To Case Prep, Or Not To Case Prep

Written by Sierra Bullets Ballistic Technician Gary Prisendorf

ruger-american-predator-in-223-remington

Around a year ago I bought a Ruger American Predator rifle chambered in .223 Remington, with the goal of turning it into a coyote extermination machine.

While working up a load for it, I went through all my typical brass prep steps, weighing cases, annealing case necks, uniforming primer pockets and deburring flash holes.

I started wondering just how much difference all my brass prep would really matter for a factory rifle at normal hunting ranges.  So I decided to do a little experiment and load up 15 rounds using fully prepped cases and 15 rounds with very minimal brass prep and compare the group sizes at 100 yards.

I weighed out cases until I had 15 within half of a grain of each other, annealed the case necks, uniformed the primer pockets, deburred the flash holes, full length resized, trimmed them to exactly 1.750”, chamfered and deburred the case mouths.

Then I picked out 15 more cases, full length resized them and only checked to be sure that they were shorter than the maximum case length of 1.760”.

I primed all of the cases with CCI #400 small rifle primers, charged them with 24 grains of Alliant Power Pro Varmint and topped them off with a 55 grain Sierra BlitzKing #1455 seated to 2.275” O.A.L.*

So on a beautiful day for February, it reached 60 degrees and very little wind, it was time to burn some powder. From a bench, using sandbags for a rest, I fired 3 five-shot groups with both the prepped and unprepped cases at 100 yards. The results were interesting but not surprising.  The best two groups of the day were indeed from the prepped cases, but then again so was the worst group of the day.

Here is how it broke down:

Prepped cases, Group #1 = .975”, Group #2 = .884”, Group #3 = 1.127” (Average .995”).prepped_cases_55_gr_blitzking_sierra_bullets

Unprepped cases, Group #1 = 1.115”, Group #2 = 1.093”, Group #3 = 1.060” (Average 1.089”).unprepped_cases_55_gr_blitzking_sierra_bullets

My mixed results did show that the fully prepped cases did average .094” better than the unprepped cases, but the largest group fired from the prepped brass was .012” worse than the largest group fired from the unprepped brass.

In all reality, we can read a million different things into the results. I guess the lesson I learned from this little test is whether I prep my cases or not, I should be able to hit a coyote at 100 yards.  I don’t think the coyote will be asking if I prepped my brass or not.

*Disclaimer: Load data represented here may not be safe in your rifle.

This entry was posted in Reloading, Uncategorized. Bookmark the permalink.

11 Responses to To Case Prep, Or Not To Case Prep

  1. Brittius says:

    Reblogged this on .

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  2. roger estes says:

    Good article Gary. I shoot in rifle competitions and one is always hearing about maximum case prep, ad infinitum. Sometimes I think I should just give my cases to the preparers and they could just prepare, not shoot. Anyway, now I know what I’m going to do…..same as always.
    Thank you Gary,
    Roger

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  3. Bobby Beliawsky says:

    Brass prep is the foundation for a good load. My Ruger American Preditor in 6.5 CM ,action glass bedded in a Boyd’s stock in consistently sub MOA.
    I won’t question your marksmanship. Maybe the scope mount shook loose.

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  4. Danny East says:

    Depending on the company who made your seating die make a noticeable difference. All my dies are of the RCBS variety. I picked up a hint a few years ago by seating the bullet in 3 steps. 1st is just getting the bullet snug in the neck, turn the case in 120° increments while seating deeper. BTW, after all case prep is done, i use a neck sizing die minus the stem to increase neck tension. I’m just a cheapskate who tries all the little tricks I’ve learned from surfing the Net. When reloading cases on the 2nd or 3rd time only the neck sizer trick is used along with shell holders keeping fired cases separate according to rifle fired in. I had a friend who owns a machine shop take a few thousandths off to level the top which pushes the shoulder back a 3 or 4 thousandths of an inch and makes for easy chambering. If I get over 3/4″ groups it’s my fault. Brass lasts longer it seems due to less working it.

