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    Nerf Stampede "Brass Breech" Mod Guide!

    SgNerf
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    Post  SgNerf Fri Jan 27, 2012 8:08 am

    There has been alot of keen interest on this topic in this forum, so i'll re-post this mod guide here for reference and discussion.

    This mod guide will look into my "Brass Breech" modification for the Nerf Stampede.

    --

    Introduction:

    The stock stampede plastic breech does not have an air-tight bolt to barrel seal, hence the plastic bolt itself is essentially the barrel. Once the foam dart is fired out the bolt, the foam dart already starts losing power and velocity. In addition, most of the air pressure from the plunger is wasted once the foam dart leaves the bolt.

    For those new to the brass breech concept, the design objective of an air-tight brass breech system is to create a 100% air-tight seal all the way from the plunger through to the barrel, thereby providing efficient air pressure delivery to propel the foam darts further. This would result in more power within each shot, with greater firing distance and faster dart velocity.

    For a Stampede brass breech to work, it requires the air-tight connection of matching brass tubes and a guide cover to ensure that all the moving parts are aligned properly.

    My design is optimized to work with stefans (short length customized foam darts), although it could be adapted to use normal length foam darts, they usually wouldn't perform as accurately or consistently, and may result in much higher rates of jams.

    The following guide will cover my customized version of the "Brass Breech" mod.


    Credits:

    My brass breech design for the Stampede is based on the excellent "PVC guide cover" design by Oxymoron at the OzNerf forum, full credit goes to him for that design.

    Link to the original "Oxy's Stampede Breech" thread by Oxymoron at the OzNerf forum


    Important Note:

    The "Brass Breech" mod is a more advanced mod project that should only be performed by those who are already familiar with modding the Stampede.

    For new modders, please refer to my Nerf Stampede Mod Guide to get familiar with the modding basics first.

    Disclaimer: Modify at your own risk. Modifications may wear out or damage your blaster. Please be careful when using hobby tools!


    Lets start...

    Step 1: You will need to obtain 3 different sizes of brass tubes (Brand: K&S Engineering) and a suitable PVC pipe for nesting them into.

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B01

    The brass tube sizes are: 1/2", 17/32" and 9/16". All of them are 0.014" wall thickness. They are usually supplied at hobby shops in either 1 ft or 3 ft length tubes.

    I use a 13mm SingaPlastics brand PVC pipe which can nest the 9/16" brass tube. This pipe will be used to create the PVC guide cover.

    For modders in Oz, 20mm orange conduit (as shown in Oxymoron's thread) would be the local substitute.

    Note that the inner diameters (ID) of PVC pipes often tend to have variations, even within the same length of pipe, so you have to test different sections and make sure it fits the brass tubes before usage.

    Its recommended to prepare and polish the brass tubes with some metal polish to remove any oxidization that may have occurred both externally and inside the tubes, this helps smoothen out the surfaces for lower friction and better fit.

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B02

    As you can see, the brass tubes nest perfectly within each other and they all form an instant 100% air-tight seal. Those who have worked with brass breech systems will be very familiar with this unique characteristic.


    Step 2:

    Lets start with the PVC guide cover, this is the most essential part of the Stampede brass breech system. The guide cover ensures that the moving brass bolt chambers each foam dart into the barrel properly and consistently.

    Take the PVC pipe and mount the N-Strike clip on it.

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B03

    Use a marker to trace the outline of the clip's shape.

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B04

    Use a Dremel with cut-off wheel to cut out the traced lines.

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B05

    As the top section of the guide cover ends up being a rather thin strip of PVC (which will tend to flex too much), i cut out another shaped part from a larger 16mm SingaPlastics brand PVC pipe which is then glued on the top to further reinforce and stiffen that section.

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B07

    The PVC guide cover is done!


    Step 3:

    Now we proceed on to the brass barrel section.

