Brass breeched Longshot mod!

Sup reader,
It has been a long time coming, but I have finally finished modding my Longshot! After royally fucking up my breech the first time, I have revamped my original design to make it even better than the original. Inspirations for this mod include SgNerf's original brass breech, SgNerf's quarter pipe upgrade, and Samurai_kidd's Alternative Sealing Method for Longshot Plunger Tubes write-up. My design serves to eliminate the most possible dead space while maintaining a leak-free seal between the plunger tube and brass bolt. Let's get down to brass tax!
Required materials:

• 1/2'' brass tubing (1' length)
• 17/32'' brass tubing (1' length)
• 9/16'' brass tubing (1' length) x 2
• 19/32'' brass tubing (1' length)
• 5/8'' brass tubing (1' length)
• 21/32'' brass tubing (1' length)
• 3/4'' PVC (3'' length) x 2
• 1/2'' PVC (3'' length)
• sheet metal
• coat hanger
• K26 spring
• Stronger catch spring
• JB Weld
• Claw hammer
• Scroll saw
• Silicone grease
• Teflon tape
• Clothespins or small clamps
• Dremel with sanding bit, grinding bit, and cutting wheel
• Plunger padding

Write-up:
This write-up is almost identical to SgNerf's, but I have made a few changes to his design. I will try to point out our design differences throughout the write-up. Without further ado, let's start out with the brass bolt. Here are the lengths you will need for the different sizes of brass:
1/2'' - 12.5cm
17/32'' - 2cm x 2
9/16 - 2cm
19/32'' - 17cm (4cm quarter-pipe)
Cut them all out and deburr them with a grinding bit on your Dremel.

Below is the brass bolt diagram from SgNerf's original write-up:

Design differences:
I cut my quarter-pipe to be 1.5cm shorter than SgNerf's and increased the length of the 1/2'' piece by 1.5cm. This has a few implications:

1. I can no longer chamber streamlines. Honestly, I could care less about chambering crappy streamlines.
2. The tip of the barrel's quarter-pipe now rests inside the brass bolt when the breech is fully opened. It no longer "floats," and allows the barrel to be guided into the bolt perfectly every time. My first attempt left the barrel quarter-pipe "floating," and it ended up ramming into the bolt every time and failed to slide in.
3. I use a 2cm stub of 17/32'' brass (yellow) on the very left side of the 1/2'' piece (orange). This is my personal addition to SgNerf's mod that eliminates all the dead space in the bolt when the breech is closed. It was mentioned in the comments of SgNerf's write-up, so I put it into action--this is the reason that I decided to modify SgNerf's design in the first place!
4. Darts get pushed into the barrel slightly farther, effectively decreasing the barrel length slightly. A small price to pay for almost zero dead space and flawless chambering!

Now cut off the end of the old bolt to get it separated from the plunger tube and cut off the bottom part that sits in the plunger. Leave a little bit of a lip on top of it to make it easier to glue. Use some fast-setting epoxy to affix the bottom of the bolt to the brass, then fill up all the dead space in the bottom with hot glue. Dremel off the small lip you left on the black part.

Cut a small 1/2'' ring off of the old bolt from underneath the air release hole.

Epoxy it into the end of the plunger tube, making sure to plug the seam completely. This will allow the 19/32'' brass bolt to seal nicely with the plunger tube. SgNerf left the air gap there in his mod to allow for more surface area to attach the plastic bolt sled attachment nub, so I made a sacrifice to get things leak-free.

Now let's work on the barrel supports. Chop off a 1'' piece the faux barrel, 19/32'' brass, 5/8'' brass, and 21/32'' brass.

Glue them all together and glue the entire thing to the orange muzzle. They should all nest together perfectly! I would recommend letting it dry upside down, however, so the pieces don't accidentally slide out of place.

Now let's do the second barrel mount. Take a 1'' stub of 19/32'' brass and 5/8'' brass and cut out slightly more than a quarter pipe on each piece, then glue it into the dart tooth.

Glue it into the end of the dart tooth.

Design differences:
In SgNerf's mod, he uses electrical tape around the barrel to secure it in the original orange faux barrel. This makes it removable, but probably not the most secure in the long run. My barrel is not removable, but it's not going anywhere! When I dreamed up the idea of expanding the side holes to get a view of the brass barrel, I knew that I would need to come up with a way to keep things centered and secure while also showcasing as much of the barrel as possible. Voila!

Now let's do some reinforcement. Start with the bolt sled--a lot of stress will be on this piece, since the entire spring load is tugging on the top of the bolt sled. Cut out some L-shaped supports out of your sheet metal. Here are the dimensions:

I should note that the other side is slightly different--the 5/8'' on the right side is actually less. Here is what they look like when cut out:

Bust out the JB Weld and use your clothespins to keep things pressed together.

Make sure that no sharp sheet metal edges are protruding upwards, or your plunger tube will literally get sliced open with repeated use. The finished product:

Due to the thickness of the sheet metal, you should sand down the fins on the dart tooth so the bolt sled doesn't get stuck moving forwards.

The other thing that needs to be reinforced is the trigger. I had to trim down this corner on both sides:

Coat hangers are the perfect size for the Longshot trigger. I used JB Weld to adhere the  pieces of bent coat hanger. Check it out!

