can anyone recomend a relpacement vehicle mounted m2 barrel ,,,i require one for my m1a1 abrams and 1 for my aavp7a1,, ive tryed google and ebay and keep coming up with barrels with changing handel or ww11 .
any help is greatly apreciated, thanks in advace

Tamiya's old 1/35 scale Infantry Weapons Set comes with two spare M2 barrels, without handle.

Here are a few I can think of that will help you out.

Lionmark: http://www.lionmarc.com/Product_Barrels/LM10026.html
Lionroar: LB3528 .50 Machine Gun Metal Barrel
Adlers Nest: ANM35024 Browning M2 Machine Gun Barrel
Adlers Nest: ANM35024B Browning M2 Machine Gun Barrel SBF(Steel Blue Finish)
RB Models: 35B13 12,7mm (0,5") Browning M2 (this one may not work for you).

would the turned M2 barrels from RB models be suitable? after all 2 barrels with postage is about £7.

Griffon Models set LB35024 (designed for the M16 MGMC) includes 4 barrels. You can get it from Lucky Models with free shipping for $25.99 :
http://www.luckymodel.com/scale.aspx?item_no=GRM-LB35024

PMMS has a comparative review for some of the available barrels :
http://www.perthmilitarymodelling.com/reviews/vehicles/50cal/50cal.html

Frenchy

thanks to all who have replyed , you have given me so much help , now im spoilt for choice ,, which one's to pick ,,errrrrr ,,,,dam right , got it , i think i will go for the lion marc offerring , and at £14 thats not too bad .
thanks again guys

Just to add another cheap option, Academy's American machine gun set comes with spare barrels, including a/c types as well as modern and WW2