8 replies to this topic

[Buffdaddy]

We've had a few modifications to the Sonic Bazooka and its knockoff cousins before. All can get decent ranges, but the design is hampered. Being a backpressure tank, the goal is to dump the air out of the pilot volume as quickly as possible. The "blast button" the trigger presses is a pretty small orifice, and can't be helped without losing the stock look (there are possibilities, though). Instead, I elected to reduce the pilot volume.


Using available tools (I simply used the knife off my Leatherman multitool to carve and punch), cut a hole in the rear of the air tank. This opens up the pilot volume. The range tab is the blast button, while the whitish disc is the check valve for the pump. NO MATTER WHAT YOU DO, DO NOT IMPEDE/BLOCK THESE. They're kinda important to blaster function.


I elected to use cheapo plumber's epoxy to fill in the pilot volume. Essentially, I reduced the diameter of that part by about a third. I wold recommend making your hole wide enough to accept a 2/3 circle of PVC (by estimation, possibly 1" SCH. 80 PVC) and then filling around it with the plumber's epoxy. Seal off the hole you cut with the piece you removed, and cover that with some epoxy to make a good seal. Let cure.


Reassemble and slap on your coupler of choice.

Without plugging the pump, the OPV was going of on the second pump. With the pump plugged, a foot of PETG in that PVC sheath, and 1.5" slug darts, I was getting 90' with 4 pumps, and 105' with 5 pumps.

Edited by Buffdaddy, 01 October 2011 - 11:02 PM.

[Cannonball]

Nice work. I never thought of doing that, though I'll admit I'm not too savvy with back-pressure tanks and the like. I expanded the tanks on my knock-offs to get that extra range boost to make them able to compete with other blasters you usually find on the field. I'll have to go and buy another one now to compare. May be we'll see more of these instead of Big blasts now.

[Buffdaddy]

I also got these on Amazon for $5, with free shipping (already had Amazon Prime), and I've sen them at Big Lots for $8 or so. They're cheap!

I thought about doing a tank expansion, but I put priority on this first. Besides, you get into some complicated things with tank expansions, sealing issues as things try to fly apart, etc. "Filling in" is easier to deal with than "filling out".

[Cannonball]

I suppose. You do preserve the stock look, at least. Won't be able to do that with a hopper though. You do have to use that tiny pump less in order to prime the thing, which is nice. I think it's the worst thing about the blaster... I haven't handled an original Sonic Bazooka, but I can't imagine the pump is any better.

I've been picking mine up at Big lots, and although the $8 price tag isn't the most appealing, these things are pretty nice if you get them up to snuff. Definitely one of the least cumbersome blasters around, considering it's size. Maybe a little awkward to hold for that same reason though.

[andtheherois]

This is great. I saw these knock offs long ago for 6 at some store, but I looked them up on the spot and thought they weren't worth it. Maybe now I'll have to go by pick one up. Good job!

[dizzyduck]

Just a word of warning for those of you looking to do extensive mods on these: the plastic is of terrible quality (think Wayne TriTech Blaster or Monsters vs. Aliens Area 51 Blaster caliber plastic) and the check valve on mine failed after about 40 shots. I didn't even plug the pump.

[Beasty Billy]

Good results! I have no experience with backpressure tanks, so could someone explain how cutting the tank helps?

[Buffdaddy]

There are several threads asking this; I would refer you to the Autopsy Thread, that has several of these tanks disassembled.

Basic premise: air goes into the rear air line/tank, and leaks around a piston to the firing tank. The pressure forces the piston to seal against the front. Then a release valve of some kind lets the air out the back air line/tank. If this is done quickly, then you will generate a large pressure difference between the two sides of the piston w/o a lot of air leaking back past it. The piston is then forced backward, opening the tank to the barrel and firing your dart/missile.

Backpressure tanks work best with a small tank/air line area behind the piston (aiming for a roughly similar cross section) and a large valve to dump that air as fast as possible. The valve to release the air on this is pretty tiny (bad thing), but the more pressing problem is the HUGE amount of air behind the piston that you have to dump before it fires. This hampers the performance more than anything. Thus the reason for my mod.

[Beasty Billy]

Ahh I see. Thanks for explaining.