Primer seating depth questions.

[bobinpa]

I've always used a Lee auto prime hand primer and just seated until they were bottomed out. This past fall my priming tool failed me and before I could figure out what was wrong, I got some erratic ignitions. Meaning, I got pierced primers and misfires like never before. What happened is that for some reason, (probably age and wear) the tool wasn't fully seating the primers.

All of that caused me to look into different/better priming tools and primer seating depths and I've been trying to educate myself on the benefits of primer seating depth. So, for those of you that check primer seating depth, I have some questions before I jump into this further....

1. Are you just seating until they bottom out?
2. Are you seating until bottomed out and then measuring your crush?
3. Are you uniforming primer pockets and seating to a desired depth below the case head?
4. Is there a specific depth below the case head that gives the best ignition/accuracy?
5. Is there a universal depth below the case head that works best "most" of the time?

I appreciate your input!

 

[lawebb21]

In my opinion every primer seater highly relies on brass case rims for indexing and therefor no matter how much you try to dial in primer seating depth i feel you will always have variance. Since coming to that understanding i have given up on trying to seat them uniformly below flush and just started seating until bottomed out and try and not crush after all cases are uniformed with brownells cutter tool. My long range benchrest gun doesnt seem care. Limited experience in this though and im sure someone out there has figured out a better way but i havent found it.

 

[chromatica]

Consensus seems to be that primers usually come to rest .005-.006 inches below the case head. That said I always let them bottom out. I am not worried about a few thou difference because my firing pin protrudes .060 past the bolt face upon firing.

 

[Gabe22BR]

I've always used a Lee auto prime hand primer and just seated until they were bottomed out. This past fall my priming tool failed me and before I could figure out what was wrong, I got some erratic ignitions. Meaning, I got pierced primers TOO HOT OF LOAD and misfires PIECE OF PIERCED PRINER IN PIN HOLE like never before. What happened is that for some reason, (probably age and wear) the tool wasn't fully seating the primers.

All of that caused me to look into different/better priming tools and primer seating depths and I've been trying to educate myself on the benefits of primer seating depth. So, for those of you that check primer seating depth, I have some questions before I jump into this further....

1. Are you just seating until they bottom out? Yep
2. Are you seating until bottomed out and then measuring your crush? You can
3. Are you uniforming primer pockets and seating to a desired depth below the case head? NO
4. Is there a specific depth below the case head that gives the best ignition/accuracy? Below case head
5. Is there a universal depth below the case head that works best "most" of the time? Below case head

I appreciate your input! WELCOME

EXPAND TO SEE ANSWERS

 

[Richard Jones]

I've always used a Lee auto prime hand primer and just seated until they were bottomed out. This past fall my priming tool failed me and before I could figure out what was wrong, I got some erratic ignitions. Meaning, I got pierced primers and misfires like never before. What happened is that for some reason, (probably age and wear) the tool wasn't fully seating the primers.

All of that caused me to look into different/better priming tools and primer seating depths and I've been trying to educate myself on the benefits of primer seating depth. So, for those of you that check primer seating depth, I have some questions before I jump into this further....

1. Are you just seating until they bottom out? No
2. Are you seating until bottomed out and then measuring your crush? Yes
3. Are you uniforming primer pockets and seating to a desired depth below the case head? Yes
4. Is there a specific depth below the case head that gives the best ignition/accuracy? U/k No issues with ignition. Not enough testing to know about accuracy differences.
5. Is there a universal depth below the case head that works best "most" of the time? About .005, not sure that's the best.

I appreciate your input!

Dusty's thread on priming/primers should be a must read.....My 'process' is based on his process/findings.

 

[M-61]

Until they bottom. Must be at least flush when they bottom. Stand them on a square of plate glass to see if they ‘rock’.
I crush nothing.
Works for me and still does after 60+ years.

 

[Fast14riot]

In my opinion every primer seater highly relies on brass case rims for indexing and therefor no matter how much you try to dial in primer seating depth i feel you will always have variance. Since coming to that understanding i have given up on trying to seat them uniformly below flush and just started seating until bottomed out and try and not crush after all cases are uniformed with brownells cutter tool. My long range benchrest gun doesnt seem care. Limited experience in this though and im sure someone out there has figured out a better way but i havent found it.

Any priming tool that locks the case down is not rim thickness dependant. Lee ACP bench primer is actually an excellent priming tool with great repeatability in primer depth, and is not rim dependant.

