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I decided to do some experimenting with my 5.56mm loads out of my Hornady manual. Why? I read an article about experienced reloaders that successfully load up and above the maximum listed loads. Some years ago, I met a gentleman who loaded above max. At that time, I was not ready to experiment. Now, after ten years of reloading, I decided to up my skill level and move forwards. I understand the dangers associated and I understand that my experiment was for me and my personal knowledge. I want to share some information, too. My rifle is an AR15 with a 14.5" barrel, carbine gas, and chambered in 5.56mm.
To start, I watched a video on how to determine maximum pressure via a bolt-action rifle. This video is not to cross-reference a gas gun (AR15). In fact, I have learned that a 5.56mm case is proportional to a case such as a .308 due to case capacity. Xman helped me with that knowledge (thank you, Sir). I knew that in the back of my mind but it helps when someone reassures that knowledge. The video states that you load 2.5 grains above max. This works fine with a .308 cartridge which holds more powder than a .223/5.56mm case. My estimate is that a .223/5.56mm case holds about 60% of a .308 case. We can get real technical but that's where I started. I multiplied .60 x 2.5 = 1.5. I have a working number of 1.5 grains proportionally.
I used Hornady 1x fired brass, WSR primers, Hornady 60gr Vmax, and CFE 223 power. I shot my rounds in a controlled environment (indoor). It was at a 50 yard range. I fired three shot groups to measure the accuracy. Overall, the purpose of my test was to find maximum pressure by examining the primers and cases. I learned to measure the pressure band as well. I measured the pressure band in three ways: the band from a factory cartridge, a sized cartridge, and then fired cartridge to see the expansion. Please see the chart below:
Note: The maximum 5.56mm load in the Hornady book was 27.7 grains (9th Ed.). I started to see flat primers at 27.6 grains. At 28.2, I could feel a crater in the primer which Constructor referenced (thank you, Sir). My finger nail hung up on the crater. ***I waited to fire 28.5 grains until I was outdoors. I used a remote system to fire that round. I saw gas leaks around the primer and the pressure band expanded more. See chart above.
I have a final load of 28.5. I am not sure if I will test that one. If I do, I will remote detonate to avoid danger and it will be outdoors. At this point, I successfully loaded a 1/2 grain above max. Hornady had the max pressure right at 27.7grains. In my experience, their manuals are on the light side.
Note: 27.9 grains produced a group measured at .375."
In the words of Chief Fundak: Do NOT do what I do.
TC
To start, I watched a video on how to determine maximum pressure via a bolt-action rifle. This video is not to cross-reference a gas gun (AR15). In fact, I have learned that a 5.56mm case is proportional to a case such as a .308 due to case capacity. Xman helped me with that knowledge (thank you, Sir). I knew that in the back of my mind but it helps when someone reassures that knowledge. The video states that you load 2.5 grains above max. This works fine with a .308 cartridge which holds more powder than a .223/5.56mm case. My estimate is that a .223/5.56mm case holds about 60% of a .308 case. We can get real technical but that's where I started. I multiplied .60 x 2.5 = 1.5. I have a working number of 1.5 grains proportionally.
I used Hornady 1x fired brass, WSR primers, Hornady 60gr Vmax, and CFE 223 power. I shot my rounds in a controlled environment (indoor). It was at a 50 yard range. I fired three shot groups to measure the accuracy. Overall, the purpose of my test was to find maximum pressure by examining the primers and cases. I learned to measure the pressure band as well. I measured the pressure band in three ways: the band from a factory cartridge, a sized cartridge, and then fired cartridge to see the expansion. Please see the chart below:
| Powder | Charge | Flat Primer | Groups @ 50 yds | FactoryPband | Pbsized | PBafter | |||
| CFE223 | 27 | 0 | 1.25" | 0.471 | 0.472 | 0.473 | |||
| CFE223 | 27.3 | 0 | 1.875" | 0.471 | 0.472 | 0.474 | |||
| CFE223 | 27.6 | 1 of 3 | 1.75" | 0.471 | 0.473 | 0.474 | |||
| CFE223 | 27.9 | 1 of 3 | .375" | 0.471 | 0.472 | 0.474 | |||
| CFE223 | 28.2 | 1 of 3 | .500" | 0.471 | 0.473 | 0.474 | |||
| CFE223 | 28.5 | 3 of 3 | Null | 0.471 | 0.472 | 0.475 |
Note: The maximum 5.56mm load in the Hornady book was 27.7 grains (9th Ed.). I started to see flat primers at 27.6 grains. At 28.2, I could feel a crater in the primer which Constructor referenced (thank you, Sir). My finger nail hung up on the crater. ***I waited to fire 28.5 grains until I was outdoors. I used a remote system to fire that round. I saw gas leaks around the primer and the pressure band expanded more. See chart above.
I have a final load of 28.5. I am not sure if I will test that one. If I do, I will remote detonate to avoid danger and it will be outdoors. At this point, I successfully loaded a 1/2 grain above max. Hornady had the max pressure right at 27.7grains. In my experience, their manuals are on the light side.
Note: 27.9 grains produced a group measured at .375."
In the words of Chief Fundak: Do NOT do what I do.
TC
