At my club, 200 yards is the max I can reach out to, so the regular old 55 grain FMJ-BT is my bullet of choice. These days what powder I use depends on where I can get some for a very low price or free. Since I’m still going through powder I have scrounged from various sources, I’m not all that familiar with the wide array of choices. I generally have been sticking to Varget, H322, IMR4895 and I just came across a few pounds of Varmint and IMR4198.
I know a couple of guys who occasionally head to a 600-yard range near Atglen to do some long-range silhouette shooting. I haven’t really shot Silhouette in years, because it’s honestly about as much fun as watching paint dry if you’re not getting better. I don’t have the time, patience, or desire to master the sport. Those Silhouette guys helped improve my shooting a lot, but there came a point where it had done everything it was going to do for me without devoting more time to the game than I was willing to give.
But turn it into a precision rifle event with half-scale animals at ridiculous distances? You once again have my attention. That’ll be fun even if I’m missing a lot, and it gives me an excuse to tinker, which never gets old.
However, the most precisionist rifle I have is my AR, which isn’t anything to write home about. I bought it during the height of the ban almost 20 years ago by this point and it’s 100% stock, save the bayonet lug and birdcage flash suppressor I put on after the ban. It has regular old A2 furniture. A few weeks ago I uncased at the club and had some young guy say, “Wow. That’s old school!” It seems like just yesterday it was me saying shit like that to grey haired shooters. I resisted the urge to come back with, “You know, back in my day, we didn’t have any of these free-floatin’ barrels and fancy-dancy ACOGs with illuminated reticles.”
Old school or not, I’m thinking of slapping a halfway decent optic on it, and taking it out to see how I do at that distance with so-so equipment. But no way I’m taking my regular 55 grain load. I’m interested in the capabilities of the Mk. 262 round for reaching out to 600 yards. For those of you who may not be familiar, the Mk.262 is a 5.56x45mm round developed by SOCOM for longer range work. It uses a 77-grain Sierra Match King bullet. It is about as decent a round as you can get and still be able to stuff them into a magazine. I want to work with a practical round and not with loadings that have to be single-loaded into the rifle.
The trouble is, I’m not used to working with bullets that heavy in this chambering, and I’m paranoid about overpressure. A few months ago, I ran into a supply of 75gr HPBT bullets, and I am starting with those. That bullet with 22gr of H322 driving it isn’t yet a compressed load at 2.26″ OAL. Hodgdon says that’ll push out at about 2785ft/sec with 48,100 CUP from a 24″ test barrel. For a 77gr bullet, 21.8grs of H322 pushes 2,721ft/sec a 50,900 CUP. Black Hills seems to get close to 2900ft/sec out of a 20″ Colt AR barrel, so I’m guessing they have to be loading over the SAAMI spec and closer to the NATO spec on chamber pressure, which is about 10,000CUP higher. Anyone have any experience trying to replicate this load to get the same performance as the factory Black Hills load?