Some .22 rim thickness measuring

[TassieTiger]

Screw the .22 brass - this is the diligence needed to find a cure for cov!!!
Big props for doing this. Cheers.

[Bugman]

You have certainly put a lot of time and effort into this exercise. One of the things that come to mind, is that a while back I had various results in my target scores
obviously attributed to the ammo I was using in my Pardini SP. I bought a few boxes of various makes of 22 ammo and weighed each and every round for
each manufacturer (Eley through to CCI).
I separated those rounds that were close to similar weight and tested same. 5 shot groups. Allowing for my own shooting ability, I did get a better group
improvement with the rounds of same/similar weight and total crap with those of dissimilar weight variances.
Your testing has answered some of my own questions, so well done. Powder weight/projectile weight/brass conformity etc play a big part in the accuracy of
the humble 22.

[bladeracer]

You have certainly put a lot of time and effort into this exercise. One of the things that come to mind, is that a while back I had various results in my target scores
obviously attributed to the ammo I was using in my Pardini SP. I bought a few boxes of various makes of 22 ammo and weighed each and every round for
each manufacturer (Eley through to CCI).
I separated those rounds that were close to similar weight and tested same. 5 shot groups. Allowing for my own shooting ability, I did get a better group
improvement with the rounds of same/similar weight and total crap with those of dissimilar weight variances.
Your testing has answered some of my own questions, so well done. Powder weight/projectile weight/brass conformity etc play a big part in the accuracy of
the humble 22.

I have played with weight batching but saw no improvement at all.

[bladeracer]

I've measured 11,791 rounds (and still well short of halfway through the pile), about 10,000 more than I'd recommend anybody do!
A good percentage were measured more than once, I went back through the smaller batches to confirm I'd gotten the correct measurements. I had to clean and lube the caliper three times to keep it running smoothly. And I patched the collet through every few hundred rounds or they became fiddly to tip out due to lube build up. The rim of the collet and the anvil both need to be wiped continuously to clear off lube to get accurate measurements.

The SK stuff was filthy to do due to the copious smothering of liquid lube over the entire cartridges, a real mess. Handling all this ammo I was surprised that only one type left any discolouration on my fingers, the CCI Short HVRN, but it wiped away easily.

I've only got the Eley stuff to finish, but it's all coming out at .032" now and I don't see much point in continuing, I'm about over it by now I think
I have plenty of the remaining Eley types so I can measure them anytime in the future if I feel the need. I was _very_ surprised at the amount of variation in the Eley Standard Bulk, but I guess that goes with the bulk price - I paid $70 for 500rds.

As I find time to test fire them all I'll try to keep this thread updated.

I got 30kg of bullets on Thursday that I want to sort through as well now.

[bladeracer]

Hornady (One type - still can't get the Subsonic):

I test fired the Hornady High Velocity today at the end of the SK testing.
I'd say it's 2MoA ammo in my RPR, good enough for foxes, but a lot louder than the subsonic stuff I normally use.
I think I paid $20 for 100rds so not too outrageous.
Velocity went from 1129fps up to 1203fps, averaging 1161fps ES74fps.

[bladeracer]

SK ammo (Eight types):

There was no wind this arvo and I found a couple hours for a test shoot.
I grabbed the pile of SK.
I have not cleaned the bore since before the S&B test so it had 307rds down it when I started, and I put 288rds through it today. I shot off the bipod on the table with a rear bag and the VK 10-40x56 scope.
I started with CCI Standard Velocity for a baseline, shooting three 5rd groups, with a best of 13.5mm at 50m. After all the SK and the single Hornady I had for testing I finished off with another three groups of CCI SV as a baseline, with a best of 13.5mm. I think it's probably good for another 300rd test before it'll need cleaning.

20200425_172130b.jpg (304.93 KiB) Viewed 9848 times

Then I fired 55rds of SK Standard+ to thoroughly coat the bore (with the copious lubricant SK uses - horrible stuff).
Five groups of unbatched ammo with a best of 13.5mm, then three groups of .034" rim thickness giving a 14mm group, and three groups of .035" rims with nothing special. A couple of sub-MoA groups but I'd call it 2MoA ammo. I forgot to turn the chrono on for the first round, I'll get some velocities for the SK Std+ during the next test.

