I bought my first AR15 as advertised and use it for 5 months and fired at least 200 rounds of 55 grains ammo. Then found out that the rifling twist rate and barrel length were not the one as said as it should be. I managed to negotiate the return/replace of the rifle but banned in making business with the store. Now, still thinking whether to return the gun or just keep it to preserve the good relationship. Your opinion will be appreciated. I am new to rifle and just took the words of store's rep and online ad.