@Varminterror, is there a consensus on how bullet jump affects accuracy/precision. I'd read many years ago that seating the bullet near the lands increases the chance of properly aligning the bullet to the bore. But is bullet seating at .040" increments essentially changing the bullet barrel time enough to affect precision. I was fascinated by the observation that powder charge isn't the driver here. It seems that many start with bullet jump and then fine tune the powder once the best bullet jump has been determined. Talk about flipping load development on its head!
COAL that "jams" the bullet into the lands
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I have read a few articles but not done exhaustive research but believe that the timing is the critical part of the seating depth test.
Varminterror
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I cut this up a bit to fit how my mind processed the subject matter - even though it’s a little backwards of how you asked:
There’s a PRB article flipping a lot of us on our heads right now. For my 25yrs of reloading, I have been taught, have observed, and have subsequently taught others that “charge weight is the big knob, and seating depth is a small knob.” This new info seems to flip that.
I have read the article, but haven’t reconciled it fully yet against my own experiences - admittedly, that is a hot topic for my reading and research interest, following the current book I’m reading. Maybe a year from now I will say the opposite, but personally, I don’t expect it to be so - Far too many times tweaking both of these to believe the roles and ranks will magically change after reading the article and retesting the hypothesis myself. But - I love learning and proving old paradigms invalid, so I’m excited to recreate and stress test the article’s proposals.
Chris Long’s OBT is one that I’ve really struggled with, for many reasons. His science appears sound, but I simply haven’t observed it to hold true - I can develop a load in a long barrel and have it remain forgiving in a shorter barrel, even a specialty pistol. Adding suppressors also influences barrel time, throat erosion does as well... temperature variations, powder lot variations... if we’re talking about a very specific barrel time, then I shouldn’t see the results I see.
I would go as far to say I believe far more in a forgiving charge weight window (not necessarily claiming Dan Newberry as champion here, so don’t misinterpret my statement here) than I do in an optimal barrel time. We might be able to intuit a tangible link between bullet dwell time and the natural Barrel harmonic, but I’m not convinced. So I will rarely ever say “velocity node,” as I’m not convinced the velocity is the driving influence. As a specific example of a counterargument to OBT or velocity nodes; I’ve shared here frequently my disappointment with a Rock Creek barrel two years ago which I would say failed very young. I lost over 100fps before 700 rounds, and lost ~15fps per 100rnds until 1,000rnds and then ~35fps from 1100-1400. Do that math, I was a few hundred feet per second slower at the end than the beginning. I did Satterlee, OCW, and Audette Ladders repeatedly in its life, and my powder charge nodes didn’t move. The correlation between powder and speed slowed down, but the flat spots in the Satterlee curve appeared at the same charge weights, and I saw the same clustering in 600yrd Ladders. I even added over a grain more powder, jumping up a node, and was still slower than when the barrel was new - so why did a charge weight node persist through dramatically changing barrel time and dramatically changing velocity? A touch over 3000fps fell to low 2700’s, and the charge weight node never changed. If OBT is the critical knob, it certainly doesn’t explain that experience. Equally, I’ve taken far too many loads across dramatic barrel length changes - you might recognize a 10.5” barrel has a different barrel time than an 18”, or a 14” barrel different than a 24”. But the node sustains... If OBT is the knob, how is that possible?
So back on point here - There doesn’t seem to remain a consensus, not any longer at least. We all were told secant ogive bullets with flat bases and long bearing surfaces have been the standard of short-range precision (aka, raw precision) for generations. Why? Because the bullets enter the leade consistently, grip the barrel consistently, and establish pressure consistently. Everything we do to bullets to make them more aerodynamic or more forgiving tends to hurt this raw precision - boat tails and tangent ogives, short bearing surfaces, etc. So we’ve chased that standard and tried to discover more and more ways to make the penalty lighter. We might really be there today, such we know how to make ammo and bullets and barrels sufficiently forgiving to close the gap... I can’t say. But I know I can’t claim to shoot small enough to tell the difference, undeniably, that any particular design or load method - including jump - makes an absolutely definitive step change. Not to say it doesn’t matter, but to say I am never surprised to hear someone say they are loading a bullet to a very different jump than I do, and getting the same results.
