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    #1

    New brass length variance

    Prepping some new PPU brass in 300 Win. Noticed that it ranges from 2.603” to 2.613”. Case trim recommendation is 2.610”. I’ve heard it’s common for some to trim under min length, I’ve never done that though. How would you tackle this? Trim the long ones down to 2.610” to reduce variance or trim down closer to the shortest case (2.603”)


    2.603” on left and 2.613” on right.


    Sent from my iPhone using Tapatalk
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    #2
    Shoot them all once then trim them all the same.

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      #3
      Originally posted by Old Bald Guy View Post
      Shoot them all once then trim them all the same.

      Yep especially in 300 Win Mag.


      Sent from my iPhone using Tapatalk Pro

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        #4
        If you are using this brass to do initial load work up I would trim those longer brass to Trim-to-length and use those cases to do your load work up.

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          #5
          Originally posted by McClain View Post
          If you are using this brass to do initial load work up I would trim those longer brass to Trim-to-length and use those cases to do your load work up.
          Exactly. Kill two birds with one stone….develop a load and fire form at the same time. Then fine tune it with the fire formed cases.

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            #6
            I’d put it back in the box, sell it and get a box of Lapua. Should be available. If not then get the cheapest bullets you can find, fireform em all and let the brass flow and then find the shortest and trim to that length.

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              #7
              Belted cases should headspace off the belt. Once fired they stretch and fill the chamber. Full length resize and bump the should back .002 to .003 so they headspace off the belt again. After that check and trim so they are all the same. Eventually they will all get to the same length with some annealing.

              OR, toss them and get some new Peterson brass---OUCH $1.50 each
              Peterson Brass 300 Winchester Mag Unprimed Box of 50 - Graf & Sons
              https://www.grafs.com/retail/catalog/product/productId/76157
              300 Winchester Magnum All Peterson Cartridge casings come in one of their plastic ammo boxes.  Made in the U.S.A.   Peterson makes the traditional SAAMI spec’d version that headspaces off the belt. But it also makes a version that headspaces off the shoulder. Peterson calls that version the .300 Win Mag- Long. This listing is the SAAMI spec version. “I am extremely pleased to announce that as of July 20th, 2020, Peterson Cartridge has now added .300 Winchester Magnum brass to its’ product line,” stated president, Derek Peterson. “The road for us to produce this belted magnum case has been long, frustrating, and expensive. It has taken us over three years to release this cartridge and cost us well over $50,000 in experimental tooling alone.” Peterson continued, “Producing a brass casing with a really good belt is a difficult thing. Getting the tooling just right is an iterative process, and these .300 Win Mags took more iterations than I care to remember. “To make a new caliber casing for the first time, we design and order all the tooling. After it arrives, we do what we call a proof-of-concept (p-o-c) run. With most of the 30+ new tool packs we’ve designed, we end up with a “Best Vision” casing after one or two iterations. “But these .300 Win Mags! With many of the p-o-c runs, the resultant belt wasn’t crisp enough. So we would redesign and order different tooling and try again. With some runs we’d get a good belt, but it wasn’t in the exact correct location. Some runs, the belt was good and in the correct location, but the equipment wouldn’t run it efficiently or the scrap rate was too high. It took a few different tooling iterations to get the grain structure in the casing walls just right. After some of the failed iterations we would speculate, maybe the problem is with the dimensions of the brass cups we are using as raw material. So, we’d redesign those, and try again. “But after three years of unsettling self-doubt, and countless iterations WE GOT THE BELT. We can now make belted magnum casings! And we have really good .300 Win Mag casings on the shelf, with as good a belt as any in the industry. Our ballistician has shot some of these 20 times in a row, at SAAMI max pressure, with a minimum shoulder resize and they are still holding up well.” Peterson concluded, “If you are one of the many customers who’ve called us every week to say, “When are you people ever going to release .300 Win Mag,” we have two responses. First, thank you for waiting. Second, FINALLY, here you go; we got the belt!” Warning: Only use Peterson Cartridge Co. casings in firearms in good condition, designed, marked, and chambered for this cartridge. Do not use Peterson Cartridge Co casings for “fire forming” or any other purpose other than what they were designed and tested for. Peterson retains no responsibility for the enclosed casings if they are used outside of the manufacturer’s recommendations. This is not loaded ammunition.

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