Primer Seating Depth

steelrat · February 16, 2007, 12:33 PM

I'm having some issues with seating my primers. I have the RCBS hand primer tool and can't get any consistency out of it. In the instructions it says that the primer depth should be between .003" and .005" I put a case in and pull the handle and feel the primer seat, then give it a little extra squeeze and some times it works, sometimes it goes too far. I've measured cases that range anywhere from .002" and .010". Any suggestions on what I can do to get consistent depths? Thanks for all the info.

30Cal · February 16, 2007, 12:42 PM

Cut the primer pockets to a uniform depth (or clean them if they've been fired).

steelrat · February 16, 2007, 01:09 PM

If I did that then it would push them in beond the .003" to .005" depth?

lockedcj7 · February 16, 2007, 01:27 PM

I always thought that you just wanted the primer to seat completely in the pocket (i.e. the metal of the cup is against the metal of the pocket.)

If it's not seated completely, won't it give when the the firing pin hits it? Wouldn't this cause a slightly delayed ignition or (worst-case) no ignition?

I use a Lee hand-priming tool and I just seat them until I feel them hit bottom.

Wild Bill Bucks · February 16, 2007, 01:32 PM

It takes some practice to get good consistency, It took me a while to get the right feel for it also. I don't measure my depth, I just try to get the primers level with the brass so they don't go in to far, or rock when I stand them on a flat counter.

cheygriz · February 16, 2007, 07:17 PM

The primer should ALWAYS be seated to the bottom of the pocket!! NO EXCEPTIONS! It's impossible to seat a primer too deep!

Failure to seat to the bottom of the pocket can cause misfires, and poor accuracy. The primer anvil should be resting solidly on the bottom of the pocket when the firing pin strikes it.

G56 · February 16, 2007, 07:20 PM

Theoretically you can crush a primer if it's seated too deep, that can cause a misfire, in practice I've never seen that though.

cheygriz · February 16, 2007, 07:33 PM

G56,

You are absolutely correct. You can crush the primer with too much force. I've done it!

But the primer should be seated as deep as possible without crushing.

Ideally, the pocked should be formed so that the top of the primer will be .005 below flush with a properly seated primer. In reality, pockets are formed that will only allow the primer to be seated flush, in one extreme, and seated as much a .015 deep on the other extreme. the primer should be indented approx. .020 when fired.

Most guns have a firing pin protrusion of at least .025 to allow reliable ignition with the vatiations in primer pocket depth. One of my AK-47s has a pin protrusion of .067!

mjrodney · February 16, 2007, 07:53 PM

You worry too much.

You are not going too far.

Seat the primer about as firmly as a good handshake and so it's slightly below the surface of the brass.

Go shoot.

Measure your group sizes, not your primer depth.

cheygriz · February 16, 2007, 07:56 PM

mjrodney

Good response!

February 16, 2007, 12:33 PM	#1
steelrat Member Join Date: February 8, 2007 Location: Utah Posts: 66	Primer Seating Depth I'm having some issues with seating my primers. I have the RCBS hand primer tool and can't get any consistency out of it. In the instructions it says that the primer depth should be between .003" and .005" I put a case in and pull the handle and feel the primer seat, then give it a little extra squeeze and some times it works, sometimes it goes too far. I've measured cases that range anywhere from .002" and .010". Any suggestions on what I can do to get consistent depths? Thanks for all the info.

February 16, 2007, 07:17 PM	#6
cheygriz Senior Member Join Date: May 11, 2002 Location: high up in the rockies Posts: 2,289	The primer should ALWAYS be seated to the bottom of the pocket!! NO EXCEPTIONS! It's impossible to seat a primer too deep! Failure to seat to the bottom of the pocket can cause misfires, and poor accuracy. The primer anvil should be resting solidly on the bottom of the pocket when the firing pin strikes it. __________________ If you think a mighty military force is expensive, wait 'til you see what a weak one costs.

February 16, 2007, 07:20 PM	#7
G56 Senior Member Join Date: June 10, 2004 Location: Oklahoma Posts: 302	Theoretically you can crush a primer if it's seated too deep, that can cause a misfire, in practice I've never seen that though. __________________ John

February 16, 2007, 07:33 PM	#8
cheygriz Senior Member Join Date: May 11, 2002 Location: high up in the rockies Posts: 2,289	G56, You are absolutely correct. You can crush the primer with too much force. I've done it! But the primer should be seated as deep as possible without crushing. Ideally, the pocked should be formed so that the top of the primer will be .005 below flush with a properly seated primer. In reality, pockets are formed that will only allow the primer to be seated flush, in one extreme, and seated as much a .015 deep on the other extreme. the primer should be indented approx. .020 when fired. Most guns have a firing pin protrusion of at least .025 to allow reliable ignition with the vatiations in primer pocket depth. One of my AK-47s has a pin protrusion of .067! __________________ If you think a mighty military force is expensive, wait 'til you see what a weak one costs.

February 16, 2007, 07:53 PM	#9
mjrodney Senior Member Join Date: March 5, 2006 Location: SW Florida Posts: 435	You worry too much. You are not going too far. Seat the primer about as firmly as a good handshake and so it's slightly below the surface of the brass. Go shoot. Measure your group sizes, not your primer depth. __________________ Proud supporter of the NRA

February 16, 2007, 12:42 PM	#2
30Cal Senior Member Join Date: December 3, 2002 Posts: 1,264	Cut the primer pockets to a uniform depth (or clean them if they've been fired).

February 16, 2007, 01:09 PM	#3
steelrat Member Join Date: February 8, 2007 Location: Utah Posts: 66	If I did that then it would push them in beond the .003" to .005" depth?

February 16, 2007, 01:27 PM	#4
lockedcj7 Senior Member Join Date: February 15, 2007 Posts: 1,215	I always thought that you just wanted the primer to seat completely in the pocket (i.e. the metal of the cup is against the metal of the pocket.) If it's not seated completely, won't it give when the the firing pin hits it? Wouldn't this cause a slightly delayed ignition or (worst-case) no ignition? I use a Lee hand-priming tool and I just seat them until I feel them hit bottom.

February 16, 2007, 01:32 PM	#5
Wild Bill Bucks Senior Member Join Date: December 28, 2005 Location: Southeastern Oklahoma, Next door to Sasquatch Posts: 1,266	It takes some practice to get good consistency, It took me a while to get the right feel for it also. I don't measure my depth, I just try to get the primers level with the brass so they don't go in to far, or rock when I stand them on a flat counter.

February 16, 2007, 07:56 PM	#10
cheygriz Senior Member Join Date: May 11, 2002 Location: high up in the rockies Posts: 2,289	mjrodney Good response! __________________ If you think a mighty military force is expensive, wait 'til you see what a weak one costs.