Primer seating depth and primer seating force

[taylorw]

If I'm understanding correctly, the theory is that seating depth can be tuned almost the same as powder charge, but the primer seating depth affects where the powder will tune as well--just like seating depth can affect powder charge.

I have never used a fancy primer seater with the ability to control depth, but it does have my curiosity. If I start with a given primer seating depth THEN tune powder charge, will I ultimately have a more consistent load? Or if I come up with a powder charge with a hand primer, how much gain can I then get tuning primer seating depth? What about bullet seating depth? Will one ultimately end up with a similar load no matter which between powder charge/bullet depth/primer depth is tuned first? Which one should one start with?

Or does primer seating not matter at all in the real world so long as they are consistent and contacting the bottom of the primer pocket?

I’m not sure to be honest. Think it’s interconnected, where one thing will affect all. I did this testing with known loads. Just changed the primer seating depth..

I was kinda debating wether or not I should post this, since it’s a little controversial. The reason I did was bcs of the common results between my 3 rifles and what I believe mikecr reported, with the CCI primers.

SPJ does make a good point.. All of these rifles, that I did this testing with, shot well before measuring so I think you either tune to your starting primer seating depth, by feel, or you end up close to the correct depth, just seating by feel.
Either way, it’s a lot of work and kinda takes the fun out of it for me. Lol

 

[rogina]

Lots of longe range records were set this year by one shooter setting primers by feel only.

That is known as single point data.

 

[mikecr]

That is known as single point data.

It dismisses resolution of all those who seated primers by feel, and shot like holy crap, leading to no records. That is, unless it was meant to suggest that seating by feel is somehow better than actual measure.
Or, that a blind squirrel can get a nut regardless of primer seating.

taylorw, I do not believe that correct seating for a given manufacture of primer is tuning.
Instead, it seems clearing of a detrimental condition otherwise.
I see setting of tested and proven optimum crush for a given primer as an appropriate prerequisite action.

Many things we do are not tuning -even while nearly everything affects tune in some regard.

 

[PigButtons]

I'm not a Rocket Surgeon so I'm easily confused, please bear with me. If anyone is still watching this thread, can you explain to me what is being "crushed" in this seating process that moves the external surface of the primer cup .00?" past where the rim of the cup bottoms out in the primer pocket. It's not like the primer cup walls accordion to shrink so the only thing I can imagine is that the round edges at the base of the cup flatten down. But then how do you distinguish early pressure signs from primer seating crush? And if you are moving the cup surface away from the bolt face doesn't that reduce firing pin depth into the cup, increase lock time, and possibly deform the compound inside the primer?

I have no dog in this hunt because I don't shoot long range, and I've learned a lot reading all 8 pages so far, ( both from a technical standpoint and a social interaction standpoint ), and it is just curiosity that makes me ask. So if you think it worth your while, I'd just like to know.

 

[RegionRat]

@PigButtons there are different primer designs floating around, so keep that in mind as you go.

When you see most primers, the anvil sticks up above the cup. When the dimension of the primer is gently measured at first, that value is used in the math with the depth of the primer pocket.

When the reloader seats the primer at a depth setting that forces the original length of the primer to be less than that original length, we call that compressed or "crushed".

You see the issue clearly, that there will be a limit to that crush before things go wonky.

 

[mikecr]

There is a priming compound(a 'pill') between the cup face and internal anvil.
Primer 'sensitizing' is also coined 'Crush'.
A proper crush establishes a sensitized condition, allowing for most consistent primer function.
Excess crush can distort/damage the pill, to the detriment of consistent primer function.
Under or no crush leads to varying primer travel, and varying striking energy, to ignite pills. Similar to a headspace issue, which also affects primer firing.

 

[PigButtons]

There is a priming compound(a 'pill') between the cup face and internal anvil.
Primer 'sensitizing' is also coined 'Crush'.
A proper crush establishes a sensitized condition, allowing for most consistent primer function.
Excess crush can distort/damage the pill, to the detriment of consistent primer function.
Under or no crush leads to varying primer travel, and varying striking energy, to ignite pills. Similar to a headspace issue, which also affects primer firing.

@PigButtons there are different primer designs floating around, so keep that in mind as you go.

When you see most primers, the anvil sticks up above the cup. When the dimension of the primer is gently measured at first, that value is used in the math with the depth of the primer pocket.