So I’m resigned to enjoy reading it all, but believing my own eyes when I run through data on my own bench. If I can replicate data easily and definitively, I believe it is definitive. When I can’t, well, I don’t find it sufficiently definitive to totally upturn my apple carts.
There’s a PRB article flipping a lot of us on our heads right now. For my 25yrs of reloading, I have been taught, have observed, and have subsequently taught others that “charge weight is the big knob, and seating depth is a small knob.” This new info seems to flip that.
I have read the article, but haven’t reconciled it fully yet against my own experiences - admittedly, that is a hot topic for my reading and research interest, following the current book I’m reading. Maybe a year from now I will say the opposite, but personally, I don’t expect it to be so - Far too many times tweaking both of these to believe the roles and ranks will magically change after reading the article and retesting the hypothesis myself. But - I love learning and proving old paradigms invalid, so I’m excited to recreate and stress test the article’s proposals.
Chris Long’s OBT is one that I’ve really struggled with, for many reasons. His science appears sound, but I simply haven’t observed it to hold true - I can develop a load in a long barrel and have it remain forgiving in a shorter barrel, even a specialty pistol. Adding suppressors also influences barrel time, throat erosion does as well... temperature variations, powder lot variations... if we’re talking about a very specific barrel time, then I shouldn’t see the results I see.
I would go as far to say I believe far more in a forgiving charge weight window (not necessarily claiming Dan Newberry as champion here, so don’t misinterpret my statement here) than I do in an optimal barrel time. We might be able to intuit a tangible link between bullet dwell time and the natural Barrel harmonic, but I’m not convinced. So I will rarely ever say “velocity node,” as I’m not convinced the velocity is the driving influence. As a specific example of a counterargument to OBT or velocity nodes; I’ve shared here frequently my disappointment with a Rock Creek barrel two years ago which I would say failed very young. I lost over 100fps before 700 rounds, and lost ~15fps per 100rnds until 1,000rnds and then ~35fps from 1100-1400. Do that math, I was a few hundred feet per second slower at the end than the beginning. I did Satterlee, OCW, and Audette Ladders repeatedly in its life, and my powder charge nodes didn’t move. The correlation between powder and speed slowed down, but the flat spots in the Satterlee curve appeared at the same charge weights, and I saw the same clustering in 600yrd Ladders. I even added over a grain more powder, jumping up a node, and was still slower than when the barrel was new - so why did a charge weight node persist through dramatically changing barrel time and dramatically changing velocity? A touch over 3000fps fell to low 2700’s, and the charge weight node never changed. If OBT is the critical knob, it certainly doesn’t explain that experience. Equally, I’ve taken far too many loads across dramatic barrel length changes - you might recognize a 10.5” barrel has a different barrel time than an 18”, or a 14” barrel different than a 24”. But the node sustains... If OBT is the knob, how is that possible?
So back on point here - There doesn’t seem to remain a consensus, not any longer at least. We all were told secant ogive bullets with flat bases and long bearing surfaces have been the standard of short-range precision (aka, raw precision) for generations. Why? Because the bullets enter the leade consistently, grip the barrel consistently, and establish pressure consistently. Everything we do to bullets to make them more aerodynamic or more forgiving tends to hurt this raw precision - boat tails and tangent ogives, short bearing surfaces, etc. So we’ve chased that standard and tried to discover more and more ways to make the penalty lighter. We might really be there today, such we know how to make ammo and bullets and barrels sufficiently forgiving to close the gap... I can’t say. But I know I can’t claim to shoot small enough to tell the difference, undeniably, that any particular design or load method - including jump - makes an absolutely definitive step change. Not to say it doesn’t matter, but to say I am never surprised to hear someone say they are loading a bullet to a very different jump than I do, and getting the same results.
