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Nerf Stampede "Brass Breech" Mod Guide!

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#26 ice

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Posted 30 January 2012 - 07:23 PM

So I took on this project for myself last weekend, here are the results;

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I did my breech slightly differently then SG did, I have a piece of 19/32's over the 9/16's on the bolt, which feeds through normal clear 1/2 PVC (from mcmaster) quite nicely. I also did the barrel quite differently, I have a 2" nub of 19/32's, which has a 2" nub of 9/16's nesting inside. I then have a 17/32's barrel nested into the 9/16's about an inch in, which gives enough room for the 17/32's from the bolt to fit completely in while not touching the 17/32's barrel piece. The 17/32's barrel is 6 inches, cause my darts have a rather tight fit into 17/32's. The whole system feeds incredibly well, took a few hours to tweak it, but it works perfect.



Now the problems.

The stock spring that pushes the plunger tube and bolt assembly back to the end of the shell isn't quite strong enough to get the job done. Usually it returns just fine, but sometimes it isn't quick enough and the gears start pushing the plunger tube forward again before the plunger moves back far enough to engage the catch.

It's super dart picky. Some darts fly through the barrel, while others of the same foam type and weight get jammed half way through, so when the next dart is pushed into the barrel, it double fires, resulting in poor ranges. I think I'm going to switch it out for a 9/16's barrel with tightening rings, cause even though I use 17/32's and CPVC in all my springers, the stampede plunger tube is only the size of that of a nightfinder more or less, and also has a few inches extra dead space, it's just not powerful enough. Hopefully 9/16's with tightening rings will be enough to give a seal to most darts yet not double feed.

I'm only hitting about 70 flat with the best of the darts I've been using. I have a full quad shot spring in it, in which it was hitting 75 flat with hotglue tipped streamlines and the normal breech.

It's a hard mod, and I don't see it as being worth anything at this point.
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<!--quoteo(post=206428:date=Jan 25 2009, 05:17 PM:name=Mukersman)--><div class='quotetop'>QUOTE(Mukersman @ Jan 25 2009, 05:17 PM) View Post</div><div class='quotemain'><!--quotec-->
Turd stefans. When I pulled these out of the pillow case i was just like, what... the... fuck...
Muker
<!--QuoteEnd--></div><!--QuoteEEnd-->

#27 Guitarzan

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Posted 30 January 2012 - 09:22 PM

Now the problems.

The stock spring that pushes the plunger tube and bolt assembly back to the end of the shell isn't quite strong enough to get the job done. Usually it returns just fine, but sometimes it isn't quick enough and the gears start pushing the plunger tube forward again before the plunger moves back far enough to engage the catch.

It's super dart picky. Some darts fly through the barrel, while others of the same foam type and weight get jammed half way through, so when the next dart is pushed into the barrel, it double fires, resulting in poor ranges. I think I'm going to switch it out for a 9/16's barrel with tightening rings, cause even though I use 17/32's and CPVC in all my springers, the stampede plunger tube is only the size of that of a nightfinder more or less, and also has a few inches extra dead space, it's just not powerful enough. Hopefully 9/16's with tightening rings will be enough to give a seal to most darts yet not double feed.

I'm only hitting about 70 flat with the best of the darts I've been using. I have a full quad shot spring in it, in which it was hitting 75 flat with hotglue tipped streamlines and the normal breech.

It's a hard mod, and I don't see it as being worth anything at this point.

Thanks for posting your results with this mod. I've never actually owned a stampede, so I don't really know what the internals look like. But I'm wondering if you could just strengthen the return spring and solve the double firing problem? Did you use the same voltage that SG did? And how powerful is a quadshot spring next to the 9Kg spring SG used? I only ask because I'm very hopeful that this mod will work out for me when I try it. I follow your youtube channel and trust your opinion though

Edited by Guitarzan, 30 January 2012 - 09:38 PM.

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#28 andtheherois

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Posted 30 January 2012 - 09:30 PM

So I took on this project for myself last weekend, here are the results;


I tried something similar a long time ago when i first saw the posts by Oxy on OZnerf. Using SGNerf's spring kit, I was able to hit 100 on some darts, and jams on others. I did it more or less the same way you did, only with opaque PVC. The problem is that our 1/2 PVC is too big, so you have to make sure the barrel is centered just right with the breech or else it'll spaz out, since it flexes a bit inside. If you try this again, I would suggest using the part that i posted and see how that works.
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#29 ice

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Posted 30 January 2012 - 10:40 PM

I tried something similar a long time ago when i first saw the posts by Oxy on OZnerf. Using SGNerf's spring kit, I was able to hit 100 on some darts, and jams on others. I did it more or less the same way you did, only with opaque PVC. The problem is that our 1/2 PVC is too big, so you have to make sure the barrel is centered just right with the breech or else it'll spaz out, since it flexes a bit inside. If you try this again, I would suggest using the part that i posted and see how that works.

My barrel is centered just right. The bolt connects with the barrel 100% of the time, thats not the problem. I need a better dart fit and a stronger return spring, those are my issues.
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<!--quoteo(post=206428:date=Jan 25 2009, 05:17 PM:name=Mukersman)--><div class='quotetop'>QUOTE(Mukersman @ Jan 25 2009, 05:17 PM) View Post</div><div class='quotemain'><!--quotec-->
Turd stefans. When I pulled these out of the pillow case i was just like, what... the... fuck...
Muker
<!--QuoteEnd--></div><!--QuoteEEnd-->

#30 SgNerf

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Posted 31 January 2012 - 01:45 AM

Great job ice! :)

That's a nice adaptation of the breech design using 1/2" SCH40 PVC, i see that you use 19/32" brass as spacers which ensures that the brass parts are aligned properly within that pipe dimensions.

Due to its automated firing system, the Stampede is definitely alot less forgiving in terms of chambering errors (compared to manually primed blasters like brass breeched Longshots).

The dart fit must be perfect (not too tight or too loose), so that each stefan gets fired out immediately before the bolt retracts, or else they'll end up getting stuck inside the barrel.

As for the return spring issue, before you install a stronger return spring (as that would put abit of extra load on the motor), try tweaking the existing bolt movement smoother and reduce the overall resistance by sanding the parts abit more or applying grease on the parts that slide against each other. Sometimes the combined friction between various parts could cause the return stroke to slow down enough to cause the bolt cycling issues.
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#31 SgNerf

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Posted 28 June 2012 - 03:18 AM

Update!

For modders who have been sending me requests to showcase the Brass Breech Stampede in action, here is a video of it being used at a recent local scenario Nerf game event in SG:



:)

Edited by SgNerf, 28 June 2012 - 03:23 AM.

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