When the reloader seats the primer at a depth setting that forces the original length of the primer to be less than that original length, we call that compressed or "crushed".

You see the issue clearly, that there will be a limit to that crush before things go wonky.

Thanks to both of you for your time and insight. I knew I was missing something and now I can let it go in my mind. My primers will be thoroughly inspected as up to now I have assumed they were a fixed entity over which there was no control. Silly me.

 

[mikecr]

SPJ, I don't think it will hurt to test it, and that there is potential to find even more from your system.

 

[rogina]

Very true but sometimes less equals more, all I’m saying is that even though I plan on doing some testing on ignition this year and being able to assign a number to depth and crush to hopefully trim my aggs a bit. It may be a fools errand

I am doing the same, starting today if the wind lets up a little.

 

[Webster]

I would say that you seem to be one of those that have a predilection for making things more complicated than they have to be. People who shoot better than you or I will ever shoot simply squeeze the handle until they feel it firmly stop. Why are you trying to make a simple thing complicated? Do you own a set of wind flags or tune loading at the range?

The discussion will never end. 99% of the guys on this website that ask about measuring bullets, weighing and sorting things will never shoot competitive scores. Tony Boyer said in an interview that he got tired of giving BR lessons because he had to keep telling guys that their equipment wasn’t good enough to be competitive. I would think it was expensive equipment. He also said that many of the guys on a firing line had good equipment but they didn’t have the ability to win. I also read that someone once said that many guys buy expensive equipment and after a couple of years of competing, they realize they cannot keep up with the better shooters. It’s kind of like any sport, you cannot buy an expensive tennis racket or golf club and expect to do well on the pro circuit just because you practice a lot. Every sport has special skills. Did you ever watch a pro basketball player bowl. They are extremely good athletes but they look awkward.

 

[mikecr]

99% of the guys on this website that ask about measuring bullets, weighing and sorting things will never shoot competitive scores.

My guess is that 99.999% of us do not shoot point blank BR.
Did your god TB have any advice for 600-1kyd competition?
Maybe hitting a LR mark with single cold bore hunting shots?

If not, if he hadn't replaced all thinking there, then the discussions will likely continue.

 

[dr foxtail]

What he told me was they want the anvil pushed up into the cup to the point where the bottoms of the feet are even with the edge of the cup. Take a look at a primer. That is quite a bit deeper than just having the feet touch the bottom of the pocket.

I know, it's an old thread.
To me that means the cup is touching the bottom of the pocket, no? ie, full crush. ie, so the primer can't move forward when struck by the firing pin?

 

[mikecr]

To me that means the cup is touching the bottom of the pocket, no? ie, full crush. ie, so the primer can't move forward when struck by the firing pin?

Pretty sure that would be way too much. You'd be smashing the primer to a point where it could not be smashed anymore. No fancy tool or feel or measure needed for that much.
When I seat primers too deep, I get flyers. But that's not with a 6PPC..

 

[BoydAllen]

I know, it's an old thread.
To me that means the cup is touching the bottom of the pocket, no? ie, full crush. ie, so the primer can't move forward when struck by the firing pin?

The cup just touches the bottom of the pocket. If you do what people seem to have not done for a while and seat an remove a few primers as a test, seating with a hand tool. Obviously care is called for when I removed the seated primer. With about all the force that I can come up with with one big hand, the cup was just barely there. Duplicate my experiment and come back and tell us what you find. To see the positions of the bottoms of the anvil feet the easiest way is to put the seated and removed primers between the wide part of the jaws of your calipers and examine the primer with a loupe.

 

[dr foxtail]

Why is it wrong? In his two tests he found .009" crush to be the best with his combination which aligns closely to SAAMI maximum depth which is .008" (which would have resulted in ~.008" crush with his pockets and primers). He was using primer pockets and primers within SAAMI specs which suggests SAAMI was on to something in their recommendation. I previously posted a screenshot of his drawing with his dimensions he was working with and I'll post it again here.

