Rim Sorting .22LR

[TheMoondog]

After testing weight sorted Federal Champion 22LR LRN and finding that they produced 60% smaller groups than non weight-sorted cartridges, I decided to test the other big old-school 22LR accuracy technique: sorting cartridges by rim thickness.

The thickness of the a 22LR rim can effect the amount of headspace of the bullet in the chamber. And presumably, the thickness could also effect the amount and burn rate of the primer inside it.

Your milage may vary.

 

[justin amateur]

Again, limited sample size allows for incorrect conclusions.

How will measuring the rim, provide any information
regarding any other cartridge variable?

Will it relate to overall cartridge length?
Ogive length? Bullet seating depth? Bullet weight?
Powder weight/chemistry? Primer weight/chemistry?
Brass hardness? Case diameter? Bullet diameter?
Bullet seating angle? Bullet asymmetry? Crimp tension?
Will weight sorting provide information regarding
damage incurred during the handling and assembly
of the cartridges on the factory production line?

If you can't answer the questions above,
then what exactly have you accomplished?

What use is measuring one variable,
in a system of multiply interconnected variables?

Afterthought....the purpose of match ammunition is to hit what you aim at.
Based on the results of the testing, sorting did not accomplish that goal.

 

[Dstoenner]

Measuring the rim is measuring headspace. Consistent headspace is consistent ignition and hence better performance. I used to do this with the SK built Wolf Match Extra. I used to get about 2 flyers for every box. I sorted on rim thickness and found about 2 that were out, either thick or thin. Low and behold the flyers went away. But on Eley Black box or 10X, RWS R50 or Lapua Center-X it doesn't matter. They are produced to more exacting standards then you can simple measure.

Davud

 

[justin amateur]

And yet Calfee claimed headspace wasn't that critical...wonder why?

 

[demolitionman]

Is there any merit to taking same batch rimfire and weighing them into subsequent batches?

 

[justin amateur]

Comparing overall cartridge weights from batch to batch?
I suppose it'd be an interesting topic for those of us with OCD.
If you take the time to weigh the individual components, brass, bullet, primer and powder,
the resulting information might lead you to wonder why folks think weighing cartridges will improve accuracy.
When weighing the entire cartridge, you have no idea which component is responsible for the variations.
Is it the powder? Primer? Bullet? Brass?

for your perusal....CCI SV components weighed to the 1/100th of a grain

Eley Tenex components to 1/100th grain

and just because, CCI 22WMR 40 gr TMJ

 

[Dstoenner]

And yet Calfee claimed headspace wasn't that critical...wonder why?

Yet Calfee was all about ignition and headspace a part in that. So is firing pin contact shape.

David

 

[justin amateur]

I don't know DS.
I've played with firing pins, reshaped the tip, polished the pin surfaces,
polished the interior bolt surfaces, changed lengths and springs but the chronograph gave no joy.
Can't fix junk ammo...just too many other problems messing with my results.
Maybe if I had access to actual test facilities, I could document improvement,
but being limited to outdoors with wind, humidity and temperature variations,
along with component variations, no way to determine what is actually causing the mv differences,
or if the results are entirely lot number related.

 

[Cowpokey]

I don't know DS.
I've played with firing pins, reshaped the tip, polished the pin surfaces,
polished the interior bolt surfaces, changed lengths and springs but the chronograph gave no joy.
Can't fix junk ammo...just too many other problems messing with my results.
Maybe if I had access to actual test facilities, I could document improvement,
but being limited to outdoors with wind, humidity and temperature variations,
along with component variations, no way to determine what is actually causing the mv differences,
or if the results are entirely lot number related.

It's probably the amount of bend in the second knuckle of your trigger finger...you need to keep it the same every time. </sarcasm>

 

[acudaowner]

no

 

[justin amateur]

There's cuda for ya'... succinct as always.


CP, the sarcasm font, really?

 

[Cowpokey]

CP, the sarcasm font, really?

I couldn't help myself.

 

[grauhanen]

Yet Calfee was all about ignition and headspace a part in that. So is firing pin contact shape.

The "killer ignition" Calfee desired isn't dependent on one particular headspace. It's possible with a range of them.

 

[littlesister]

The "killer ignition" Calfee desired isn't dependent on one particular headspace. It's possible with a range of them.

I followed an experiment on head spacing several years ago. An individual increased his guns head spacing by small increments until he reached FTF. There was absolutely no change in accuracy until he started having FTFs. On the other hand if head spacing is too tight and you have to force the bolt down on a round. It will effect accuracy.