 

[fkimble@charter.net]

1. Are you just seating until they bottom out?
Yes. uniform primer pockets on precision ammo
2. Are you seating until bottomed out and then measuring your crush?
Bottomed yes measuring no need it can't go any further with out causing damage
3. Are you uniforming primer pockets and seating to a desired depth below the case head?
uniforming yes desired depth no
4. Is there a specific depth below the case head that gives the best ignition/accuracy?
Attempting to seat further than bottomed out can damage primer and affect ignition & accuracy, not seated all the way will cause erratic ignition due to primer seating when firing pin strikes it
5. Is there a universal depth below the case head that works best "most" of the time?
Yes, bottomed out

Frank

 

[epags1]

The OP wrote: .....I've always used a Lee auto prime hand primer and just seated until they were bottomed out. This past fall my priming tool failed me and before I could figure out what was wrong, I got some erratic ignitions. Meaning, I got pierced primers and misfires like never before. What happened is that for some reason, (probably age and wear) the tool wasn't fully seating the primers......

First, I always 'bottom out' my primers, by hand press and by (Dillon) 550 progressive press.
I have never (and I hope that statement stands in the future). Having said that, I had a batch of Winchester primers that were recalled due to the fact they were susceptible to piercing...never happened to me but I returned them anyway.
By the term 'misfires' are you saying failure to fire (FTF) or delayed ignition. FTF normally indicates a week firing pin spring or failure to seat the primer deep enough (and normally it will fire the scecond time since the first firing seats it.

 

[HTSmith]

You have to have one of these- Priming tool or you are just wasting your time. Not. Seat until they bottom. I uniform pockets for target rounds mostly to get a good square edge at the bottom of the pocket.

 

[Uncle Ed]

 

[6.5 forever]

View attachment 1634558

Good picture!

 

[Straightshooter1]

I've always used a Lee auto prime hand primer and just seated until they were bottomed out. This past fall my priming tool failed me and before I could figure out what was wrong, I got some erratic ignitions. Meaning, I got pierced primers and misfires like never before. What happened is that for some reason, (probably age and wear) the tool wasn't fully seating the primers.

All of that caused me to look into different/better priming tools and primer seating depths and I've been trying to educate myself on the benefits of primer seating depth. So, for those of you that check primer seating depth, I have some questions before I jump into this further....

1. Are you just seating until they bottom out?
2. Are you seating until bottomed out and then measuring your crush?
3. Are you uniforming primer pockets and seating to a desired depth below the case head?
4. Is there a specific depth below the case head that gives the best ignition/accuracy?
5. Is there a universal depth below the case head that works best "most" of the time?

I appreciate your input!

In trying to produce as consistent results as possible, I uniform primer pockets and measure the primers I'm putting in to get a good idea how far down the primer should be below flush. Different brands of primers have different cup heights. I allow .003 of crush (the distance the anvil is pushed into the primer cup (see Uncle Ed's illustration above) so that the primers cups are seated to touching the base of the primer pocket. Depending on the particular brand of brass, as some have much deep pockets than others) and the height of the primer, some primers might be seated to flush where others might be .009' deeper than flush. It just depends on the combination. And that's why I measure it all.

For example: my 6.5 PRC Lapua LRP pocket depth is .121" and my Peterson 6.5 PRC LRP pockets are .129". without the anvil compressed, CCI 200's are .126 high, Federal 210's are .128" and Remington 9 1/2's are .132". According to a Rifle Primer Dimension Chart, primer cup heights for CCI LRP is .118", Federal is .117" and Remington is .119". Put the Remington primer into the Lapua case where anvil is compressed properly and you're seated .002" below flush and with the Peterson brass you're .010" below flush where the Federal 210's would be .012" below flush.

The two tools I have that I like best is my Lee ACP priming tool as it doesn't rely on the case rim thickness, which produces very very consistent seating, and I've made it adjustable to get the seating I want for a particular brand of brass and primers. The hand tool I like best is the 21st Century hand priming tool which is adjustable and provides a hard stop for a seating depth, only it is subject to variations of the case rim thickness. Otherwise, the 21st Century tools works really well and its leverage is really easy on my old hands, even if it's not an automatic feed type of priming tool.

I find the best ignition and most consistent results are when the primers are seating where the anvil has been compressed and the cups are touching the bottom of the primer pocket. Worse results come when the primer is crushed too much or when seated too shallow. I've really got some poor ignition when the primer was crushed too much.

