Major Factor in Primer Seating Depth Variability
- Thread starter Sniper King 2020
- Start date
We seat to the bottom of the primer pockets and if necessary give it a little crush so the primer is flush with the bottom of the case. To do what you advocate requires primer pocket uniforming and seating short of the bottom which may reduce reliability.
He didn't advocate doing anything at all. He merely correlated primer seating depth error with rim thickness when using priming tools that rely on the rim (shell holders and such).
He's already shown in previous videos that it's very bad to not have the primer seated to the bottom of the pocket. So he's obviously not advocating that you do anything at all that would prohibit that. He's also shown that you can have precision differences with different amounts of crush or below flush seating. However, he's shooting a 6ppc for short range Benchrest.....so it's likely not enough for most people on the Hide to care about.
You have a few choices how to handle this. You can sort cases via rim thickness, or you can use a tool or add on that negates that rim thickness. Such as the Lee primer tool.....or the F Class Products add on for the Primal Rights Seating tool.
Or, you can set up a tool that will seat far below anything you'd need and seat to the bottom of the pocket via feel. Which is probably just fine for anyone on this forum. However, if you don't have something like the FCP Primal Rights add on, you won't be able to consistently crush the primer past the bottom of the pocket.
You could also sort your loaded ammo via the amount below flush the primer is seated.
But, he definitely didn't show anything in this video that would necessitate uniforming pockets and not seating to the bottom.
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If you're using a priming tool that uses a shell holder or similar, you'd have to do this on every single case to ensure consistency. That's the point of the video.
Let's say you measure the thickness of a primer and the depth of the pocket and decide you need the primer to be .005 below flush, then put in in a Primal Rights tool.....you'll have to adjust the tool until you measure your primer .005 below flush. That's all fine.
But on the very next case, if the rim is .001 thicker, your primer will now be .004 below flush and possibly not touching the bottom of the pocket. Even if you made sure to add say .005 crush and go .010 below flush on the first case you measured, you're now going to be .009 below flush instead of .010.
He said the sweet spot is .008” below flush. That requires pp uniforming otherwise you’ll crush the primer.
Does that seating tool not have micrometer or screw adjustment? If loading on range could you not set it "shallow" separate everything that fits your target band, then go again a touch deeper, go separate again then deeper once more, given you are measuring each one anyway I suspect it will be only marginally more labour time in practice and result in less discarded brass.
Dumb follow up question, if components are so available in the US you are happy to discard unfired primers, can you not prime everything at home on the Lee and just throw charges at the range if load tuning?
Would it be practical to, rather than scaling from shell holder component for seating depth on those tools, have an additional shoulder that is pressed to the back of the case that the primer anvil is scaled to to negate the rim thickness?
Dumb follow up question, if components are so available in the US you are happy to discard unfired primers, can you not prime everything at home on the Lee and just throw charges at the range if load tuning?
Would it be practical to, rather than scaling from shell holder component for seating depth on those tools, have an additional shoulder that is pressed to the back of the case that the primer anvil is scaled to to negate the rim thickness?
He's obviously crushing the primers and you can watch his past videos showing statistically significant increases in precision doing so.
He was BR shooter of the year. So, at worst, the crush isn't doing anything helpful, but the crush definitely isn't hurting him.
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There's definitely different ways that are likely more beneficial to most on this forum.
He's a short range BR shooter. So seating them, then checking them after isn't a big deal since he's not trying to get 300 rounds for a match.
Bottom line . Consistency aids in accuracy. What he showed is that the $100 Lee acp press is more consistent than the $600 Primal Rights CPS or any seater using a shell holder. Due to rim thickness.
@Bryan Zolnikov is the Lee referencing off the rod against the inside of the case web, or is it referencing off the 'face' of the case head and the rod is just backing things up?
I would check out F Class John’s vids in this topic. He seems to have inspected this thing a whole lot more than I have. I just got mine a few weeks ago and have been super busy shooting, kids b-day party, Halloween, etc. that I haven’t been able to take the thing apart and see exactly how this thing works. From the info on the Lee website, I see that a rod enters the case mouth and holds the case down which is why there is no effect from variable rim thickness. There are other things I have observed but I want to take this thing apart before I make any assertions regarding how it all actually works.
