Ok, this is probably going to warrant another thread in the competition section, however, today was my 2nd ever F-AR match. Again 600 yards.
Temperature starting in the low 40°s and up to the mid 50°s by the end of match.
To summarize our format, I was in first group today, so the first string was shot at ~8:30am, then I'm off to pull targets for second group to shoot BOTH of their strings. When complete, I returned to the line to complete my 2nd string. This is in effort to keep the early morning shooters wind conditions mixed with the late morning shooters.
Wind was a vector sum of ~5mph right to left with about a 2-3mph toward the shooter. It changed almost to an opposite by noon (see the format above to know now why we do this). Noon - tail wind of ~3mph, and right to left of approx 3mph, but far steadier than the early am wind.
Overall score @ 600 yards: 375 5x. Two other competitors today in F-AR, one shot 372 4x, another shot 392 9x (new local record).
OK enough about how the match went, my topic for further discussion is thus:
600 yard shooting, I see two philosophies from reloaders for this specific competition. Again, to summarize: 600 yards, 1:7 barrel, Mag Length required.
#1 which seems the popular here, Load for Velocity! Several guys are shooting the 77gr upwards of 2850fps out of their match chambers (24" barrel). (Old N140, or H4895).
#2 which seems more popular to long-range shooting in general: Load in an accuracy node for your barrel and rifle. I may be mistaken and there may be an accuracy node at 2850 for the 77gr bullet, but I'm not overpressuring it to find out.
My load for today's competition:
77gr Sierra Matchking (others are using 77gr Berger, or 77 Nosler).
Same Brass lot, which was matched by weight (I had to sort it somehow).
Federal 205M
23.4gr Varget
2650fps average (20" barrel).
I found the load by ladder testing and Chrono work. 23.4 gives 2650fps average,
Vertical grouping at 230 yards was best between 23.2 and 23.5 for my rifle.
Obviously if I keep practicing with my current load, I'll do just fine. Score today showed that. Hypothetically, however, at 600 yards the 2650fps bullet will drift 6.2MOA in a 10mph wind (38.7"). The same bullet at 2850 (200fps faster) will drift 5.7MOA (35.7"). As far as scores go, that means a difference of the diameter of the X-ring, so without any sight adjustment it will make an X into a 10.
From a competitor's standpoint, would you rather have the velocity and risk Vertical dispersion from loading/powder charge difference, or would you rely on your shooting abilities to time the wind correctly? As you can see in 10mph wind, you're going to need to set some clicks in the scope anyway right?
-Mac