So I finally did it. It wasn't as clean as your pics since my bits kept trying to spin the tiny pieces of poly and I had to use a Dremel instead a band saw. I ended up using my Dremel a lot for cutting and grinding but it worked out well enough. The mounted seal looked good and worked with a little grease. I also cut out the little xman symbols at the back of the orange barrels.
However there was no noticable difference for me in range..haha oh well. I may mess with it some more; try to get a better seal where the white tube meets the barrels. It was fun for my first nerf mod. If I ever do the barrel extension I'll be sure to post it in mods section. Thanks again!

You don't put any on the back. You put one in the middle that matches the ID of the skirt seal (7/8") so it stays put, and you put one on the front that's just large enough (1 1/4") to hold the skirt on.

Did you use a hole saw to cut the poly? I was planning on using one but not sure if the center drill bit part would be larger than the 9/64 hole you said to drill for the screw.

Thanks snakerbot. I ordered the skirt and the polycarbonate. I'm thinking of trying thin walled pvc and buying longer springs for the second part of my ridiculous mod instead of cutting up another ballzooka.

The only mod writeup I've ever seen for that blaster is the one I did. I'm not sure it's a great mod, but it exists.
 
To answer your questions, it's a manual plunger blaster, sometimes called  "push-pull" blaster, for obvious reasons. Lately I've seen this style of blaster called HAMPs, after Kane's blaster of that name. I'm not sure about extending the inline clips. I've never seen it done.

Hey so I ordered the rubber seal but reading over your instructions for the polycarbonate I'm a little confused.

Are there two pieces I should cut? (One for front and back?)

Click "Image Archive" at the top right. They were a victim of the imageshack apocalypse a few years ago, but survive in that archive.

Great! I couldn't see it because I wasn't on fullsite mode. Okay so now I just need to find another cheap, available ballzooka. A broken one I can part out.

If you are looking for more old ballistic ball ammo, I can confirm that the following on Amazon are an exact match. Work for my old Master blaster.

https://www.amazon.c...i_Qc6dEbHZNECM6

Awesome thanks! Now I don't have to order from AliExpress and wait a month for p active golf balls

Just saw your post. Awesome! For some reason the images don't load for me but I think I can make sense of it.

I recently just surprised the kids with the ballzooka and they were intimidated by the size and noise alone even though their blasters are far more powerful...hilarious.

It may be awhile before I mod. I'm going to try a few other blasters first.
Thanks for the response and input!

Humor me.
I recently got an original ballzooka for 8 bucks and was thinking of modding it. Why you ask? Nostalgia.
I work at a children's home where the kids love to play Nerf (ages 5 to 17) in the house. A ballzooka was my first ever Nerf gun and I doubt these kids have ever seen one, let alone have heard the ridiculous clanging noise as ball ammo larger than they've ever seen is grenaded at them.
The gun works about a good as any ballastic gun does....ha... However, my curiosity is getting the best of me and I wanted to run some ideas up the flag pole before I ruined this gun, especially since I've never modded a gun before.
1) Is this considered a spring action gun or air pump? You don't pump it but I guess you push the air...so a plunger gun? I wanted to see if I could tighten up the gun inside to seal up any places air leaks out...basically more air power and either harder hits or farther distance.
2) Just humor me a little more... I also was thinking how awesome it would be if I could make the barrels longer....maybe buy another ballzooka, chop the barrels, chop the tops of the original gun barrels, connect both sets of barrels, replace springs with longer ones and hold twice as many balls (not too concerned with accuracy ... I'm aware the barrels wouldn't be perfect).... Would the gun have enough power? It sure as hell would be front heavy.... But intimidating.

Thanks in advance.

So I realize this topic is 7 YEARS OLD! But I just came across it for help, took a chance and purchased some practice golf balls on Amazon and found it works perfect as ball ammo for the original ballzooka. They are practice golf balls but NO dimples and a perfect fit. The website says 42 mm which is supposedly too small..but I don't think they should be any bigger...thought I'd share:

20 pcs Yellow Foam Golf Ball Indoor Exercise Ball Eva Solid Color https://www.amazon.c...i_MZs.DbZ4Z9EFD