"Sorry boss, but this thing is FUBARed."
"What did you do to my gun?"
"Nothing that's the thing. Magnets are cracked. Can't just glue them back together. Technically speaking - a magnet is heated to its Currie point, where the atoms are free to move, then their set in one direction with another em field, and cooled, locking the atoms in a set orientation. When you drop a magnet hard enough, be it a gauss weapon or an advertising trinket from on the fridge - things get out of alignment, and it becomes a bit demagnetized."
"And yet with the million dollar college education to explain all this, you can't do something about it?"
Without a furnace, liquid nitrogen, and some properly tuned free-electron lasers - you can't fix these rifles."
"No work around? Can't hayduke it to use fewer magnets?"
"A large artillery cannon might be able to have the power to spare and barrel length to use simple wire and generated fields - but to keep this infantry portable, they used from pretty amazing materials science."
"Who came up with the idea of an infantry rifle that can't be dropped?!"
"To be fair, the magnets are set in some pretty shock absorbing material and inside a tough casing - so you did a bit more than just drop the gun over a normal distance."
"Its called planning for worst case scenario."
"In that case, one, the soldiers would have side-arms. Secondly, the military could afford to have spare guns on hand. Comparatively speaking, one gun that can snipe, act as a battle rifle, and a silenced sub-machinegun, that uses cheap mostly iron caseless ammunition and needs next to no oil or cleaning is enough of a savings overall to buy spares. Plus there is the bigger picture."
"Which would be?"
"Its really difficult to replace old military rifles. Aside from fighting with conservative brass and the suppliers there is the problem of retraining and sourcing all the spare parts, and if you change ammunition - replacing literally billions of rounds. If you try to stay compatible with the old stuff, well then the new weapon doesn't really sow an improvement. Same length barrel, same bullet - same effect. The rest of the weapon is just a matter of user interface."
"Still a bad idea."
"No, Gauss guns are just fine. Letting an alien war machine grab it and throw the gun fifty meters - that is a bad idea.