Labradar chrono analysis of 300 BLK Handloads (it's good to have friends with toys).

One of the advanatges of having friends that shoot is getting to borrow their toys, which is exactly what I’ve been able to do for the last few days, specifically a Labradar doppler based chronograph.  I’ve had a 8″ 300 BLK SBR (Noveske Barrel) for a while now and have slowly assembled the components to load subsonic ammo: H110 powder and 208 grain HPBT Match King bullets specifically.  The chrono was the last missing piece I needed to make sure I was loading right up to but just enough under supersonic.
I grabbed some load data from the Hornady website which suggested 9.6 grains for s subsonic load.  With that as a base, I rainbowed up .3 grains to 9.9 and down .5 grains to 9.1, loading 5 rounds of each with a crimp.
This was my first time using the Labradar and I have to say I am impressed.  Maybe not ~$600 impressed, but again, it’s good to have friends ;-).  Overall it worked well, although I could not get it to trigger acoustically when my SBR was suppressed, but the doppler based triggering seemed to work fine.
Overall conclusions:

  • I think I will load out the rest of the 208 grain bullets I have with 9.8 grains.  I had one 9.9 that went supersonic.  It was around 43 degrees today so I am thinking 9.8 should keep me right under sub sonic even when it gets warmer.  Although the 9.9 was my best group by far…maybe I need some more experimentation with a better powder measure (see next point).
  • I need a more accurate powder measure.  I was really suprised with the velocity spread on some of the rounds.  I suppose it could be that the Labradar wasn’t triggering or tracking well, but I don’t think so.
  • I found it interesting that all loads cycled the gun with no issues and even locked it back when done.  I will have to try the final load unsupressed to see that is a factor.

Details for each load below:

9.1 grains H110

Stats – Average 926.32 fps
Stats – Highest 936.87 fps
Stats – Lowest 910.69 fps
Stats – Ext. Spread 26.19 fps
Stats – Std. Dev 9.81 fps


9.2 grains H110

Stats – Average 942.55 fps
Stats – Highest 964.82 fps
Stats – Lowest 902.65 fps
Stats – Ext. Spread 62.17 fps
Stats – Std. Dev 34.63 fps


9.3 grains H110

(NO data …I forgot to arm the Labradar… 🙁 )

9.4 grains H110

Stats – Average 939.41 fps
Stats – Highest 1033.25 fps
Stats – Lowest 663.13 fps
Stats – Ext. Spread 370.12 fps
Stats – Std. Dev 136.89 fps


9.5 grains H110

Stats – Average 956.69 fps
Stats – Highest 1038.89 fps
Stats – Lowest 815.3 fps
Stats – Ext. Spread 223.59 fps
Stats – Std. Dev 97.55 fps


9.6 grains H110

(This was my first set of shots and there were only 4 captured since it took me the first shot to figure out that the acoustic triggering wouldn’t work…and even of the 4 I think there were some triggering or tracking issues so this data is probably bogus)

Stats – Average 863.54 fps
Stats – Highest 1058.76 fps
Stats – Lowest 679.97 fps
Stats – Ext. Spread 378.79 fps
Stats – Std. Dev 173.61 fps


9.7 grains H110

Stats – Average 1025.33 fps
Stats – Highest 1083.55 fps
Stats – Lowest 1005.14 fps
Stats – Ext. Spread 78.4 fps
Stats – Std. Dev 38.81 fps


9.8 grains H110

Stats – Average 1060.98 fps
Stats – Highest 1082.36 fps
Stats – Lowest 1043.84 fps
Stats – Ext. Spread 38.51 fps
Stats – Std. Dev 14.01 fps


9.9 grains H110

Stats – Average 1044.19 fps
Stats – Highest 1119.09 fps
Stats – Lowest 882.99 fps
Stats – Ext. Spread 236.09 fps
Stats – Std. Dev 82.18 fps

I kept coming up with things to do with the Labradar.  I ended up measuring 10 shots of 55 grain 5.56 over 23.6 grains of varget from a 11.5 in SBR supressed, the same SBR unsupressed and then a 16″ standard rifle just to see the differences in velocity:

SBR – Suppressed SBR Standard Rifle
Stats – Average 2172.45 2158.08 2439.6 fps
Stats – Highest 2250.56 2221.8 2463.82 fps
Stats – Lowest 2122.62 2099.7 2410.31 fps
Stats – Ext. Spread 127.95 122.1 53.51 fps
Stats – Std. Dev 45.59 38.86 19.53 fps

The velocity spread on these shots was much smaller, so maybe H110 just doesn’t meter as well as Varget?  Lots more to do before I have to give back the toys 😉






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