Primer depth for accuracy

[Mulligan]

My biggest question relates to just how we go about measuring the actual crush amount. Sure, we can uniform pockets and measure the depth below flush, but if the primers have some variation as well...do we measure each primer, both cup and overall, or what? I don't think we can get the full story by measuring how deep from flush.

That is what the K & M priming tool does.
Donavan Moran posted some info on this a while back........ I just haven't found it yet.
If.... and that is a big if, if I remember correctly, his targets proved that sorting primers by weight mattered, and seating with the correct crush mattered. He arrived at the correct crush for each case by using the K & M tool to measure primer height and pocket depth.
I haven't seen Donavan on the forum in a long while.... maybe he will help us out here. @dmoran
CW

 

[gunsandgunsmithing]

That is what the K & M priming tool does.
Donavan Moran posted some info on this a while back........ I just haven't found it yet.
If.... and that is a big if, if I remember correctly, his targets proved that sorting primers by weight mattered, and seating with the correct crush mattered. He arrived at the correct crush for each case by using the K & M tool to measure primer height and pocket depth.
I haven't seen Donavan on the forum in a long while.... maybe he will help us out here. @dmoran
CW

Ok, I need someone to explain to me how it seats to a certain depth but gives the same crush, if the primers are different in height. I'm not arguing, just wanting to know more on how this tool can compensate for differences in the primer height. If seats to a set depth below flush and all pockets are identical..but primers are not, would that not yield varying amounts of crush, dependent on primer height..both the cup and the overall?

For grins, I just measured several primer heights, both for the cup and the overall height, from bottom to on top of the anvil. Most were within a couple of thou both ways, fwiw. I also measured several primed cases to see how consistently I was seating by feel. I correlated directly to actual primer height but they were all withing about .002. Better than I thought they would be actually, as I was expecting more than that. If this holds true, then logically, feel is the only way I know of the compensate for different primers heights well. It might boil down to what I said a few pages back, that some people can feel things while others have to have things better quantified. Just the way we are wired.

 

[Mulligan]

Ok, I need someone to explain to me how it seats to a certain depth but gives the same crush, if the primers are different in height. I'm not arguing, just wanting to know more on how this tool can compensate for differences in the primer height. If seats to a set depth below flush and all pockets are identical..but primers are not, would that not yield varying amounts of crush, dependent on primer height..both the cup and the overall?

For grins, I just measured several primer heights, both for the cup and the overall height, from bottom to on top of the anvil. Most were within a couple of thou both ways, fwiw. I also measured several primed cases to see how consistently I was seating by feel. I correlated directly to actual primer height but they were all withing about .002. Better than I thought they would be actually, as I was expecting more than that. If this holds true, then logically, feel is the only way I know of the compensate for different primers heights well. It might boil down to what I said a few pages back, that some people can feel things while others have to have things better quantified. Just the way we are wired.

Dandy video explaining how the tool works
CW

 

[gunsandgunsmithing]

Dandy video explaining how the tool works
CW

That is a good video. Thanks for sharing it Clay. So, if I understand it right, the tool physically measures each primer and pocket. Seems like a precise but slow way to do it. Is a thou or two worth the effort? Does it show on target. You answered my previous question well, thank you for that. I can see now, how the tool works, I think. Pretty slick, indeed.

 

[Mulligan]

@gunsandgunsmithing Mike, I have been tryin to draft up a way to test primer seating depth for some time now. I just have not figured out a good way to write it up. Identifilying the problem needing solved is the easy part, how to intelligently perform the test is what is kicking my backside. I have acquired an RCBS bench primer seater with the Holland imporvments and a local small arms mfg sent a primal rights seating gizmo over to me to help with the test. I will likely use a dasher barrel in my rail to do the testing. Just need to flesh out the details of the test.

