happened, not going to recite it now. Incredible round that has been badly burned by a .272” neck.
This idea that .002” clearance is “no turn” needs to die. This is the expressway to these kinds of issues. And while we’re talking about ideas that need to die:
I read many threads calling the 6x47 Lapua finicky. It made no sense to me, so I had one made anyway. Well, I found out why. The “no turn” neck reamer left only 1 or maybe 2 thousandths of clearance. I know the history of how that happened, not going to recite it now. Incredible round that has been badly burned by a .272” neck.
This idea that .002” clearance is “no turn” needs to die. This is the expressway to these kinds of issues. And while we’re talking about ideas that need to die:
There are no woodland pressure gnomes. This kind of pressure only comes from a few areas. The relevant information has been plain for guys that have this t-shirt.
Why not address Frank directly ?... You've now just added to the post count and offered nothing to the OP...
Not arguing that turning wouldn’t help the situation but the new brass that produces no pressure issues is larger dia than the fired brass that is showing pressure.
You can “feel” that bullets seat harder harder in the new sized and annealed brass than resized fired brass also.
You can “feel” that bullets seat harder harder in the new sized and annealed brass than resized fired brass also.
Measured with mic.
Fired reloaded rnd - at mouth .3381”, parallel too .100 above neck jct, taper starts .3390 at jct.
New loaded brass - mouth .3397”, has same slight .001” taper starting at same point on neck.
With where my seated bullet sits even if there was a donut at the neck jct it is having zero impact.
My Creedmoor has .004” neck clearance and zero pressure issues. Incidentally Mr. Jakelly was right about virgin cases being faster than fireformed cases in an AI chamber. I confirmed that over the past few range trips. Not in an improved chamber but a standard chamber with undersized brass. The undersized case didn’t absorb any energy and the FF cases needed a half grain more powder to catch up.
So that leaves donut or neck thickness but DKcampbl did not see a donut and he has the same clearance as I do.
I think that another powder should be tried before cutting on the necks or the chamber.
Different powder idea is worth a shot. You don't see a lot of info for RL50 and its on the slow end for this cartridge. RL33 is a lot more common along with H1000, Retumbo and N570.
DK, one thing you just mentioned was that seating was harder on the 1x brass. My experience was that the unprepped brass bullet combo was already pretty firm. I had to go to a .334 bushing (using expander ball, not mandrel) to duplicate the felt seating force. Still haven't run thru my new brass and the only reason I did this was to see what impacts on performance I could expect with the shoulder pushing out (.014" in my case) on first firing. For me 0x and 1x performed the same. Without going back thru all the pages, what size bushing and mandrel are you using? As soon as my labradar gets back from the shop I'm gonna see if I can duplicate your results.
DK, one thing you just mentioned was that seating was harder on the 1x brass. My experience was that the unprepped brass bullet combo was already pretty firm. I had to go to a .334 bushing (using expander ball, not mandrel) to duplicate the felt seating force. Still haven't run thru my new brass and the only reason I did this was to see what impacts on performance I could expect with the shoulder pushing out (.014" in my case) on first firing. For me 0x and 1x performed the same. Without going back thru all the pages, what size bushing and mandrel are you using? As soon as my labradar gets back from the shop I'm gonna see if I can duplicate your results.
I know I don’t have statistically valid numbers for this, but in my conversations with Sierra and other data providers I found out that some powders are not listed for a particular application not because they didn’t feel like it, or because of case fill issues, or because they are too slow burning necessarily, but because they produce erratic results. Something to do with the shape of the powder column. I dunno how that works. But my understanding is RE50 is a 50BMG powder and maybe it belongs in the 50.
I'm not going to parse through 147 posts just to find out two things.
Do you still not have a headspace gauge?
It there any possibility that any walnut tumbling media got left in the case before the charge was added?
Whatever is happening is occurring between the time the case is tumbled and charged.
Is it possible that the resizing die is pushing the shoulders too far back? (If the case shoulders are short, but the bullet is engaged in the rifling, the firing pin can still ignite the cartridge; and this can result in a pressure spike.)
I've seen wet case interiors cause porous tumbling media to expand and lock together inside the bases of cases, decreasing case capacity. It won't shake out of the case, but it will exit the case on firing. Do unexplained powder granules appear during case charging?
Greg
Do you still not have a headspace gauge?
It there any possibility that any walnut tumbling media got left in the case before the charge was added?
Whatever is happening is occurring between the time the case is tumbled and charged.
Is it possible that the resizing die is pushing the shoulders too far back? (If the case shoulders are short, but the bullet is engaged in the rifling, the firing pin can still ignite the cartridge; and this can result in a pressure spike.)
I've seen wet case interiors cause porous tumbling media to expand and lock together inside the bases of cases, decreasing case capacity. It won't shake out of the case, but it will exit the case on firing. Do unexplained powder granules appear during case charging?
Greg
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-No on the media in cases, all clean.
-I started this project with retumbo and r33. Both ran decent but no spectacular so did a little digging for something else. As y’all know powder was scarce but ran across a bottle of r50 at the LGS so grabbed it. Low and behold it shot fantastic, .250” with the new brass. Still does with the new brass.
That said I have a brand new keg of N570 ready to go but wanted to try and figure out what was up with this r50 and fired brass.
-No don’t have a headspace gauge but only bumping the shoulder back .001”, .020” off the rifling. Don’t think there’s any movement like your talking.
-No oil or moisture on cases.
-.332” neck bushing so could maybe play with that.
-I started this project with retumbo and r33. Both ran decent but no spectacular so did a little digging for something else. As y’all know powder was scarce but ran across a bottle of r50 at the LGS so grabbed it. Low and behold it shot fantastic, .250” with the new brass. Still does with the new brass.
That said I have a brand new keg of N570 ready to go but wanted to try and figure out what was up with this r50 and fired brass.
-No don’t have a headspace gauge but only bumping the shoulder back .001”, .020” off the rifling. Don’t think there’s any movement like your talking.
-No oil or moisture on cases.
-.332” neck bushing so could maybe play with that.
