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Reverse Plunger Dead Space Killing Method


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#1 nihil413

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Posted 14 February 2010 - 04:31 PM

Here's a pretty quick, easy and effective way to kill deadspace in a stock barreled reverse plunger systems:

Items needed:
- Reverse Plunger System
- Foam Backer Rod (FBR) (Either thicker 1/2 inch or 3/4 inch cheap Home Depot/ Lowes foam)
- Longer 1/4 inch drill bit
- Drinking Straw
- Scissors

Find some FBR that fits tightly into the back end of the Reverse Plunger/ Barrel Piece (for lack of a better term I'll just refer to it as the reverse plunger in this writeup)

Measure the length of deadspace in the back or the reverse plunger/ barrel piece. (Longstrike, if I remember correctly was @ 4-3/4 inches)
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Cut the FBR and Straw to the Length of the deadspace
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Take a 1/4 inch drill bit and drill through the center of the FBR ( I would recommend holding the bit and hand drilling it through as opposed to using a power drill... it's safer and straighter... )
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Once you have the FBR Drilled through twist the straw through the hole in the FBR (I would recommend sticking the 1/4 drill bit inside the straw so you don't collapse the straw and you may want to plumbers goop the outside of the straw to help it's air seal)
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Once that is done twist the FBR into the back of the reverse plunger and it's done.
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I did this with my Longstrike and got an immediate recognizable difference in velocity and impact with the wall as the dart rebounded much further than before the FBR was added even though I started by power drilling so the hole wasn't perfectly straight. I also left about a milimeter of FBR sticking out of the back to act as padding on the plunger head.

Edited by nihil413, 17 February 2010 - 12:17 AM.

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#2 death by cheez

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Posted 14 February 2010 - 04:35 PM

Hmm... I think this is actually pretty cool, you straw modded a LK. Creati--well, maybe not creative, as it's been done before to other blasters, but clever nonetheless. Two thing I can think of for improving this are a larger-only slightly- bit of foam to further improve the seal, and put a bit more foam out of the back, because 1 millimeter of foam won't do much to cushion it.

Edited by death by cheez, 14 February 2010 - 04:35 PM.

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#3 Roschili

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Posted 14 February 2010 - 04:38 PM

That looks really good, I am going to try this on my Recon. Could you post a picture from the other side of the plunger so I can see how far in the foam goes, or could you tell me about how long you think the foam should be for a recon. Thanks!
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#4 nihil413

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Posted 14 February 2010 - 04:55 PM

Hmm... I think this is actually pretty cool, you straw modded a LK. Creati--well, maybe not creative, as it's been done before to other blasters, but clever nonetheless. Two thing I can think of for improving this are a larger-only slightly- bit of foam to further improve the seal, and put a bit more foam out of the back, because 1 millimeter of foam won't do much to cushion it.

I'm aware the straw mod has been done, but I personally, have only seen write ups using expanding foam which I find to be a pain to work with and more of a pain to remove if need be. So I thought this write up may be useful to someone out there, who, like me, does not like permanent. As far as the foam I'm using... it's a 1/2 inch foam that can actually fit snugly in 1/2 inch PVC and barely fits in PETG and was incredibly difficult to twist into the back of the reverse plunger so it's pretty well sealed. Also I have the Plunger Head padded already so this is just a little extra padding.

That looks really good, I am going to try this on my Recon. Could you post a picture from the other side of the plunger so I can see how far in the foam goes, or could you tell me about how long you think the foam should be for a recon. Thanks!

To get measurements simply stick the straw or some other item into the back of the reverse plunger until it hits where the original air restrictor is, mark that and measure it.
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#5 TantumBull

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Posted 14 February 2010 - 05:21 PM

Straw modding doesn't help guns with recon internals. Flow > deadspace in these.
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#6 nihil413

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Posted 14 February 2010 - 05:39 PM

Straw modding doesn't help guns with recon internals. Flow > deadspace in these.


That was an argument I've heard before and why I wanted to do something that could be reverted back to stock if I failed when testing it... but from test firing it, it's added noticeably to the speed of my darts and the rebound they are getting once they hit. So, unless for some reason my Longstrike is the exception to the rule, this may actually work.

And for those that will ask, I haven't range tested it outside, it's winter in Ohio and I don't feel like going outside.
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#7 lakewoodz

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Posted 14 February 2010 - 07:15 PM

nice, I'm getting a longstrike soon so, i was wondering what size fbr you used? 1/2 inch?
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#8 nihil413

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Posted 14 February 2010 - 07:54 PM

nice, I'm getting a longstrike soon so, i was wondering what size fbr you used? 1/2 inch?

You will need to find a FBR that fits as tightly as you can twist into the reverse plunger.

Items needed:
- Reverse Plunger System
- Foam Backer Rod (FBR) (Either thicker 1/2 inch or 3/4 inch cheap Home Depot/ Lowes foam)

As far as the foam I'm using... it's a 1/2 inch foam that can actually fit snugly in 1/2 inch PVC and barely fits in PETG and was incredibly difficult to twist into the back of the reverse plunger


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#9 LotusNerf

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Posted 14 February 2010 - 08:19 PM

Straw modding doesn't help guns with recon internals. Flow > deadspace in these.