Any thoughts/suggestions from the collective AS brain-trust?
CW

 

[BoydAllen]

@gunsandgunsmithing Mike, I have been tryin to draft up a way to test primer seating depth for some time now. I just have not figured out a good way to write it up. Identifilying the problem needing solved is the easy part, how to intelligently perform the test is what is kicking my backside. I have acquired an RCBS bench primer seater with the Holland imporvments and a local small arms mfg sent a primal rights seating gizmo over to me to help with the test. I will likely use a dasher barrel in my rail to do the testing. Just need to flesh out the details of the test.

Any thoughts/suggestions from the collective AS brain-trust?
CW

Do you think that the differences in primer seating depth will show up on a chronograph? Conditions between the shooter and the target can turn on a dime, and there is no way to detect when this happens. Trickier conditions produce larger groups. Given all of this, it would seem that there are resolution limits that are built into any test, and that the only way around is to have very large samples.

 

[MikeMcCasland]

@gunsandgunsmithing
Any thoughts/suggestions from the collective AS brain-trust?
CW

Just a suggestion, but I'd sort the cases by rim thickness. All primer tools index against the top side of the case rim/shell holder. It will increase your depth consistency.

 

[Mulligan]

Do you think that the differences in primer seating depth will show up on a chronograph? Conditions between the shooter and the target can turn on a dime, and there is no way to detect when this happens. Trickier conditions produce larger groups. Given all of this, it would seem that there are resolution limits that are built into any test, and that the only way around is to have very large samples.

If it doesn’t show up on a chronograph, it likely isn’t there.
The initial test will likely be just that, a simple test with the same brass. If we see anything on the chronograph, then we can stretch it out to see what the target shows. Like I said, i am still fleshing this out.
CW

 

[Mulligan]

Small changes might get lost in the white noise of the chronograph. Intelligent format huh ? A farm boy just shoots a few with increased increments of crush to see if the groups get better or worse.
I suppose that won't do....

Clay' be sure to let us know how it turns out.

Smiles..

Jim, the farm-boy approach is solid. It is the weeding out of some of the variables that takes some pondering. For example, In post 50 above, Mike brings up the differences in extractor grove thickness and a suggestion for dealing with it. You are a smart guy and have run tests like this before. You know when you do a test, there are always more questions than answers. Hopefully we get enough engagement from the collective AS group to plan in some clever ways to reduce the numbers of questions after the test is complete.
CW

 

[Fuj]

I think for most of us, seating by feel is as good as it gets but there are people that just dont do well with anything less than being able to quantify what "feel" means. Nothing wrong with that..just one example of how we arent all wired the same.

I guess "feel" is the key word here. I have the 21st Century and the
Sinclair. I prefer the Sinclair for the feel it gives me.

 

[mikecr]

The problem with taking all this to a standard is that it's such an abstract.
I determined that FEDs liked 2thou crush, and CCIs 4thou, in one cartridge, one powder, 1thou HS, with one gun's striking energies (pin dia, inertia, speed). This may be different as other conditions depart from that as a standard.

I also found out a hard way (a lost contest, spent a lot of time testing and tearing things apart at the range to find out why), If your gun is doing everything right, but the grouping isn't good enough: Test your striking.
Seat chosen primers(pick one) to a standard(as measured), and adjust pin fall (as measured) at the bolt face.
Shoot groups with each adjustment.
You may see grouping open-close-open like I did. And you might find improvement that you never would have found if not for this testing.
Now you should lock that in & log it, but it's just for that primer, that load, that gun.
The numbers are meaningless for somebody else.

Then there is more than pin fall. There is the spring, pin mass, pin diameter, and the trigger (if dragging release).
It sure would be easier if a primer going bang was all that mattered. But I'm telling you, there is more to it, and the gain or detriment here can be significant.

The K&M works by zeroing out an individual primer height to an individual pocket in a pre-seating operation. This also accounts for rim thickness. Then that primer is seated in that pocket to touching bottom (indicating zero) and adding crush (as seen on indicator). It is slow going until you get good at it.
With this, primer crush is set, and the primer depth to case head varies a bit. If the pockets were uniformed, the primers will always be slightly below case head.

