Discussion in 'On Topic' started by Pineapple Devil, Feb 4, 2006.
You planning on using optics? If not A2, if so A4, with the A4 you'll need to add carry handle or another rearsight for iron sight usage.
how much are rear sights usually? i'll eventually add some optics to it but dont know how long it will be
u can probably find one on ar15.com for around 50
You can grab a used removable carry handle with A2 sights over on arfcom for $60ish, new ones are like 80ish.. Other BUIS's run $90-160.
the one w/ the stainless barrel is probably more accurate too. if that makes a difference.
can some sort of optic be mounted to the top of option #2?
Yep they make optic mounts that go ontop of the carry handle
are they any good or is it better to go with the other one?
This for your first AR? Just go with the A2 for now, you'll end up buying whatever type you dont buy now down the road anyway. If optics aren't in your immediate future the A2 will be more cost effective its ready to shoot no need for some sort of BUIS.
Nothing wrong with the A2 style, the military has use A2 style since the 70's. I've got both types, unless your making an m4gery or going for a long range varminter A2 is fine, even long range A2 is fine, I prefer flattops only if I'm mounting optics.
yeah its my first.
16" A2 is fine choice for your first one, you can throw an optic on it later if you want or just get another upper for optics.. Once you start on AR's you wont be able to stop I started with 1 Bushy 20" A2, now I have 3 lowers and several uppers
I have a Brand New Bushmaster A2 dissipator upper that i'm looking to get rid of...
go with the A4, you can add a carry handle now and decide on optics later, plus you can get it with whatever handguards you prefer, M4, midlength, whatever. You may regret it later if you get the A2 and have that fixed carry handle since it makes it harder to use a scope.
Anyone want to help me understand the differences between the twist rates? The pros and cons if you will. The two most common ones i see are 1:7 and 1:9. Are there velocity or accuracy differences?
Basically the twist rate is related to the bullet weight you want to shoot.
1:7 is a really fast twist rate.
To sum it up:
Twist too slow and the bullet wont be very stable
Twist too fast and the bullet will be overstable, and will remain nose high during its flight so it flies sideways and is inaccurate.
Twist way way too fast and the bullet can actually fly apart.
http://www.ammo-oracle.com/body.htm gives an excellent explanation.
Rounds in flight spin for stability because of the rifling on the inside of the barrel. Depending on how much they spin, they are more or less stable in their flight and therefore more or less accurate. The earliest AR15s from the early 1960s had a twist rate of 1 complete twist every 14", or 1:14. This was increased to a twist rate of 1 turn in 12" for the M16, XM16E1, M16A1, and later rifles and carbines. The current M16A2s and up and the M4 carbines have a much faster twist rate, 1 turn in 7". The reason for the 1:7 twist is mainly to stabilize the M856 tracer bullet, which is much longer than other bullets. You will recall from above that the M856 was designed to provide 800 meters of trace out of the SAW.
While the slow 1 in 12" twist is adequate to stabilize the 55 grain M193, it will not stabilize the 62 grain M855. As a result, the newer M855 ammo will group 1-2 feet at 100 yards, with bullets flying through the air sideways, instead of shooting to about 2" at 100 yards, like military ammo should.
You can also spin them so hard they fly apart. That's rare, but it happens if you are dealing with very tight twists and very high velocities. When fired at 3200 fps in a 1-in-7 twist rifle, a round is rotating at over 300,000 rpm when it leaves the muzzle. Light, thin-jacketed varmint bullets (i.e., 40gr Hornady TNT or Federal Blitz bullets) often can't take that much spin and will pull themselves apart
1:7 is for longer heavier bullets, but I wouldn't use anything lighter than 55 grain, 1:9 is probably the most common twist rate and will shoot the lighter rounds up to all but the heavy rounds.
Awesome read. Thanks for the info. I guess I'm pretty safe with 1:9.
yeah, np. My new ar will be 1:9 too. A good useful all around choice.