03-26-2021, 07:59 PM
James Young Wrote:I have been looking into this as well. I'm curious how comparative 6.5 Grendel is versus the 300 Blackout in short barrels. So far I only have estimates based on limited data, but my numbers suggest that the short Grendel barrels should be superior to Blackout barrels 3.0" longer. A 7.5" Grendel barrel will equal the energy of a 10.5" 300 Blackout in a similar grain weight (~125) and easily outshoot it at distance. The 7.5" barrel Grendel should also have the same energy as a 77 grain 5.56 out of a 16" barrel but will struggle to keep up at distance.
The same is theoretically true in comparing 6.5 Grendel to 300 Blackout in the popular 5.5" Sig Rattler and less popular 5.5" Maxim PDX. In a 5.5" barrel the Grendel should be ~200FPS faster with ~200-300 ft lbs more energy. The problem is we have no real data at these barrel lengths, and it is not unusual for calibers to lose significant velocity at the shorter lengths.
When I get it built I'll chronograph a could factory loads out of it and post up my results. I'll have some 12.5's and some 10.5's that I have recently build that I can compare it to so we can kind of maybe get an idea of what that velocity loss looks like the shorter you go. My 8.5 inch barrel is supposed to be "magna-ported" as an option I selected which looks like its two lines of ports about .75 to 1 inch long drilled at about 45° from the top of the barrel... so those velocities may be more representative of what a 7.5 barrel may do over than of a true 8.5 inch. If this build all goes well I may contact him and see if he could make me something ridiculously short like 5-6 incher.