Some Chrono Results - 6920 SOCOM

[waffentomas]

I finally got a decent day to take the akitas out into the woods with me for some chronographing. So here are some results, a mix of hand loads and factory for anybody who cares. I'll update the thread when I get chance to do more testing.

First: The tool.



Sunny, 35 degrees, 1200 feet elevation, Barometer 29.60, Humidity 75%

All strings are 10 rounds, fired at 15 feet from device.

Nosler 80gr BTHP 25.1gr TAC

Avg: 2542
SD: 57.3
Spread:129
Kinetic Energy: 1148


Sierra 77gr BTHP 22.0gr AR COMP

Avg: 2427
SD: 43.8
Spread: 136
Kinetic Energy: 1008


HPR 75gr BTHP

Avg: 2549
SD: 44.1
Spread: 93
Kinetic Energy: 1082


HSM 55gr FMJ 5.56

Avg: 3001
SD: 42.7
Spread: 138
Kinetic Energy: 1100


Herters steel case 55gr FMJ

Avg: 2817
SD: 53.4
Spread: 130
Kinetic Energy: 970


PMC 55gr FMJ

Avg: 2755
SD: 97.2
Spread: 275
Kinetic Energy: 927


55gr SP 26.0 gr Varget

Avg: 2366
SD: 41.2
Spread: 117
Kinetic Energy: 684

[ALCOAR]

Wow, 2nd post/new member....and you drop informative data on us like that

I look forward to seeing more great contributions from you sir in the future, and it's great to see a new member already posting a valuble contribution to the M4C community.

I also appreciate groups/strings that are derived from 10rds vs. 5rds, or 3rds. Makes a big difference if using this data for precision/LR dope calculations.

[dookie1481]

I finally got a decent day to take the akitas out into the woods with me for some chronographing. So here are some results, a mix of hand loads and factory for anybody who cares. I'll update the thread when I get chance to do more testing.

First: The tool.



Sunny, 35 degrees, 1200 feet elevation, Barometer 29.60, Humidity 75%

All strings are 10 rounds, fired at 15 feet from device.

Nosler 80gr BTHP 25.1gr TAC

Avg: 2542
SD: 57.3
Spread:129
Kinetic Energy: 1148


Sierra 77gr BTHP 22.0gr AR COMP

Avg: 2427
SD: 43.8
Spread: 136
Kinetic Energy: 1008


HPR 75gr BTHP

Avg: 2549
SD: 44.1
Spread: 93
Kinetic Energy: 1082


HSM 55gr FMJ 5.56

Avg: 3001
SD: 42.7
Spread: 138
Kinetic Energy: 1100


Herters steel case 55gr FMJ

Avg: 2817
SD: 53.4
Spread: 130
Kinetic Energy: 970


PMC 55gr FMJ

Avg: 2755
SD: 97.2
Spread: 275
Kinetic Energy: 927


55gr SP 26.0 gr Varget

Avg: 2366
SD: 41.2
Spread: 117
Kinetic Energy: 684

Are those SD's about par for the course with 5.56? I thought I recalled reading that the .mil rejection criteria were something like >15 FPS...

[duece71]

Good info, thank you. Interesting that PMC has the highest SD, will have to keep that in mind during my next purchase (if it actually happens). I will probably be reloading for my ARs before I can actually purchase any more ammo at a decent price....
Thanks again.

[markm]

Are those SD's about par for the course with 5.56?

They seem painful to me...

Might be a neck tension issue or primers. Wolf primers have been kind to our SDs over the years.

[MistWolf]

Good info

What barrel length, chamber & twist?

[Hunter Rose]

He posted 6920 SOCOM barrel in title so most likely 1/7 twist 16" barrel w/ 5.56 chamber. Looks like a 16" in the pic.

[waffentomas]

He posted 6920 SOCOM barrel in title so most likely 1/7 twist 16" barrel w/ 5.56 chamber. Looks like a 16" in the pic.

Correct on all accounts.

Also, on the SD issue, they are a bit painful, but I think they would come down if I had fired more rounds in each string. 10 is a statistically viable sample, but not by much. I'd of liked to have done longer strings but I was being stingy...ammo, primers, powder and bullets are all a bit tough to come by right now.

Trident, thanks for the kind words. I was never a fan of the 5.56 as an effective 'man stopper' when I was in the Marines and swore I'd never get one. I carried an M21 in the Corps and it took some lobbying to do that. I finally got around to getting one a couple of months ago right after the AR buying frenzy began. I was at Cabelas just inquiring about them, they had been sold out of AR platforms a couple weeks, when a customer who had just gotten his 6920 SOCOM on special order decided he didn't want it. He'd placed the order in June, and it showed up in December. I had told myself right after the CT shooting, IF I was going to get one, I'd hold out for a Colt, because that is what I carried in the Marines (before I got the Springfield). I guess it was meant to be. It was $1400, but not a horrible price at the time.

Sorry for being long winded, but that's how I ended up here. Needed a good forum to reacquaint myself with the M4. I am a die hard 10mm fan, and have been carrying one since 1986, but joined the only two decent forums I could find in 1999 (don't think I supposed to mention other forums here) and was constantly posting load data on those. It's always useful and interesting information to have, so I hope to dump more data on y'all soon. I've got some NATO white box ammo, but am hoarding it. Maybe I'll pry a box lose from myself for the next session so we can get a better read on Mil-Spec standard deviations.

[T2C]

The SD of the PMC is disturbing. You would think that factory ammunition would be more consistent. Was the PMC from a newer lot or some older ammunition you had?

[markm]

The spreads are still pretty big. What kind of chrono? It could be accuracy in the Chrono.

I've been wanting to get one of those magneto speed thingies... but that attaches to the barrel... so you mess with your barrel harmonics a little.