    In my example, i use a 21 cm length (8+ inch) of 9/16" brass tube as the barrel. It is nested and glued into the PVC guide cover.

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B09

    Use a Dremel with sanding bit to bevel the inner edges of the brass barrel, this creates a funnel design to enable smoother chambering of the foam darts and brass bolt.

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B10

    I positioned the barrel and guide cover assembly to align with the internal dimensions of the Stampede, an additional PVC pipe was nested at the front of the barrel to help keep it in line with the Stampede's front casing structure piece.

    The orange collar piece is also positioned and glued to the PVC guide cover to establish a fixed securing point to the blaster casing.

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B11

    The brass barrel section is done!


    Step 4:

    Next we proceed to the brass bolt section.

    Use a pipe cutter to cut away the stock plastic bolt, as shown in this photo.

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B12

    To make the brass bolt parts, use a Dremel to separately cut out a set of brass tube sections in the following lengths:

    1/2" brass tube: 11 cm
    17/32" brass tube: 2 cm (2 x spacer sections)
    9/16" brass tube : 9 cm

    These are my custom tube measurements for the Stampede brass breech system.

    These measurements need to be as accurate as possible. Any variations may affect the overall structure and air seal of the breech system.

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B14

    Used a Dremel with sanding bit to bevel the outer edges of the brass bolt front section, this will help to further enable smoother chambering of the foam darts and brass bolt into the brass barrel.

    Here is my Nested Brass Tubes Cut-Away Diagram:

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B15

    Nest the assembled brass bolt into the plunger casing.

    Use the strongest glue you can get to glue everything together. I use "Selleys Super Strength" 2-part slow-curing epoxy glue (curing time of 3 days!). Make sure the glue cures completely for maximum bond strength.

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B16

    Note that the 1/2" brass tube acts as the air channel and helps to reduce dead space, but not too much to create an air restriction.

    The 17/32" brass tube will chamber the foam dart and connect into the 9/16" brass barrel, this is what creates the 100% air seal.

    The brass bolt section is done!


    Step 5:

    Sleeve the brass bolt into the PVC guide cover. Test the parts movement and connection with the brass barrel.

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B19

    The brass bolt must be able to move smoothly within the PVC guide cover without resistance.

    If there is resistance, use a Dremel with sanding bit to widen the inner diameter (ID) of the PVC guide cover until it fits.

    When the 17/32" brass bolt connects into the 9/16" brass barrel, it should have a 100% air-tight seal. Test the seal by closing the breech, then manually compressing the plunger while blocking the barrel exit, there should be resistance felt in the plunger rod.

    Next, install all the parts into the Stampede.

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B20

    Test the parts fit and test the movement of the brass bolt. Make sure everything moves smoothly.

    If there are parts which encounter resistance, either loosen or trim the fit and test again.

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B21

    Assemble everything together, keep testing the movement of the parts as you assemble the blaster.

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B22

    Its completed!

    Here are some close-ups of the breech system:

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B23

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2B24

    Awesome! :-)


    Stampede Brass Breech - Demo & Test Fire Video:




    Sample Test Fire Results:

    PTG: Parallel-To-Ground (Shoulder height, no elevation)
    ATG: Angled-To-Ground (Aimed higher, 30 degrees elevation)

    Distance is measured at where the dart lands (Average of 6 darts).

    Brass Breech Stampede (9kg Load Spring)
    Ammo: Customized FBR foam + 1.1 gram soft silicone tip weight
    PTG = 95-105 ft
    ATG = 120-130 ft

    Note that the test was done indoors with customized foam darts and the results are sample estimates for reference (your results may differ depending on materials and mod techniques used).


    Important User Tips:

    - Short length customized stefans work best with this breech system, make sure that the stefans used are in perfect condition and fit the brass barrel properly (not too narrow or not too wide). In addition, ensure that the back portions of the stefans are rounded without any excess foam sticking out which might get clipped by the brass breech when it closes. Taking care of these various factors will greatly reduce the chances of jamming.