If your priming tool sets primers a set value under case head, it's likely not accounting for rim thickness, nor for primer height variances. Crush would be an abstract there. And even that kind of priming should demonstrate that you can't achieve it consistently by feel.
Is there a machinist in the world who would suggest a final operation amounts to feel? No,, it's always measured.

 

[Mulligan]

The problem with taking all this to a standard is that it's such an abstract.
I determined that FEDs liked 2thou crush, and CCIs 4thou, in one cartridge, one powder, 1thou HS, with one gun's striking energies (pin dia, inertia, speed). This may be different as other conditions depart from that as a standard.

I also found out a hard way (a lost contest, spent a lot of time testing and tearing things apart at the range to find out why), If your gun is doing everything right, but the grouping isn't good enough: Test your striking.
Seat chosen primers(pick one) to a standard(as measured), and adjust pin fall (as measured) at the bolt face.
Shoot groups with each adjustment.
You may see grouping open-close-open like I did. And you might find improvement that you never would have found if not for this testing.
Now you should lock that in & log it, but it's just for that primer, that load, that gun.
The numbers are meaningless for somebody else.

Then there is more than pin fall. There is the spring, pin mass, pin diameter, and the trigger (if dragging release).
It sure would be easier if a primer going bang was all that mattered. But I'm telling you, there is more to it, and the gain or detriment here can be significant.

The K&M works by zeroing out an individual primer height to an individual pocket in a pre-seating operation. This also accounts for rim thickness. Then that primer is seated in that pocket to touching bottom (indicating zero) and adding crush (as seen on indicator). It is slow going until you get good at it.
With this, primer crush is set, and the primer depth to case head varies a bit. If the pockets were uniformed, the primers will always be slightly below case head.

If your priming tool sets primers a set value under case head, it's likely not accounting for rim thickness, nor for primer height variances. Crush would be an abstract there. And even that kind of priming should demonstrate that you can't achieve it consistently by feel.
Is there a machinist in the world who would suggest a final operation amounts to feel? No,, it's always measured.

Good stuff Mike, thanks
CW

 

[Alex Wheeler]

This topic should not blow up like it does every time it comes up. My thoughts are if you have not done any testing first hand then just reserve opinion until you do. The amount of crush does have an effect on group size. Seating by feel actually puts them pretty close to where they want to be which is why we have had luck with it. There are different games, short range and long range and some of the stuff you get away with in short range you cant in long range and vise versa, so comparing the two is pointless. A lot of the guys that are winning and setting records (or coming close) in long range fuss over the primer in a lot of aspects. I have never seen any of them post about it, so do your own testing. In fact a lot of the guys at the top in long range dont post much at all about their testing which they are always doing.

 

[Mulligan]

You are correct Alex, the attached short study on sorting primers by weight caused the same discussions and consternation prior to completion. Afterward, not so much.
CW

 

[Joe Salt]

This topic should not blow up like it does every time it comes up. My thoughts are if you have not done any testing first hand then just reserve opinion until you do. The amount of crush does have an effect on group size. Seating by feel actually puts them pretty close to where they want to be which is why we have had luck with it. There are different games, short range and long range and some of the stuff you get away with in short range you cant in long range and vise versa, so comparing the two is pointless. A lot of the guys that are winning and setting records (or coming close) in long range fuss over the primer in a lot of aspects. I have never seen any of them post about it, so do your own testing. In fact a lot of the guys at the top in long range dont post much at all about their testing which they are always doing.

Ok I'm going to give you my findings, you can take it or leave it. But I number my cases for 1000 yard shooting.
What you are doing with seating primers and crush I've been doing for years. But lately I've had a shot or two go low that have made me want to pull my hair out. And my conclusion is loose primer pockets, not to the point that you can really feel it when you seat them, but are they on the way out. because when I load them the next time, the one or two that went low, I could feel the difference. So are the loose ones losing pressure that it causes the low shot? I'm going to try some loose ones in my sigher rounds to try a figure that out.
My two cents!