Yes, all of the info I put out there should be evaluated for relevance to you. If you’re shooting glass bottles from 25 yards with a AR-15 with factory ammo, then I advise you completely ignore me. If you’re serious about precision and want to do all you can to get the most precision possible, then I might have some data that you would be interested in.
FYI, I know I shoot a lot more short range nowadays but I do have a history of shooting PRS and NRL matches and I do regularly shoot long range bench and prone. I’ll be shooting a couple long range bench matches in Nov and Dec this year. I’ll be shooting against the likes of hall of fame shooters like Jeff Locke and Bruce Teel so it’ll be difficult to win because they put Varget in their coffee and I put N133 in mine
I like to call it “anvil compression” but I hear and read the term “crush” a lot. Are we saying the same thing?
Yes, all of the info I put out there should be evaluated for relevance to you. If you’re shooting glass bottles from 25 yards with a AR-15 with factory ammo, then I advise you completely ignore me. If you’re serious about precision and want to do all you can to get the most precision possible, then I might have some data that you would be interested in.
FYI, I know I shoot a lot more short range nowadays but I do have a history of shooting PRS and NRL matches and I do regularly shoot long range bench and prone. I’ll be shooting a couple long range bench matches in Nov and Dec this year. I’ll be shooting against the likes of hall of fame shooters like Jeff Locke and Bruce Teel so it’ll be difficult to win because they put Varget in their coffee and I put N133 in mine
I can't seem to find just the seater for sale anywhere. This is the only thing I can find that you can actually buy. Are they just out right now or did that model get discontinued in favor of this?
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What is this add on? Attached is a pic of what I used in my test. Is that add on in the pic?
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They discontinued it. Might be some laying around somewhere
Oh ok. That's what it looked like. You can still get it in their press with the other stuff I guess but you can't get it without. They still sell parts to it as well so, no biggie. Thanks, always enjoy your stuff
Nope, it is here. https://www.fclassproducts.com/purchase/p_2791123/cps-priming-plate-upgrade
I measured my Alpha brass. I also checked a bunch of primed brass I did on the CPS, no add on. About 80% were at .003 below and everything else was + or - .001. I measured those case rims and they were different. Interesting stuff. I try to get a .002 crush on mine. I have not tested more but I have heard a lot of good shooters say more crush will decrease SD #s. I know when I went to using the CPS and getting a more consistent crush my SDs were cut in half, and that was the only change made on existing load.
I read their stuff but what add on changes how the cps sets the depth off of the case head vs the rim in a shell holder? Is this just a measuring device for the cps or does it change something?
I watched a few videos and it looks like it allows you to watch seating depth as it measures as you seat, so you stop when the gage hits the # you want. Still researching it.
Well, to be honest, unless they come back into production, my interest is pretty limited.
So, for $150 more in addition to the $600-650 I spend on a Primal Rights, I can get more reliable primer seating depths from a $100 Lee priming tool? How much $ do I have to keep spending with “add ons?” This is all starting to sound like a huge snake oil sale to me.
Are you interested in the $600-700 model that produces significant variances in primer seating depths?
I am not trying to sell it to you. I am not buying one either. I will be watching more closely on primer seating. The Alpha OCD brass seems very consistent with primer pocket depth and rim thickness so far but I did a very limited testing today on 23 primed pieces. It is very interesting to see primer seating playing a bigger role with #s and performance than most give credit.
Edit to add the $150 only gets the plate, the gages are more $$
. I'll pass. The Lee design makes a lot of sense too. Wish they still made it.
Edit to add the $150 only gets the plate, the gages are more $$
. I'll pass. The Lee design makes a lot of sense too. Wish they still made it.
I get it. I was not throwing this question at you but rather at the implications of the results and price point of the various tools. Sorry if this came across as directed at you…not my intent. Yes, glad this is all being discussed and data being examined.
Already had that, before the Lee was a 'thing'
I can't say it works appreciably better than the Sinclair that someone gave me as a gift, or the K&M that I used for a very long time before that. Still have them all.
If there's a way to use that Lee priming system with the APP - which I do have - or some other press/setup that *is* available, I'd be game to try that. I'm just not paying scalper prices off eBay for plastic and pot metal - I don't care how good it's supposed to be.
All good. I am curious if the shell holders can be inducing some error too. Are some shell holders more precisely made than others? In today's 23 most were at my .003 # but a few were + or - .001 and 1 was .005. Very small sampling. Primer pocket depths were very tight. Rim thickness was the difference.
