Oxy's Stampede Breech

The Stampede is a pretty cool blaster when modded, with a decent spring and enough Voltage to push it ranges of 70ft are pretty common. However, its plunger tube volume is greater than a Nite Finder so it should be capable of better ranges. The stock breech is what really lets it down.

SG Nerf started a thread on the NerfSG forums with info on the R&D he'd been doing on a Brass Breech design (HERE) but all the vibrations/movement when firing caused the brass to smash itself to bits all the time.

This got me thinking that there had to be a way to make a breech with a 95% seal at least that was sturdy enough not to break all the time.

Here is the design I came up with...



And now for the actual thing. I kept the stock return spring in the same spot. I just wrapped the conduit with about 10 layers of e-tape to act as a spring rest.



Here is the bolt section. You can see how much of the stock bolt I left here. The 1/2" Brass fits nicely inside the PETG with 1 wrap of e-tape.

Looks good mate, will be interesting to see ranges and durability.

No wonder you've been keeping quiet... haha

Cheers,

wow this is great. I hope it works but the only problem is getting the measurements to the mm because where the 2 PETG pieces meet have to be exact or some serious damage could occur. Also in my stampede i broke this piece off and it's not even functioning at all, the bolt only goes half way then goes straight back. So if you don't replicate this piece it might not work. Im not too sure

Piece mentioned:[img][/img]

That's very interesting...

I've been mulling this over for a while, but wanted to wait until I'd finished a couple of other things I've got on the burner.

Instead of having the heavy receiver running back and forth with the bolt, you've made it stationary (have you?)with a short pusher on the bolt.

Obviously this allows you to use a heavier (and cheaper) material in the orange conduit.

Have you tapered the inside of the PETG barrel where the dart enters it?

The reason I ask is that I would have thought that there was a chance of jamming due to the dart sitting higher in the orange conduit receiver, then snagging the tip of the dart on the end of the (smaller/lower) PETG barrel when it's pushed forward.

Obviously this is not the case, as you mentioned it runs on full auto, I just wondered if you took steps to prevent this.

Not fully airtight, but you could possibly cut some grooves inside the orange conduit (if you had access to a lathe) and inserted some lubricated o rings which may greatly improve that.

What about making the barrel from 9/16" brass with the end that takes the darts slightly flared (just enough to make it a tight fit in the conduit) with a 45 degree flaring tool? That would really reduce the chances of jamming.

Brilliant work mate, looks like you're going to crack it!!

9/16" brass would definitly jam much less and especially if it's flared out. The only problem is the price...

Very interested to see pics and a bit more of a write-up on how to do this!

melbnerf619 wrote:9/16" brass would definitly jam much less and especially if it's flared out. The only problem is the price...

@$%& the price!

A 100ft, accurate and hard hitting stampede running a high ROF is something I'm prepared to pay a bit more for!

But I just noticed that he said that it was only one wrap of tape to bed the PETG, which doesn't leave much room for flaring, but you could still do it a little bit for reliability..

@ Oznerfnerd...

Yeah, the conduit is stationary.

I tapered the conduit a bit where the dart enters (mainly to reduce the chance of the PETG running into it if things get thrown out of alignment under full auto) but not the PETG barrel piece. I figured the shape of the light sil tips i'll be using will be able to clear the edge no worries and it seems to work ok as is.

I doubt the 9/16 could be flared enough to allow the petg to nest inside it a couple off mm - unfortunate because that would help with the seal a lot.

The O-ring idea would be perfect too.

And I agree - who cares about the price as long as it owns.

@ melbnerf. There is no need for that piece in my design because the conduit acts as a guide for the PETG and also stops the darts fromcoming out of the clip.

Looks like I'll have to take advantage of the upcoming toy sales and bag myself a Stampede (or two) too.

An interesting, yet conventional approach.
A lot of promise there.

Ah, I see your taking the rapid-fire tek approach to an air tight breach, I never thought of that.

I thought this would have already been done so I did some research to find now. Good to see you having a go Oxy, the results should be awesome.

oxymoron wrote:@ Oznerfnerd...

Yeah, the conduit is stationary.

I tapered the conduit a bit where the dart enters (mainly to reduce the chance of the PETG running into it if things get thrown out of alignment under full auto) but not the PETG barrel piece. I figured the shape of the light sil tips i'll be using will be able to clear the edge no worries and it seems to work ok as is.

I doubt the 9/16 could be flared enough to allow the petg to nest inside it a couple off mm - unfortunate because that would help with the seal a lot.

The O-ring idea would be perfect too.

And I agree - who cares about the price as long as it owns.

@ melbnerf. There is no need for that piece in my design because the conduit acts as a guide for the PETG and also stops the darts fromcoming out of the clip.

I actually meant replacing the PETG barrel completely and replacing it with 9/16" brass flared a bit at the end that the dart feeds, nested in the orange conduit (will it fit, I'm not sure?).

You could probably put a few light tightening rings if you were keen on a tighter fit.

Just throwing it out there, I'm not that up on the exact dimensions of each type of barrel material.