Joe Salt

 

[jimmymac]

This topic should not blow up like it does every time it comes up. My thoughts are if you have not done any testing first hand then just reserve opinion until you do. The amount of crush does have an effect on group size. Seating by feel actually puts them pretty close to where they want to be which is why we have had luck with it. There are different games, short range and long range and some of the stuff you get away with in short range you cant in long range and vise versa, so comparing the two is pointless. A lot of the guys that are winning and setting records (or coming close) in long range fuss over the primer in a lot of aspects. I have never seen any of them post about it, so do your own testing. In fact a lot of the guys at the top in long range dont post much at all about their testing which they are always doing.

I feel like the bolded sentence above says it all. Maybe I'm off base here because I have no long range experience but I feel that without the benefit of seeing bullet holes at long range, obsessive reloading techniques and refinements could be critical to success. In short range, once seating depth and powder charge are sorted out it really is all about reading the conditions more so than obsessing over minutia, especially while reloading on the spot at the match where there is hardly any time between relays. A good wind and mirage reader can overcome some perceived shortcoming at the reloading bench.

 

[RegionRat]

You are correct Alex, the attached short study on sorting primers by weight caused the same discussions and consternation prior to completion. Afterward, not so much.
CW

I'm not sure why the world works this way, but you touched on something that I have found very true, that is, there are always more folks up in the bleachers than down on the field when it comes to these topics.

Like @Mulligan said, there was far more swirl before Clay Fowler's test, than afterward. Seems to be human nature but we could use more folks like Clay...

Being a sling shooter, I can't offer to shoot for these tests. While I do load development from rests, and I varmint hunt from rests, it should be left to someone with higher BR credentials. However, as someone with the IR&D background, I will walk down from the nosebleed seats for a moment and try to pitch in with some observations on the thread.

I will suggest that if a test were run, it would need to combine the findings that Clay's paper points out, as well as a method like the K&M tool with primer pockets that have been uniformed in addition to all the regular guards and pitfalls with respect to sample size and testing methods to avoid confusion.

It would be very easy to draw the wrong conclusion if the sample size were small and by bad luck either the primer batch had issues or the brass was funky.

Clay's work pointed to an effect that was easy to see but only when the tails were selected by screening a whole brick. Joe's work pointed out his hypothesis on loose pockets. It all points to how carefully a test must be constructed to avoid having the results thrown off by bad luck with brass or primer samples.

A few posts back, there was another hypothesis floated that a given gun can have a preference for a given seating parameter. If that is true, it may take more than one gun to determine if these primer seating depth results stick to the wall or not. (My own experience mirrors those theories when I see effects on tuning due to firing pin spring or trigger group changes in heavy varmint guns.)

All of this says the tester has to be an expert operator, and have the tools and supplies to sort out his brass and primers in order to populate a test that either eliminates loose primer pockets and heavy/light primers, or that those are intentionally included as test parameters by being controlled. That is a tall order in these days of shortages, but at least the tools are not rare and there seems to be a few good operators around.

Now to climb back into the bleachers.....

 

[Alex Wheeler]

I feel like the bolded sentence above says it all. Maybe I'm off base here because I have no long range experience but I feel that without the benefit of seeing bullet holes at long range, obsessive reloading techniques and refinements could be critical to success. In short range, once seating depth and powder charge are sorted out it really is all about reading the conditions more so than obsessing over minutia, especially while reloading on the spot at the match where there is hardly any time between relays. A good wind and mirage reader can overcome some perceived shortcoming at the reloading bench.