20200425_172133b.jpg (322.89 KiB) Viewed 9848 times

Then three groups with Pistol Match Special of .035" rims with a best of 9mm and a 14.5mm group, then three more groups batched at .034" rims, with nothing special. One .62MoA group is outstanding but overall I'd call it 2MoA stuff. Velocities averaged 1062fps ES51fps.

20200425_172136b.jpg (305.94 KiB) Viewed 9848 times

[bladeracer]

Since they changed the forum to limit posts to three attachments I'll have to do multiple posts (idiotic idea that was but it seems permanent).

Next up is the Long Range Match which I've really wanted to test. Three groups of unbatched ammo with a best of 14mm showing some potential. Two more groups batched at .034" rim thickness weren't anything special. Velocities averaged 1090fps, ES56fps.

20200425_172139b.jpg (294.33 KiB) Viewed 9847 times

This was an interesting test of the consistency and accuracy of the chrono I think, due to it straddling the sound barrier. SK specify it at 1099fps. Of the 25rds, six went supersonic. Those were 1122fps, 1106fps, 1107fps, 1106fps, 1103fps, and 1106fps. The fastest that did not break the sound barrier was at 1095fps. The calculated speed of sound should have been around 1116fps this arvo (15C at 165m ASL), making my readings within about 1% of reality (I have actually seen people trying to claim that cheap chronos are off by as much as 25%!) and very consistent in my opinion.

Next was Rifle Match, three groups of random ammo giving a best of 18.5mm, then two groups batched at .035" managed a best of 16mm. Consistency overall is excellent and a bit of effort on my part could see this being a solid 1MoA ammo, to 50m at least. Velocity was 1052fps, ES46fps.

20200425_172143b.jpg (280.47 KiB) Viewed 9847 times

Flat Nose Plus was nothing special, a best of 20mm. Velocity was 1042fps, ES53fps.

20200425_172147b.jpg (335.99 KiB) Viewed 9847 times

[bladeracer]

Next up was Flat Nose Basic, slightly better than the Match version. Best was a very neat 9.5mm group. The rest were a fairly consistent 20mm-ish. Velocity was 1008fps, ES69fps. The lowest velocity of the entire session was a 962fps round of this stuff.

20200425_172150b.jpg (315.76 KiB) Viewed 9846 times

SK Magazine shot very well for me today with a 9.5mm group, and some 15mm groups. Velocity was 1018fps, ES67fps.

20200425_172153b.jpg (308.55 KiB) Viewed 9846 times

Finally, I tried some of my dwindling supply of the excellent High Velocity. I only fired three groups with a best of 9mm for the last SK group of the day. Velocity was 1176fps, ES55fps. This stuff shoots amazingly in all three of my Rugers.

20200425_172201b.jpg (345.93 KiB) Viewed 9846 times

[bladeracer]

Eley (Nine types):

I managed to test the Eley stuff this arvo, they do make some good ammo.

I had 595rds down the tube without cleaning at the start of this, and fired another 310rds today.

I started with three 5rd groups to settle in, one of which went under the MoA, then I removed the VisionKing 10-40x56 scope and swapped in the Bushnell AR Optics 4.5-18x40. I was curious whether I was actually able to shoot any better with the higher magnification, it seems it perhaps does help.

20200428_171712b.jpg (265.67 KiB) Viewed 9828 times

I fired three groups with the AR Optics, then swapped the VK back on, and fired one group to confirm zero hadn't moved.
When I finished all the Eley I fired another two groups to confirm nothing had changed.

I started with the Eley Standard bulk pack, firing 50rds to coat the bore.

20200428_171633b.jpg (253.74 KiB) Viewed 9828 times

I started with a random rim-thickness group of one at .031", two at .032", one at .036" and one at .037", mixing the extremes of the rim thickness variation, but shooting a nice group. I'm not testing rim thickness batching, but as I measured 12,000rds I did keep them sorted into batches rather than mix them up again. So I shot three groups each with the .033", .034" and .035" batches.

Next was Eley Sport.

