Chrono Data Request (20" AR)

[blacklisted]

Does anyone have any chrono data for comparable loads to the ones below, fired from a 20" AR?

69gr. HPBT from 23.5 to 26.0 grains Varget
55gr. FMJ from 25.5 to 27.5 grain Varget

I would like to compare other people's results with mine, because some of my velocities seem a bit high. The only pressure sign encountered were some ejector marks with the max load of 27.5 grains Varget. The velocities that I encountered with that load were unexpected, and show why careful load development is necessary. My rifle functioned flawlessly with all loads.

All loads used CCI #41 primers. FMJ Loads used mixed military brass (LC, RORG, and a few WCC), and the MatchKing loads were all in recent (05-06) Lake City brass. Chronograph (Shooting Chrony Beta Master) was approximately 10 feet from the muzzle.

I also fired one 10 round string of 1992 production Radway Green SS109 for a source of comparison.

Data begins:

-----1992 Radway Green SS109-----

Velocity (fps):
Shot 01 3069 (first shot of the day)
Shot 02 3143
Shot 03 3106
Shot 04 3103
Shot 05 3137
Shot 06 3135
Shot 07 3123
Shot 08 3100
Shot 09 3103
Shot 10 3140

High Velocity 3143
Low Velocity 3069
Average Velocity 3116
Extreme Spread 74
Standard Deviation 23.71

-----69gr. HPBT**Maximum Load**

Velocity (fps):
Shot 01 3011
Shot 02 3039
Shot 03 3016
Shot 04 3011
Shot 05 2994
Shot 06 2986
Shot 07 3032
Shot 08 3024
Shot 09 2993
Shot 10 n/a

High Velocity 3039
Low Velocity 2986
Average Velocity 3012
Extreme Spread 53
Standard Deviation 18.21

-----55gr. FMJ**Maximum Load**

Velocity (fps):
Shot 01 3342
Shot 02 3314
Shot 03 3315
Shot 04 3310
Shot 05 3250
Shot 06 3320
Shot 07 3286
Shot 08 3332
Shot 09 3284
Shot 10 3346

High Velocity 3346
Low Velocity 3250
Average Velocity 3310
Extreme Spread 96
Standard Deviation 29.43

-----

[blacklisted]

I will also include some .45-70 data that I collected. The following strings were fired from a Marlin Model 1895 with 22" 1:20 twist barrel:

Caliber .45-70 Government
Bullet Remington 300gr. JHP
Powder 48.0gr. Alliant Reloder 7
Primer FED #210
Case Starline
Case Length 2.095”
Overall Length 2.540”
Production Date 12/26/07

Velocity (fps):
Shot 01 1894
Shot 02 1918
Shot 03 1971
Shot 04 1953
Shot 05 1948
Shot 06 1918
Shot 07 1982
Shot 08 1980
Shot 09 1939
Shot 10 2010

High Velocity 2010
Low Velocity 1894
Average Velocity 1951
Extreme Spread 116
Standard Deviation 35.38

-----

Caliber .45-70 Government
Bullet Remington 300gr. JHP
Powder 48.5gr. Alliant Reloder 7
Primer FED #210
Case Starline
Case Length 2.095”
Overall Length 2.540”
Production Date 12/26/07

Velocity (fps):
Shot 01 1946
Shot 02 1948
Shot 03 1941
Shot 04 1967
Shot 05 1976
Shot 06 1951
Shot 07 1960
Shot 08 2006
Shot 09 1974
Shot 10 1967

High Velocity 2006
Low Velocity 1941
Average Velocity 1964
Extreme Spread 65
Standard Deviation 19.2

-----

Caliber .45-70 Government
Bullet Remington 300gr. JHP
Powder 49.0gr. Alliant Reloder 7
Primer FED #210
Case Starline
Case Length 2.095”
Overall Length 2.540”
Production Date 12/26/07

Velocity (fps):
Shot 01 1937
Shot 02 1949
Shot 03 1970
Shot 04 2002
Shot 05 1952
Shot 06 1976
Shot 07 1983
Shot 08 1984
Shot 09 1955
Shot 10 1955

High Velocity 2002
Low Velocity 1937
Average Velocity 1966
Extreme Spread 65
Standard Deviation 19.98

-----

Specifications:
Caliber .45-70 Government
Bullet Remington 300gr. JHP
Powder 49.5gr. Alliant Reloder 7
Primer FED #210
Case Starline
Case Length 2.095”
Overall Length 2.540”
Production Date 12/26/07

Velocity (fps):
Shot 01 1970
Shot 02 2005
Shot 03 1978
Shot 04 2005
Shot 05 1956
Shot 06 1987
Shot 07 1978
Shot 08 1966
Shot 09 1948
Shot 10 1996

High Velocity 2005
Low Velocity 1948
Average Velocity 1979
Extreme Spread 57
Standard Deviation 19.57

-----

Caliber .45-70 Government
Bullet Remington 300gr. JHP
Powder 50.0gr. Alliant Reloder 7
Primer FED #210
Case Starline
Case Length 2.095”
Overall Length 2.540”
Production Date 12/26/07

Velocity (fps):
Shot 01 2023
Shot 02 2032
Shot 03 2033
Shot 04 2018
Shot 05 2007
Shot 06 1982
Shot 07 2017
Shot 08 1998
Shot 09 2006
Shot 10 2016

High Velocity 2033
Low Velocity 1982
Average Velocity 2013
Extreme Spread 51
Standard Deviation 15.57

-----

[6079Winston]

The average velocity of 25.0 gr Varget with the 69 gr HPBT seems in line with the data on www.njhighpower.com, although the extreme spread appears high, possibly due to mixed lots of brass of different capacity and weight? It might also be some other inconsistency in cartridge headspace, neck tension, priming or the countless other variables in reloading. The .45-70 data looks more consistent, with lower extreme spreads decreasing as charge weight increases.

[blacklisted]

End of week bump.