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Question re Seating Primers

South Pender

First, my apologies if this has been already thoroughly dealt with.

I've just started reloading for a new-to-me Sako repeater in 6 PPC. I primed the new cases today, and found myself wondering just how critical primer seating-depth is in the overall accuracy equation. I have the stainless steel Sinclair priming tool, which is a nicely-made instrument. Seating the primers was sort of spongy, and I refrained from squeezing hard on the tool, stopping just when I detected a little resistance. I checked the primed cases, and with all of them, the bottom of the primer was a little beneath the case head.

However, I could have driven them deeper. So my question is how much difference in accuracy performance would this have made? As things stand, the primers I seated will differ a little in depth in the primer pocket from one round to another because of the subjectivity in feeling where to stop with the arm of the tool.

Is there some consensus on this issue?

Thanks in advance for any insights you guys can provide on this.
 
Proper seating of the primer is about the most important element of reloading. It is necessary to seat the primer so that the anvil legs touch the bottom of the primer pocket & then the primer cup is moved forward a couple of thousandths of an inch so that the anvil & the priming material cake are in contact for optimum consistent ignition of the powder.

Run them in short (like you feel you have) will necessitate some of the firing pin's force to be used to finally seat the primer before it has an opportunity to light the powder & that can lead to irregular ignition round to round, hang fires or failure to fire.

Sounds like you could have a new skill to learn.
 
In my experience, soft seating primers can lead to ignition issues. Unless your using a measuring primer tool (such as a K&M) I suggest to crush all primers to full stroke of your Sinclair tool.
Donovan
 
Well, I've seated thousands of primers over the years, but this is my first time with the Sinclair tool. It has a lot of mechanical advantage.

I suppose it goes without saying, that seating primers with too much force is bad too--really crushing them into the pocket. Looks as if I'll have to learn the feel of this tool.
 
JohnKielly is right, and you will never get there by feel.
The only direct way to seat to target crush value is by measure. The easiest existing tool, made just for this, is the indicated K&M primer seater.
A lot of folks would imply that they never paid attention to it and all the primers go off. But with hunting capacity cartridges, my results changed with different crush for Feds -vs- CCIs -vs- Wins. I set Wins and Feds at 2thou crush & CCIs at 5thou crush. If I change that, given my load development, groups would open.
 
Ditto @JohnKielly . When all of your primer pockets are uniformed before priming, you should get a very consistent feel with a good priming tool. This will also allow an adjustable tool to seat each primer exactly in the same place relative to the bottom of the primer pocket. If you're loading mixed .223 range pickups for plinking, the feel can be all over the map.
 
I use a Sinclair's tool also, have since the RCBS I started with wore out.

Shoot some of the cases you've started to reload, see how they perform.

Your description of how your Sinclair worked for you is a good start: I typically go just a tad farther than initial resistance when seating primers. Typically this leaves me with 1/4" - 5/16" between the tool's handle and the body at the end of a stroke. I feel resistance starting @ about 3/8" for comparison.

You want the anvil firmly against the pocket bottom, but just short of actually crushing the primer 'biscuit' between it and the cup.

If you find you get a number of misfires out of those PPC cases you'll know you need to squeeze a bit harder on the next ones.
 
Last edited:
I use hand priming tools and I seat a primer till it bottoms out and here is my reasoning. Here are a few factory new primers.
Anvil%20Position.png


Looking close we can see with new primers the anvil actually rises above the rim of the primer cup. Seating a primer till it bottoms out makes sure the anvils are seated all the way. Here a white card is laid on the case heads and the seated primers are about 0.003" to 0.005" below the case heads. If we want to get really sort of OCD we can measure primer height and pocket depth and know where we will end up with the primers fully seated but I just look them over. Hand priming you become accustomed to the feel and you know when they are at the bottom of the pocket.

Primer%20Seat%202.png


Ron
 
Ron Blain said:
If we want to get really sort of OCD we can measure primer height and pocket depth and know where we will end up with the primers fully seated
Click to expand...
This is what the indicated K&M (and no other) does.
Forget misfires for feedback. Far less than misfires can affect you.
 
