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Normally I don't pay much attention to primer seating depth but I'm trying to improve my reloading technique and reload reliability/performance. Is 5 to 9 thousandth's below case head too deep? It seems to me that with Boxer primed cases, deeper is better/more reliable. Experienced reloaders please feel free to chime in and offer opinions. Thank you.
 
If shooting some sort of bench rest and stupid crazy precision. Surely it can make a difference. People that are looking at primer depths are usually shooting really expensive custom rigs where that sort of thing CAN produce the slightest variations. These sort of folks are the type that are shooting ragged 1 hole multiple shot groups at 2-3 hundred yards.

For everyday 223-556 loads for ARs and such, I really don't think it would make any difference.

My opinion of coarse.
 
This is possibly the only part of reloading I've never given thought to. I don't have the shooting ability or rifles to make a noticeable difference.
 
I did some testing and based off my testing, primer pocket reaming/ uniforming is very insignificant to the level of accuracy I require. Now some brass out of spec may need it to be safe but very rare I would think. I am a big believer in priming off the press with equipment you can feel when you are bottomed out.
 
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If you are going control the primer seating depth, you will also need to control the depth of the primer pocket. This will require a high-quality brass for reloading where there is very little deviation in brass weight, neck tolerances or primer pocket depths.

For the buck, a better investment for accuracy would be frequent annealing case necks, sorting brass by weight, controlling brass thickness in the neck area and using match seating dies.
 
For me....just below flush and I'm GTG.
BUT, But, but........I never measured exactly. I just run my finger over the primers. You can usually tell which one(s) have not been properly seated.

IF......you're using superhuman/gorilla strength to seat primers......something is probably not right.

Using a handheld primer method to reprime, you might notice that the "problem is the" primer pocket size or the actual primer brand. Yeah they are supposed to be "standardized". Anyway, some brands might be/are easier to seat while others might not be a problem at all. Keep track of which brand and combination work "better" for YOU.

Then......
Know that primer pockets can/have been known to stretch. Due to the number of re-loads and of course, the "hotness" of the loads used.

Aloha, Mark

PS......I hope this helps.


 
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If that's the case, you've got an out of spec primer pocket, and I wouldn't be loading it.

Lake City 5.56 brass is notorious for this. Upon firing, the primer gets blown out of the pocket. No damage to anything, but the rifle doesn't cycle, and you're left with a spent case in the chamber.

If the primer is set too deep, misfires can occur especially with cases that have deep pockets, as on some guns, the firing pin won't effectively reach the primer to set it off.
 
Some of the firing pin's energy is absorbed driving the primer into the bottom of the pocket.
This I believe isn't the only reason why a miss fires might happen on a boxer primer. The "anvil" in a Boxer primer would/could be driven out of the miss-seated primer into the gap between the bottom of the primer cup and the case. If there was a big enough gap due to the primer not being seated all the way the priming compound wouldn't be smashed against the anvil.
 
Normally I don't pay much attention to primer seating depth but I'm trying to improve my reloading technique and reload reliability/performance. Is 5 to 9 thousandth's below case head too deep? It seems to me that with Boxer primed cases, deeper is better/more reliable. Experienced reloaders please feel free to chime in and offer opinions. Thank you.
A .009 seating depth is close to or crushing the primer. That's to be avoided. As already mentioned flush to .003 is ideal. What you want to avoid is high primers as in a semi-automatic rifle the bolt can (and has on numerous occasions) strike a high primer and your rifle goes "poof."
 

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