The TM M4/M16 barrel is basically made up of 3 parts. The "nut" that is secured to the receiver, a tube that is hidden by the handguards and a thicker front section that is visible in front of the handguards.
The "wobble" comes from the little screws that hold the tube in the nut loosening off in time and with hard use. Keep the screws tight...and there's no wobble.
Replacement "one-piece" barrels are much sturdier. They are either 1 solid piece (right from the nut to the muzzle) or else they use a much more robust nut and set screws to secure the rest of the barrel. Typically...there's no play.
As well, the way that TM has designed their "delta ring"...the ring that screws onto the upper receiver to secure the barrel nut...the handguards rotate a bit. There's a bit of play, but it's not too bad.
Other makes (i.e. CA, G&G, etc...) use a normal delta ring (it has teeth on it and looks like a bicycle gear). They tend to "lock in" handguards a bit better.
Plastic MP5's are sturdy...but they can be "creaky". Metal body MP5's tend to be much sturdier. Fiddling with a mini battery in the handguard of an MP5 gets tiresome really quickly. With a full stock you end up with a much sturdier SMG and have zero worries with battery performance/capacity. Although when new they might be "tight", all collapsible stocks get wobbly with use and it's not something that can be tightened up.
The way MP5's are wired, if you have a collapsible stock the battery will be in the front handguard. If you have a full stock, it's in the stock. On some setups, you can pick one or the other (but you need to take the full stock off, unconnect one connection and connect the front wire, then put the stock back on). With a full stock...you'll never want to use a small battery in the handguard.
Last edited by m102404; June 15th, 2009 at 10:54..