K&M Primer uniform tool question?

[TheOtherZilla]

I used my K&M primer pocket uniformer yesterday on 223 Rem, Winchester brass. I must say I am surprised at how much brass was removed. I carefully measured a primer, with my calipers and also the depth of he new hole. Also the cutter depth. All were within spec that K&M provides. Still seems like a lot of brass removal. what's your experience?

 

[BigBlueandGoldie]

My Sinclair removes quite a bit also on some cases, but you can tell it's due to manufacturing differences in the cases. I seat with a K&M tool and my primers always seat nicely below the base and you can feel them bottom in the pocket.

 

[Nick LaFave]

My experience mirrors yours. I run with it. Other brands of brass hardly anything will be removed.
I am concerned that they are flat, consistent and the primer is below flush.

 

[Chiquita]

My buddy has the K&M tool and he also says more brass is removed compared to mine that the cutter depth is adjustable and I set it to remove little brass yet the PP is cleaned out.

I would think that more or less brass shavings are also material/manufacture dependent. Different brass has different flow rate hence more gets removed. I could be wrong.

 

[TheOtherZilla]

Thanks for the replies. I have a bunch of Lapua 222 rem brass here. I'll see what it does.

 

[ronemus]

What could you possibly gain from it, other that having prematurely loose primer pockets?

The depth of the pocket is made uniform, not the diameter; this has nothing to do with loosening primer pockets. The benefit is uniform pocket depth with a square corner - this allows uniform primer seating with all primers below flush. On each firing I remove a small amount of brass; I find that over time the primer pocket gets shallower, so eventually there could be a problem with fully seated primers standing proud of the case.

 

[ronemus]

The thickness of the web in front of the primer pocket is irrelevant to containing pressure since the flash hole allows the pressure to equilibrate rapidly; only the thickness of the primer cup contributes. The radial thickness of the web (unaltered by uniforming) contains the pressure; the bottom of the case is pressed against the bolt face and is incompressable along the axis of the bore. The case is smaller in diameter than the recess (if any) in the bolt face and at the aft end of the chamber, and is unsupported in the gap between the bolt and barrel; there the hoop strength of the case head contains the pressure. Because resizing does not alter the rim/extractor groove/lower case head (they're either in the case holder or the chamfer at the base of the die), case head expansion must be minimal or else the brass will stick in the chamber or lodge when attempting to close the bolt.

The reason the primer pocket gets shallower is that the brass contracts along the bore axis when it expands radially; uniforming keeps the depth of the primer pocket constant.

 

[BigBlueandGoldie]

I don't know that uniforming makes a difference on paper, but I do it to new brass as it makes it nice and easy to get consistent primer seating. It's an easy task in front of the TV with a power screwdriver. My 5yo helped me do 100ct last week.

 

[ronemus]

I do it to new brass as it makes it nice and easy to get consistent primer seating

It also works very well to clean primer pockets - all the residue is removed quickly and easily; I usually get down to bare metal on reloads. It's a lot less hassle than wet cleaning (ultrasonic, SS pins, etc.).

 

[Dusty Stevens]

I use the tool to remove the carbon. After a few firings it removes some brass, and every one is a different amount. If you seat primers to depth then this means that every one will have a different amount of crush. Take whatever you like away from that (if it matters to you or not)

 

[JimSC]

Coincidentally I spent a good bit of the day yesterday loading .223. I loaded some mixed year Lake City for the AR's and Lapua for my bolt gun. When uniforming the primer pockets I noticed more brass coming off the LC. The Lapua pockets needed hardly any brass removed

 

[johara1]

If I were concerned I would measure the depth of the cutter first, that will answer your question.... If it is right and you are taking a lot of brass out of the bottom of the primer pocket you have excess pressure..... jim

 

[TheOtherZilla]

If I were concerned I would measure the depth of the cutter first, that will answer your question.... If it is right and you are taking a lot of brass out of the bottom of the primer pocket you have excess pressure..... jim

I measured the cutter height. It was ~ .122". I also measured a primer. It was also ~.122. I measured the pocket depth also ~.122. K&M states it is set for .122". These measurements were as close as I could read.
A machinist could probly measure more exact, but it is as close a reading as I am capable of

 

[johara1]

So what you are telling me is it cutting a lot out of the bottom of the primer pocket? The answer is simple you are loading too heavy then..... I loaded as heavy as any one with a Dasher and hardly ever had any outings off the bottom of the primer pockets in 300 firings....... jim