Who makes a priming tool that works off of the case base?

T

tricrown

Guest
Just got a Forster Co-Ax Priming tool. I was expecting it to work like the priming tool that is on their Co-Ax press. But it is nothing more than another system that relies on the cartridge rim for seating depth and the handful of different lot cases I tried showed differing results. Please correct me if I'm wrong here.

I've looked at the K&M with dial and to get that to seat to a consistent exact depth it looks like you'd have to reset for or per-measure every primer.

The Sinclair looks like it locks the case off of the top of the case rim and also has no stop for those of us that need to prime by depth measurement instead of feel.

Every other priming tool I've found works off of a shellholder and the case groove.

The Co-Ax press works off of the case base, just like headspace measurement, and has to seat to an exact .005” every time. But it is a very time consuming single load operation and this cluts has already pushed down on the press handle hard enough to bend a case rim.

Does anyone else make a priming tool that seats off of the case base or seats to an exact .005" every time regardless of primer or case groove differences?
 
JMHO, but what determines the proper seating depth for any primer is the anvil coming into contact with the bottom of the primer pocket. After you seated a few thousand you will know exactly what that "feel' is and when to stop. Depending on a gauge or indicator may seem like a good idea at the time, but you'll eventually discard it. You can buy a lot of primers for what you'll pay for such a gizmo.

Don't forget, this is my very own opinion. Yours may be different.

ray
 
The sinclair can be set for a specific depth and also specifiy the depth off of the base. Very nice tool.

Hovis
 
I believe you should re-visit K&M.
If you desire the same primer crush, only the K&M will get you there.
It is not fast, but it zeros out primer height AND pocket depth(based on rim grip to anvil fully seated) in one move, for each seating.

Your base approach doesn't sound like it zeros out any variances, but would seat all to the same height -from the casehead only. This would result in differing primer crush. Similar with Sinclair, or any other traditional.
 
+1 for the K&M--with the dial indicator nothing else adapts the seating crush to the primer pocket depth AND the primer height
 
It ain't me babe.

I just don't trust my feel and gave up on it 40 years and many tens of thousands of primers ago. I'm thinking it is very advantageous to have the firing pin to strike at as consistent a distance as possible. For the last 10-15 years I've been using a couple of bench mounted APS systems. They are fast and adjustable for depth. But the depth works off of the top of the shellholder groove and the top of the case rim. To get every primer at the same depth, ever case has to have the exact same rim thickness.
God bless you people that can feel an anvil seat to within a thousands of an inch. Good Lord knows I can't.

Hovis, so the Sinclair doesn't have to be re-set if a case has a rim 1 or 2 thousands difference in thickness? The priming ram is always the same protrusion past the base of the case and the case head is locked down to the exact same place? The YouTube video made me think it locked up using the EDIT: bottom of the case groove and top of the shellholder groove.

Thank you.
 
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I use the K & M dial for LR primers because advancing arthritis in the hands has buggered my ability to seat them with feel. I need 2 thumbs to do the job.

Yes, you should reset the dial each primer. Experience has shown me that the anvils aren't a constant protrusion from the cup & it's the anvil/primer cake relationship that is critical, as I understand it.

I shoot mainly long range. Without changing any other element, I halved my velocity spread when I replaced my trusty old Sinclair with the K & M.
 
Bill, the fella in that video used his K&M about as well as my wife might..
You toss the shield & it's ring as the only pressure on the primer is dial indicator pressure(next to nothing), so there is no safety concern. This speeds things up.
Then, he mentioned that he 'feels' the primer touch and goes 2thou crush. That's wrong completely. He should know the primer touches at ZERO.
With any experience using the tool, and testing to know, he'd discover that the K&M measurement is way way more accurate than feel.
Also, there is no 'averaging' to it. He wasn't using the tool well enough, and it looked to me like his pocket was so deep as to be very near full stroke without the primer. I've never seen pockets that deep. And it counters the purpose of measurement to 'do a few' 'average the setting' and then continue assuming that all would be the same. Even with pockets cut to the same depth, and rims turned to the same thickness, primers still vary in height. So exactly 2thou crush setting on each will mean that some set at different heights w/resp to casehead.

I've also found that different primer brands prefer different crush values, for lowest ES.
For the consistent strike distance issue, I would adjust the firing pin, and concede up to ~5thou tolerance on it to consistent primer crush. But the best strike adjustment can't be assumed either. That is, it can't be assumed that setting all primers flush to casehead(for ex) would perform best with your action, bolface, HS, Spring, pin, trigger, pocket depths,,,

Anyway, it takes me ~30sec each seating into cut pockets. But it's kinda fun. Like use of hand dies -vs- threaded.
 
