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zimagold
11-15-2015, 22:19
General Info

I decided to do a head to head comparison of a match 77gr SMK load compared to the new 77gr TMK. Rather than comparing a hand load tuned for a specific barrel, I chose to use Black Hills loadings as a factory "Match" loading. I figured I would share the results if I was going through the work anyways.

Notes on Data:

TMK – Black Hills 77gr TMK 556 Load – New Red Box
SMK – Black Hills 77gr OTM 556 Load – New Red Box

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All velocities were recorded separately from group tests using a Magneto Speed attached at the muzzle.

100yrd groups were shot at an indoor range with ammo at room temp (~70F). All groups were shot during a 2 minute interval. Sequence: Fire 5, load 5 more, and fire second group of five. Approximately 10 seconds between rds. I was mainly looking for extreme spread during relatively rapid fire.

600yrd groups were shot outdoors on a 60-65F day with density altitude of 6700-7000ft. Winds were mild at 2-3mph. Shots were taken at a rate of 1rd per 5 minutes. I was attempting to maximize accuracy in a slow fire scenario. Environmental variables were captured using a Kestrel 4500.

Disclaimer: I am by no means an expert. This is a one batch, simple, amateur test with nothing calibrated. Results will vary.

zimagold
11-15-2015, 22:20
Tear Down
<Placeholder>

zimagold
11-15-2015, 22:20
100yrd 20” Barrel Data

Barrel Info: 20” Rainier Arms Ultra Match with Fluted DMR Profile, Rifle Gas, 1:8 Twist
Federal XM193 Velocity = 3310 FPS

SMK 10rd Chronograph Data
Average = 2795 FPS
Standard Deviation = 9.6 FPS
Max = 2812 FPS
Min = 2781 FPS
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TMK 10rd Chronograph Data
Average = 2792 FPS
Standard Deviation = 15.7 FPS
Max = 2826 FPS
Min = 2771 FPS
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Group Test - 10rds SMK
Extreme Spread = 1.47” [1.40 MOA]
Mean Radius = 0.53” [0.51 MOA]
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Group Test - 10rds TMK
Extreme Spread = 1.65” [1.58 MOA]
Mean Radius = 0.59”[0.56 MOA]
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zimagold
11-15-2015, 22:21
100yrd 16” Barrel Data

Barrel Info: 16.1” BCM Non-Hammer Forged Chrome Lined, Mid-length, Light Weight, 1:7 Twist
Federal XM193 Velocity = 3062 FPS

TMK 10rd Chronograph Data
Average = 2635 FPS
Standard Deviation = 23.5 FPS
Max = 2675 FPS
Min = 2635 FPS
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Group Test - 10rds TMK
Extreme Spread = 1.29” [1.23 MOA]
Mean Radius = 0.50” [0.48 MOA]
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zimagold
11-15-2015, 22:21
100yrd 12.5” Barrel Data

Barrel Info: 12.5” Rainier Arms Ultra Match, Carbine Gas, 1:8 Twist
Federal XM193 Velocity = 2960 FPS

TMK 10rd Chronograph Data
Average = 2540 FPS
Standard Deviation = 16.6 FPS
Max = 2575 FPS
Min = 2516 FPS
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Group Test - 10rds TMK
Extreme Spread = 2.21” [2.11 MOA]
Mean Radius = 0.63” [0.60 MOA]
Note: Taped hole is XM193 sighter, this group had a major shift in zero and crossed over targets.
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zimagold
11-15-2015, 22:22
600yrd 20” Barrel Data

BC Values used for drop calculation G1 BC / Min FPS

77gr SMK
0.372 / 3000
0.362 / 2500
0.362 / 1700
0.343 / 0

77gr TMK
0.420 / 2400
0.415 / 2000
0.395 / 1750
0.380 / 0

Group Test - 5rds SMK
Extreme Spread = 7.61” [1.21 MOA]
Mean Radius = 2.41” [0.38 MOA]
Correction from 100yrd zero = 15.0 MOA
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Group Test - 5rds TMK
Extreme Spread = 4.93” [0.79 MOA]
Mean Radius = 2.10” [0.33 MOA]
Correction from 100yrd zero = 13.8 MOA
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Calculated Advantage of TMK = 1.2 MOA Less Drop
Test Advantage of TMK = 0.9 MOA Less Drop

zimagold
11-15-2015, 22:23
Summary

The TMKs grouped well at range for a non-tuned factory load. They also seemed to be a little more forgiving in the wind shooting other targets outside the group test. Wind improvement was calculated as an 15% decrease in required hold at 600yds, I did not specifically test wind drift. Data below is calculated using the above BC values used for 600yrd tests and assumes DA of 6000FT.

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The best improvement with the new TMK seems to be Expansion/Fragmentation. Using the above data and assuming the 1900fps limit published by Sierra lines up with the real world.

20” Frag Range - 535yds
16” Frag Range - 448yds
12.5” Frag Range - 393yds

This practical range is quite impressive especially in the SBR. I have seen a few people post results from hunting that make the 1900fps limit seem like a real world value.

I'll update the above as I finish up.

Great-Kazoo
11-15-2015, 22:27
Thanks for the info. All i see is <Group Photo> No pictures.

zimagold
11-15-2015, 22:30
Group photos should be up now. Still need to process photos of fired case heads. I'll try to update the above later this week.

zimagold
11-17-2015, 21:49
Added case head photos, sequence numbers to 100yrd groups, and summary table comparing SMK/TMK in 20 inch.