That was an argument I've heard before and why I wanted to do something that could be reverted back to stock if I failed when testing it... but from test firing it, it's added noticeably to the speed of my darts and the rebound they are getting once they hit. So, unless for some reason my Longstrike is the exception to the rule, this may actually work.


This is my take on why this improves ranges, so correct me if I'm wrong.

By making the area air travels through thinner, the air has less space with the pressure, making the pressure higher inside the straw, comparing to without the straw. That's because a given amount of air in a larger area will have lower pressure than a given amount of air in a smaller area. And I guess the higher the pressure, the faster it will want to move to low pressure, making the dart travel at a higher velocity.

-Lotus
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#10 ilzot

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Posted 14 February 2010 - 09:38 PM

See, I never agreed with the whole "smaller air hole = no range change."

This'll only make sense if you've AR modded a Recon or Raider.

If you've seen the AR, like any other, you know that if you hit it dead center with a screwdriver or drill bit only the peg will come out and leave the AR ring in.

I did that on my Recon and it got great ranges.

When I went to mod my friend's Recon, I hammered out the whole damn AR, peg ring and all.

So in simpler terms, my Recon had a probably 1/4 inch air hole and his had a 1/2 - 3/4 inch air hole.

His went 9 feet, mine went 47.

It might've been dumb luck but imagine a NF without its AR directing air flow.

It would be just an air cannon that would suck.


So all in all, I see plenty of merit in this idea.

Nice job, I like its potential and removability.
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QUOTE(Vinnie D. @ Feb 1 2010, 05:28 AM) View Post

... to be able to get a better burst or sustained fire, rather than blowing the whole load at once.


#11 TantumBull

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Posted 14 February 2010 - 09:47 PM

When you modded it, did you test fire in between every single mod? If you did, than that would explain it, although I don't know anyone who mods this way.

ilzot: There's likely other variables involved that you missed. A better flow with a not mentionable change in deadspace will not lower your range by 30+ feet.

Edited by TantumBull, 14 February 2010 - 09:48 PM.

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#12 ilzot

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Posted 14 February 2010 - 09:55 PM

I mean the only variables in it would be the O-ring, as everything else was controlled.

I plugged the retarded hole on both, no powerstock or PT etape and wire wrapping or spring stretching or the like.

Both just had an AR removal.
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QUOTE(Vinnie D. @ Feb 1 2010, 05:28 AM) View Post

... to be able to get a better burst or sustained fire, rather than blowing the whole load at once.


#13 death by cheez

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Posted 14 February 2010 - 09:59 PM

Hairline crack in the plunger tube maybe? It happened to my nite finder, which is why it suddenly went from mid 60's to around 10 feet.
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#14 bourbon

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Posted 15 February 2010 - 01:11 AM

If you've seen the AR, like any other, you know that if you hit it dead center with a screwdriver or drill bit only the peg will come out and leave the AR ring in. I did that on my Recon and it got great ranges.

When I went to mod my friend's Recon, I hammered out the whole damn AR, peg ring and all. His went 9 feet, mine went 47.

>>>It might've been dumb luck<<<


Gee, you think?


When I modded my Recon I drilled out the whole AR. You probably broke his bolt somehow by taking a hammer to it. Implying removing a small ring of plastic caused a range reduction of 500% ... wow.

I did the "dead space reduction" mod to my Recon as well, but I used stock Nerf foam. Just cut up three or four stock darts, and jam them in there. Stick a straw through the whole thing, carefully goop both ends. No attempting to drill through foam backing rod required.

My Recon broke because I did this before I thought to pad the back of the plunger tube, but I was getting 60' easy with a industrial NF spring in the power stock. I forget the name of the spring K-26 is +bow, what was NF again? Whatever, doesn't matter. Point is, it works just as well with stock dart foam for half the effort.

Edited by bourbon, 15 February 2010 - 01:17 AM.

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#15 pjotrkuh

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Posted 15 February 2010 - 03:08 AM

When I modded my Recon I drilled out the whole AR. You probably broke his bolt somehow by taking a hammer to it. Implying removing a small ring of plastic caused a range reduction of 500% ... wow.


?? I didn't read the part in his post where the dart flew out the back of the plungertube and got a range of +100ft..................

Alright it if it really works I might take a go at this mod, probably will try this on my mav first though....
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#16 TantumBull

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Posted 15 February 2010 - 12:45 PM

This does wonders with the mav, definitely do it on that.
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#17 ilzot

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Posted 16 February 2010 - 08:47 PM

bourbon, this was my 6th Recon modded.

2 of my own, 1 of my friends, 1 of my other friends, and my little brother's.

I have the mod down pat. I did the AR mod on all of them, where only the peg and not the plastic ring was removed.