View attachment 1303051

That is only the case because in his example the primer pocket is the same depth as the total thickness of the primer (cup and anvil).
The current brass I'm working with has pocket depth of .124 and the 450 primers I have are .117 total and .112 cup only. That means I need to seat my primers .007 below flush just to get the feet to touch the bottom of the pocket and .008 below would result in only a .001 crush with a maximum crush of .005 when the cup bottomed out in the pocket. In addition the bottom of the primer pocket is narrower than the opening by .004 meaning I really have to push them hard to even a little crush so hard that it is deforming the exposed bottom of the cup. There is a little circular protrusion. See picture.
Based on the picture from the SAAMI book earlier in the thread, the thickest allowable primer doesn't fit in the shallowness allowable pocket without a .009 crush and at that rate it is only flush. Even the deepest allowable pocket requires a .003 crush to be flush.
I know that's a lot for an old thread but I just got this CPS seater and I'm trying to figure things out.
Thanks for putting up with me.

 

[dr foxtail]

Pretty sure that would be way too much. You'd be smashing the primer to a point where it could not be smashed anymore. No fancy tool or feel or measure needed for that much.
When I seat primers too deep, I get flyers. But that's not with a 6PPC..

I agree it's too much but
1) apparently that's how Federal says to seat them per an earlier entry in the thread which is what prompted my comment and
2) that's exactly what he is showing in his drawing on the right side, the 450 primers, the cup is bottomed out in the pocket.

 

[Sixgun]

K&M Primer Pocket Unforming tool after depriming....Nothing to worry about. It chips out the carbon as it maintains the dimentions so you're not seating primers on a layer of carbon.

 

[BoydAllen]

That is only the case because in his example the primer pocket is the same depth as the total thickness of the primer (cup and anvil).
The current brass I'm working with has pocket depth of .124 and the 450 primers I have are .117 total and .112 cup only. That means I need to seat my primers .007 below flush just to get the feet to touch the bottom of the pocket and .008 below would result in only a .001 crush with a maximum crush of .005 when the cup bottomed out in the pocket. In addition the bottom of the primer pocket is narrower than the opening by .004 meaning I really have to push them hard to even a little crush so hard that it is deforming the exposed bottom of the cup. There is a little circular protrusion. See picture.
Based on the picture from the SAAMI book earlier in the thread, the thickest allowable primer doesn't fit in the shallowness allowable pocket without a .009 crush and at that rate it is only flush. Even the deepest allowable pocket requires a .003 crush to be flush.
I know that's a lot for an old thread but I just got this CPS seater and I'm trying to figure things out.
Thanks for putting up with me.

I don't know if you saw it, but I actually called CCI and asked one of their technicians what they recommend. He told me, in no uncertain terms that they recommend seating so that the bottoms of the anvil feet are flush with the edge of the cup. I suggest that you try different amounts of pressure using your favorite hand tool, seating primers in the same pocket, measuring the resultant depth, and then removing them to look at where the bottoms of the anvil feet are in relation to the edge of the cup. I have done a little of that and in my experience it takes a lot of pressure on a hand tool to achieve their recommended seating. The other think that I noticed was that with a primer seated that way, I could see no evidence of damage to the pellet, or the cup. To be able to see the position of the anvil feet, I trapped the primer in the jaws of my dial calipers and used a 20X loupe.

 

[TylerFromMS]

@BoydAllen Do you feel like the anvil stays in the same place after the primer is removed? This is something I hadn't thought of and sounds interesting. I've been using a good old fashioned outside mic for the primers and a depth mic stuck down through a shellholder for the primer pockets to measure.

I have done a little of that and in my experience it takes a lot of pressure on a hand tool to achieve their recommended seating.

And here we are full circle back to the $600 priming tool

 

[BoydAllen]

@BoydAllen Do you feel like the anvil stays in the same place after the primer is removed? This is something I hadn't thought of and sounds interesting. I've been using a good old fashioned outside mic for the primers and a depth mic stuck down through a shellholder for the primer pockets to measure.


And here we are full circle back to the $600 priming tool

I do. There seems to be a lot of friction between the sides of the anvil feet and the inside of the cup. Play around with some fired primers and I think you may come to the same conclusion. It takes very little force to remove a primer and I believe that I have a sensitive feel. I do not jerk on the handle or rush things. I bring it down until I barely feel the primer, and then slowly remove it. If you do this, be cautious. Wear eye protection. Until I got quite a bit of experience, I would hold up a piece of wood or a thickly folded bath towel between my face and the case. I have never set one off in many years of doing it.
On the $600 dollar priming tool. All of the HOF members and record holders that I know seat by feel. I think that there is a lot of merchandising going on. People want to be told that more complicated and expensive things will shrink their groups when in fact they need to buy a set of flags, tune at the range, and learn how to keep their loads in tune as conditions change, but that is just my opinion.