I'm just gonna throw this out there. Take it as you like. 
Maggot gun.
So, a weapon that you fire at a zombie, wait a few weeks, and then he'll fall apart? 
I think throwing jars of maple syrup at the zombies would have much the same effect, and also has the advantage of not having to run the risk of a maggot infection every time you reload with an open wound.
Good point. Although I'm not sure about it taking weeks (I guess it's dependent on whether you have the 2# hopper or the 20#). Alas, it's a moot point. 'Not quick enough' is what I'm hearing. Well this isn't a quick fix to get you out of the tight situation kinda thing. This is an end-to-the-entire-problem type fix. 
You're not looking at the big picture. Zombie attacks are alien species' method of helping us save ourselves. Let me spell it out for you.
You see, here's how it works. Maggot guns are dispersed by various forward thinking world governments for the eventuality of zombie attack (let's face it, we all know it's coming). 
Step 1. After the initial onslaught, there's still several million people alive. Those people then shoot their Maggot guns at targets non stop for about a week (Of course being able to reload with the supplied "U.S. Maggot Farm" [supply your own excrement]).
Step 2. Zombies sprayed with said maggots begin to decay rapidly. 
Step 3. Zombies return home after a long day's brain eating and pass on the maggots to their zombie wife and children. The children then pass on even MORE maggots to the kids at Zombie School and their zombie teachers.
Step 4. Hold up in the Winchester with your best mate and wait for the calvery. 
Step 5. After 2 weeks, Repeat previous steps with Government supplied "Bat gun" to deal with the left over pestilent fly population.
Step 6. Bats go fill up caves with Guano. Excess bats die off in said caves.
Step 7. Hippies mysteriously grow most potent Cannabis crops in the history of the world
Step 8. World Peace is declared 4 months later.
See. Undead invasions are for our own good.