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  5. John Snell says:

    Unles your rifle/load are in the 0.5 MOA or better range, you would be better off just doing whatever initial case prep you want to do, then neck sizing, and confirming case/bullet concentricity. Use an Audette test to plot where your muzzle is pointing at incremental powder charges, pick the load with the least vertical dispersion, then shoot groups to adjust seating depth for best group size. Once you have that load the full case prep makes a difference in consistency. Doing the least work to a fired case results in the most concentric loaded round, that will lay in the chamber closer to coaxial. Combining that with the barrel vibration timing from the Audette test may result in a load that shoots well below 0.5 MOA consistently. Guss I forgot to mention your case necks need to have uniform neck thickness to maintain concentricity. If measurement reveals necks have more than 0.002″ variation in wall thicknes turn, or ream them. (I prefer turning). Only take off enough to remove 1/2 of the high spot. Since this operation falls in the one-and-done category, it doesn’t hurt to do all of these material removal steps before you fire the case for the first time. Case neck tension should be about 0.002″ (neck diameter change between sized and loaded), and needs to be uniform case to case. Do the Audette test at as close to zero jump as you can, expect best groups with a jump, amount varies by bullet shape.

    For more info on barrel vibration see my web site below under ‘Finding The Right Load’, ‘Initial Physics’.

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  6. firstriverbend says:

    Gary, great article and great tests!
    As you state, results as to be expected. 🙂
    How often do people forget what they are doing, as it relates to what the needed results are? I would say, all too often.
    Some people really enjoy squeezing the last tiny bit out of a particular round/loading/firearm combination. Others are happy when that same combination goes bang and does not blow up! 🙂

    I find most reloaders fall somewhere into the middle. If the combination does a reasonable job of accuracy and does the intended purpose down range, little else matters to them.
    At one time I would spend hours trying to do “all” of the “right” things for my reloads. It took me a lot of time to get these “perfect” loads. Then one time I heard a question asked of a several time World Champion shooter. “Do you worry about cleaning your primer pockets?”. The answer was no!
    Revelation!!
    Did it really matter if I cleaned my pockets for the shooting I was doing? Did a few tests and the answer was no. Imagine my surprise. We were shooting thousands of round per year, not cleaning the pockets saved dozens of hours or time. The loads were just as reliable, just as for the shooting requirements and gave us a lot more time to shoot, relax and enjoy shooting!!!

    If one wants to ring the absolute last bit from a particular combination, it does take a great deal of prep and not just of the ammo, but the firearm as well! I have experienced more accuracy and reliability issues from springs than all other problems combined! Lots of shooting puts lots of wear on springs. 😦

    Thanks for one more wonderful, insightful article!! Keep them coming. 🙂

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  7. Reblogged this on The way I see things … and commented:
    Visit the page for details that led to the results. Always practice safe handling for YOUR firearm!
    —————————-
    My mixed results did show that the fully prepped cases did average .094” better than the unprepped cases, but the largest group fired from the prepped brass was .012” worse than the largest group fired from the unprepped brass.

    In all reality, we can read a million different things into the results. I guess the lesson I learned from this little test is whether I prep my cases or not, I should be able to hit a coyote at 100 yards. I don’t think the coyote will be asking if I prepped my brass or not.

    *Disclaimer: Load data represented here may not be safe in your rifle.

    Like

  8. Robert Ruder says:

    Interesting test Gary, although it does make me feel like I have been wasting my time. (Kidding). The reality for me: I do everything I can to “fully prep” my cases. I am 76 yrs. old and now only shoot from a bench with my 22-250. (I have a post in the June 2016 Archives–Bob’s old custom Mauser 22-250) I do not shoot competition except against “myself”, and the last good group I may have shot.
    The good part being retired, I do have TIME to do everything in my arsenal of tools & tricks to search for that ultimate super group. Many of the shooters are still working jobs and I can see only a small about of difference in your groups. Small difference that is, IF you are a hunter, or not a wanna-be-benchrest champ. There is much time involved doing all that I do, but I can’t bring myself to go to that bench knowing I did not do all I could to shoot good groups. My rifle is good; I have shot “clover-leafs” groups @ 100 yds. My loading equipment is mostly all Forster. (the press a Forster Co-Ax)…. so that leaves “human error”. I hate when that happens! 🙂

    Liked by 1 person

  9. Shaggy says:

    Here in New Mexico, coyotes always ask about the brass prep. 😐

    Liked by 1 person

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