Originally Posted by MadMax
I abandoned my own mortar project for exactly this reason. US military doctrine for dropping a motor down a tube is to follow through downwards such that the loaders head is below the barrel end and thus well out of the way of the launched round. After firing early proof of concepts, I found myself wanting to drop the round and keep my eyes up downrange to see where the round landed. This puts the loaders head above the barrel end and potentially in the way of the projectile if something unexpected happens like a loss of balance. I never got hurt, but I just couldn't see the general public deploying an effective mortar safely. We don't have the discipline.
An emplacement also needs strict area control to assure that other players don't walk past the firing axis. Obstructions like a sandbag ring could prevent the uninitiated from walking past the barrel during firing, but this kind of site building is not typical in most airsoft skirms. Mortar crews must be well trained for them to be safe.
All these safety issues coupled with the need for the round to be light (so as to be safe downrange) makes it difficult to make something with a significant effect at the impact site. That and you have to be willing to lose the round too.
I've always wondered why they never upscaled the 40mm grenade say 90mm to make a quasi recoilness rifle. Ethier Shooting Foam or rubber balls for Anti armour or lots of BBS for antipersonal. I guess maybe cost is the major factor.