I'll start off by saying, yup, I'm a newbie when it comes to these type of firearms.  I've always wanted a M4 type AR.  Am now doing some research before I buy.  Have decided that I want a pre-ban, but Colts seem to have a 1 in 7 twist and Bushmaster a 1 in 9.  Didn't Colt change their rate of twist to the  1 in 7 for better accuracey?  All the help you can give is greatly appreciated.

I tried a search on rate of twist and didn't get any hits.  Sorry if this question has been asked a million times or so.

Bob

Colt went to the fast twist to stabilize tracers to 700 meters. Unless you shoot bullets heavier than 69 grains, 1:9 is better. They get a miniscule amount of velocity gain, and the barrels supposedly last longer. If you find a good deal on a Colt don't worry about the twist, it works fine. Colts are more expensive than BM though, and you don't get a better product. Make sure you don't get a transitional Colt, with the big pins and sear block. they are a pain in the ass.

Rcd567, I agree with the advise above except



I like the transitional Colts especially those with the small front pivot when they are drilled for the mil-spec push pin.  The sear block only prevents a few activities but I like a Jewell trigger in my AR-15 and these work 100% every time in a blocked lower.  I also don't care if my trigger pins are the large or small pin as Jewells come in both!  There are MUCH less options in Large pin triggers but the standard Colt group is quite good and the Jewell is excellent...  That's good enough for me!

So, if this is your first purchase, let me suggest that you try to learn as much as you can.  Colt's are a very complicated AR-15 as there are more options and differences between the various Colts then I would ever care to try and list.  If you go with most anything else, they rifles will all be basically the same with 100% interchangable parts.

One more warning that you should know is that not all lowers will be 100% to spec.  I have seen SGW and EA lowers that were out of spec such that uppers had to be fitted to work with them.  This can be a real pain!

Instead of me trying to write a book here, please visit [url]http://quarterbore.com/library/books/index.html[/url]....  One of my favorite books is "Complete AR-15/M16 Sourcebook: What Every Shooter Needs to Know" by by Duncan Long.  It's under $30 and is one of the best books for a very good overview of the history of the AR-15!

"...EA lowers..."??? Essential Arms or Eagle Arms?? Just curious.

Thanks for all the help!  The links you guys gave me should keep me busy for awhile.

:)

The one I had seen that was bad was an Essential Arms J-15.  These are cast lowers....

Now, I also owned a RR conversion done on a J15 lower and it worked 100%....  It's just a good idea to make sure the lower will mount to another upper if you are paying full price as you can fit an upper to these lowers....  it's just a pain and makes the lower worth less money in my book!

Link Troy directed ya to should be require reading for someone asking the question you asked.

You first need to determine what the intended purpose of your AR will be,.....

this will get ya to the type of ammo you'll most likely want to shoot,...... (it's all there in the Ammo Faq)

followed by the decision on the best twist rate for your intended purpose.

Mike

Both Colt and Bushmaster make 1/7 and 1/9 twists.  I have a Bushmaster 1/7 twist M4 barrel and Colt makes M4s in both twists too.  You will probably be fine with just a 1/9 twist.  The 1/7 is really only needed for the newer rounds like the 75, 77 and 100 grain ammo.

a high twist rate such as 1 in 7 is great for accuracy, but has been developed for special loads. Such as heavy bullets, or slow moving bullets. A subsonic round to be used with a suppressor really needs some twist on it to keep it from going end over end when it slows a little more. The 1 in 7 will work great with any bullet, but it also wears faster, being that there is more friction happening in the barrel. But I doubt that any normal shooter would ever be able to completely shoot out this barrel unless they had money stock piled just to buy ammo!!!