If you're not replacing the spring (I don't have any extras around) you don't have to open up the white part, just push in on the bottom edge of the plunger tube that faces away from you and push up. It will slide right out.
Here's the rear of the A/R assembly. Unfortunately, the front of the plunger tube is glued together, which is always a pain. Instead of messing with that you want to drill out the triangular area in the middle, and then take your screwdriver and push hard through each hole in the front.
Since everything is orange it's a little tough to see here, but when you do it correctly those back plates should snap off cleanly. It worked on the top two, but I think the bottom one was drilled a bit too close to the side of the plunger tube. Once you get the springs and other air restrictor garbage out of there it's easy to widen the front holes and clean up the rest with your dremal.
The downside is that you're left with a lot of deadspace in the front of the plunger tube. I eyeballed it wrong, and this piece of foam doesn't even come close to the end of the plunger tube. I put a slightly bigger piece in there for now, but I'll have to hit up Ax-Man again for some more.
I don't use a tape measure for ranges, but our house is about 50 feet long. Before the mod most shots were falling short, after the mod they all went past it (all stock darts). I'd guess there's about a ten foot improvement, mostly it seems to help the shots stay consistent.
I didn't see any shell refill packs, I'd like to get one before I mess around with the barrels too much. I got this mostly to have fun at an all Defend the Core war, but I bet a singled rear-loading shell would be an easy and effective mod for swapping in and out.
Update with some HammerShot info. I didn't think it was really big enough to make another thread.
Like the SledgeFire you're also left with some dead space at the front of the plunger tube. I did the same thing with a smaller piece of foam on the plunger rod and took out the posts in the barrels. It's pretty nice compared to dealing with the barrel A/R's on a Maverick.
Unfortunately there wasn't much if any range increase with streamlines (although they still hit a good 60 feet), and slugs only go about 45' or so. It probably needs to be rebarreled to make it worthwhile.
Edited by VelveetaAvenger, 09 August 2013 - 05:43 PM.