20200428_171637b.jpg (243.31 KiB) Viewed 9828 times

Only one of six groups went sub-MoA.

[bladeracer]

Then Eley Club.

20200428_171640b.jpg (221.05 KiB) Viewed 9828 times

Five groups, one getting very close to half-MoA.

Then Eley Edge.

20200428_171643b.jpg (216.88 KiB) Viewed 9828 times

One went under MoA and another went well under a half-minute, and my best ever group at 6mm.

Then Eley Match. I had thirty rounds of the old box, and some new stuff. I was going to test both but decided I didn't need to.

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[bladeracer]

Next was Eley Match OSP.

20200428_171657b.jpg (159.81 KiB) Viewed 9828 times

Eley Tenex.

20200428_171700b.jpg (233.91 KiB) Viewed 9828 times

Eley HVHP was a nice surprise.

20200428_171702b.jpg (266.42 KiB) Viewed 9828 times

[bladeracer]

And finished off with Eley Subsonic HP.

20200428_171705b.jpg (274.86 KiB) Viewed 9825 times

Then I had a play with the air-rifle at 50m until it got too dark to see the lines on the paper to aim at

[bladeracer]

Rather than add the velocity data to separate posts I thought I'd just do a graphic of all the Eley.

Eley test velocities.JPG (184.28 KiB) Viewed 9200 times

The CCI is the final fifteen rounds I finished the session with.
The Crosman is just some readings I took on the air-rifle with H&N Field Target Trophy while I was out.

Two shots went 1101fps and had a supersonic crack, the highest that did not go supersonic was 1098fps.

Statistical Deviation of 9fps for Tenex and Match, 10fps for Edge and CCI Std Velocity.
But 5fps for the .177" air-rifle surprised me, especially with the cheap H&N's.

I used the MTM rest for this test.

20200428_150132b.jpg (705.38 KiB) Viewed 9200 times

The VisionKing 10-40x56 is a monster, but I haven't had any problems with it so far.
Very limited elevation adjustment so I had to shim the front ring .012" to be able to get a 50m zero for this testing.

[straightshooter]

bladeracer

For some reason after looking at your tactical peashooter I can't extirpate from my mind's eye the image of the host of the series Man vs. Food eating a 42 inch pizza with all the toppings.

[bladeracer]

bladeracer

For some reason after looking at your tactical peashooter I can't extirpate from my mind's eye the image of the host of the series Man vs. Food eating a 42 inch pizza with all the toppings.

Not being familiar with the show I don't know what that means, but I only see pizza about once a year, they don't deliver this far out of town

[bladeracer]

After a bit of a break I managed to get out for another session.
This time it was the Federal and Highland, a total of 364rds - 24 15rd mags, plus 5rds to empty a box.
I was sitting there for exactly two hours and my feet were frozen numb at the end, it was 9.4 degrees out there in the paddock, but at least there was no wind at all.
I have to say that I am getting a little sick of lugging the huge VK 10-40x56 around on the .22, looking forward to completing this and swapping the AR Optics back on.

20200611_165716b.jpg (599.5 KiB) Viewed 8459 times

I forgot my original plan to shoot five 5rd groups for each type, I shot one 15rd mag of each this time. I also screwed up the chrono, for some reason I was convinced it held 200rd strings so I switched it midway through. Unfortunately, it only holds 100rd strings, so I lost some data. I may shoot those again in the next session.

One weird shot occurred with the Federal F712, I fired a clean shot but I couldn't find a hole in the target, must've gone through another hole. Then I spotted the damned hole five-minutes low and two-minutes to the right (the grid is 2MoA at 50m), what the hell! I _know_ the shot was good. The other two groups were terrible though (49mm and 73mm) so it was probably just four rounds clustered in 22mm in the top left of a group with the fifth at the extreme bottom right, making a 78mm group. This was some of the lost velocity data, but I didn't notice anything with the shot.

