My 30cal Neck Tension Journey

rustyinbend

GySgt USMC 1976-1992
Full Member
Minuteman
  • Dec 9, 2018
    2,382
    2,308
    Bend, Oregon
    I reload 300 Win Mag, 300-PRC, and 300 Norma Mag ... and I've been wrestling with neck tension as I've tried different bushings, different mandrels, and followed all kinds of different advice. Bottom line ... here's what works perfectly for me, and by coincidence, it's exactly the same for all three rifles:

    Short Action Customs .333 Bushing
    21st Century .3050 Mandrel

    This combination gives me smooth seating with consistent neck tension (albeit by "feel" since I'm just not buying an Arbor Press), great concentricity, and single-digit SD's across the board. I wish I'd figured that out sooner ... would have saved me a lot of time and money and supplies. I guess it's all part of the journey, eh?

    Just wanted to share that for anyone else still searching as I was for a long time. Frankly, it surprised me that the same bushing and mandrel produced remarkably consistent results for all three of my 30-cal cartridges. Have any of you guys experienced this same phenomenon (multiple caliber variants - same bushing/mandrel combo)? Just curious ...

    If interested ... other component data follows.
    • Redding Type-S Bushing Dies
    • Redding Competition Micrometer Seating Dies
    • Berger Bullets
      • 300-WM is Berger 200.20x Hybrid
      • 300-PRC is Berger 220 Long Range Hybrid Target
      • 300-NM is Berger 230 Hybrid OTM Tactical
    • Brass
      • 300-WM is Peterson
      • 300-PRC and 300-NM are both Lapua
      • Brass is all on its second or third firing
    • Rifles
      • MPA 300-WMBA
      • Barrett MRAD 300-PRC
      • MPA 300-NMBA
    • Other
      • Everything is wet-tumbled (Frankford), annealed (AMP), and trimmed (Henderson) after every firing.
     
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    Bacarrat

    Gunny Sergeant
    Full Member
    Minuteman
  • Jan 22, 2007
    3,346
    846
    Houston, TX
    What's your loaded round measuring? Most people I know run a .335-.338 bushing on their 30 cals. I run a .336 on my 308 Lapua brass and .337 on the 300NM Lapua brass.
     

    jmornoinf

    Supporter
    Supporter
    Full Member
    Minuteman
    Mar 27, 2019
    153
    87
    What's your loaded round measuring? Most people I know run a .335-.338 bushing on their 30 cals. I run a .336 on my 308 Lapua brass and .337 on the 300NM Lapua brass.
    I am running a .335 busing with a Sinclair .3070 mandrel for 300 PRC Lapua brass. I am convinced a smaller bushing paired with a mandrel is the way to go.

    I am achieving 8ish SD...which is good enough. Low SDs on 300 PRC seem to be hard to do. I am at 5ish with 6 Creed
     

    rustyinbend

    GySgt USMC 1976-1992
    Full Member
    Minuteman
  • Dec 9, 2018
    2,382
    2,308
    Bend, Oregon
    What's your loaded round measuring? Most people I know run a .335-.338 bushing on their 30 cals. I run a .336 on my 308 Lapua brass and .337 on the 300NM Lapua brass.
    300-WM ... .335
    300-NM ... .337
    No 300-PRC loaded up right now
     

    rustyinbend

    GySgt USMC 1976-1992
    Full Member
    Minuteman
  • Dec 9, 2018
    2,382
    2,308
    Bend, Oregon
    I am running a .335 busing with a Sinclair .3070 mandrel for 300 PRC Lapua brass. I am convinced a smaller bushing paired with a mandrel is the way to go.

    I am achieving 8ish SD...which is good enough. Low SDs on 300 PRC seem to be hard to do. I am at 5ish with 6 Creed
    I've really gotten my 300-PRC dialed in recently. On Lapua brass with .333 bushing and .3050 mandrel I'm getting SD's in the low 6's. Anything larger for bushings and mandrels and I'd just get neck tension that felt way to light. The thing that's really crazy is that the book G7 BC on my Berger LRHT 220's is .369 ... but my actual adjusted BC measured between 1000 and 1400 yards is .399 on velocities averaging 2878. Some would say that I should seek higher velocities, but this is where my Barrett MRAD settled ... which is fine with me if I can hit a 1-mile target (most of the time).