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Primer depth for accuracy

mikecr said:
Here is another perspective about this:
Primer seating is sizing, similar to other sizing that leaves an interference fit.
We add energy to components while doing this, and that energy will seek lowest levels, most at first, and somehow find more relief with time.

So we seat primers, typically for ammo use in the same week. I don't know, I assume most of us reloaders do that. But if seating primers for seasonal ammo that may not be used for months, the original seated conditions often change over that period. Just like neck tension can change over that much time.

The primer cup/pocket act as a spring that actually wiggles the primers outward & off crush (itself a spring condition). This is something I've tested because I do load ammo for seasonal use. The weekend before I head to PA for GH hunting, I reseat primers to deepest in group. This has worked, I think because for THAT ammo, i had picked out primers that measured the same heights, for pockets which are uniformed. I use the same 50 cases year after year, always firing them up to keep reload cycles the same.
I also do not put up with loose primer pockets, and would not use Norma brass if it was free (because of this). The primers move even in tight pockets, but worse in loose pockets.

Sometime in the past, I shot some ammo right before a hunt and hit less than stellar performance. That led me to this notion, and confirmation of it over the years.
Before hunting I also check chambering of each round.

The potential for changing neck tension was handled by bullet pre-seating with a mandrel.
Expanded necks spring back inward, which would continue over time, but bullets will not let this continue.
If you size down necks without expansion, that outward spring back will continue over time, reducing tension over time.
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So you size the brass more than is needed then expand back up. Isn't this contrary to your goal. The neck wants to go back to it's fired dimension after sizing. Over sizing and then expanding doesn't change that. Does it establish initial neck tension? Yes It doesn't change the way the brass wants to travel which is back to its fired state. As always YMMV
 
Mulligan said:
Hopefully we get enough engagement from the collective AS group to plan in some clever ways to reduce the numbers of questions after the test is complete.
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Were you satisfied with the method in that previous primer sorting routine in terms of serialized cases and rotating them through the firing order as the primer depth is changed?
That should either eliminate or at least track any issues from an individual primer pocket or case sample issue.
Seems like the method of zeroing out on each case the way the K&M does, cancels out rim thickness issues fair enough, but something that can help dial in and stop short of flush or crush might be easier with a bench mounted rig using a longer lever or mechanical stop in order to seat to +0.001, +0.002, etc.. (where positive means the primer is short of flush)
Flush and crush seems easy enough on the K&M.
The only other thing I can add, is it takes a little gage pressure to establish the total height of the primer while the anvil is still protruding. So establishing the initial flush installation has a little inherent uncertainty while the anvil squirms and flattens out.
 
Mulligan said:
We had a good dusting a week ago in the high-country. From now until mid-Dec it will tease us here in the valley, 12 weeks later it is spring.
CW
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With something like 33 trips for the 3rd rifle season going through your neighborhood on the way to Craig, it is always a barometer for what kind of hunt I am going to have when I see the condition of your orchards and vineyards along I-70.
Some years look like the leaves are all green and that makes it a tough season, other years the leaves are completely stripped and we are in snow where the season is "easy". There have been lots of in between seasons where the leaves are part way through changing.
I'm hoping the frosts and snows are not very late this year for the sake of the deer and big horns up north as there has been a Blue Tongue outbreak in B.C. and I think snow and frost is the only thing that stops it.

Does the gun range near Palisade stay open during winter or does your testing stop due to snow?
 
RegionRat said:
With something like 33 trips for the 3rd rifle season going through your neighborhood on the way to Craig, it is always a barometer for what kind of hunt I am going to have when I see the condition of your orchards and vineyards along I-70.
Some years look like the leaves are all green and that makes it a tough season, other years the leaves are completely stripped and we are in snow where the season is "easy". There have been lots of in between seasons where the leaves are part way through changing.
I'm hoping the frosts and snows are not very late this year for the sake of the deer and big horns up north as there has been a Blue Tongue outbreak in B.C. and I think snow and frost is the only thing that stops it.

Does the gun range near Palisade stay open during winter or does your testing stop due to snow?
Click to expand...
We shoot registered IBS 600 yard matches the year around….. well sort of, we take a month or two off some years in mid summer to escape the heat. We shoot F-Class all months except Dec and Jan….. i think?
Yes, I test the year around. We only get about 9” of precipitation a year here, so not many cloudy days. In the winter, a sunny 30* day is amazing for the soul, shooting and group therapy!
CW
 
SPJ said:
Then what is point your you where making ?
Click to expand...


I think I made myself pretty clear Jim. In your game maybe it matters...maybe. In mine it is white noise. I have better stuff to do than obsess with primer seating depth or buying a $1000 scale. That clear it up for you?
 
One good post .
This is the road to 1000 yard Perfection .
Weight you Primer anvils . When replacing then just pinch of Bull Eye . Seat then with a hand tool just to point they start to flatten. Everyone of them will go Bang .
 
logical question, the only thing to add would be this if you ponder tuning or rifle performance improvements based off a "personal thought" just take the time to test it regardless of what others have found often what gets me further is not at all what others are doing. This question of primer depth, compression, or pre loading anvil to a equal position or deeper crush depth is know different see it through let your rifle and you decide not your shooting community.. In closing I suggest tinkering with this idea at no closer than 400 yards further would be even better happy tuning. your looking for clean grouping with lack of spitters 100% of shots not 85% of your group, not sub small grouping but clean grouping. good luck

Shawn Williams
 
I uniform to .124. Seat using a Sinclair hand tool. I seat by feel, to the bottom. I just started doing this, so no results yet.

PopCharlie
 
In he short range game, (6PPC Group), the primer pockets are usually so loose after 3 to 4 firings that all of this becomes a moot point.

about 2 years ago, when this very topic was then discussed, I took 100 new Lapua 6BR cases and actually measured the depth of each primer pocket with a depth mic. I could not find more than .0005 inch difference in any.

This leads me to believe that with cases of this quality, all most are doing with their “uniformer” is increasing the depth of the pocket.

We strive for that ideal firing pin protrusion in our rifles, and then insist on subtracting from that by making the pockets deeper.

I agree with Alex Wheeler in that in the 600 to 1000 yard disciplines, the smallest things do become more important. The thing that has always puzzled me is many of these shooters are going to extremes with all of these minute details while shooting what amounts to semi-custom bullets.
 
I will preface by saying that this is by no means a complete test or perhaps even a statistically valid one. But it definitely has gotten my attention and I will do more testing and see if the results are repeatable. This was at 100 yds and I think 600 yds will be more meaningful.

Here are the results from my first test. I had loaded 100 rounds for a competition and my Accuracy One primer depth gauge just happened to come in. I measured the primer seating depths on all 100 loaded rounds and picked 5 from each end of the group. 5 were flush with the base and 5 were .005 below flush. When I shot them, I alternated between the two groups. For the flush group, the ES was 16 and for the .005 below it was 11. They were as follows: 2830, 2833, 2842, 2846, 2844 and 2825, 2830, 2836, 2831, 2831
Pictured below are the two five shot groups. The larger group is the flush group.

20210902_105445.jpg20210902_105452.jpg
 
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