I have come up with a conversion that makes the needle strike down, instead of up. It is (fairly) simple to make and is completly reversible. The only alteration to the gun itself is to remove a small ammount of metal just below the hammer where it strikes the anvil (the part which holds the needle). This does not harm or weaken the pick gun in anyway.
I shall now TRY to explain how I did it
All that needs to be made is two small metal plates of similar thickness to the metal of the pick gun (0.8mm) and two spacer tubes 5mm o.d.X 10mm long, with a 3.2mm hole through the centre. For those of you without a lathe, this is a standard nickel plated brass PCB spacer, R.S. stock number 606-765, about £3.00 for 50!
Cut the two plates to size and drill the four 3.2mm holes as in the drawing. I recommend that you drill with the two plates clamped together so that the holes line up perfectly.
http://tinypic.com/view.html?pic=5l5phj
Now on one of the plates open up the two upper holes to 4.5mm, the reason for this will become clear later.
Now it's time to open her up
Lay the pick gun on a table infront of you (screws up) and remove the five screws that hold it together. Remove the anvil and its return spring, and put it to one side. Cut away the 10mm of metal from each half as shown in the picture.
http://www.tinypic.com/view.html?pic=5l6mmp
This is to allow the anvil, when inverted, to make contact with the hammer. Next lay the lower half of the pick gun (the half with the pivot pins for the anvil) on the table, and slide the plate with the two 4.5mm holes over the pivot pins (see pic2). From below insert two 3mm X 16 mm screws up through the two remaining holes. Then place the two spacers over the 3mm screws and reassemble the anvil onto the spacers in a position an exact mirror image of where it originally was. Replace the top half of the pick gun case, and use the two screws that go into the original pivot pins to secure in place the second plate that you have made (the one with four 3.2mm holes). Ensure that the protruding ends of the two 3 X 16 screws pass through the lower two holes of this plate, and then secure them in place with two 3mm nuts. Replace all screws and tighten everything up, and hey presto, you now have a snap gun that works the right way up for euro locks.
From concept to completion this took around 45 minutes. But the I am an engineer and had everything to hand. And as I have said this is completely reversible if you want to use your pick gun the other way up again.
Apologies in advance.
1) For the explaination which I am sure will be missing something, I am better at doing than teaching.
2) For all the other people that have probably thought of this before me, but I did do a search and couldn't find any posts for "coverted pick gun"
See what you mean, it's enough to put you off yer lunch 
), to be honest i havent had a go at it yet as im getting a guide redy for making an electric pick gun from a bosh screwdriver but soon as thats done i will start on that project.
If it ain't broke.....pull it down and see how it works anyway!