subsonic loads

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by HawkeyeFan, Aug 12, 2010.

  1. HawkeyeFan

    HawkeyeFan Member

    Apr 25, 2010
    I am interested in using subsonic loads for deer. I have no idea what bullet to use when a starting velocity for a .308 is down around 1000 fps. I am assuming a soft bullet like an A-max but don't know. With such a mild loads what would be shot limitations. 100 yds?, 150? This is a whole new ball game for me. Any advice would be greatly appreciated.


    Kickoff is coming and that means hunting is soon to follow.
  2. azsugarbear

    azsugarbear Well-Known Member

    Sep 20, 2005
    I shoot a 300 Whisper on an AR-15 platform. Lots of research done on this caliber concerning 30 cal bullets @ 1000 fps. Bottom line: there is no commercial bullet out there that will open up at subsonic velocities. There is one custom bullet maker that has a 30 cal the will open up at 1000 fps, but they are pricey:

    .308 - Outlaw State Bullets LLC

    A 30 cal. subsonic round is most effective on game when it tumbles. This requires using heavy for caliber bullets and a slow twist barrel. Most 300 Whisper shooters use a 220 or 240 SMK; 200 Accubond, or 208 A-Max. You will need a 1-8 twist to stabilize. If your 308 has a 1-11 twist, you might try a 180 - 190 grain bullet.

    I've also heard of some loading flat-based bullets backward or utilizing 30 cal flatnose bullets designed for the feeding and slower velocity of the 30-30 cal.
  3. tackb

    tackb Well-Known Member

    Jun 5, 2007
    I've done a bit of stuff with subs in a 308, i ended up with a 180g flat base round nose over about 7 grains of unique ish ?

    shot placement is critical with subsonic rounds , i could group about an inch at 100m which i thought was about the limit maybe 150m to hit a deer in the heart and remember nothing is going to go far with a 308 hole in their heart?

    good luck it's great fun.

    i didn't know about those outlaw state bullets at the time though, they look coooool ( i wonder how i can get them in the uk?)
    Last edited: Aug 13, 2010
  4. Shane G.

    Shane G. Active Member

    Apr 29, 2010
    I was using 175's in my .308 with 10grains of trailboss at around 1050fps in a 26" barrel. I would say to start out just a bit over subsonic as you don't want a bullet stuck halfway down your barrel,seen that a few times. Then work back over a chrony.
  5. LouBoyd

    LouBoyd Well-Known Member

    Oct 15, 2007
    I'd suggest you read the approximately 127 posts in this thread on the Quarterbore forum.
    308 subsonic - Quarterbore's Forums

    If that doesn't work go to
    Quarterbore's Forums
    then forums
    then 300 Whisper Forums
    then Other Subsonic Topics
    then 308 Subsonic

    It's a good thread which covers many aspects of shooting a dual use super and subsonic, bolt and semi-auto 308 rifles.
    It's easy to get a bullet to leave a 308 rifle at around 1000 fps. What's not easy is to do that with low velocity spread, properly stabilized, clean burning, with a high enough BC to deliver useful energy and which will expand at a reasonable depth in the game.

    Ssubsonic bullet will have less than 20% of the energy of a standard 308 in the 100 to 200 yard range. Shot placement is critical with lower energy but harder to achieve with the vertical stringing that's hard to avoid with subsonics.

    Without a suppressor the supersonic crack will be gone but the muzzle blast will still be roughly as loud as standard 308 at about 3 times the distance. Hearing protection is still needed.

    Personally I don't see much point in shooting a 308 Subsonic. It can be done but why? There are other cartridges which are much more suitable.
    Last edited: Aug 13, 2010
  6. sniper762mm

    sniper762mm Well-Known Member

    Jul 23, 2010
    i loaded 200gr. cast gas check projos with 7gr. of unique (info given to me by sierra) which chronographed out of my m1a at 1050 fps. i had to adjust my scope to its normal load (168gr. hpbt at 2650fps) to the 500 yard zero to hit at 100 yards.