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Old 08-28-2012, 2:35 PM
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Velocity duplicates of Black Hills 77-grain “blue box” according to Quickload
(scroll down for chart)

Black Hills 77-grain “blue box” ammo consistently chronographs about 2710 fps through the rifle I use for all my AR15 ammo testing.

These loads were determined by Quickload version 3.6.
Quickload is a fairly expensive computer program for reloaders.
Quickload has been around in various forms since 1987.

Comparison history
The only load listed here, and actually tested over a chronograph, is the load for TAC powder. For all intents and purposes, TAC provided a velocity identical to the velocity obtained from Black Hills “blue box” 77-grain ammo with the Sierra 77-grain MatchKing bullet. Moreover, the powder I inspected from an actual 77-grain “blue box” cartridge weighed exactly 23.9 grains, and had an appearance exactly like Ramshot TAC powder.

Quickload consistently predicts about 90 FPS faster velocities than actually obtained over a chronograph.
Based on my empirical testing of various loads over the chronograph, and comparing the chronographed velocities of those various loads, I have discovered that Quickload routinely predicts a velocity 80 to 100 feet per second faster than the velocity actually obtained by chronograph measurement when the ammo is fired in an AR15 type rifle. My theory for the consistent velocity discrepancy is that Quickload does not account for the loss of pressure due to gas escape through the AR15 gas port.

Black Hills 77-grain “blue box” ammo consistently chronographs about 2710 fps through the rifle I use for all my AR15 ammo testing. Similarly, 23.9 grains of TAC provides the same velocity with the same bullet. Quickload suggests that 23.9 grains should generate 2807 fps from an un-ported 20-inch barrel. Based on this consistent discrepancy, I have selected for my investigation, loads modeled by Quickload which also are predicted to be in the approximate 2800 fps range.

Magazine-length dimensions
All Quickload modeled loads assume bullet seated to 2.250” overall cartridge length.
SAAMI specification maximum length is 2.260”
I find that ammo loaded to SAAMI maximum length will sometimes be just a bit too long for AR15 magazines.
Ammo loaded to 2.250” or less never causes a feed-malfunction due to excess length.

Pressure info
The SAAMI industry specification for 5.56 NATO ammunition is 62,366 maximum PSI.
According to Quickload, all loads listed in the following chart fall below SAAMI maximum pressure, at 70 degrees temperature. This modeling exercise does not attempt to account for any variations which may occur due to temperature.

This information is provided only for educational purposes. None of these loads are specifically recommended for any particular, or general, purpose. Persons using this information to construct live ammunition do so at their own risk, and with the understanding that this information may not be accurate, and that the result of use of this information may result in damage to property or injury to person.

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