The airflow between the plunger tube and the turret is pretty sad, for what it is. It can be widened to 7/16" without compromising the seal to the turret. This can be done with a dremel/drill/exacto/sandpaper, just be careful, alright?
Here is the stock Arrowstorm plunger head assembly, great, but the existing seal only makes a good seal for the last inch or so of travel, WHICH IS UNACCEPTABLE.
So just rip off the old seal, which is garbage. You'll notice that either a U-cup seal or skirt seal will work, however the skirt seal seems to have less friction towards the end of travel.
Drill a hole in as close as you can get to the dead center of the plunger head (diameter of 27/32" if you really needed to know, 7/8" if you don't wanna go to nuts)
Next, cut a circle of 1/8" polycarb, between 1" and 1+1/8" in diameter with a 1/8 hole (up to 5/32, if you care) in the center. I chose to put a 1/16" thick washer in the middle of the plunger head to relive stress on the skirt seal.
Then use a 6-32 bolt to assemble your plunger head, doesn't matter if the phillips head is on the outside or inside, you can do whichever if you have a longer screwdriver or socket wrench. You can check to make sure it's airtight by blowing air in the back of the plunger head assembly and see if any air escapes. If you've done all of this right, you should have something like what you see below. Throw a bunch of silicone lube/whatever you want on the inside of the tube and on the skirt seal.
That is what most people need, the rest of this write-up to show how to make perfect rear loading ports.
First off, choose your barrel material and length, cut all 6 barrels, and add enough electrical tape to secure them in place right up against the taper for the plunger tube's nesting point.
You can glue them in place, but if you use the electrical tape properly, it's not necessary.
Once the barrels are mounted, take a sharpie and put electrical tape on it so that both sections of electrical tape on the marker are the same as the ID of the barrel material (it should slide in and out fairly easily).
Assemble your Arrowstorm completely now, and drop the sharpie down the four barrels that should be rear loading (make sure they hit bottom) Now disassemble your Arrowstorm once more!
Now use the sharpie mark for the center of the rear loading holes.
A good way to do that is to drill a 7/64" hole and tap it with a 6-32 bit. Use a screw to attach a washer, I used a 1" diameter washer with a 1/8" hole in the middle.
Trace around the washers with a sharpie and then remove the washers.
Dremel/drill/whatever until you're up to the sharpie mark. Seems to work quite well, all the holes were just the right size for the washers to fit though. Finish with sandpaper, I used 400 grit, seemed to work great.
Looks off center in the pic, but it is quite well centered.
That's about it, I have a couple more ideas, but it's gonna be a while before I get around to them, so I figured I'd post this for you all to enjoy in the meantime. Also I don't think I cursed enough in there, fuck it all, props to my boizzzz over at #nerfhaven.
EDIT: Picture links have been corrected, thanks to WSU Cowboy and LordNikonX for bugging me to get this fixed. I may have an addendum to this mod at sometime in the future.
Edited by Jlego, 13 July 2014 - 08:47 PM.