F712 dropped a shot.jpg (372.58 KiB) Viewed 8459 times

And what $75 worth of holes looks like Top left target is for CCI SV, 15rds to start the session (38mm, 22mm and 22.5mm), then 15rds between switching from the Federal to the Highland (11.5mm, 17mm and 31mm with a nasty flier - 11.5mm without the flier), then 20rds to end the test as a control (31.5mm, 21.5mm, 13.5mm, and 21mm to end the session), to monitor my own and the rifle's performance. If my shooting is falling apart during the session, the final control group should be significantly worse than the first control group. Again, I get the tightest group of the session with the CCI SV at 11.5mm.

20200611_165131c.jpg (259.84 KiB) Viewed 8459 times

And the back of the 3mm MDF sheet after about 1500 bullets have passed through it, tons of life left in it yet, and only $8 at Bunnings.

20200611_165600.jpg (313 KiB) Viewed 8459 times

The CCI SV control target.

20200611_173054b.jpg (407.61 KiB) Viewed 8455 times

[bladeracer]

I started with the bulk Federal Auto Match.
The first group, at 21.5mm was looking good, but the next eight groups were not great, between 27mm and 50mm. These were batched by rim thickness but I'm not seeing any measureable difference between them. Velocity was 1157fps, ES 94fps, SD 22fps.

20200611_173140b.jpg (420.74 KiB) Viewed 8455 times

Then we have the American Eagle HVHP (40rd boxes), nothing special at 33mm to 44mm groups. Velocity was 1212fps, ES 112fps, SD 32fps.
Then AE Suppressor with similar results. Velocity was 973fps, ES 61fps, SD 16fps.

20200611_173233b.jpg (436.06 KiB) Viewed 8455 times

I had high hopes for the Federal F510, and it's good stuff, even cheaper than the CCI Std Velocity. Six groups around 20mm to 25mm, very consistent. Velocity was 1274fps, ES 48fps, SD 16fps.

20200611_173310b.jpg (380.09 KiB) Viewed 8455 times

Then the F710 which shows some promise at 20mm to 33mm groups. Lost the velocity data
F712 was pretty awful at 50mm to 75mm groups. Also no velocity data.

20200611_173501b.jpg (416.09 KiB) Viewed 8455 times

F714 looks fairly consistent with 28mm to 36mm groups.
F724 was pretty awful at 35mm to 60mm groups.

20200611_173026b.jpg (376.52 KiB) Viewed 8455 times

F711B started out with an excellent 13mm group, but opened up to an awful 48mm group.
F922B did similar with an 18mm group opening out to 42mm. Velocity was 1042fps, ES 39fps, SD 12fps. Very greasy though, horrible to handle.

20200611_172910b.jpg (389.9 KiB) Viewed 8454 times

Then I fired three groups of CCI SV before switching to the Highland stuff.

[bladeracer]

Three groups of CCI SV shows no change in my shooting so it's onto the Highland.
I start with the RX HVHP which has always been pretty consistent for me, though not especially accurate. Groups from 21mm to 31mm. Velocity was 1287fps, ES 44fps, SD 12fps.
Then the RX Subsonic HP, also fairly consistent with 25mm to 34mm groups. Velocity was 1071fps, ES 82fps, SD 25fps.

20200611_172827b.jpg (409.11 KiB) Viewed 8454 times

RX Target also shows excellent consistency with neat groups and no fliers, but around 18mm to 26mm for six groups. Velocity was 1178fps, ES 69fps, SD 17fps. All I can find when looking online is "Highland RX Target Standard Velocity 36gn Hollow Point", but they always have a picture of a box of "RX Target Solid Point". I have never seen the roundnose stuff, only the hollow point, and this stuff is definitely high-velocity. I can't explain it

20200611_172644b.jpg (337.41 KiB) Viewed 8454 times

The RX HVRN opens up a little bit to 19mm to 35mm groups. Velocity was 1266fps, ES 41fps, SD 14fps.

20200611_173346b.jpg (405.32 KiB) Viewed 8454 times

Finally, the ZX Super Quiet lacks consistency, grouping 23mm to 54mm but with no pattern to the group. No velocity data unfortunately, but definitely subsonic. It's supposed to run 840fps. The VK has a dual retical with a second crosshair 5MoA below the centre one. I expected the ZX to drop significantly so I held on the lower crosshair, but was surprised to see very little drop at all.