Some say they have feel when the primer is seated properly. But in some detailed tests, taking measurements, the "feel" was not really as reliable as the participant thought. But, going by feel can certainly be good enough . . . if you've got a good feel for it.

 

[foxguy]

OP,

I did a search on this site. Here is some previous discussion on Primer seating.
It's a Good Read.

Understanding Primer Seating Depth, How much "crush" is good.

I was getting ready to prime about 1000 pieces of 20 Vartarg, so I can load a bunch up for spring, and making the sage rats fly! But in the past, I have always just seated primers flush with the case head, because that's what my RCBS Universal Priming tool does. I have since purchased a...

forum.accurateshooter.com

 

[K22]

I use a Sinclair Hand Priming Tool seating the primer to "bottom out" by feel. I never had any issues with primer seating and I've loading literally thousands of rifle and pistol rounds with this tool for over 20 years.

This tool is expensive but it's the last priming tool you'll ever buy. Very well designed and made with high quality materials.

 

[PhilC]

I use a Sinclair Hand Priming Tool seating the primer to "bottom out" by feel. I never had any issues with primer seating and I've loading literally thousands of rifle and pistol rounds with this tool for over 20 years.

This tool is expensive but it's the last priming tool you'll ever buy. Very well designed and made with high quality materials.

I've had one since the early 90s, it is my 'go to' priming tool for small quantity loading and use an RCBS bench prime for volume. I also use the Sinclair fixed depth uniformers - every time.

 

[Wild Bill IV]

I've always used a Lee auto prime hand primer and just seated until they were bottomed out. This past fall my priming tool failed me and before I could figure out what was wrong, I got some erratic ignitions. Meaning, I got pierced primers and misfires like never before. What happened is that for some reason, (probably age and wear) the tool wasn't fully seating the primers.

All of that caused me to look into different/better priming tools and primer seating depths and I've been trying to educate myself on the benefits of primer seating depth. So, for those of you that check primer seating depth, I have some questions before I jump into this further....

1. Are you just seating until they bottom out?
2. Are you seating until bottomed out and then measuring your crush?
3. Are you uniforming primer pockets and seating to a desired depth below the case head?
4. Is there a specific depth below the case head that gives the best ignition/accuracy?
5. Is there a universal depth below the case head that works best "most" of the time?

I appreciate your input!

Here is a little advice of getting consistent depth and crush that all long range shooters over look!!

I tried for years to get the primers to be more uniform and finally one day, I decided to do an experiment with amazing results!! At the time, brass was cheap and I was reloading for a 7-08 necking down 308 brass!! I had a whole $5.00 for 20 cases on the line (Federal 308 Match Brass)!! I lightly filed the bases of the 20 vigin cases until it was flat!! While filing the bases, I notice the area around the primer pockets were irregular!! Some showing a depression and others showing protrusion!! My observation concluded that the primer pocket extrusion from the factory caused this irregularity!!!

The cases prior to this filing procedure when using the Sinclair primer pocket uniformer hand tool, the convexed cases measured less than the concaved case primer seating depth!!

The lightly filed, then uniformed cases were more consistent in primer pocket depth!!

Lightly filing the bases is the 1st step in my virgin brass case prep with uni forming the primer pocket being the 2 step!!! An the Target tests showed improved accuracy in the filed cases!!! Also, the case stretch was more uniform from case to case!!!

aim small,
HIT BIG!!!!
BILL

 

[Webster]

View attachment 1634558

On a out of the box primer has anvil legs don't protrude above the cup (like the top pix) how can you get any so called crush of the powder pellet. You cannot move the anvil if it's inside the cup. If you could push on the legs maybe they bend without moving the anvil point downword??? I need to verify that some of my primer brands have anvil legs even with the top of the cup. There are more important things to worry about for accuracy. Some guya are measuring primer dimenions to a 1/2 thou and it's an average factory rifle not intended for real small groups. A little OCD.

 

[Timon]

View attachment 1634558

What “Uncle Ed” posted, which takes me to about 5 thousands below level. I use a PMA hand primer and seat to a stop, then a little bit more to set the anvil.

 

[misser]

flush with base is one thing with new brass ,with used brass the pocket will get loose .its imperative with used brass that the primer does touch the bottom .even pushed tight below flush .i'm going with .006 below flush