South Pender said:
First, my apologies if this has been already thoroughly dealt with.

I've just started reloading for a new-to-me Sako repeater in 6 PPC. I primed the new cases today, and found myself wondering just how critical primer seating-depth is in the overall accuracy equation. I have the stainless steel Sinclair priming tool, which is a nicely-made instrument. Seating the primers was sort of spongy, and I refrained from squeezing hard on the tool, stopping just when I detected a little resistance. I checked the primed cases, and with all of them, the bottom of the primer was a little beneath the case head.

However, I could have driven them deeper. So my question is how much difference in accuracy performance would this have made? As things stand, the primers I seated will differ a little in depth in the primer pocket from one round to another because of the subjectivity in feeling where to stop with the arm of the tool.

Is there some consensus on this issue?

Thanks in advance for any insights you guys can provide on this.
Click to expand...

I use a Lee primer seating die in my press . It's somewhat slow since you have to feed the primers one at a time but seems to do a good job and is very inexpensive and I can easily feel the pressure needed when seating them. The depth is adjusted by the position of the die. (An old picture, I no longer have this press). And like Ron said, they should be slightly below the surface. One that is above is a recipe for disaster.
press.jpg
 
One of my old standby priming tools is this RCBS bench mount on which I can prime using one primer at a time. :) While hardly a high speed tool it works just fine and has a nice feel as I prime. Sympathetic detonation is not an issue. While I have a few old progressive presses lying around just about everything I load is done one at a time on an old RCBS Rockchucker or an old Lee O type press. Being retired does have a few merits like I am never in a hurry to get from A to B.

Old%20RCBS%20Bench%20Priming%20Tool.png


I should popint out the pictured tool is a file photo I found online which saved me taking a picture. :) If I ever see another one of these complete at a gun show I will buy it just for spare parts. They really work great.

Ron
 
Ron Blain said:
One of my old standby priming tools is this RCBS bench mount on which I can prime using one primer at a time. :) While hardly a high speed tool it works just fine and has a nice feel as I prime. Sympathetic detonation is not an issue. While I have a few old progressive presses lying around just about everything I load is done one at a time on an old RCBS Rockchucker or an old Lee O type press. Being retired does have a few merits like I am never in a hurry to get from A to B.

Old%20RCBS%20Bench%20Priming%20Tool.png


I should popint out the pictured tool is a file photo I found online which saved me taking a picture. :) If I ever see another one of these complete at a gun show I will buy it just for spare parts. They really work great.

Ron
Click to expand...
Lee came out with a new one. Don't know about the quality but only $26 from Midway. It would save loading each primer by hand. (of course I never drop any!)
Prime.jpg
Now if I can find room to mount it.
 
T-shooter said:
Lee came out with a new one. Don't know about the quality but only $26 from Midway. It would save loading each primer by hand. (of course I never drop any!) Now if I can find room to mount it.
Click to expand...
Bought one of them for the reasons you said. They seat fine, but the primer tray is the worst thing that Lee has ever fielded.
 
Ron Blain said:
One of my old standby priming tools is this RCBS bench mount on which I can prime using one primer at a time. :) While hardly a high speed tool it works just fine and has a nice feel as I prime. Sympathetic detonation is not an issue. While I have a few old progressive presses lying around just about everything I load is done one at a time on an old RCBS Rockchucker or an old Lee O type press. Being retired does have a few merits like I am never in a hurry to get from A to B.

Old%20RCBS%20Bench%20Priming%20Tool.png


I should popint out the pictured tool is a file photo I found online which saved me taking a picture. :) If I ever see another one of these complete at a gun show I will buy it just for spare parts. They really work great.

Ron
Click to expand...

I passed up one up around 1980 for $12. LOL. Believe RCBS bought Lachmiller out on this . Been looking for one forever.
 
T-shooter said:
A nice piece of equipment.
Click to expand...

I have one of these and really like it. Feel?? Not so much in my opinion. However, I use my old standby Lee and then set the Holland's to seat the primer the same depth as the Lee. Then you can seat your primers to the same depth. Like the Holland's a lot.
 
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