So I’m resigned to enjoy reading it all, but believing my own eyes when I run through data on my own bench. If I can replicate data easily and definitively, I believe it is definitive. When I can’t, well, I don’t find it sufficiently definitive to totally upturn my apple carts.
In Benchrest I seated into the lands with very light neck tension with a tight necked chamber.
I load into the lands to fire form 6 Dasher from 6 BR.
With either one you have to be careful with and work it up seated where you will be in the end, don't decide to jam a load you already worked up not jamming. period, and if you change anything back off and work up again.
I would never jam for hunting where function is paramount, don't care if it gets me a tighter group.
Since starting PRS I have played with seating depths, but have no interest in rounds that are jammed. I did it the first match because I threw it all together in a hurry and hadn't gotten good measurements yet. I did work it up at the seating depth though.
After the first match I used this method to get base to ogive measurements on the three bullets I had and have been at least .010 off the lands for everything. Function is very important, and we have to remove chambered/unfired rounds if we run out of time on a stage, so I don't want to be jammed. I have had no issue getting acceptable loads that way.
Jammed by its self is no guarantee of better accuracy.
I load into the lands to fire form 6 Dasher from 6 BR.
With either one you have to be careful with and work it up seated where you will be in the end, don't decide to jam a load you already worked up not jamming. period, and if you change anything back off and work up again.
I would never jam for hunting where function is paramount, don't care if it gets me a tighter group.
Since starting PRS I have played with seating depths, but have no interest in rounds that are jammed. I did it the first match because I threw it all together in a hurry and hadn't gotten good measurements yet. I did work it up at the seating depth though.
After the first match I used this method to get base to ogive measurements on the three bullets I had and have been at least .010 off the lands for everything. Function is very important, and we have to remove chambered/unfired rounds if we run out of time on a stage, so I don't want to be jammed. I have had no issue getting acceptable loads that way.
Jammed by its self is no guarantee of better accuracy.
@Walkalong, I've started using Alex Wheeler's method too. The Mark Gordon method doesn't account for the location of the bolt face so I don't know how it's considered to be accurate.
Yes, I saw Mark's video and found it interesting. And you are right, there has to be .001 or so (+/-) variance vs Wheeler's video.
But I never try to get it to the nearest .001, too many variables. I got it to where I knew I was within a .005 spread. My last 6 Dasher load was ".010 to .015 off the lands" as I recorded it.
But I never try to get it to the nearest .001, too many variables. I got it to where I knew I was within a .005 spread. My last 6 Dasher load was ".010 to .015 off the lands" as I recorded it.
That's what I love about this profession/sport/hobby ... I'm always learning. I knew from the get go that the Barnes 175gr LRX bullet would be off the lands, but after reading the linked articles and reading some of the responses here I'm interested in doing more experimenting with the load described above. Perhaps I'll stay with the 44.1gr charge but seat the bullet .040", .080" and .120" off the lands to see what I get. Maybe I'll drop the charge a bit for the test to avoid over pressure. I'll most likely start working up the 175gr LRX load and then revisit the 178gr A-MAX load since I have a good shooting load already.
The other appealing aspect of a big jump is that you don't need to be +/- .0005" on the location of the lands relative to the bolt face.
The other appealing aspect of a big jump is that you don't need to be +/- .0005" on the location of the lands relative to the bolt face.
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Varminterror
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Same principle in this Mark Gordon method as the Alex Wheeler - using extraction as the indicator. But one requires the barrel to be removed, one doesn’t. No brainer for me.
The Difference between the two - the Gordon method is likely safer - Gordon’s method lives on the distance between the shoulder and the leade, whereas the Wheeler method lives on the distance between the bolt face and the leade.