But I imagine the automatic feeding would work best with a barrel with a lighter drag, just my guess.

Even if you don't get it airtight there should be an increase in power and accuracy.

Love to see your result soon!

I've just added some actual pics to the first post for reference. I have all the measurements I used as well but I can't add them to the design pic until I'm back at work (unless someone knows how to edit it on a Mac like I would in Paint on a PC)

As you can see in the pics, I only had stuff e-taped together for my first tests so I'm gluing everything properly before I try it with my 13Kg spring.

This looks very interesting, if this works awesome then I'll definitely try it out.

I recently tried this and came across an issue of the two pieces of PETG not sealing against each other enough.

How did you get around this?

Pronga wrote:I recently tried this and came across an issue of the two pieces of PETG not sealing against each other enough.

How did you get around this?

Shop around until you find a tight batch of conduit, or add a tightening ring where the two pieces meet?

I'm a stampede noob and i don't fully understand this breech, but I'd like to think i know my way around a bit of orange conduit.

mister_elliott wrote:

Pronga wrote:I recently tried this and came across an issue of the two pieces of PETG not sealing against each other enough.

How did you get around this?

Shop around until you find a tight batch of conduit, or add a tightening ring where the two pieces meet?

I'm a stampede noob and i don't fully understand this breech, but I'd like to think i know my way around a bit of orange conduit.

You're suggesting making the PETG air tight inside the orange conduit? If I do that the PETG Bolt Section wont freely slide. I've put some etape on the PETG Barrel Section to make that air tight.

What do you mean by tightening ring?

Yeah I had the same problem with the PETG although the seal is a lot better than the stock one obviously.

I think for this mod to actually increase range you need to minimise the front of the Stampede to allow use of a shorter barrel and to use a brass barrel somehow. I've put my WIP on the shelf for now.

Oxymoron,

This is probably a necro for the thread, but there is good reason for it!

Figured i'll just post here instead of creating a whole new thread.

I've managed to make a variant of the brass breeched Stampede based on your PVC guide cover design. Instead of PETG, i created it using a full assembly of brass tubes, along with various tweaks and adjustments... the result is 100% air seal achieved and it works flawlessly!

Check out the full mod guide here:

http://www.modworks.blogspot.com/2012/01/nerf-stampede-brass-breech-mod-guide.html

Full credits to you for your excellent design!

Haha I don't care if it's a necro! I'm glad that one of our members inspired you to create such a perfect seal. I was just curious. Does it use streamlines?

Your blaster has now inspired me as well, I'm going to be making an aussie version of this. hopefully it'll work out alright.

littlebro05 wrote:Haha I don't care if it's a necro! I'm glad that one of our members inspired you to create such a perfect seal. I was just curious. Does it use streamlines?

Your blaster has now inspired me as well, I'm going to be making an aussie version of this. hopefully it'll work out alright.

Well, my particular design is mainly optimized for stefans 'cos i was focusing on firing consistency and reliability. The shorter lengths of stefans allows a much higher margin of error during the chambering process, hence greater reliability.

I guess its possible to widen the breech gap just enough to fit standard length foam darts, though it requires even more precise tweaking of the measurements to fit those type of foam darts and also have the brass tubes nest securely to create the necessary air-tight seal.

Looking forward to see more brass breeched Stampedes popping up too!

Challenge accepted! Since it's Aussie Day... I guess I'll have to try to do it tomorrow lol.

note the stampede has 1mm more draw than an ls, this shouldn't be TOO difficult, but seriously, 105' flat? out of a freakin sully auto clip-fed blaster? this is a new rape gun.

Ok if i ever find the free time to do this mod, then my epeen stampede (which already hits 100ft, spring only (this spring is not available for purchase as it makes not so pretty noises from the stampede)) Makes me wonder what a breech upgrade could turn that monster into.

Servulus wrote:Ok if i ever find the free time to do this mod, then my epeen stampede (which already hits 100ft, spring only (this spring is not available for purchase as it makes not so pretty noises from the stampede)) Makes me wonder what a breech upgrade could turn that monster into.

I want to find out!

The Stampede I've modified for Joey and inf0rm3r hit 100ft as well (angled of course). So, we're not living in the dark at all XD. It's just a BT + stock stampede spring. These guys can confirm as well.

My current stampede only hits about 60-75ft :(. It doesn't have that spring combo in it :(.

Just to encourage you servulus. I think you can do better than that. Get that stampede a new motor and put the biggest possible spring in there. Put that brass breech in there and I bet I'll see 40metres-50metres.

I am pretty sure you would need to reinforce/replace parts of the stampede if you don't want it to break, at that spring load (what does the load add up to?) but that load+reinforcements+breach= awesome, probably 120' flat or more. (that is on par with un-plugged air guns)

40m Flat or more from a stampede would bring a whole new meaning to the word "Rape Cannon"

With all the keen interest in this topic, i've re-posted my mod guide on this forum for reference and discussion.

Check it out here:

http://www.oznerf.com/t4341-nerf-stampede-brass-breech-mod-guide

I've also updated it with my brass breech Stampede "SMG" variant too!