1-in-7 barrel

[Guest CrazyLincoln]

Ok guys,

My 556 came with a 1 in 7 barrel. Now obviously the heavier grain ammo will shoot more accurately than the 55gr practice stuff. However, my friend said the 55gr. bullets will spin so fast they will actually damage the rifling of the barrel.

Is this true?

I don't mind the heaver stuff when I need accuracy, but its nice to have cheap ammo to plink with.

[SkWaShDeM]

62gr FMJ ammo should be about $0.50-$1.50 more per box than the 55gr stuff. If memory serves, 62gr is fine for for the faster twist barrels like yours. So it should stay relatively cheap. Short of loading your own, or maybe ordering from Black Hills in bulk, I don't know of any convenient way to get relatively inexpensive 70gr+ ammo for a .223/5.56.

[dcloudy777]

55 grain ammo genrally performs fine in 1-in-7" twist barrels. I've fired thousands out of my three gun rifle, which has the fast twist barrel. Some of the ultralight and super fast projectiles, like 40gr and below, have been known to "overstabilize" and perform poorly, or even come apart in flight by being twisted too violently. Any detrimental effects of barrel twist, either too fast or too slow, will only be seen in bullet performance or point of impact, neither problem can damage a barrel. Go ahead and shoot the cheap stuff, you'll likely find that at ranges out to 200m or so, accuracy will be pretty much the same. The heavier bullets do better at extended ranges, mainly because of higher ballistic coeffecients (they are longer), and more resistance to wind.

By the way, its the length, not the weight, of the heavier projectiles that cause them to require a faster twist barrel to stabilize. Now you can show off your knowledge to your friend.

DanO

... who is just happy to help...

[Guest Mugster]

+1 on what Dan said. You may find that the federal fbhp in 50gr is one of the most accurate rounds you can get off the shelf for 300 yards and in. It should work fine.

Some smaller bullets will work well, but it depends on how they are constructed. You can't overstabilize a bullet, but you can spin it so fast it just comes apart. If you found a really tough heavy jacketed bullet in a lower weight like 40gr it would probably shoot fine in your rifle. The problem is most of those bullets have a thin jacket because they are varmint rounds and they are made flimsy to explode on impact. 55gr Ball ammo is relatively pretty tough with a thick jacket, although it fragments in phonebooks or gellatin too under 100 yards or so.