Wyo7200
Handloader
- Aug 20, 2014
- 565
- 1
Wondering out loud, and someday I may test it though I think the variables of this thought has been tested independently in one way or another.
Conventional wisdom is once fired brass (same rifle) needs a minor bump in powder to achieve the same, or better accuracy. Something like the energy is needed to expand the brass on the first firing or something.
In QL, we use fired brass for accurate estimates, regardless if virgin, once fired or 20 firings.
It's known (maybe?) that the carbon and copper left over from the first firing produces a lube of some sort in the case neck...
Difference in neck tension (example-ball expander vs mandrel) can increase or decrease velocity- same influence as using lube for seating the bullet, or cleaned brass from ssm or sonic cleaning. (6mmbr has a topic on this)
Is the once fired case needing more powder (or seated deeper) due to the first firing's lube, and not because of the case capacity changed/ case is formed to the chamber?
I'm trying to lower the es I've been getting and I feel like it's in the neck tension/ssm cleaning. Conventional methods of walnut and corn, conventional load work up after the first firing. If I ssm tumble the brass after the first firing and not change anything else, the charge could in theory stay the same. If I use a little dry neck lube for sizing, I may have to adjust seating depth to regain the little bit of pressure loss.
What has me wondering about this is my 22-250 and .260... Maybe others. Seated straight from ssm tumbling, the 22-250 is 40 fps faster than if I pulled a case, and re-seated it, without changing anything else.
I don't have tumbler, so hopefully I can get some confirmations with dry neck lube.
Conventional wisdom is once fired brass (same rifle) needs a minor bump in powder to achieve the same, or better accuracy. Something like the energy is needed to expand the brass on the first firing or something.
In QL, we use fired brass for accurate estimates, regardless if virgin, once fired or 20 firings.
It's known (maybe?) that the carbon and copper left over from the first firing produces a lube of some sort in the case neck...
Difference in neck tension (example-ball expander vs mandrel) can increase or decrease velocity- same influence as using lube for seating the bullet, or cleaned brass from ssm or sonic cleaning. (6mmbr has a topic on this)
Is the once fired case needing more powder (or seated deeper) due to the first firing's lube, and not because of the case capacity changed/ case is formed to the chamber?
I'm trying to lower the es I've been getting and I feel like it's in the neck tension/ssm cleaning. Conventional methods of walnut and corn, conventional load work up after the first firing. If I ssm tumble the brass after the first firing and not change anything else, the charge could in theory stay the same. If I use a little dry neck lube for sizing, I may have to adjust seating depth to regain the little bit of pressure loss.
What has me wondering about this is my 22-250 and .260... Maybe others. Seated straight from ssm tumbling, the 22-250 is 40 fps faster than if I pulled a case, and re-seated it, without changing anything else.
I don't have tumbler, so hopefully I can get some confirmations with dry neck lube.