20200611_172952b.jpg (373.33 KiB) Viewed 8454 times

[bladeracer]

I haven't cleaned the bore since I started this test on March 24th so we now have 1272rds down the tube of 39 different types.
It is still grouping well within the realm of what it was grouping after a thorough clean at the start (19mm, 17mm and 16mm were the first three groups), so I'm not yet ready to clean it.

[rc42]

Thanks for posting all of this, it was an interesting read.

I just got myself a reasonable digital caliper, a Kincrome from Bunnings that claims to measure accurately below 0.001", some digital scales that measure 0.01g and I have a Hornady rim thickness guage on the way so I'll be repeating some of what you've done here and sorting Eley Standard bulk into batches to see if I can improve grouping at 50m

The ammo will be used for prone target shooting onto electronic targets and my rifle already groups well with the budget bulk Eley ammo but still suffers from regular fliers and odd changes in group size from one series of 10 to the next. I don't want to train with better ammo at 2 or 3 times the price so I'm hoping that sorting will be enough.

I have around 8,000 rounds of Eley bulk but will start with just a few hundred, sorting by rim thickness and then secondary sorting by weight until I have a number of closely matched batches that I can shoot groups with. I don't have a chronograph but my barrel tuner claims to compensate for small differences in muzzle velocity so it will be interesting.
The Eley use a hard parafin wax coating so sticky fingers and gunge should be minimized, I'll post back when I have some results.

I've been looking for a 22LR projectile resizing die too but they don't seem to exist in Australia and are even difficult to find elsewhere, if I can get one that will be my next phase.

[marksman]

l second that blade, very interesting thanks for going to the trouble posting it all up

[bladeracer]

I've gotten a little distracted lately but I'll get back to this soon I hope.
While I don't consider a chronograph to be essential, for the price I do find it very useful. I haven't seen a distinct improvement in accuracy due to tighter Standard Deviation or Extreme Spread, so I don't agree with trying to develop accurate loads just from velocity data, or in chasing smaller SD or ES on the chronograph, I just chase smaller groups on the target. For a large-scale test as you're planning, with hundreds of rounds and likely dozens of hours, I really would invest in a chronograph. I'm on my second ProChrono Digital and haven't found it lacking in any way. I just checked Ebay though and I see the dollar's collapse has them up around $350 currently.

I keep meaning to make a .22LR bullet swaging die but never manage to get around to it, one day

Thanks for posting all of this, it was an interesting read.

I just got myself a reasonable digital caliper, a Kincrome from Bunnings that claims to measure accurately below 0.001", some digital scales that measure 0.01g and I have a Hornady rim thickness guage on the way so I'll be repeating some of what you've done here and sorting Eley Standard bulk into batches to see if I can improve grouping at 50m

The ammo will be used for prone target shooting onto electronic targets and my rifle already groups well with the budget bulk Eley ammo but still suffers from regular fliers and odd changes in group size from one series of 10 to the next. I don't want to train with better ammo at 2 or 3 times the price so I'm hoping that sorting will be enough.

I have around 8,000 rounds of Eley bulk but will start with just a few hundred, sorting by rim thickness and then secondary sorting by weight until I have a number of closely matched batches that I can shoot groups with. I don't have a chronograph but my barrel tuner claims to compensate for small differences in muzzle velocity so it will be interesting.
The Eley use a hard parafin wax coating so sticky fingers and gunge should be minimized, I'll post back when I have some results.

I've been looking for a 22LR projectile resizing die too but they don't seem to exist in Australia and are even difficult to find elsewhere, if I can get one that will be my next phase.

[rc42]

Hornady rim thickness gauge arrived this afternoon so I spent much of the afternoon and evening working through a few boxes of Eley Std bulk.
The rim thickness seems to match previous shooting results, picking rounds from the box there will be between 5 and 20 of nearly the same rim thickness, then one way off and a couple somewhat near, hopefully the sorted batches will shoot more consistently and group better.
The rounds give a slightly different result if rotated but are generally within 1 thou and I have grouped them on the thickness in thou measured in half thou increments as reported on the caliper.

