Primer seat depth

[bench]

How much below flush with the case head do you seat primers?
I built a adjustable screw on my RCBS handle so I could keep them all the same for my AR-15 and it is set at .008 below flush is this a bit to deep for a good bolt gun.

 

[Millsaps75]

To my knowledge you carefully bottom them out at least that's what I do and I've been loading my own for 25 years. If you didn't wouldn't the firing pin have to bottom them out before they ignited?

 

[bench]

Millsaps
I started using an adjustment on my hand primer a few years back when I had some 243wssm brass that had deep primer pockets and I had to make sure I did not set them to deep or would have a fail to fire. They have worked without fail and did not have to throw away a bunch of good brass.So I quessed at the time that the friction fit of the primer to the brass was good enough to hold the primer in place well enough to get them to not bottom out and no more fail to fire problems.If the did move when the pin hit them I wonder how hard they have to be hit to make them ignite.

 

[amlevin]

I had a primer pocket uniformer that was improperly adjusted and I ended up with a large batch of brass with really deep pockets. Lots of misfires.

Recently got a Redding that has no adjustment to slip while using. Any case that doesn't get at least a little "scrape" from the uniformer goes in the recycling bin, new, used, free, I don't care.

As a direct answer to the question here's a statement from Nosler in a "Step by Step Rifle reloading" paper.

As primers are seated to the proper depth, the anvil is pressed slightly deeper into the cup, lightly compressing the primer pellet. This sensitizes or arms the primer so that it will be ignited by the blow of the firing pin. However, primers that are seated too deep are hazardous as the anvil may be pressed into the priming pellet too far making the primer dangerously sensitive. Ideally, primers should be seated approximately .005” below flush with the case head. At this depth, they are sufficiently deep to be safe and sensitized, but are not so deep as to be out of reach of the firing pin.

 

[BoydAllen]

I think that primers should be seated by feel. As far as I am aware, pretty much all of the short range benchrest crowd does it that way. If you need to make adjustments for different primer pocket depths, the stainless 21st Century Shooting tool is set up to do that as easily as changing the setting on a target type scope turret. I have always seated this way, and have never had, or heard of a problem caused by doing so.

 

[amlevin]

I think that primers should be seated by feel. As far as I am aware, pretty much all of the short range benchrest crowd does it that way. If you need to make adjustments for different primer pocket depths, the stainless 21st Century Shooting tool is set up to do that as easily as changing the setting on a target type scope turret. I have always seated this way, and have never had, or heard of a problem caused by doing so.

But what of primer pockets that are too deep?

 

[necchi]

If I had "New" brass that had primer pockets too deep, I wouldn't be messing around trying to compensate, they would be going back to the store or manufacturer for replacement.

If I had used brass that either myself or someone else messed up modifying the pockets I guess I'd have to write it down for experience and move on.

I simply wouldn't use the compromised brass, wouldn't be worth the headache

 

[amlevin]

If I had "New" brass that had primer pockets too deep, I wouldn't be messing around trying to compensate, they would be going back to the store or manufacturer for replacement.

If I had used brass that either myself or someone else messed up modifying the pockets I guess I'd have to write it down for experience and move on.

I simply wouldn't use the compromised brass, wouldn't be worth the headache

Kind of my feeling too, that's why I use the uniforming tool on all brass whether "out of the box/bag" for off the ground at the range.

I've also discovered that I can adjust seating (or as some might also say "crush" depth) with my recently re-engineered Hornady Hand Priming tool.

 

[Webster]

I agree bench rest shooters seat by feel. I don't believe an adjustment stop on a seating tool is the way to go. There is a stack up of tolerances. There is no constant value to hit. Seating by feel puts the anvil legs on the bottom of pocket. If you look at a primer from the side you will see that the anvil legs protrude outside of the cup. When you seat by feel you are pushing the primer in until the anvil legs touch the bottom of the primer pocket. If the legs don't touch the bottom of the pocket the firing pin must push the primer in deeper? I use an old Lee hand seater. The handle position varies when seating by feel when using the same box of primers and cases from the same Lapua blue box. I would think normal firing pin protrusion reach would take care of slight variation in pocket depth. I believe the pockets are created during the extrusion process, not machined. The walls are smooth without cutting tool marks. I find it hard to believe some cases have abnormally deep pockets. If they did I would buy a different brand.

 

[Leaddog]

The 21st Century primer tool is the best I have ever used. None better. Load them one at a time and never worry about a tray full of primers blowing up in your face.

 

[STS]

I remember reading some research from a primer manufacturer many years ago that stated the correct way to seat a primer was the have the anvil in contact with the bottom of the primer pocket, and then to have a few thousands of "preload" or crush on the primer for peak performance. Obviously seating to a specific depth below the case head will not give you this condition unless is is by accident.

 

[WyleWD]

The 21st Century primer tool is the best I have ever used. None better. Load them one at a time and never worry about a tray full of primers blowing up in your face.

