Ok I'm kinna new at all this but I bought a Colt Pre ban Ar-15 Cov.Carbine M-4gery with a newer Colt M-4 upper and also a 24" bull barrel upper (Stainless)that came as kinna a package BUT the guy couldnt tell me what kind of Bull barrel I had so I was wandering if there were any way to tell the rifle twist and also the maker. Thanks in advance for the help!

Christopher

If you can see under the handgaurd/float tube there could be some markings.
If it's a DPMS, it will be marked DPMS 1x8 SS.

You might be SOL on the maker unless it is marked under the handguard. The twist can be determined with a ruler, cleaning rod and tight fitting patch or brush. Run the brush/patch a few inches into the barrel to engege the riflings and draw a line along the top length of the cleaning rod (magic marker), and a cross line to this at the point where the rod enters the barrel extension. Continue to push the rod thru till the line along the top of the rod rotates a full turn and comes top again. Mark another cross mark at this point, withdraw the rod and measure the distance between the 'cross' marks. This tells you the twist rate, "X" inches for one complete turn. Might do that a few times and average it out.

rimfire50's method will tell you the approximate twist, but there could be some slippage.  The twist could be faster than that shows, but it won't be slower.

Colt's Accurized Rifle was a 24" stainless with free floated tube.  If it has 2 sling swivels on the tube it might be that, but I would think Colt would mark their barrel in front of the gas block.

How would you tell if it is crome or not? Are all stainless barells chrome?
Thanks

No stainless barrels are chrome.  Only chromoly barrels are lined.

I think the Colt M4 barrels are fully lined, but some Colt barrels have only the chamber lined.  You should be able to see a silver ring around the chamber and muzzle where the parkerizing didn't stick to the chrome.