Barnes 120g mb and ar comp

[LRRPF52]

Be careful when working up a load with AR Comp under anything 120gr and higher cup and core.

You’ll start to reach the top in the mid 27.x grain charge weight. Some rifles and chambers might handle up to 28.0gr ok with a more conventional 120-123gr cup and core bullet like an SST, A-MAX, ELD-M, or Nosler Ballistic Tip, but under harder/thicker jacketed bullets, it will hit maximum peak pressure sooner.

In the Grendel Handbooks, there is data with it under several 120-123gr bullets.

I would do a ladder starting with 26.0gr under the 120gr Match Burner in single strings of increasing charge weight by no more than .3gr over a chronograph and see what it shows you.

That’s assuming using one of the common cases, whether they be Lapua, Hornady, Norma, or Starline.

I would not load past 28.0gr. AR-Comp has a similar density and burn rate to 8208 XBR, so both are slightly on the fast side for bullets over 107gr.