Thickness and number of rounds so far in that group are as below:

34.0 54
35.0 13
36.0 3
37.0 30
37.5 102
38.0 296
38.5 620
39.0 538
39.5 140
40.0 47
41.0 9
42.0 46
43.0 26

[bladeracer]

Hornady rim thickness gauge arrived this afternoon so I spent much of the afternoon and evening working through a few boxes of Eley Std bulk.
The rim thickness seems to match previous shooting results, picking rounds from the box there will be between 5 and 20 of nearly the same rim thickness, then one way off and a couple somewhat near, hopefully the sorted batches will shoot more consistently and group better.
The rounds give a slightly different result if rotated but are generally within 1 thou and I have grouped them on the thickness in thou measured in half thou increments as reported on the caliper.

Thickness and number of rounds so far in that group are as below:

34.0 54
35.0 13
36.0 3
37.0 30
37.5 102
38.0 296
38.5 620
39.0 538
39.5 140
40.0 47
41.0 9
42.0 46
43.0 26

Wow, you are seeing very different results to mine, although I only measured a single box, which may be an anomaly. I'll have a closer look at your numbers tomorrow.

Have double-checked many to confirm you are getting consistent measurements, turning the round to take several measurements to find the thinnest part of the rim?

[bladeracer]

Comparing your figures with mine.
I only measured one box, 355rds.

BR Eley Standard Batching.JPG (38.15 KiB) Viewed 8266 times

You measured four boxes, 1924rds, a far more relevant sample.

RC42 Eley Standard Batching.JPG (45.63 KiB) Viewed 8266 times

Yours spread across .009", mine across only .006". Mine measure from .031" to .037", and all but two rounds are from .032" to .036", but that could simply be due to my smaller sample. It's odd that using identical equipment you are measuring in a higher range than mine, probably just due to technique, yours are in the .034" to .043" range. Having so many more samples at the higher end though leaves me wondering if they might not fall into smaller batches when measured again.

I very regularly pulled rounds from batches I'd already measured and measured them again to confirm they were correct. And all of the smaller batches I measured again and found almost all of them actually measured smaller than my first measurements. This is why it is vital to turn the cartridge several times to ensure you are finding the smallest possible measurement of the rim. It is also very important to regularly clean the anvil and the chamber as lube residue builds up fairly quickly. The brass rim is not manufactured to half-thou precision, in my opinion, even .001" might be stretching it, and I think anything under .002" difference between cartridges is irrelevant at the target, from what I've seen. I did find that the consistency of thickness around the rim on Eley ammo is better than many of the other brands though.

Overall, I think we can see a similar pattern in consistency of manufacture, both our data show about 90% of them to be within .003". I didn't see any measurable difference in group size though. I fired one group taken from the extreme outliers of my sample (one at .031", two at .032", one at .036" and one at .037"), and the group was better than most of the batched groups, and only bettered by one group of .034" batched.

As you have 80rds in your extreme batches you could shoot groups with each, and with these two batches mixed, and see if there's a difference.

I'm thinking that due to the consistency of manufacture of the higher-quality ammo, the rim thickness/primer distribution is far less relevant than the bullet itself.

I consider Eley Standard to be the very worst of an exceptional manufacturer (most of their ammo measures within .001", throughout the entire batch), by a very wide margin, though still better than many other brands' best stuff. I would assume they take the brass that is rejected from their other lines, and use it to make this bulk ammo, but it is still very good. Assuming they do the same with their bullets, I think the weight, balance and symmetry of the 40gn bullet plays a bigger role in results at the target. Any production line that can turn out millions of rounds with consistently-measured 1gn powder charges can probably be relied upon for very consistent bullet weights also, so bullet diameter and shape are the best targets to address I think.

Looking forward to seeing more results!

[rc42]

Had another sorting session today and stopped when I was only a little past the point of wishing I'd never started.
Got through another two bulk boxes with just over 500 in each, I think they add a few to the stated 500 to avoid making false claims.

Anyway, cumulative sorted boxes now contain the following:
34 78
35 23
36 3
37 31
37.5 113
38 443
38.5 1050
39 823
39.5 200
40 58
41 13
42 64
43 33

The two boxes were from different batches but the numbers were close so may have been the same day (3117 30323) and (3117 30335), the first of those had mostly 38-39 and the second was mostly 38.5-39.5, it seems that using boxes from different batches is skewing the results somewhat in terms of what a purchaser of one box (or even case) should expect. It seems reasonable that other batches would be centered around the 34-35 thickness as bladeracer's were.

