Deformed primers

[Akhunting]

i was recently going through some loads and cleaning up my bench. I noticed my last batch of loads had some misshapen primers and on closer inspection they were all showing a noticeable distortion to the top of the cup. The top of the distorted cups are displaying two distinct planes with a line in the middle where the two planes meet. I am confident my priming tool stem is tweaked and not hitting the primer true. New priming tool is in my near future.

When priming I have the habit of doing an initial seat (all the way seated), rotate the cartridge 180 degrees and give it a final seat. I do this in the belief that I get a consistent seat if the cartridge is a little off and the second seat will feel different and maybe true the primer in the pocket. After seating I feel the primer with my fingertip to make sure it is properly seated and then put it in my tray for powder and final loading.

My question is what are people's thoughts on this effecting accuracy? I had no ftf with any of these I shot and accuracy seemed on par, but I was not shooting for score. I imagine this has to effect accuracy and consistency, thoughts?

 

[dok7mm]

You did not mention what primer tool you were using, but I would check to see if everything is clean and double check the depth adjustment. If this was new brass, you may benefit by uniforming primer pockets. In a nutshell, I believe consistent primer seating will have an effect on velocity, therefor on accuracy.

 

[Akhunting]

After my old Lee hand primer bit the dust I started using the press priming tool on my Lee Classic Cast press. It was not perfect, but seemed to work well and seated primers to spec initially. The primer pockets were trued.

My SD has been bigger lately and this could very well be the culprit.

 

[dok7mm]

I am a big fan of the K&M hand tool with the dial indicator. It will let you measure the depth of each primer seated and you can even sort primers by their individual depth.

 

[MagnumManiac]

I can tell you that over seating, which many people do, is worse for initial start pressure than not quite seating enough.
A primer is made of 3 main parts, these parts are made to fit so that their proper fit between the 3 is done when a primer is seated .005"-.008" below flush when in the case.
A new primer has the primer compound pellet seated in it, then a 'foil', generally made of paper, is placed over the top of the pellet, then the anvil is seated lastly and is left 'proud' of the primer cup. This is done to provide a safety cushion where the anvil is NOT compressing the pellet in any way. When you seat the primer, the anvil first touches the pocket bottom, then the cup is pushed down to meet the pocket, this pre-stresses the pellet so the firing pin strike detonates the pellet with little trouble. This is where the .005"-.008" below flush comes into play.
If you seat high, the cup moving forward to meet the pocket bottom takes up most of the firing pin energy, if you seat too deep and have distorted the cup by flattening it, you have also damaged the pellet, which will most likely crack into smaller pieces.
Both of these situations cause ignition inconsistencies, very detrimental to good accuracy and totally detrimental to any target type precision.
I have deliberately done both in a known rifle that will shoot in the 1's at 200 with tuned loads. Doing this opened those groups dramatically and the over-stressed primers were the worst groups by far.
With a hand tool like the RCBS, you can feel when the spongy bounce of the primer ceases as the anvil touches the bottom of the pocket and the cup then takes up the room. When the sponginess stops, the primer is home.

Cheers.

 

[Pmacc60]

I am a big fan of the K&M hand tool with the dial indicator. It will let you measure the depth of each primer seated and you can even sort primers by their individual depth.

I use the RCBS and as Magnum maniac stated you feel the spongy resistance and the primer is home. I still stress over this part of the handloading procedure. The KM priming tool with the gauge may be the answer. Thanks for the tip .

 

[Akhunting]

MagnumManiac - thanks for the concise and detailed response. I had read a little of this in the past, but not as straightforward and well explained.

 

[243winxb]

When priming I have the habit of doing an initial seat (all the way seated), rotate the cartridge 180 degrees and give it a final seat

This is how i do it also.

Most shell holders have enough slop, that leaves the primer crooked in the pocket. The 180 turn and 2nd seat fixes it.

Does it make a difference on target? Probabley not.