Yes, it is made from cheap stuff. The Sinclair is made from quality stuff so for a hand primer, may be worth trying. I have a buddy sending me his now for me to try.
I do notice that some shell holders have smaller tolerances than others. I am able to sort out those that are too thick based on a certain brand of shell holder. Still doesn’t eliminate the effect of rim thickness but can reduce it to a degree.
Somewhere along the line I ended up with the FCP dial indicator add-on for the CPS. Zero instructions, only found one 64 second video of someone priming away with it, no narration or explanation of any kind. I *think* it's supposed to be you seat the primer until you 'feel' it stop, then push on until you get the desired amount of 'crush'. Seemed very flexy in practice to me, and like I said, I was basically guessing at how it was *supposed* to be used. Not entirely sure how that's supposed to negate the effect of the variation from the case rim thickness?
These “feel” methods are very subjective. I have a friend whose “feel” is so severe that when he is measuring BTO on a copper jacket bullet, he digs several thousandths into the jacket whereas I barely make a mark on the jacket when I establish BTO. I guess there is some degree of subjectivity in all of this but I was able to do some testing on the effects of anvil compression that tell me exactly what depth I should seat with a given primer and pocket depth.
Couple other things I just thought of to consider. The primer pins that come with the CPS are not precision ground. We machined ours to a true flat. We also rotate 180 a run ram 2nd time to ensure primers are not canted. So process can also induce error, just a thought. But we will look at a larger batch of 100 pieces of lot matched Alpha OCD and measure it all just to see how much variation we get in seating depth. Would be interesting if you could play with the CPS a bit more and see if these things can be accounted for and reduce the error you had in your test.
Not sure if 'feel' is the right term or not. I'd dial it to where it felt like the CPS was at a hard stop... but then I could push it a little further to get the dial indicator to read what I want. Apparently from bits and pieces I've picked up here and there, that's supposed to be a) the cup bottoming out and b) seating to 'crush' the anvil whatever amount a person decides is optimum.
I realize that different devices have different designs and correspondingly different amounts of mechanical advantage... but the amount I have to lean on the CPS to seat primers feels like a whole lot more work than what ever did using the K&M.
I don’t have a Primal Rights. I had to use a friends who said he spoke with Primal Rights when setting the thing up. I also have received data full of seating depth measurements from the Primal Rights showing considerable variance in seating depths that are not accounted for my pocket depth or primer height.
@Bryan Zolnikov now you've got me curious
How was the CPS mounted to the bench? Sitting on it, or bolted down?
I haven't gone through and tried all this testing on mine - though now I probably will have to
Gotta have something to pass the time as the weather turns colder...
How was the CPS mounted to the bench? Sitting on it, or bolted down?
I haven't gone through and tried all this testing on mine - though now I probably will have to
Gotta have something to pass the time as the weather turns colder...
Attached is a pic. It was bolted to the bench top.@Bryan Zolnikov now you've got me curious
How was the CPS mounted to the bench? Sitting on it, or bolted down?
I haven't gone through and tried all this testing on mine - though now I probably will have to
Gotta have something to pass the time as the weather turns colder...
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Cool. I was wondering, because you'd mentioned that it tended to seat shallow, and that seemed to be a large part of the variation. I know Primal Rights has a video out there that mentions that people tend to have a really hard time seating consistently and/or deep enough if it wasn't bolted down solidly. He also discussed body position relative to the press... which I get what he's saying but it seems a little silly that something that solidly built would have that low of mechanical advantage to where that's actually a concern.
I've seen his videos (and others) where they're seating primers and measuring the resulting seating depth on dedicated tools and apparently getting much better results than what you (and others) have been getting. Seems like there's a disconnect somewhere - some people (not just the guy selling it) seem to get very consistent results, and some get very *in*consistent results. I wonder why that is
I've seen his videos (and others) where they're seating primers and measuring the resulting seating depth on dedicated tools and apparently getting much better results than what you (and others) have been getting. Seems like there's a disconnect somewhere - some people (not just the guy selling it) seem to get very consistent results, and some get very *in*consistent results. I wonder why that is
I have been following this for a while with primers and seating ect and I wondered the same thing. @Bryan Zolnikov , did you say it was norma brass you used? Also I guess number of firings would have some effect too or maybe not? Lapua vs ADG vs Norma will probably provide some variation due to the rim thickness and variation among each lot.Cool. I was wondering, because you'd mentioned that it tended to seat shallow, and that seemed to be a large part of the variation. I know Primal Rights has a video out there that mentions that people tend to have a really hard time seating consistently and/or deep enough if it wasn't bolted down solidly. He also discussed body position relative to the press... which I get what he's saying but it seems a little silly that something that solidly built would have that low of mechanical advantage to where that's actually a concern.
