How deep should a primer pocket be?
- Thread starter Scrumbag
- Start date
On my small rifle primers, I uniform the pockets to .121"
and seat to flush, 002 below flush or ?
I use an RCBS pocket trimmer. The depth is fixed. It removes no more than a few thou from new Lapua 6BR cases. A few new cases there is zero removal. I just run the tool in on new cases and forget and don't worry about getting technical.
Takes a bit of feel (force back against mic) but I get 0.117" to .120" with my 22N (Dogtown brass).
I don't uniform but probably should start to.
Calipers should be OK if you zero the dial, spring loaded dial indicator would be easier.
I don't uniform but probably should start to.
Calipers should be OK if you zero the dial, spring loaded dial indicator would be easier.
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I don't understand why you would want to know. I guess if they were to shallow you could surely cut them deeper. But if they are too deep how could you fix them? Buy good brass for a rifle that is good enough to take advantage of good brass, and let the guy that makes the brass worry about primer pocket depth. There are many things in the process of making an accurate rifle that you have little or no control over, worry about the ones that you can control.. I have seen 2 dozen threads about how deep to set primers. Really?? to the bottom of the pocket, then they can't move from a firing pin hit.
Most of the guys that ask technical questions don't and never will shoot in any serious competition. They are trying to make an ordinary rifle shoot very small groups. I do some work to improve accuracy but I draw a limit as to how far I will go. I think I was lucky to buy 2 barrels that deserve to be on a better riffle. GH don't know the difference between a decent factory rifle and one with a lot of money in it. I see guys on this websight recommending a $1500 scope on a deer hunting rifle.. Almost all the GH fields in Ohio are under 400 yards across.
As you can see in the illustration for primer pockets and primers, there's quite a variation within the specs. One brand of brass can have a substantially different primer pocket depth. If you're going to uniform the depth for your various brass, you'll want uniform them all to the deepest one's for consistency. Another factor to keep in mind is how deep can you go before your firing pin doesn't strike the primer well enough, where is may not only be the length of the firing pin but also the strength to the firing pin spring. So, you see, it's not just a matter of a set depth for everyone. The main thing is to have the primers set to the bottom of the pocket, maybe with a little crush, so the anvil works properly for primer ignition. It'd be a good idea to take some measurement for those pockets and primers to give you an idea of what you're actually dealing with.
D-4297
Gold $$ Contributor
On new brass ; Lapua SRP , I use my primer pocket tool to do two things . Get them all to the same depth , and insure that the tool takes out the corner radius at the bottom om the pocket . I actually feel that cutting the "square" corner in the bottom is more important on new brass , because that is where the cup edge will sit , when pressed into the pocket . Seems to work as I haven't had a mis-fire , or hang-fire for thousands of rounds . SD number is between 6 and 7 1/2 . Making the pocket consistent is what I'm after . I do also use the same tool to knock out the crud after each firing , and before wet tumble , no pins . Does it make a difference ? I don't know , and I'm not sure there is any way to check . But it's what I do .
I clean my primer pockets.
I’ve never bothered to measure their depth
Every primer gets bottomed out
If I thought there was the slightest chance that measuring would improve my groups I’d do it.
Not having a primer bottomed takes you on the road to FTF
When the trigger is squeezed the first thing the firing pin does when striking the primer is to move the case forward. If it has to fully seat-the primer first because you haven’t….
Flush or a bit below is all the same to me, and apparently to the target too.
I don’t weigh primers either.
The above is my experience in my rifles.
I’ve never bothered to measure their depth
Every primer gets bottomed out
If I thought there was the slightest chance that measuring would improve my groups I’d do it.
Not having a primer bottomed takes you on the road to FTF
When the trigger is squeezed the first thing the firing pin does when striking the primer is to move the case forward. If it has to fully seat-the primer first because you haven’t….
Flush or a bit below is all the same to me, and apparently to the target too.
I don’t weigh primers either.
The above is my experience in my rifles.
Man, that’s a real rare occurrence. Has to be quite startling.
ALWAYS TO THE BOTTOM OF THE POCKET
Sure. Why be concerned about the only totally unsupported part of a cartridge? 50,000+ psi slamming back on this small section. But if they, in the end, all measure the same you have reached your goal.
But whatever it is, there should be a moments reflection on ‘how much’ is too much.
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