So Wheeler’s method might run the risk of unintentionally jamming if you use a case too short, but the correct COAL. Gordon’s method runs the risk of excessive jump if you use a short shouldered case. If we pretend our case headspace lengths are consistent and ideal in both methods, then the result should be exactly the same, and the consistency of measurement by either method would be based on how well calibrated are your fingernail or finger. I know pulling my FPA is a lot easier for me than pulling my barrel, so I know which method I’m going to keep using.
Varminterror said:
But with the Gordon method who knows where the bolt face is! It doesn't help me to have a measurement from the datum on the case shoulder to the leade since I have no way of reproducing that measurement. I prefer the Wheeler method since as you say, no need to remove the barrel, and the measurement is from the bolt face to the leade which is what I'm measuring with a caliper and appropriate tool to set up my handloads. Just my opinion which is always subject to change as new evidence presents itself.
I used the Stoney Point tool with modified cases for years but there's inherent error if your chamber doesn't have the same headspace as the modified case which is supposedly SAAMI minimum.
I have to say, when I started this thread I had no idea that it would have such an impact on my approach to reloading. This has been a good learning thread for me. Thanks to everyone for your participation.
I do, within a .002 spread. But an excellent point.
I am assuming the people that will use this method will have all that covered, because they will be as careful with everything else as they are getting that measurement, but another excellent point.
Another point is how we go from that measurement. As I got my "setting' for the seater when doing the wheeler method I logged both the number I got with my Sinclair base to ogive tool as well as the seater setting that gave me less than .005 jump. (I moved in .005 increments, not .001, as noted above).
So, after that I experimented a bit with seating deeper and measuring with the Sinclair tool again. I found that another .005 movement on the micrometer top did not always coincide with a .005 difference in the number from the tool. Well crap, which one is right? And we think we are holding the nearest .001 with every round when seating? I don't.
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@Walkalong - for the record, I do too.
Nature Boy
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Whether we are holding +/- 0.001” is one thing, whether we are good enough to constantly measure it is another.
This is why I’m not sorting bullets for base to ogive variation. My measurement technique and equipment isn’t reliable enough to trust the data
AJC1
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There are more than a few that they control things like shoulder bump to .0005 so I just accept I'm not at that level nor have the tools to measure those tolerances. If I can measure and hold tolerances to .002 on seating depth I'm happy happy.
I would agree, I am not going to go to that much trouble, although when my annealer gets here it might tighten up the sizing spread some, we'll see.
But right now I am happy with shoulder position from base to datum being not varying over .001,
as noted in my log....
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I'll have to respectfully disagree here. It is VERY unlikely any hobbyist is holding tool steel tolerances in the tenths on a brass tube squeezed into a die using a series of linkages actuated by a human and measured with uncalibrated calipers.
I'll be willing to put money on that.
I also don't believe it's necessary.
Me either, didn't hold that on my 6 PPC cases in my Bench gun. The nearest .001 isn't to hard to measure consistently, .0001 is.
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I dont think its realistic either but I'm not claiming I'm doing it. My claim was happy with .002. I'm sure they are using the best tools because they measure powder down to the grain on scales that cost a grand. I dont care to dispute the claims of people with world records but you can. I'll PM you the site if your intrested.
I neck size always and bump the case shoulder as necessary and have been doing this with Redding dies for at least 12 years. About 10 years ago in an attempt to better control shoulder bump which gets near impossible to control as the case hardens, I bought some sets of Redding's Competition Shell Holders but I've never had much success with them but that's probably due to an error on my part. Annealing can certainly make a huge difference and I was surprised to hear Scott Satterlee's comment in a podcast that he doesn't care if he neck sizes before or after annealing.
