Can someone help out a newb... 300 blackout sizing problem | Carolina Shooters Club

Can someone help out a newb... 300 blackout sizing problem

Discussion in 'Reloading' started by Bigdave0924, Nov 16, 2020.

  1. Bigdave0924

    Bigdave0924 Member

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    I got my tax stamps back for my suppressors a few weeks ago and got caught with my pants down in regards to subsonic 300 blackout.

    I have a Hornady LnL progressive press and I’m using Lyman dies. Before I went started seating primers and dropping powders I made a couple “dummy” rounds with neither primers nor powder. I ran 5 pieces of factory 300 brass through the size by die, and it fell right into the case gauge. I seat 208 gr bullets to 2.25 and none of the dummy rounds pass the case gauge. In the spirit of full disclosure to this point I’ve mostly only reloaded 9mm, 10mm, and about 1200 .223.

    I know I’m a newb but my dies were taken apart and cleaned and I e played with my sizing die and different OAL and can’t get one to fall all the way into the case gauge.
     
  2. Bigdave0924

    Bigdave0924 Member

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    Here’s a pic of one of the dummy rounds and you can notice a ring near the top of the brass that looks odd. A7CD1335-A58F-4416-9CBC-059A9E646274.jpeg
     
  3. SkydivnShooter

    SkydivnShooter Staff Member Staff Member Lifetime Member Club Subscribed

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    Looks like the crimp could be too tight? That'll cause the shoulders of the case to push out of spec and could cause the ring.
     
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  4. Bigdave0924

    Bigdave0924 Member

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    That’s what someone locally said too but I haven’t even crimped them yet??
     
  5. Crunchy Frog

    Crunchy Frog Registered Member

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    The second die is a seating/crimping die. If you have the die too deep into the press it will collapse the shoulder as seen here. Back it out a little and try again. If you are loading jacketed bullets you probably don’t need to crimp anyhow.
     
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  6. Bigdave0924

    Bigdave0924 Member

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    That was it thank you.

    Now I’m going to load some that should be about 1100 fps and slowly work down and get subsonic and hopefully run in my gun with the suppressor on it. My chrono is still back ordered hopefully it’ll be here by Christmas.
     
  7. Manny

    Manny Registered Member

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    Just think of the shoulders the second way you would with 223.
    If that sizing die is off just enough it will look fine till you seat that bullet.
    So you have the right idea to drop them into the case gauge.
    That's where I went wrong when I started making ammo I didn't have a case Gage.
    Now won't ammo without it.
     
  8. Ben W.

    Ben W. Registered Member

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    What Manny said!
     
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