I know the community has been waiting on this post since October, considering how the last one was lost in the great Bullpup Forum collapse of 2022. I just had my follow on range day and tested M80 Ball, 150 Grain FMJBT, and 178 Grain HPBT. The later two were complete reloads using IMR 4166, CCI 200 Primers, and Hornady Bullets.

Spoiler: I am not happy, but it is what it is.

https://www.docdroid.net/qAA2rSh/mdrx-reloading-performance-20220531-pdf

Interesting. Thanks for the legwork.

The problem with reloading is there are so many things that can be introduced to make your results worse.
It takes time to get good at not being the thing that screws up your own results.
Then when you are consistent with all the ...moving parts..your hand loads start to become voodoo magic.

What reloading manual are you using for the powders?
My Hornday  8th and 9th edition do not list 4166 as a powder for that bullet weight.
hodgdon reloading data center Says..if you went with the 175gr for 4166 bullet data..There was still more to go. (up to 43gr)
Try again, with a fouled barrel (no bore snake). See if that changes anything.

Other useful notes:

-Range Buddy was used for MOA calculation, with Odin's Help
-All shots were taken from the Bench at 100 Yards

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Inaccuracies and differences between batches

Agreed on the results, also the reason to include FPS values.,

The 150 Grain FMJBT 41.8 grain tests were made in two different batches of ammo and their accuracy is pretty close for the test.  It shows consistency.

Shooter definitely is a considerable impact.

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Load Data

As far as what grain loads used, 4064 is equivalent tot 4166 in performance and grain.  4166 is 4064 with the fouling suppressants so when I did my evaluation for max and min points I used the following sources.  Hornady's latest reloading manual (latest app version), Nosler's reloading manual, and of course Hodgen's reported data.  Here are the results:



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Press Details and Safe Max selection

For extreme spread my progressive press throws IMR 4166 with +- 0.3 grain accuracy (at the time, I have since improved it to +-0.15).
I used the lowest max (Usually from Hornady) and then gave myself a 20% reduction below max load (between Min and Max as long as it was lower than my extreme spread) as my safe max.  Examples:

Load Planning 150 Grain Hornady FMJBT - IMR 4166
Press Throw Accuracy: +-0.3
Load Increment:0.5
Min Start:41.8
Max:44.9
Safe Max:44.3

Load Planning 178 Grain Hornady FMJ  - IMR 4166
Press Throw Accuracy: +-0.3
Load Increment:0.5
Min Start:37.7
Max:41.7
Safe Max:40.9

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Increasing Grain Loads

And yes, I could definitely load another load increment on each test hotter safely.  
Note the M80 Ball ammo velocity was equivalent to the 150 grain FMJBT 44.3 grain IMR 4166 load velocity.

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Cleaning and Fowling

As far as bore cleaning/fowling.  Sounds good when I do the Oppressor test I will see if not cleaning it has any affect.

Revved the report to include some comments.