I manged to shoot one 60 shot practice match with sorted 38.5 rim thickness and there did seem to be fewer wide flyers but the wind was a little too gusty to be sure, it will certainly be interesting to see what the rifles does with the different rim thicknesses but that's going to take some time.

Sorting rim thickness certainly won't turn practice ammo into high end match ammo and my ability is also a limit on the testing but I'm hoping to get some meaningful results in regard to improved grouping eventually.

[bladeracer]

Had another sorting session today and stopped when I was only a little past the point of wishing I'd never started.

I remember that feeling well

[rc42]

A few notes to anyone else following this crazy path.

The Hornady rim thickness gauge isn't the best quality, the plate that the rim sits against during measurement isn't flat so the actual measurement is taken between the top of the rim and some point off center on the back of it, because of the stamped logo this makes it very prone to changes in measurement as the round is rotated.
I put the plate onto a flat grindstone and the picture shows how the high point was removed from it until the stone was touching the entire face, the additional scratches are from measuring 3,000 rounds.

The alignment against the tube that holds the round also needs some tweaking, I pushed them together with some fine grade abrasive paper between them which I then pulled out to get the top of the tube to sit completely flat against the back plate. By doing this first rotating the rounds often made no difference to the measurements but worst case was about 0.001" variation. This helped speed things up as I eventually moved to single measurements on each round unless they were extremes or the display was flapping between measurements.

Eley Standard is parfin wax lubricated so doesn't have the oily gunking up problem of other types but still needed cleaning every 30-50 measurements using a cotton bud with some G96 on it.
I have another 5,000 rounds still boxed but I'm not going to measure further, I have plenty of sorted rounds for testing and it's going to take me months to put those downrange and try to identify any meaningful benefit to the sorting process.

[bladeracer]

Don't lose sight of what it is that we're measuring, both the precision of measurement required, and the precision of the manufacturing process. .22LR rims are not turned on a lathe, they are punched out of enormous sheets of brass at rates of many thousands per hour, all the time rolling around in huge piles, and being spat from one process to the next at speed.

And I don't believe we need to batch them down to even one-thou variations, I would think even .1mm (or .004") would be sufficient. We could batch them down to ten-thous, but virtually every batch would have just a handful of rounds in it, with most of your ammo being discarded for excess thickness variation around the rim. Then we find that twenty to thirty batches all shoot identically on the target - meaning they could all have been batched together anyway.

All we're trying to do is weed out the extreme anomalies in an attempt to reduce fliers.

Some of the ammo I measured had several thou variation around the rims, but Eley does not, at least outside of their bulk offering.

[rc42]

Had a fun shooting session at the range this evening after some sighters I shot 6 groups of 10 sorted rounds onto electronic targets, almost no wind so variations were down to myself, flyers and the different rim thicknesses.

I shot batches 34, 37, 38, 39, 40, 42, corresponding scores were 98.4, 96.8, 99.3, 101.8, 100.8, 95.2
Grouping in the 38-40 range was noticeably better than the smaller or larger extremes but all groups still had flyers except the 34 which helped the score despite otherwise poor grouping.

Following that I shot a full 60 shot match with a 38.5 batch, scores were 99.7, 98.8, 95.7, 100.2, 99.2, 100.8
Total score was 594.4 which is actually the second best result I've ever got from Eley Std ammo (by about 1 point) and the main loss of points were those dammed flyers that I know weren't my fault, clearly the bad flyers aren't caused by rounds with a different rim thickness.

Testing will continue, I have nearly 3,000 sorted rounds and batching by rim thickness does seem to have improved things but cheap bulk ammo has a lot of flyers whilst expensive match grade ammo has very few. Hopefully sub-sorting by weight with further improve grouping.

Interestingly the Tenex that I have measures at 39 rim thickness, which my rifle really likes, with about a dozen measured showing almost no variation in rim thickness or weight.