For clarity; how do you define "hard pressed"? From my centerfire reloading experience the difference was measurable. Is it measurable in rimfire? After all, a gain is a gain, no matterhow small...
Resizing, rim / weight sorting
- Thread starter GPSMapNut
- Start date
Interesting reading. Unfortunately focused on safety shooting any ammo and not on matching headspace to a particular batch of ammo. My question remains unanswered.
Well, no, he didn't answer a question whether matching headspace to ammo improves accuracy or not. He talked a lot about too much and not enough. Virtually nothing about just right.
Leuchtkafer
Member
If headspace was a significant factor in rimfire precision, his testing would have shown that increasing the headspace would have resulted in worsening accuracy. His testing showed no change until ignition was affected. If there is a slight benefit to be gained at "just right", it is so insignificant it is grossly overshadowed by other factors as to be indiscernible. Unlike centre-fire and the consistency in cartridges that can be achieved via hand loading, rimfire ammo factory loads, no matter how expensive, are subject to inconsistency that remains a significant limiting factor in this platform. Everything that is done to the barrel and actions is an attempt to limit their contribution to the inherent dispersion built into the ammo.
I'll just throw out some food for thought, would headspace in centre-fire be as noticeable as you've seen if tuners were more widely used? If one thinks about it, you're adjusting the load parameters to get the barrel to behave a certain way so as to achieve best accuracy, and you can make the ammo consistent enough so that no random cartridge operates outside of that parameter... you never have to think about how the rifle can mitigate cartridges that are outside the ideal spec. Of course, there's nothing that can be done about ammo that is too far out of spec.
I'll say this, the next leap up in rimfire precision will only come from being able to hand load cartridges to a greater degree of consistency than the factories are willing to produce. Everything else with regards to barrels and actions is an attempt to gain a breadcrumb at considerable cost. The barrels and actions produced today are capable of far better than the ammo can deliver.
Head space and rim thickness are two different things. Hard closing is one thing, head space, another. Hard closing generally is due to crushing the head of the cartridge (I have used headspace as a descriptor concerning this, but likely the wrong terminology).
Last edited:
Sounds like you only skimmed it rather than reading it all.
You are right. Today I read it again much more carefully. In fact he says that inbhis tests accuracy / vertical dispersion was affected. Let me quote:
I set one of my test barrels in this action and set the headspace at .042”. I shot a series of 5 shot groups, then re-set the headspace to .044”, then .046”, then .048”, then .050” and finally .052”. When the headspace reached .048”. I started to get vertical dispersion. I saw no loss of accuracy up to .046”. But I have made sure this little 52 has killer ignition too.
When I reached .050”, accuracy worsened and at .052”, I started getting misfires. I had pulled the extractors from the breech bolt during these tests."
This is my take on it. As long as the headspace is such that strong and consistent ignition is achieved (.043" being a normal baseline) then there is not much effect on accuracy.
Chamber dimensions and the amount of bullet engraving, can have a considerable effect on accuracy, IMO.
Chamber dimensions and the amount of bullet engraving, can have a considerable effect on accuracy, IMO.
The number you named may be the number correct for cartridges with the rim thickness that are right for it. In the referenced article, I can only assume that an expert used good quality ammo hence consistent rim thickness. For that particular ammo, .048 was the accuracy border. We don't know what would be the border for ammo with a different rim thickness. As a side note; I'm just starting to play with it all. As a mathematician, physicist and a mechanical engineer, I feel (yeah, square heads do have feelings and hunches) that science can improve my chances of getting good groups on the budget. I just finished weighting a bunch of various ammo. Sure, most of you will say it's pointless. To me it just proves why so many like CCI SV.. Only by consistency of the weight, it was right next to decent Eley and far above the cheaper Eley. In order words, don't blow your money on the name. Spend it on performance. Let the numbers speak for themselves... at least speak to the ones who are willing to hear...
Eley tenex 40gr Eley hv hp 38gr Browning BPR Fragmenting 37 gr CCI CleanHVPoly Target red 40gr CCI Mini-Mag 40gr Aqula Super Extra 40gr Winchester HP copper 38gr CCI SV Target 40gr
Average 333.14 316.92 322.82 330.62 331.14 336.1 315.2 330.92
Std. dev. 0.9478224237 2.546225698 1.965934373 2.009061107 1.761377012 3.705851229 6.266203486 1.084962145
Min 331 314 319 327 327 329 307 329
Max 335 331 327 335 334 344 330 333
Spread 4 17 8 8 7 15 23 4
Spread% of average 1.20% 5.36% 2.48% 2.42% 2.11% 4.46% 7.30% 1.21%
Crap, can't paste it as something that makes good sense. In any case, only CCI had as little spread as Elay Tenex. Only Winchester Hollow Point 38gr was worse than Eley high velocity hollow point 38gr.
Love me or hate me but be assured that I'm just starting to play with your minds...Or... I just find it pointless and dissappear into abyss like so many before me...
You aren't the first mathematician, physicist or engineer to walk this path. It just confounds me when guys insist on starting at the beginning rather than building on what is already known. No first year physics student insists on going to Italy to drop cannonballs out of the leaning tower ... or have things changed that much.
Correct. After all, I'm not on a quest to test all the ammo. I got a box of decent Eley only to have a benchmark. I also got a box of cheaper Eley out of curiosity. The first one, as expected, had consistent weight. The second was worse than the cheapest I had in my drawer. Hmm, is it an effect of post production sorting?
Funny. Pointless but Funny.
I'm not on a quest to rediscover gravity nor finding out which manufacturer makes quality ammo. All that is well proven. I'm interested in things that are controversial and such is sorting.
Yeah. I just came to a fork and took it.
yep...
Even when you can reload... how do you make the bullets to exact specs? In centerfire, there is still variations but given the mass, it is tolerable.
how do you measure and dispense powder to the levels that make a difference? in centerfire, holding to 0.02-0.04gr in a 24gr load matters. In a FTR load, you can see what a tenth or two of powder does way down range. In rimfire, you are dealing with a load of less then 2gr of power... that is some high tech scales and load rooms.
It is a huge rabbit hole with cartridges this small.
Jerry
Last edited:
