Hello guys,I have 2 questions:
1)I need some info about the differences between preban and postban rifles, what does the words "preban" and "postban" mean?
2)Are there some differences between .223 remington barrels and 5,56 NATO barrels? Are there some differences in the chamber? If positive, can You give me the pressure difference?
Thank You very much.

Thank you very much Troy,I have a COLT Post-ban (CSTxxxxx) AR15 with a 20" 5,56 NATO barrel, what is the differences between my rifle and a militar rifle (not considering the full auto parts)? Could I obtain a pre-ban rifle with a flash suppressor and the bayo lug?
Thank You very much.

Sure, you can purchase a PREBAN rifle. That means a preban lower, not a preban style upper for your postban lower. How bad do you need a bayonet?

Right...I don't need a bayo because I have the M203 under my barrel (deactivated)...I want only the flash suppressor...can I thread the barrel or It's too hard?
I know that It'snt legal but I'll do It...in Italy the laws about preban and postban aren't like the US ones.
Bye.

IIRC you can still use the bayo even if you have an M203 on there. Yes, a gunsmith coulf thread the barrel end and then you could put on a flash supressor. Depending on the barrel diameter the barrel may have to be turned down on a lathe first before it can be threaded.

The difference in your rifle to current US production military M16A2's is that military barrels are skinny under the handguards (to save weight) and HBAR ahead of the handguards, they have bayo lugs, they have threaded barrels with flash suppressors, they fire semi-auto and 3 round burst. Also I don't know what colt is doing these days, but the trigger/hammer/take down pins may be a non-standard diameter, and you may have a block in the lower receiver.

For between $200 and $300 USD, you could simply get a new barrel that has the bayo lug, threaded muzzle with suppressor, skinny under the handguards, 5.56 chambering, and simply swap barrels. Don't know what gunsmiths and machinists charge, but for only a little bit more you could get a better result. Then sell the old barrel and get most of your money back anyway. Then you will probably save money instead of spending it all on machining.

M4Guy,
I want only install the flash suppressor,now I have installed it without threading the barrel..It's well fixed but I don't like very much its look.
My barrel is exactly as You described..just like the military one "skinny under the handguards (to save weight) and HBAR ahead of the handguards" but without flash suppressor and bayo lug.
About the receiver I have the block,I don't know if "the trigger/hammer/take down pins may be a non-standard diameter",but it doesn't matter..I like the external look.
With a HBAR muzzle can I thread the barrel?Is this the right diameter? The material is too hard?Thank You guys.

About a new barrel...It's right..It's easier,but I don't know where I could buy It. Troy, I cannot import the barrel,they give me the licence only for orders of at least $1000! I'd like to buy the barrels from USA but I can't.
I'll search here in Italy I'll ask to the importer (only 1 in Italy :( ).
For all this reasons I need to consider all the possibilities.

Thank You very much guys.

Ok,thank You very much guys ;)