A Forgotten Predathor
For about a year and a half I have had a Predathor Vuoto 85 stacked away disassembled in the back of a closet. I have always liked the idea of the Predathor as an affordable and seemingly well-built off-the-shelf vacuum barrel gun but honestly, I haven't even gotten my own one wet. I have shot them and recommended them to others, but I had a perfectly good Seac in the same size so no real need for this one. But I think it's time to get this one going, too - it just seems a shame to not get it onto some fish, either in my hands or a friends.
I am in no particular hurry with this but being the tinkerer I am, I thought I might as well make a few upgrades.
I am thinking of a custom grip, as I really don't like the stock one much. Perhaps a carbon fiber reservoir but I have used the ones I had and I haven't had much luck sourcing a new batch, yet. Also, one of the few minor gripes I have heard people have with this gun is that the trigger pull can be a bit hard and with my recent experiences making new triggers for my Mirages, I thought that would be my first modification.
Trigger Pin Modification
One way to make the trigger pull lighter is to decrease the diameter of the trigger pin - later I will see what can be done about the spring and I will polish the sear and tail of the piston, too.
As stock, the Predathor comes with a 2mm pin but I will be using a 1.4mm one. At 20 bar, the force on a 2mm pin is 640gf but for an 1.4mm pin it is 314gf so almost half. Now, the trigger pull weight wont be halved as there is still friction and the trigger spring which acts on the trigger.
Anyways, enough talk, let's get into some pics. I didn't really shoot much of the machining but it was pretty straight forward. Actually, the hardest part was measuring the trigger seat in the handle to figure out the dimensions.
The first pic shows the original 2mm trigger assembly to the left and my 1.4mm version to the right:
Honestly, it doesn't really show a huge difference as all the mojo happens on the inside of the bushing. As an aside, I settled for brass for this little project, just because it is so easy to machine.
BTW, in real life these bushings look much, much cleaner! The macro lens is just ruthless;-)
Next up is a pic of the top of the bushings:
The stock one is solid and only uses one o-ring but for these reduced trigger sets, you need to seal in two places which is why the bushing on the modified version is hollow and holds two smaller o-rings. Normally, 1.5mm trigger sets use one o-ring on the inside. Since I have the space to actually fit two, I have done that in this and my previous ones for my Mirages. It just gives me more peace of mind.
Here's a pic of my trigger showing all the parts:
The "guiding tube" in the top right of the image has an outer diameter of 2.4mm and an inner bore of 1.5mm. This is because the hole in the handle that the original trigger pin goes through is 2.5mm and I want to make this bushing so that it would work without any modifications to the handle.
And a pic for scale with an AA battery:
A quick pic to show the bottom of the two bushings:
I figured out a way to hold the bushing in my tool holder so that I could put an 1.5mm end mill in the lathe chuck and use the lathe as a milling machine to make the slot for inserting the bushing. Turned out much, much better than when I free-handed it on my earlier bushings.
Finally, I copied Dima's idea for an insertion tool using a cut-off from an 8mm 17-4ph shaft and again I used the lathe as a mill to make the the flange:
As you might have noticed my bushing is a bit longer than the original. After measuring the handle, I realized I could use more of the thread length in the handle seat which seemed like a good idea. The overall length of my bushing including the top part is obviously longer, too and pretty much as long as it can be: had the guide tube been a few 1/10ths of a mm longer it would have interfered with inserting the barrel into the handle. But I believe making the guide tube as long as possible and also sitting as snug as possible in the original trigger pin hole in the handle adds a lot more support to the trigger pin. I would say that despite the trigger pin now being 1.4mm, rather than 2mm, it is actually better supported than the original one is.
I guess at some point I think it would make sense to actually assemble the gun and check for leaks to make sure I got the dimensions right on this little trigger project;-)
For about a year and a half I have had a Predathor Vuoto 85 stacked away disassembled in the back of a closet. I have always liked the idea of the Predathor as an affordable and seemingly well-built off-the-shelf vacuum barrel gun but honestly, I haven't even gotten my own one wet. I have shot them and recommended them to others, but I had a perfectly good Seac in the same size so no real need for this one. But I think it's time to get this one going, too - it just seems a shame to not get it onto some fish, either in my hands or a friends.
I am in no particular hurry with this but being the tinkerer I am, I thought I might as well make a few upgrades.
I am thinking of a custom grip, as I really don't like the stock one much. Perhaps a carbon fiber reservoir but I have used the ones I had and I haven't had much luck sourcing a new batch, yet. Also, one of the few minor gripes I have heard people have with this gun is that the trigger pull can be a bit hard and with my recent experiences making new triggers for my Mirages, I thought that would be my first modification.
Trigger Pin Modification
One way to make the trigger pull lighter is to decrease the diameter of the trigger pin - later I will see what can be done about the spring and I will polish the sear and tail of the piston, too.
As stock, the Predathor comes with a 2mm pin but I will be using a 1.4mm one. At 20 bar, the force on a 2mm pin is 640gf but for an 1.4mm pin it is 314gf so almost half. Now, the trigger pull weight wont be halved as there is still friction and the trigger spring which acts on the trigger.
Anyways, enough talk, let's get into some pics. I didn't really shoot much of the machining but it was pretty straight forward. Actually, the hardest part was measuring the trigger seat in the handle to figure out the dimensions.
The first pic shows the original 2mm trigger assembly to the left and my 1.4mm version to the right:
Honestly, it doesn't really show a huge difference as all the mojo happens on the inside of the bushing. As an aside, I settled for brass for this little project, just because it is so easy to machine.
BTW, in real life these bushings look much, much cleaner! The macro lens is just ruthless;-)
Next up is a pic of the top of the bushings:
The stock one is solid and only uses one o-ring but for these reduced trigger sets, you need to seal in two places which is why the bushing on the modified version is hollow and holds two smaller o-rings. Normally, 1.5mm trigger sets use one o-ring on the inside. Since I have the space to actually fit two, I have done that in this and my previous ones for my Mirages. It just gives me more peace of mind.
Here's a pic of my trigger showing all the parts:
The "guiding tube" in the top right of the image has an outer diameter of 2.4mm and an inner bore of 1.5mm. This is because the hole in the handle that the original trigger pin goes through is 2.5mm and I want to make this bushing so that it would work without any modifications to the handle.
And a pic for scale with an AA battery:
A quick pic to show the bottom of the two bushings:
I figured out a way to hold the bushing in my tool holder so that I could put an 1.5mm end mill in the lathe chuck and use the lathe as a milling machine to make the slot for inserting the bushing. Turned out much, much better than when I free-handed it on my earlier bushings.
Finally, I copied Dima's idea for an insertion tool using a cut-off from an 8mm 17-4ph shaft and again I used the lathe as a mill to make the the flange:
As you might have noticed my bushing is a bit longer than the original. After measuring the handle, I realized I could use more of the thread length in the handle seat which seemed like a good idea. The overall length of my bushing including the top part is obviously longer, too and pretty much as long as it can be: had the guide tube been a few 1/10ths of a mm longer it would have interfered with inserting the barrel into the handle. But I believe making the guide tube as long as possible and also sitting as snug as possible in the original trigger pin hole in the handle adds a lot more support to the trigger pin. I would say that despite the trigger pin now being 1.4mm, rather than 2mm, it is actually better supported than the original one is.
I guess at some point I think it would make sense to actually assemble the gun and check for leaks to make sure I got the dimensions right on this little trigger project;-)
Last edited: