Off Center Primer Strikes

[JPB4BAMA]

This peaked my curiosity and wondering if anyone has any thoughts on the cause. This is new first fired Peterson brass. I notices that some of the primer strikes are nearly dead center and some are quite a bit off center. So my gut feeling is that since this is brand new brass and not fire formed to my chamber that it is just a tad "loose" and each round lines up just a little different on chambering? I've seen off center before and never gave it much thought, but this batch for some reason caught my attention and the curiosity is gnawing on me. And if my supposition is correct, I would think that this off center lock up might show up downrange as some increased dispersion? Thus why some folks say to never do your load work up or competition loads on new brass?

 

[nmkid]

I don't know. Maybe your firing pin?

 

[Big Mc]

This peaked my curiosity and wondering if anyone has any thoughts on the cause. This is new first fired Peterson brass. I notices that some of the primer strikes are nearly dead center and some are quite a bit off center. So my gut feeling is that since this is brand new brass and not fire formed to my chamber that it is just a tad "loose" and each round lines up just a little different on chambering? I've seen off center before and never gave it much thought, but this batch for some reason caught my attention and the curiosity is gnawing on me. And if my supposition is correct, I would think that this off center lock up might show up downrange as some increased dispersion? Thus why some folks say to never do your load work up or competition loads on new brass?

I think you got it right. Nothing to cause a problem. Tommy Mc

 

[LCazador]

Understand that new brass is undersize so it will fit all chambers. I'd say the off center primer strikes are due to some slop. If it doesn't go away after fireforming then you may have a brass or chamber problem or sloppy bolt fit. I would sort these cases and then run a load test with them only. Yes this is reason you should always fireform first and then do load tests.

 

[jackieschmidt]

This is not that uncommon.

If you ever pick up brass at a range, you will notice that the unusual thing would be for many to actually be on center.

 

[LCazador]

This is not that uncommon.

If you ever pick up brass at a range, you will notice that the unusual thing would be for many to actually be on center.

Exactly! Why pick range brass or somebody else's problem.

 

[MikeRu]

This is not that uncommon.

If you ever pick up brass at a range, you will notice that the unusual thing would be for many to actually be on center.

Agree I’m pretty sure I’ve seen that quite a bit

 

[Alex Wheeler]

The threads can be off the bolt center of the action, or the firing pin hole can be off center in the bolt. I guess the chamber could be off center of the threads as well. I had a custom action the threads were off the center of the bolt .006". It looks worse than it is. I bet if you spun those cases in a v block and measure it with a height gauge your less than .010 off center. Probably closer to .005". Its not causing an accuracy issue. The firing pin is plenty large enough to cover the anvil in the primer even when off center a little.

 

[butchlambert]

New brass could be laying loose in the chamber causing this. I would be more interested in looking at an already fireformed piece of brass that was fired after fireforming.

 

[ORjeff]

The fact that it's centered on some and not on others is curious. Does that action have an ejector or is it a drop port? Even if there's slop a typical ejector will push the shoulders together and that is what aligns the case to the chamber. If it was misalignment because of the threads, which are not very good at controlling concentricity, I would expect it to be more consistent. Once the headspace of the case matches the chamber you will likely see a more consistent result.

 

[dellet]

The if you’re interested, index a few cases so you can see which direction the strike is off center, and if it is repeated. You would expect a round lose in the chamber to be hit high at 12. Random hits, maybe a firing pin with a loose fit in the bolt.

Maybe a good winter project done in front of the wood stove with primers only and you can tell everyone you were doing some shooting experiments and research.

 

[Coyotefurharvester]

A careful wrap of 1/2 width tape at the .200 line should determine if the new brass is small for the chamber.