All reached typical modded Recon ranges (40-50').

Except my friends with the ring out completely.

Just to make you happy, last night I went and popped out the ring on my last Recon.

I did a nice official range test for you with my ringless Recon.

2 clips with 6 darts a piece.

11'
14'
12'
9'
10'
16'


17'
17'
16'
10'
17'
13'


Ok, slightly better than my friends. But I'm not happy with it.

Hopefully this is enough evidence of this.

I'm going to my basement to put the spring in my Longshot, that's how shitty it is.
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QUOTE(Vinnie D. @ Feb 1 2010, 05:28 AM) View Post

... to be able to get a better burst or sustained fire, rather than blowing the whole load at once.


#18 TantumBull

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Posted 16 February 2010 - 08:50 PM

Oh wow, are you drilling from the front?
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#19 death by cheez

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Posted 16 February 2010 - 08:51 PM

Drill from the back, not from the front.

Edited by death by cheez, 16 February 2010 - 09:28 PM.

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#20 Hubb

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Posted 17 February 2010 - 11:15 AM

Nice mod. But it seems like a pain to have to drill out foam. Couldn't you just use a stock dart since it already has a hole in it? This way, the hole for the straw would be in the direct center every time. If it needs to be thicker, then electrical tape could be wrapped around the dart before it's placed in.

As far as the performance increase, LotusNerf was on the right track.

Using the equations P1V1 = P2V2, it shows that the pressure will increase as the volume is decreased. Say the plunger, unmodded, will generate 10psi and the volume of it is 2in^3. By placing the straw in, let's say that the volume is cut in half, which would be 1in^3. Using the above formula, the new pressure generated would be double that of what originally was created. This means that the smaller the volume, the higher the pressure is going to be. Of course, there is a spot where this will do no good and actually hurt performance, but that's gonna be based on barrel friction, dart weight, surface area, etc.
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#21 minsc

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Posted 17 February 2010 - 04:42 PM

Nice mod. But it seems like a pain to have to drill out foam. Couldn't you just use a stock dart since it already has a hole in it? This way, the hole for the straw would be in the direct center every time. If it needs to be thicker, then electrical tape could be wrapped around the dart before it's placed in.

As far as the performance increase, LotusNerf was on the right track.

Using the equations P1V1 = P2V2, it shows that the pressure will increase as the volume is decreased. Say the plunger, unmodded, will generate 10psi and the volume of it is 2in^3. By placing the straw in, let's say that the volume is cut in half, which would be 1in^3. Using the above formula, the new pressure generated would be double that of what originally was created. This means that the smaller the volume, the higher the pressure is going to be. Of course, there is a spot where this will do no good and actually hurt performance, but that's gonna be based on barrel friction, dart weight, surface area, etc.


Your equations are correct. That is all though. The false assumption you are making is that the plunger will move at the same speed no matter what size the opening is, which is untrue because the spring force is unaffected by the opening. A smaller hole = less airflow/second = slower plunger movement. This pretty much cancels out any pressure gains you claim.
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QUOTE(Zorn's Lemma @ Jul 25 2010, 12:18 AM) View Post

You'll do a lot better if you spread the lips with the front. Trying to wriggle the back in there first seems a bit counterintuitive.

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#22 Hubb

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Posted 17 February 2010 - 05:08 PM

Well, it looked good on paper... :D

Seriously, though. The pressure and volume are only small aspects. Of course there are other things needed to make it actually work as a lot of other forces at work rather than just a moving plunger. Now, getting into that is a completely different subject and is probably one that will be rather lengthy and confusing.
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#23 VelveetaAvenger

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Posted 17 February 2010 - 05:38 PM

Straw modding doesn't help guns with recon internals. Flow > deadspace in these.



This does wonders with the mav, definitely do it on that.


Any particular reason why this works on Mavericks and not Recons, or are you just being sarcastic and I missed it? I don't own a Recon, but I don't see how the plunger itself is different then a Maverick.

I've also always wondered why people don't make custom plunger heads/rods that attach to the back of reverse plungers to turn them into normal plungers, has anybody tried it? I might give it a go on my Furyfire for my next project, now that this thread has rekindled my interest.

↓ Neato.

Edited by VelveetaAvenger, 17 February 2010 - 06:30 PM.

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#24 TantumBull

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Posted 17 February 2010 - 05:45 PM

No sarcasm. The mav is already limited to a certain amount of flow because of the turret holes. Whether or not it makes sense, it's true. I've done real tesing on a raider on this subject.
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#25 bourbon

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Posted 17 February 2010 - 08:01 PM

@ Ilzot

what are you using to drill out the ARs on your Recons? I used a 1/2" wood boring bit, like this one. Through the back of course.

Posted Image


I am completely perplexed by this tiny plastic ring having such a dramatic effect on performance. It just doesn't make sense that having the air forced through a 3/8" hole would be so much better than a 1/2" one. Maybe it has to do with the speed of the air release.

Edited by bourbon, 17 February 2010 - 08:01 PM.

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