I believe Battlefield Las Vegas attribute those problems to worn recoil springs.
The recoil spring is a completely different beast. By not changing it often enough, you will eventually destroy your receiver. The problem with the recoil spring is that it's right in front of your face but it rarely got changed up until recently. We now have a PC in the armory so the armorers can leave reminders to change springs out after three months. We've lost MP5 and G3/HK91 receivers because not changing the recoil springs. The receiver will start to bulge where the bolt carrier bottoms out at the stock. The weak recoil spring allows the bolt to come back with so much force that the rollers eventually to put reverse dimples/bulges on both side of the receiver. If not caught soon enough, the roller will eventually just start getting caught in those dimples and the bolt carrier will stay stuck to the rear. The other issue that occurs is the receiver will crack where the rear stock pins attach. Both issues are caused by the bolt carrier group slamming back so hard that the sheet metal eventually gives
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