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Their findings resulted in zero malfunctions for the brass, but a combined 24 malfs for the steel cased. Lucky Gunner tested 10,000 rounds of two kinds of steel cased ammo (20k rounds total) and 10k rounds of brass cased. Malfunctions are more common with steel case ammo, but not horribly so. The brands that use “XM” say they use it to differentiate from their “M” SKUs that are tested and sold to military or LEO customers.Â
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Some manufacturers call their ammo “XM” and some call it “M”. Technically speaking, this isn’t regulated terminology. You’ll run into a few types of ammo like XM855 or XM193 and you might be wondering what makes them different than the official military M855 and M193 (or any of the other XMs and Ms).īasically, nothing. The 1:8 twist is much better for anyone not constrained to what the military does. 55gr will do well in it and the heavier 62gr and 77gr will do amazing.įor a varmint hunting barrel, the classic 1:12 is beastly.ġ:7 was the gold standard for do-all rifles and is the standard for M4 rifles, but this is mostly due to the need to stabilize tracer rounds that are longer than normal. If you want a do-all barrel I highly recommend a 1:8 twist. Popular super common weights for the AR-15 in 5.56 NATO range from 55gr to 77gr.Īnything lower is really only used for varmint hunting and anything higher is heavy for caliber long-range precision rounds. However, length is annoying for people to pay attention to and since weight very closely correlates to how long a bullet will be – we generally use the weight of the bullet to match the twist.įor any normal application, this is totally fine. Technically speaking, how much twist a bullet needs to be in the sweet spot depends on how long the bullet is. In fact, oddly enough a bullet will be spun enough with as little as 1″ of barrel. A 1:8 would be 1 twist per 8 inches.ĭon’t worry if your barrel is shorter than your twist, you don’t actually need to fully twist the bullet to get the right spin.
556 AMMO INSTOCK FULL
So a 1:12 means the bullet twists a full revolition, every 12 inches of barrel. Just like a football through the air with the perfect spiral, adding a twist to the bullet makes it fly with a lot more stability.įor barrels, this is expressed as 1 twist per inches. Twist rate is the speed that your barrel imparts a twist on the bullet. 223 Remington barrels are very rare in AR-15s these days, but there are some very rare exceptions out there. This gives you the ability to use both ammo types but also squeeze out some extra accuracy. To offset that, the chamber is cut slightly larger.