Once the epoxy on barrel supports has fully cured, we can prepare the barrel. Take 1' of 9/16'' brass and cut a 3 1/8'' quarter-pipe on one end.

The tightening rings should be farther from the barrel inlet--this was a failed first attempt.

Now we must make some careful markings. Insert the barrel into both barrel supports and put it into place, along with the bolt sled, plunger tube, and brass bolt. The inlet of the barrel should barely be poking out into the magazine well. Make dots adjacent to where you need to glue the barrel to the mounts.

Hold the barrel in place and push the brass bolt all the way onto the barrel. Now you can get a glimpse at how my design works--the barrel's quarter-pipe is constantly inside the bolt. This keeps it from ramming into the bolt and also guides the barrel into the bolt smoothly with each prime. Make a mark on the 19/32'' bolt where the bolt sled attachment piece will go.

Now pull out everything, making sure to keep the bolt and barrel locked together in their current positions. Make a mark on the barrel right where the bolt ends (not the quarter-pipe). This is where the tightening rings will start. I made as many as I could in a 1 1/4'' length (length of my darts). Also make some marks to designate where the quarter-pipe cutout is on the dart pusher end. You don't want epoxy in that quarter-pipe gap.

Design differences:
The quarter pipe for the barrel is shorter than SgNerf's. When the breech is fully opened, the very tip of the quarter-pipe rests inside the bolt in between the 19/32'' brass and 17/32'' ring I added. This is how I prevent the quarter-pipe from colliding with the 17/32'' ring like in my first failed breech. A shorter quarter-pipe also means a longer effective barrel, though it is cancelled out by the longer 1/2'' piece which pushes darts in slightly farther.

Glue the barrel into place.

The last major step is to glue on the bolt sled attachment piece. Unfortunately, even the strongest epoxies I had weren't strong enough to withstand the load of my K26 spring. To make things worse, every single mod write-up called for attaching this piece with epoxy! I don't know how the hell any of those mods lasted more than 100 shots. In typical T da B fashion, I set out to improvise.

I decided that joining plastic to metal was a lesson in futility, so I did my research online and learned how to join metals with a butane torch, silver solder, and acid flux.

The metal bar is copper that I used for my homemade bolt sled nub

In the end, I was victorious! Read the full write-up here.

This next step is completely cosmetic, but it gave me some good practice with the scroll saw and I'm ecstatic at how it turned out!

For every hole I had to

1. Remove the scroll saw blade
2. Move the Longshot into position
3. Thread the blade through the hole and secure it
4. Make the cut

It took a while, but after sanding it looks super legit!

LS6

At this point, there's only the basics left. Wipe down your K26 with some Brasso and slap it on your plunge rod. Mine was a little longer than 4''. Put some Teflon tape under the O-ring until there is decent friction with the plunger tube walls. Glue on a piece of plunger padding--I used my classic natural gum foam from Mcmaster.

I even left a hole for screwing :)

Pop a new spring on your trigger catch as well. It has to be pretty small--I used a Ace/OSH #1. I thought about reinforcing the catch, but honestly there isn't much room to work with and most things will just fall off over time and rattle around in the shell. If it breaks I'll make a new one out of polycarbonate.

Put everything in place and lube up all moving parts, including the bolt sled, bolt, trigger, and catch. I added hot glue around where my catch spring contacts the top of the shell, since it kept bending out of position. Here's what it should look like:

Close it up and grab your stock. We are going to perform a "stock block," and I took the lazy route and only glued things into one side of the stock. I used two pieces of 3/4'' PVC and one piece of 1/2'' PVC stacked in a triangle.

Top piece should be 1/2''

And you're done!

Baller shit.

LGT6

Final thoughts:
After loading up my modded 18-round magazine with Stefans and inserting it into the Longshot, I knew that a massive boner was imminent. SgNerf's Longshot managed to hit 210 feet per second in his write-up, so I was hoping to do better than that. Let's see if T da B's mod is an improvement:

Jesus Tapdancing Christ!

And I just came in my pants. I didn't even believe this number when I first saw it, but then two shots later I hit 299fps and I knew that it wasn't a fluke. Keep in mind, however, SgNerf is using heavier 1.1 gram Stefans, so his velocity will naturally be lower. For my ammunition I used #6 slugs with Mod Man's red foam--it seems to be an absolute perfect fit in 9/16'' brass. Say hello to my first springer that shoots harder than 300fps! Hot damn.

Update (6/8/2013):
My Longshot trigger catch is officially deceased. The morning of the war I attended recently, my Longshot failed to catch. I guess I was lucky that it happened then and not on the battlefield. I could see markings at the top of the trigger catch opening where the plunger end had ripped off plastic over time. Oh well--to quote myself: "If it breaks I'll make a new one out of polycarbonate." I will also be doing the plunger rod and a shotgun grip, since my Longshot deserves the best health care.

I also put a very short 1/4'' set screw through the shell to act as a spring rest for the trigger catch. Check it out:

Sigh--it never ends, does it?

Link to Part 2
Link to Brazed Brass Breech Band-aid Build
Link to Part 3

I hope you all enjoyed another one of my write-ups.
~T da B