We have been using branded weapons in our Q3 mod for close to 15 years now and have not heard a peep but manufactures are going after trademark infringement more than they are the make and model of what would be considered an ambiguous design.
On your side is you can’t trademark numbers or letters, even though Apple would have you believe other wise, so the fact that the M4A1 in the marketplace is identical to the design of the weapon it would be considered copyright as well as trademark safe as it is not “branded” as “the” COLT M4A1.
Since you mentioned the 1911 this weapon in particular by it’s self would establish an argument as to prior art as to copyrights as the issue as to the use of branding and trademark infringement due to the fact that the patent has expired long ago and compare it to the number of manufactures who are manufacturing this weapon with out paying licensing fees to the Browning estate and continue to call it the model 1911.
In general since Browning was responsible for most if not all automatic weapon designed during WW2 it can be assumed that the designs are no longer covered by patents and any manufacture who wishes can make use of the designs that would also included virtual weapons so by becoming you own manufacturer (granted in digital form) and not calling the 1911 a Colt 1911 there is no much anyone can do about it.
Not being a lawyer though it’s something you need to research and not take as being legally correct as some companies will sue you for no other reason than they can in hopes of getting a few go away bucks and generally wait until you become big as say EA.