I am considering a flattop kit from J & T.  What are the opinions out there on barrel length?  I think they are offered in 16", 20" and either 22" or 24".
Thanks. By the way, thanks to all the folks who answered my question on 7.62 x 39 uppers.  I can't seem to stay logged in from page to page so I've been unable to reply on the thread.    

Have you tried deleting your AR-15.Com cookies from your browser. This seems to fix the problem of constantly being logged out for most people. I'm not sure how to do it on a windows computer (I have a Mac) but is probably simple enough.


As far as barrel lengths it really decides what type of rifle you want to build. 16", 20", and 24" are the basics and are most common. Carbines are real handy so the 16" barrel is nice to start out with. I think most people buy a rifle with 20" barrel and eventually get a carbine. Getting a 24" barrel would be less of a handy tactical rifle and more of a bench type rifle.

I regularly delete all my cookies, at least once a week.  Should I dump them as soon as I come on to the website?  

So, is barrel length a function of the rifles inherent accuracy? i.e. (longer barrel, more accuracy?)  

I have the J&T 16" bull barrel kit. It is very accurate, and handy. I also prefer it to the longer barrels for range work. However, any JT kit will be great. Good Luck
Austin

Barrel length determines the velocity of the bullet, and that has a significant effect on accuracy.

About 2.5" of barrel will achieve stabilizing spin.

Highest velocity is achieved when the full load of gunpowder burns behind the bullet prior to the bullet leaving the barrel.  Muzzle flash is powder burning behind the bullet subsequent to its leaving the barrel (i.e., wasted potential energy).  With greater velocity, the hyperbolic arc of the bullet is extended, making the bullet move in a "flatter" trajectory.

The rule of thumb for .308 shells is that it will take approximately 26" of barrel to completely use all of the powder as propellant.  I'm not that sure about .223 powder charges, but my guess is that one should get a complete powder burn with between 22" and 24" barrels.

Anyone out there know more about this than me?

Also, there are a variety of other aspects that can have the same effect.  For example, a tighter crimp can have a similar effect to a longer barrel.  Different powders will have different burning effects.

Does anyone out there know if manufacturers hav experimented with barrels that initiate spin via rifling and then become smoothbores?

Barrel length has no positive effect on accuracy.  In fact, shorter barrels will tend to be more accurate.  The barrel whips around more with a longer barrel.

Longer barrels will have more velocity, so you will have more energy and the bullet will not drop as much at any given range.  The difference is really pretty minor however - like 4%.

A longer barrel does give you a longer sight radius, theoretically increasing accuracy with iron sights.  With practice the difference is minimal.  With a scope, there is no difference.

IMHO 16" carbines are the way to go.  Handy, good accuracy, and light weight.

5.56 has burmed its powder by the end of a 20" barrel.  Barrel length has very little effect on shortrange accuracy, but at 500 yards 300 FPS is going to make a big difference.

Barrel length "DOES NOT" effect accuracy!  Some people get accuracy, velocity and maximum effective range confused.

Also a bullet having a "flatter" trajectory does not make it more accurate either.  Zeroing your sights or scope for a specific range compensates for that.

Rambosky