Ya, just different games. You could put a sea of flags out to 1k and my money would still be on the fast shooter over the picker at that distance. The same methods that we are using to test things like primers are the same methods being used to tune rifles that are breaking current records. I get why some people dont think you can do meaningful testing at 1k, but we do and the results prove that it is not only possible but preferable in my opinion. In my experiance the farther you shoot the more critical everything becomes, tune wise. Even at 600 the powder windows are wider and things like neck tension and primer choice are more forgiving. I have tuned a lot of rifles at mid range that fell apart at 1k and needed retuning at that distance. So just because you see no difference at short or mid range does not mean you wont at 1k or father. But I think most would agree that primer seating is not holding most guys back unless they are already winning.

 

[gunsandgunsmithing]

@gunsandgunsmithing Mike, I have been tryin to draft up a way to test primer seating depth for some time now. I just have not figured out a good way to write it up. Identifilying the problem needing solved is the easy part, how to intelligently perform the test is what is kicking my backside. I have acquired an RCBS bench primer seater with the Holland imporvments and a local small arms mfg sent a primal rights seating gizmo over to me to help with the test. I will likely use a dasher barrel in my rail to do the testing. Just need to flesh out the details of the test.

Any thoughts/suggestions from the collective AS brain-trust?
CW

Just a couple of thoughts...The amount of crush or lack of and primer height etc, is affecting, ultimately, how the primer compound is reacting to the firing pin strike. My point is that the ignition system is a factor as much or maybe more so than the amount of crush and or its consistency. Nothing wrong with all aspects being as close to perfect as possible but what if the ignition system could be designed to make the amount of crush less critical than it already is. I think we will agree that the goal is to have ideal and consistent ignition. So, we have to conclude, what makes that happen. Things like fp tip shape, pin weight, speed, spring weight, lube or dirt in the bolt, upward sear spring drag, headspace consistency, temperature effect on both the primer compound as well as spring tensions, etc.

My point is that maybe there is a reason why, as mentioned in a previous post, that some primers like different crush and that may even change in a different rifle.

The rimfire guys have been debating ignition for years now, with different schools of thought about firing pin design and tip shapes, etc. Calfee preaches proper ignition as the holy grail of rimfire accuracy. Ultimately, we have to ask ourselves why there is an ideal amount of crush and what are the effects, both positive and negative on ignition, and what are ALL the components involved in achieving perfect ignition. Perhaps there is a pin tip shape and other factors that minimize how critical a perfect preload on the primer anvil is, for example. This makes me think of the old Remington Etronix system.

Carry on. I just wanted to unload a few thoughts.

 

[mikecr]

lately I've had a shot or two go low that have made me want to pull my hair out. And my conclusion is loose primer pockets, not to the point that you can really feel it when you seat them, but are they on the way out. because when I load them the next time, the one or two that went low, I could feel the difference. So are the loose ones losing pressure that it causes the low shot?

Here is another perspective about this:
Primer seating is sizing, similar to other sizing that leaves an interference fit.
We add energy to components while doing this, and that energy will seek lowest levels, most at first, and somehow find more relief with time.

So we seat primers, typically for ammo use in the same week. I don't know, I assume most of us reloaders do that. But if seating primers for seasonal ammo that may not be used for months, the original seated conditions often change over that period. Just like neck tension can change over that much time.

The primer cup/pocket act as a spring that actually wiggles the primers outward & off crush (itself a spring condition). This is something I've tested because I do load ammo for seasonal use. The weekend before I head to PA for GH hunting, I reseat primers to deepest in group. This has worked, I think because for THAT ammo, i had picked out primers that measured the same heights, for pockets which are uniformed. I use the same 50 cases year after year, always firing them up to keep reload cycles the same.
I also do not put up with loose primer pockets, and would not use Norma brass if it was free (because of this). The primers move even in tight pockets, but worse in loose pockets.

Sometime in the past, I shot some ammo right before a hunt and hit less than stellar performance. That led me to this notion, and confirmation of it over the years.
Before hunting I also check chambering of each round.

The potential for changing neck tension was handled by bullet pre-seating with a mandrel.
Expanded necks spring back inward, which would continue over time, but bullets will not let this continue.
If you size down necks without expansion, that outward spring back will continue over time, reducing tension over time.