AR Comp and XBR Velocities 24" Barrel AR

[LRRPF52]

Is your barrel bedded with a trued receiver face?

[Mark611]

I would like to know what your velocity's were at these charge weights?

[AR-180]

The rifle is an AR that I assembled. It’s not trued. The barrel is floated.

The velocities are listed above.

[ported45]

I bolded and color-coded based on pressure. Notice the 42fps jump from 28.2gr to 28.4gr with the 120gr ELD-M, which is a major departure from the trend line, followed by a slight velocity decrease with a charge weight increase.

Also notice the departure from the trend under the 130gr, where you saw ~30fps increase between 26.4gr and 26.6gr.

These are the things I look for when doing pressure ladders like this.

For 120gr ELD-M, if it were my rifle, I wouldn’t load over 27.8gr of AR Comp.

For the 130gr ELD-M, I wouldn’t load more than 26.4gr, unless there is room to extend your COL some.

I thought a large departure from the typical velocity increases was a big indicator of pressure being too high???

[LRRPF52]

I thought a large departure from the typical velocity increases was a big indicator of pressure being too high???

.2gr per 30fps increase is something that sticks out at me.

With a lot of ball powders, we typically see 18-25fps per .3gr under a 120-123gr.

AR Comp as a faster stick powder generating 30fps increase per .2gr of charge weight.