I've seen his videos (and others) where they're seating primers and measuring the resulting seating depth on dedicated tools and apparently getting much better results than what you (and others) have been getting. Seems like there's a disconnect somewhere - some people (not just the guy selling it) seem to get very consistent results, and some get very *in*consistent results. I wonder why that is
That's kind of the issue though right? Anything that uses a shell holder yo keep the case from moving when the primer is pushed in will have the variation of the rim of that lot of brass. Spacing measured off the head of the case seems to be a more consistent way to do though probably a lot harder way to actually hold the brass in place and get good results. It see.s the Lee system with a hold down rod does do it well though so.......
Just my 2 cents
It’s physically impossible for a system using a shell holder to have consistent results unless the rims are consistent.
Anyone who’s showing consistent results with the primal rights (or others using a shell holder), is because the rims are consistent. Be it because they sorted, or their brass is just consistent even though they didn’t sort.
Yea, there can be some user error.
But you can’t escape the fundamental limitations of a piece of equipment.
I love my Primal Rights seater. But you can’t just “use it right” and get seating depth the same if the rims are different.
You either have to sort rims or you have to use an add on like the FCP plate for Primal Rights.
Anyone who’s showing consistent results with the primal rights (or others using a shell holder), is because the rims are consistent. Be it because they sorted, or their brass is just consistent even though they didn’t sort.
Yea, there can be some user error.
But you can’t escape the fundamental limitations of a piece of equipment.
I love my Primal Rights seater. But you can’t just “use it right” and get seating depth the same if the rims are different.
You either have to sort rims or you have to use an add on like the FCP plate for Primal Rights.
Basically uses and indicator. You seat until the primer stops at the bottom of the pocket and then use the indicator to get a consistent crush past the stopping point.
There are obviously some issues that are still possible. Tight pockets might “feel” like the primer bottom out. Or the depth of pocket varies.
But the CPS has quite a bit of leverage, so shouldn’t be too bad on friction being an issue. It does get rid of the rim consistency issue though.
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I think it’s the same thing. I’m sure you could go too far and “crush” the anvil into the primer material.
I personally just go to flush and then set the CPS for .005 under and go to town for PRS ammo. As the .005 should account for rim thickness. And for PRS, none of these small details like anvil compression will be the reason you lose a match.
When I need better ammo for other types of competition (or when selling ammo that is marketed as extremely high quality, then the primer plate above is used, and ammo is checked after for consistency).
Yes, I know a person who made a rim thickness gauge and measure rim thickness before seating with the PR. Makes sense to get consistent depths.
Glad there is something out there for the PR users to correct this potential error. Comes at a cost though.Basically uses and indicator. You seat until the primer stops at the bottom of the pocket and then use the indicator to get a consistent crush past the stopping point.
There are obviously some issues that are still possible. Tight pockets might “feel” like the primer bottom out. Or the depth of pocket varies.
But the CPS has quite a bit of leverage, so shouldn’t be too bad on friction being an issue. It does get rid of the rim consistency issue though.
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Of course Greg and some others are going to insist someone isn’t using the product correctly.
But limitations are limitations. I didn’t realize it wasn’t common knowledge that shell holder setups are slaves to rim thickness by default.
The only setting tool I've ever seen that uses the bottom of the case as a datum is the M2 Precision fore 50 cases.
Yes, agree. Having good dope, stable platform, getting on target, and good core body strength are huge factors in PRS type tactical matches. Nitpicking a .001” or two in primer depth isn’t going to make or break it in that type of match. Cool. I miss hearing that steel gong! Just ran into Mark Le who is on the way to the PRS finale so I hope he does well as well as you all here who are competing in the big match!
I wouldn’t say it’s common knowledge which is why I wanted to have data that demonstrated the effect. Hopefully it becomes better known out there in the shooting world…it can be frustrating to have a flier, too much vertical, and/or too much horizontal because your seating depths are variable to a great degree.
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