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Mike, So the K&M takes the primer height into account and seats to a consistent crush? That means that the amount the primer is seated below the case will vary even on evenly cut primer pockets? The only better alternative would be to use something like the Forster Co-Ax's press seater on sorted primers in uniformed pockets? Or to use most other make seaters with rim uniformed cases and sorted primers also? And from what I gather telling even benchrest shooters that they should sort primers will get you counted as crazy as fast as telling most deer hunters that they oughta sort their bullets for bearing surface.

I cut off 10 old trashed various BR cases so I could get mic readings on them. Used a ball mic on the primer and a regular 1” mic on the web. I was surprised how good of a reading I could get and found the Forster press seats to +/- a couple .0001”. While my APS, with its positive stop, still varies by as much as a couple .001” among different cases and even on the same case primed 10 times. I didn't bother to try the RCBS hand primer or press.
 
I just bought one of the 21st centurys and its good. I do like it.
As I understand it he also designed tools for other companies for many years.
 
Tricrown...

I wrote about this subject years ago in Precision Shooting. The article was back around 1993 or '94.

For optimum results you want a .002" crush on SR primers and a .003" crush on LR primers. I have a letter from Federal so stating. I checked a LOT of primers for thickness and never found one 100 count box that had less than .008" variation.

Bottom line... you have to do them one at a time and use the K & M tool. (Unless something new is out there that I don't know about.)

I have two of the K & M tools that I would sell if anyone's interested.

Dick Wright
 
Bill, while it sounds like you've resolved the Forster as -good as it gets. And while there are a lot of good seaters people are happy with,,
None are doing what a K&M does. So none are really an alternative to it.

Seating primers so that their height is the same -vs- measuring crush, is analogous to weighing cases -vs- measuring case capacity.
Do you want easy, or accurate?
 
wrong....
the primer must be seated firmly against the bottom of the primer pocket for consistant ignition.
seating to a given depth that is not the bottom of the pockeet means the firing pin must first move the primer to the bottom of the pocket, then set it off. this leads to inconsistance based the energy used to seat the primer with the firing pin.
your milage may vary...as will your shot to shot consistancy.
uniform the pockets for depth and then seat them on the bottom with a small crush...yep...a small crush.
mike in co
tricrown said:
I'm thinking it is very advantageous to have the firing pin to strike at as consistent a distance as possible.
.
Click to expand...
 
mikecr said:
Anyway, it takes me ~30sec each seating into ***cut*** pockets. But it's kinda fun. Like use of hand dies -vs- threaded.
Click to expand...

Mike,
Do you find it necessary to square the bottom of the primer pocket for the apparent crush to be consistent enough to reduce ES? (So the primer seats against a flat bottom instead of riding a radiused corner.) Any data on this?

Thanks,
Keith
 
epiphany time for me

Ah, so the firing pin's distance traveled,EDIT: as in the difference in depth of properly seated primers, of itself has no or little effect. Miniscule lock time variation? As long as the pin can ignite the primer in a consistent time and distance after it first starts pushing on the primer and case. And that consistency is best achieved by the anvil crush being set to as sensitive a depth as that primer calls for and consistent headspace.
 
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Keith, pockets vary from lot to lot and some are not an issue. But I do consider cutting of the pockets(uniforming) to be important no matter what.
The primer anvil tabs are very near the edges of their cups, which we're pressing in. So it seems appropriate to me to sharpen the pocket circumference.
I also think it's better to have every pocket at the same depth. In fact, the depth that was used for seated primers when testing/adjusting the firing pin depth for lowest ES, would probably be best(unless best didn't turn out achievable there).
I haven't measured and logged this with a scientific method Kieth. But based on my last efforts, I suspect many factors combine here to affect ES as uniquely as seating depth is for accuracy. I also suspect that little of it matters for small cartrridges run at extreme pressures(6PPC). But for LR cartridges, absolutely every bit of it will matter.


Bill, ideally every factor imagined would be consistent. Of course it's hard to get there, but we can reduce em one by one for less overall variance. By setting crush we've pinned one factor. Uniforming pockets is another pinned,, Setting your pin,, your HS,, your shroud,, your trigger sear,,,
Mike in co is talking about consistency in effective energy of the strike. I share his concern.
 
Firing pin speed/travel...

Years back Ken Markle (K & M) calculated the difference in time it took for a firing pin to hit a primer when the primer was properly seated (see above) but varied in thickness... i.e. thickest primer vs thinnest primer. As previously stated all primers vary a lot in thickness.

Ken used an old 98 Mauser action for his test vehicle. They are noted for a very slow lock time. The primer pockets had been uniformed and the primers seated to a proper crush as per above.

Ken told me that the difference between the thickest and thinnest primers was a very few millionths of a second. Once he arrived at these numbers he decided that it would be best to discount the difference and to worry about other things.

Since modern BR actions have a much faster lock time, the difference would be even smaller.

FWIW Ken is a successful engineer as can be seen by his products and there is every reason to believe his numbers.

Dick Wright
 
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