https://moderndaysniper.podbean.com/e/mds-episode-0014-scott-satterlee-and-hand-loading/
I would say at my very best with a case that's appropriately soft I can keep the shoulder to +/- .001" and maybe slightly tighter. What I've never taken the time to figure out is how much bump is ideal. I try to move the case shoulder .002" off the datum in the chamber so there's no resistance to chambering a round but also so that the case doesn't have to grow too much before it stops. When I worked at Remington developing ammunition, we tried to keep all shoulders at SAAMI - .005" to avoid interference issues in any chamber. I've noticed that a lot of factory ammunition and Lapua brass appears to be very close to SAAMI minimum, with some being over SAAMI minimum.
https://moderndaysniper.podbean.com/e/mds-episode-0014-scott-satterlee-and-hand-loading/
I would say at my very best with a case that's appropriately soft I can keep the shoulder to +/- .001" and maybe slightly tighter. What I've never taken the time to figure out is how much bump is ideal. I try to move the case shoulder .002" off the datum in the chamber so there's no resistance to chambering a round but also so that the case doesn't have to grow too much before it stops. When I worked at Remington developing ammunition, we tried to keep all shoulders at SAAMI - .005" to avoid interference issues in any chamber. I've noticed that a lot of factory ammunition and Lapua brass appears to be very close to SAAMI minimum, with some being over SAAMI minimum.
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It's not my intention to dispute anyone's success in the shooting sports, especially world record holders or start an internet argument.
But we are talking about something specific here as it relates to our ability to reliably hold very tight tolerances and measure those dimensions with confidence.
Without getting too far into the weeds, I have some experience in this area. My professional career is in manufacturing. I’m responsible for factories that make products demanding six sigma level quality utilizing validated processes. I'm also responsible for tool and die makers who make the tooling used in those validated process and a metrology lab that calibrates hundreds of measurement devices to insure we meet very strict standards. In other words, it is a very data driven world.
With that said, and in my opinion, it would be nearly impossible to hold a dimension of 0.0005 given the variations in the process.
And if someone claims that they do it doesn’t hurt my feelings one bit
AJC1
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To be honest I scoffed as well because a garage or reloading room is far from a metrology controlled lab environment. The exact number was shoulder bump of .0015 which indicates control of that last digit.It's not my intention to dispute anyone's success in the shooting sports, especially world record holders or start an internet argument.
But we are talking about something specific here as it relates to our ability to reliably hold very tight tolerances and measure those dimensions with confidence.
Without getting too far into the weeds, I have some experience in this area. My professional career is in manufacturing. I’m responsible for factories that make products demanding six sigma level quality utilizing validated processes. I'm also responsible for tool and die makers who make the tooling used in those validated process and a metrology lab that calibrates hundreds of measurement devices to insure we meet very strict standards. In other words, it is a very data driven world.
With that said, and in my opinion, it would be nearly impossible to hold a dimension of 0.0005 given the variations in the process.
And if someone claims that they do it doesn’t hurt my feelings one bit
Sounds more like they keep it under .002 spread, which is certainly feasible. If one is willing to adjust sizers/sort sized brass, sure it could be kept to the nearest .001 +/- 2 or 3 ten thousandths. And again, I am sure annealing would help that, because then theoretically all the brass would react the same to the sizer. I'll be finding that out soon, as I will now be annealing before every sizing, instead of as needed, which is usually after three firings, even though after 2 would have been better, and every time better than that. Annealing by hand doesn't encourage doing it every time.
Walkalong said:
Which annealer did you order/receive? This isn't a big revelation, but I found once I started annealing I was much better able control neck size and shoulder bump. My annealing system is ok (Annie), but could be better if it were automated.
Varminterror
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Have you looked into coupling a Giraud case feeder with your Annie?
Varminterror said:
I had been checking on that option fairly regularly but sort of gave up since I didn't see much in the way of progress being made. I just looked on their website and spoke with a nice woman there and they're no longer supporting the Fluxeon "Annie" products. Supposedly they're developing their own induction annealing/feeding system but I was informed that the project is on the back burner. Oh well ...
That could be a good thing, too bad it's on the back burner.
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