+1 on Charlie's post. And this tool can be easily adjusted to get consistent seating depth, including a slight deeper than flush with the case depth. By far the best tool I've ever used. And GREAT people to work with if you have a question. WD

 

[jlow]

If you are not seating the primer so that it touches the bottom of the pocket, then you are setting yourself up for a misfire. At least in pistol reloading seating a primer high will cause some of that energy from the firing pin to be used to push the primer in instead of cratering and firing the primer and you will get that light primer strike - have seen this happen many times. In the same manner, a case with too deep pockets will allow the firing pin to push the primer in instead of firing it.

 

[eww1350]

Seat them flush with a priming tool that is adjustable..if your primer pockets are tight you will not have mis-fires...a rifle with good ignition will set off the primer without pushing it to the bottom of the pocket...

I shoot short range BR and use this method successfully...no mis-fires period...


Eddie in Texas

 

[jlow]

I guess since you are shooting short range BR, my guess is you are always shooting light loads and so your primer pockets stays tight, but that seems to me to be more of an exception than a rule for most people?

 

[STS]

I guess since you are shooting short range BR, my guess is you are always shooting light loads and so your primer pockets stays tight, but that seems to me to be more of an exception than a rule for most people?

It would not be a correct assumption that BR shooters shoot relatively light loads. In fact BR shooters probably operate at the highest chamber pressures of any shooting discipline.

 

[BoydAllen]

I have a suggestion. Don't take our word for it. Get a hold of the top ten shooters in the Benchrest hall of fame, and ask them what they think about seating primers so that they are flush with the case head. I'll give you a dollar for every one that thinks that it is the way to go, and you give me one for every one that doesn't, and fer criminy sakes, don't you think that the people who make primers know how best to seat them. You could probably load for a match with Lee dippers, but that does not make it the best way.
End of rant.

 

[jlow]

I guess since you are shooting short range BR, my guess is you are always shooting light loads and so your primer pockets stays tight, but that seems to me to be more of an exception than a rule for most people?

It would not be a correct assumption that BR shooters shoot relatively light loads. In fact BR shooters probably operate at the highest chamber pressures of any shooting discipline.

OK, for the sake of discussion, let’s say BR shooter (short range) operates at the highest chamber pressure, how do you keep your primer pockets tight enough not to have mis-fires? I wish I could go with highest chamber pressure and keep all my pockets tight, but it’s just not possible at least for me.

To me the problem is if you don’t absolutely know how tight your pockets are i.e. they are tight enough to grip the primers so that they will 100% not move when that firing pin hits it, you are risking a misfire. Since there is no way to measure this, and you are not measuring it, you are basically just flapping in the wind and hoping for the best.

 

[STS]

I guess since you are shooting short range BR, my guess is you are always shooting light loads and so your primer pockets stays tight, but that seems to me to be more of an exception than a rule for most people?

It would not be a correct assumption that BR shooters shoot relatively light loads. In fact BR shooters probably operate at the highest chamber pressures of any shooting discipline.

OK, for the sake of discussion, let’s say BR shooter (short range) operates at the highest chamber pressure, how do you keep your primer pockets tight enough not to have mis-fires? I wish I could go with highest chamber pressure and keep all my pockets tight, but it’s just not possible at least for me.

To me the problem is if you don’t absolutely know how tight your pockets are i.e. they are tight enough to grip the primers so that they will 100% not move when that firing pin hits it, you are risking a misfire. Since there is no way to measure this, and you are not measuring it, you are basically just flapping in the wind and hoping for the best.

We don't rely on the primer pocket tension to ensure adequate ignition. We seat the primer anvil on the bottom of a uniformed (flat bottomed and uniform depth) primer pocket. The high pressures will eventually cause the primer pockets to loosen up but the higher quality (hard case head) brass like Lapua resists the expansion much longer. Seat the primers on the bottom of the pocket and fire away. That is as good as it gets. ;D

 

[jlow]

I guess since you are shooting short range BR, my guess is you are always shooting light loads and so your primer pockets stays tight, but that seems to me to be more of an exception than a rule for most people?

It would not be a correct assumption that BR shooters shoot relatively light loads. In fact BR shooters probably operate at the highest chamber pressures of any shooting discipline.

OK, for the sake of discussion, let’s say BR shooter (short range) operates at the highest chamber pressure, how do you keep your primer pockets tight enough not to have mis-fires? I wish I could go with highest chamber pressure and keep all my pockets tight, but it’s just not possible at least for me.

To me the problem is if you don’t absolutely know how tight your pockets are i.e. they are tight enough to grip the primers so that they will 100% not move when that firing pin hits it, you are risking a misfire. Since there is no way to measure this, and you are not measuring it, you are basically just flapping in the wind and hoping for the best.

We don't rely on the primer pocket tension to ensure adequate ignition. We seat the primer anvil on the bottom of a uniformed (flat bottomed and uniform depth) primer pocket. The high pressures will eventually cause the primer pockets to loosen up but the higher quality (hard case head) brass like Lapua resists the expansion much longer. Seat the primers on the bottom of the pocket and fire away. That is as good as it gets. ;D

Dude, good for you, you are sane LOL!

But if you read the whole thread, you would realize that we are not talking about how hot BR reloaders load but just trying to make sense of Reply #13. :