    - With the clip and trigger locks removed, do not put your fingers into the breech section when the blaster when the brass breech is in operation, as this can result in injuries.

    - The better the foam dart fit in the brass barrel, the better the range results.


    Variants:

    For fans of minimized Stampedes... check out the brass breech mod done on my "SMG" Variant!

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2BSMG%2BVariant%2B-%2B30

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2BSMG%2BVariant%2B-%2B31

    Nerf Stampede "Brass Breech" Mod Guide! Stampede%2BBrass%2BBreech%2BMod%2B-%2BSMG%2BVariant%2B-%2B32

    Note the extra length of PVC pipe and coupler covering the brass barrel in front, it is designed to cover the brass tube edges for safety in Nerf games.


    Last edited by SgNerf on Mon Feb 06, 2012 6:26 am; edited 5 times in total
    Kaine
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    Post  Kaine Fri Jan 27, 2012 1:12 pm

    First of all, great job with refining Oxymoron's design, it looks simple yet elegant.

    Two queries though if you don't mind:
    1. In regards to the plunger/bolt assembly, how much should the 1/2" brass tube protrude from the 17/32" brass tube?
    2. What length foam darts would be optimal for this design?

    And Thirdly, that wouldn't perchance be a belt clip on the mini-Stampede now would it?
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    Post  natious Fri Jan 27, 2012 2:02 pm

    Excellent work, can't wait to start this
    Joey
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    Post  Joey Fri Jan 27, 2012 2:43 pm

    Friggin brilliant, as always SGnerf, that is all.
    SgNerf
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    Post  SgNerf Fri Jan 27, 2012 3:48 pm

    Kaine wrote:First of all, great job with refining Oxymoron's design, it looks simple yet elegant.

    Two queries though if you don't mind:
    1. In regards to the plunger/bolt assembly, how much should the 1/2" brass tube protrude from the 17/32" brass tube?
    2. What length foam darts would be optimal for this design?

    And Thirdly, that wouldn't perchance be a belt clip on the mini-Stampede now would it?
    Thanks!

    I just protrude the 1/2" brass tube out by 1mm from the 17/32" brass tube, its mainly to allow for the creation of a nice layered bevel in that section, helps to create a smoother chambering with the 9/16" brass barrel.

    For the foam darts, i use 3cm length FBR with silicone tips, so the total length of my stefans are around 3.5cm. I've found that to be an optimal stefan length to use. Basically, the shorter the stefan the wider the margin for error ('cos there is more space and time within the chambering cycle for the stefan to advance up the clip properly, especially when firing in full-auto), hence the lower chances of jams occurring.

    Yup, you got it right... the metal handle attached to the side of the casing is my "holstering system", for hooking the blaster to my belt when i'm moving around during Nerf games. Its made from a re-purposed window latch. :-)
    oznerfnerd
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    Post  oznerfnerd Sun Jan 29, 2012 1:31 am

    Hey SG,

    Congratulations mate, it looks good.

    It's great to see, but bittersweet cause I've got almost exactly the same thing laying on my bench half done.

    For Aussie modders, the orange PVC conduit won't fit straight into the nose piece and rear clamp like your Singaplastics.

    I've got 5 barrel guides cut and was looking for a lathe to machine down the ends to fit perfectly.

    I based my design on full length darts (I almost always do) and was looking at a heavy walled aluminium tube with an o ring slotted into the end as a bolt for sealing.

    Obviously this is not necessary.

    As I have a plumbing flaring tool in the box, I was going to flare the end of the 9/16 barrel for smoother feeding.

    These Singaplastic products have served you well, I wonder if I can get them in Australia.

    Top job mate, you smashed that one!

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    Post  natious Sun Jan 29, 2012 6:05 am

    oznerfnerd wrote:Hey SG,

    These Singaplastic products have served you well, I wonder if I can get them in Australia.