 

[obx22]

You guys are killing all my sacred cows!
I have written in the past (RFC) of sorting a brick of mid grade ammo by weight, which gave 7 different lots. Taking 50 from the center lot, and 50 by 1 round from each lot in a tray, row after row.
I then blind tested them with a friend in a barrel well seasoned with that ammo.

Next was the same process with rim thickness, and same test process.

In both cases I saw a reduction of of 30% group size, for a net 60% improvement. During this same period I disassembled an entire box of cartridges of the 3 grades of this brand. Admittedly my scale wasn’t commercial, but still showed the biggest variable was the slug, not the powder or primed case.

Later I acquired a Sako Finnfire, one of 4 rifle designs I know of with slip-fit adjustable barrel seating through a clamping receiver. I was able to set headspacing for the dominant rim thickness of the sorted rounds and the rifle grouped better with those rounds.

(A note on rim thickness measurements: perhaps my tools are better, or mfg standards are worse, but some samples now have different rim thickness AROUND THE RIM OF THE SAME CARTRIDGE ! )

I don’t know how to quantify my results any better than with tiny groups. Perhaps all this testing which also involves a lot of shooting, just made me better with the rifle? Made me believe in it and know in my heart that the missed rounds were on me?


I haven’t yet made an ogive to rim-base measurement tool yet for testing. I question tools which attempt to measure concentricity run-out, or have any probes bearing on the slugs surface, so I’m still pondering…

 

[justin amateur]

Obx, I finally came up with a way to test if sorting will improve results.

Seriously.....but you ain't gonna like it.

In fact anyone who claims "submoa all day long" might need to rethink the idea.

Groups are not how to test for improvement by sorting.

Use the Grid...you won't like what you see.

Sorted or not, the Grid will not lie the way groups will.
Groups can make you feel good about y'erself,
but the Grid will point out just how bad those bulk cartridges are straying.
Hem and haw all ya' want, but you can't argue when those bullets hit everywhere but where y'er aiming.

 

[obx22]

Obx, I finally came up with a way to test if sorting will improve results.

Seriously.....but you ain't gonna like it.

In fact anyone who claims "submoa all day long" might need to rethink the idea.

Groups are not how to test for improvement by sorting.

Use the Grid...you won't like what you see.

Sorted or not, the Grid will not lie the way groups will.
Groups can make you feel good about y'erself,
but the Grid will point out just how bad those bulk cartridges are straying.
Hem and haw all ya' want, but you can't argue when those bullets hit everywhere but where y'er aiming.

This is where you and I diverge in our assessment of data.
I consider the grid, or 25 bulls card testing as more a test of the entire system,-shooter included.
The grid introduces a couple of more variables, rifle reset to a completely different aiming point, different tilt, different target, different grip, different set in the rest, etc.etc.
Group shooting is more a “same-same” shot to shot until the mag empties. Less variables equals more conclusive results?

 

[obx22]

This is where you and I diverge in our assessment of data.
I consider the grid, or 25 bulls card testing as more a test of the entire system,-shooter included.
The grid introduces a couple of more variables, rifle reset to a completely different aiming point, different tilt, different target, different grip, different set in the rest, etc.etc.
Group shooting is more a “same-same” shot to shot until the mag empties. Less variables equals more conclusive results?

I’m gonna also add, that we both know poop ammo isn’t gonna hit the grid, but sorted ammo imho is gonna hit closer, and group shooting will give a more graphic impression of the improvement (less fliers).

 

[justin amateur]

I wonder what would happen if'n ya' built the group aggregates?
Do you think the resulting overall spread would be better or worse than the overall spread from the Grid?

Hint....I've done just that.

Just for giggles, give it a try.
Shoot ten 5 shot groups, then measure the overall spread, relative to point of aim.
Then shoot a Grid, 50 shots at 50 separate aim points, then measure the overall spread.
My results with the Grid produced a smaller aggregate than the groups did.
Those worries about shifting positions and different aimpoints turned out to be "insignificant".

 

[B y r o n]

I was always under the impression that sorting by rim thickness was more akin to uniforming primer pockets on center fire ammo. You end up with more consistent ignition. Since rimfire rifles/pistols headspace is the distance between the end of the barrel and the face of the bolt, ammo that is closest to this dimension also make ignition more consistent.

Quality of the ammo you are using normally makes for better accuracy because components are generally more consistent. It is always about obtaining consistency and then having a gun/barrel that likes it.

 

[nikonNUT]

Great read and thought provoking! All I know is at my first match I dropped 45 points (53/102) so ammo isn't my concern... Yet! It's that one gun part aka the NUT behind the trigger!

