Rethinking 75/77 grain .223/5.56mm loads for longer range

[Suburban]

I have been messing with a 6.5 Grendel AR-15 upper for a while, which has lead me to rethinking 75/77gr .223/5.56mm loads.

We have gotten used to the price of common mass-produced 55gr and 62gr .223 and 5.56mm ammo. The heavier bullet weights are significantly more expensive. At least in my case, at 100 yards, the bullets that my primary AR shoots best with are 55 grain varmint bullets, despite the barrel having a 1 in 7* twist rate. There are 69, 75, and 77 grain bullets that the same barrel shoots almost as well. It's pretty much a certainty that the heavier bullets will shoot better at over 300 yards. Maybe with a barrel tuner, or a lot of experimentation with charge weights and overall cartridge length, I might be able to get the heavier bullets to shoot better.

Before you consider sidelining your .223/5.56mm rifle for longer range shooting, I think you should consider a few things.

6.5mm Grendel from Starline will be about 60 cents a piece, with good bullets being at least 30 cents a piece, probably closer to 50 cents each. Lapua Grendel brass is the gold standard, but it*s going to be around $1.25 for each shell, if you can find any for sale. The only 6mm ARC brass I see available is Hornady, at a little less than a buck each, with bullets being similarly priced to 6.5mm. In more than a decade of scrounging brass, I had less than 20 pieces of mixed Grendel brass, and only a little more than that in 7.62x39mm reloadable brass to convert. I don*t think I*ve found any once fired 6mm ARC yet. You will also run into other cost and availability problems with dies, and you'll have to spend more time collecting load data. Your powder choices will be limited to what you can find load data for. With current bullet, primer, and powder availability issues, the cost effectiveness of reloading is not as simple as it used to be a few years ago.

At the moment, Wolf steel case 6.5mm Grendel ammo is about 75 cents a round, but is not capable of the accuracy you are probably looking for. Hornady ammo is $1.75 per round, plus shipping, and is probably what you want. 6mm ARC is a little less, around $1.50 per round.

The 6mm ARC and Grendel AR bolts are similar to 7.62x39mm bolts, and more prone to breaking locking lugs than 5.56mm bolts, because the bore in the bolt head is larger. The Grendel ammo also has significantly more recoil than any .223/5.56mm load, I imagine 6mm ARC is similar.

Suddenly, the 77gr .223/5.56mm ammo at about a dollar a round doesn*t look so bad. Using once-fired brass tips the scales hugely in favor of .223 for reloading, at least in terms of cost. Reliable magazines in 5.56mm are significatly easier to find, as are ammo boxes.

[Brick]

Completion shooters firing the CMP Service Rifle Matches typically use bullet weights in this range. Their course of fire is 300 and 600 yards. There should be LOTS of load data available for those. I know my son has his favorite loads. IIRC i believe he said something about the heavier bullets needing a couple hundred yards to stabilize. He went Distinguished a few years ago and is now heavy into High-power competition but prefers the 6mm Norma BR for that

[West Chester]

77smk @2778fps out of a 223 wylde 20" works very well for me at 500 meters. 4-6" groups depending on how much caffeine I had that morning.