    Top job mate, you smashed that one!


    According to their website they export to Australia, so just need to find a supplier
    oznerfnerd
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    Post  oznerfnerd Sun Jan 29, 2012 7:33 am

    natious wrote:
    oznerfnerd wrote:Hey SG,

    These Singaplastic products have served you well, I wonder if I can get them in Australia.

    Top job mate, you smashed that one!


    According to their website they export to Australia, so just need to find a supplier

    I've sent them an email.

    I'll let you know.
    oxymoron
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    Post  oxymoron Tue Jan 31, 2012 6:47 am

    I'm stoked to see this idea finished! No one could have done it better than you SG. Thanks for crediting me too. Not that I think I really deserved it.

    As for the Singaplastics. I happen to have a box full right here I was planning on selling it, but now I'm not so sure....

    Philb2323
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    Post  Philb2323 Tue Jan 31, 2012 8:05 am

    looks amazing SG! I come from a engineering background, and would like to compliment you on the quality of all your mods that I have been trolling through.
    littlebro05
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    Post  littlebro05 Tue Jan 31, 2012 9:25 am

    I've almost finished my conduit breech. I may have to shorten the barrel at the moment since I'musing a 20cm long barrel. Might be too much friction <,<. Just need to wait for the 3day epoxy to dry. Then expect a write-up from me for the next week. If it works of course.
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    Post  natious Tue Jan 31, 2012 9:29 am

    littlebro05 wrote:I've almost finished my conduit breech. I may have to shorten the barrel at the moment since I'musing a 20cm long barrel. Might be too much friction <,<. Just need to wait for the 3day epoxy to dry. Then expect a write-up from me for the next week. If it works of course.

    What materials did you use, singaplastics?
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    Post  oznerfnerd Tue Jan 31, 2012 9:32 am

    littlebro05 wrote:I've almost finished my conduit breech. I may have to shorten the barrel at the moment since I'musing a 20cm long barrel. Might be too much friction <,<. Just need to wait for the 3day epoxy to dry. Then expect a write-up from me for the next week. If it works of course.

    Are you using 20mm orange?

    How'd you go fitting it in the nosepiece and spring retaining collar?

    Mine's OD is a bit too big, and I don't like the choices of sanding/machining down the conduit or sanding out the nerf plastics.

    The singaplastic tube seems the go for a clean fit.
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    Post  |Shadow| Tue Jan 31, 2012 9:38 am

    oznerfnerd wrote:
    littlebro05 wrote:I've almost finished my conduit breech. I may have to shorten the barrel at the moment since I'musing a 20cm long barrel. Might be too much friction <,<. Just need to wait for the 3day epoxy to dry. Then expect a write-up from me for the next week. If it works of course.

    Are you using 20mm orange?

    How'd you go fitting it in the nosepiece and spring retaining collar?

    Mine's OD is a bit too big, and I don't like the choices of sanding/machining down the conduit or sanding out the nerf plastics.

    The singaplastic tube seems the go for a clean fit.

    I was think some Aluminium tubing but maybe not a good idea? not strong enough?
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    Post  littlebro05 Tue Jan 31, 2012 9:45 am

    Mines's all Aussie Materials and are accessible from electrical suppliers just like Dietzie's. I used 20mm Grey Conduit. Otherwise, there wouldn't be a point of me making it if I couldn't get all the things I need from Aus.
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    Post  |Shadow| Tue Jan 31, 2012 9:47 am

    littlebro05 wrote:Mines's all Aussie Materials and are accessible from electrical suppliers just like Dietzie's. I used 20mm Grey Conduit. Otherwise, there wouldn't be a point of me making it if I couldn't get all the things I need from Aus.

    Sweet, did you have to sand/cut the 20mm or did it fit in nicely?
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    Post  littlebro05 Tue Jan 31, 2012 10:07 am

    I had to sand the 16mm conduit down for it to fit the 20mm conduit.

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