 

[obx22]

I wonder what would happen if'n ya' built the group aggregates?
Do you think the resulting overall spread would be better or worse than the overall spread from the Grid?

Hint....I've done just that.

Just for giggles, give it a try.
Shoot ten 5 shot groups, then measure the overall spread, relative to point of aim.
Then shoot a Grid, 50 shots at 50 separate aim points, then measure the overall spread.
My results with the Grid produced a smaller aggregate than the groups did.
Those worries about shifting positions and different aimpoints turned out to be "insignificant".

Your a lot better at it than I am!

 

[obx22]

I was always under the impression that sorting by rim thickness was more akin to uniforming primer pockets on center fire ammo. You end up with more consistent ignition. Since rimfire rifles/pistols headspace is the distance between the end of the barrel and the face of the bolt, ammo that is closest to this dimension also make ignition more consistent.

Quality of the ammo you are using normally makes for better accuracy because components are generally more consistent. It is always about obtaining consistency and then having a gun/barrel that likes it.

If you have excessive headspacing, and a chamber who’s lead engraves the slug, the cartridge stops moving forward once you lock the bolt. The case rim is against the bolt face, not the chamber rim. Now when you fire, the pin pushes the case forward to stop at the chamber rim before crushing the brass. That equals wasted energy, slows the crush, and results in variable ignition. How could it be any other way?
Now if the case rim is against the chamber rim, all the firing pin blow is directed at crushing the rim till it stops. Must be better, right?

 

[justin amateur]

Had to go looking to find the post with groups compared to grid...

The Grid at 50 yards

A YIKES moment! Looks like the action did well in directing the gas downwards. :t This grid thread makes interesting reading. Don't have adequate magnification to try anything like it.

www.rimfirecentral.com

 

[Cowpokey]

Had to go looking to find the post with groups compared to grid...

The Grid at 50 yards

A YIKES moment! Looks like the action did well in directing the gas downwards. :t This grid thread makes interesting reading. Don't have adequate magnification to try anything like it.

www.rimfirecentral.com

The Birchwood Casey 8" shoot-n-see targets have a lot of aiming points. I could have done better, some was sighting in both rifles, some was good shooting, some was me. I buy these in packs of 15 for less than $7 usually...a lot less work than drawing a grid yourself...perfect 1" grids.

ETA: that red circle bottom left is a 10 round group, it defiantly should have been better than that...it was shooter, not the ammo or equipment.

 

[hlee]

Great read and thought provoking! All I know is at my first match I dropped 45 points (53/102) so ammo isn't my concern... Yet! It's that one gun part aka the NUT behind the trigger!

You are thinking about this all wrong. Have you sorted by rim thickness? Then, sort those by weight. Then sort those by base to ogive length. Then sort those for deformations. If not, you can probably account for 40 of those 45 misses. Given the ammo handicap, you pretty much won.

 

[Westcoast308]

You guys are killing all my sacred cows!
I have written in the past (RFC) of sorting a brick of mid grade ammo by weight, which gave 7 different lots. Taking 50 from the center lot, and 50 by 1 round from each lot in a tray, row after row.
I then blind tested them with a friend in a barrel well seasoned with that ammo.

Next was the same process with rim thickness, and same test process.

In both cases I saw a reduction of of 30% group size, for a net 60% improvement. During this same period I disassembled an entire box of cartridges of the 3 grades of this brand. Admittedly my scale wasn’t commercial, but still showed the biggest variable was the slug, not the powder or primed case.

Later I acquired a Sako Finnfire, one of 4 rifle designs I know of with slip-fit adjustable barrel seating through a clamping receiver. I was able to set headspacing for the dominant rim thickness of the sorted rounds and the rifle grouped better with those rounds.

(A note on rim thickness measurements: perhaps my tools are better, or mfg standards are worse, but some samples now have different rim thickness AROUND THE RIM OF THE SAME CARTRIDGE ! )

I don’t know how to quantify my results any better than with tiny groups. Perhaps all this testing which also involves a lot of shooting, just made me better with the rifle? Made me believe in it and know in my heart that the missed rounds were on me?


I haven’t yet made an ogive to rim-base measurement tool yet for testing. I question tools which attempt to measure concentricity run-out, or have any probes bearing on the slugs surface, so I’m still pondering…

Base to Ogive measuring tool. https://bulletin.accurateshooter.co...hickness-tool-and-base-to-ogive-length-gauge/
If your free this winter…………..