32 replies to this topic

[hereticorp]

This is CaptainSlug's design, but a formal writeup was never posted, so I'm posting it.

All the design is his work, the pictures are mine. Credit goes to Slug.

Parts Needed:

1- 1 1/2" OD, 1/4" ID 1/16" Thick Rubber Washer
1 - 90126A509 - Zinc-Plated Steel SAE Flat Washer #6 Size, 5/32" Id, 3/8" Od, .036" Min Thickness = $0.97 per 100
2 - 91090A104 - Zinc-Plated Steel Large-Od Flat Washer 10 Screw Size, 7/32" Id, 1-1/4" Od, .042"-.052" Thk = $7.41 per 100

McMaster does NOT carry the correct rubber washer for this modification, but the steel washers they have are perfect. The rubber washers can be purchased from Lowes or Home Despot or any other hardware store that carries such things.

From Ace Hardware:

1 - Rubber Washer, 1 1/2" OD, 1/4" ID, 1/16" Thick [Ace #RM1214]=$.85 each.
2 - Flat Washer #6 Size, 5/32" ID, 3/8" OD [Ace #546563]=$.09 each.
2 - Flat Washer, 1/4" ID, 1-1/4" OD [Ace #546608]=$.29 each.

The last washer ID is 1/4" instead of 7/32", but it works fine.

To clarify, that goes Small Metal, Large Metal, Rubber, Large Metal, Small Metal. That provides some extra backstopping on the plunger for those of you too lazy to do the CPVC mod below.

Thanks Sputnik!

Begin with a longshot plunger tube.


Remove the two silver screws from the back


Pull the plunger head and rod out of the tube and take out the front silver screw


Detach and set aside the stock plunger head, keep the screw


These are the materials used, including the stock screw


Cut a 1/4" piece of 1/2" CPVC and place it on top of the stock plunger rod. It should be a perfect fit, OD to OD. Then fill in the gap between the stock attachment point and the CPVC with hot glue.


Overfill the top a little to provide some back-pressure on the plunger head.


Arrange the materials as pictured, metal, rubber, metal, metal


Center the rubber washer on the metal washers for an even seal


Attach the plunger head to the stock plunger rod using the stock screw


View from the side

Re-insert the plunger head into the tube, it will be difficult because the washer needs to bend to fit into the tube, it will fit though and will provide you with a perfect seal for your longshot.

You WILL need an additional spring, or a more powerful one. A cut down AR-15 or a BBB or a MaxShot spring are all valid options. I personally prefer a LS+AR-15 spring combo.

Edited by hereticorp, 25 February 2009 - 08:37 AM.

[hereticorp]

I would recommend a plastic bushing on the reduced-size portion of the rod, underneath the washers. Because of the higher forces involved, it might take only a little off-center friction to snap off the plunger rod right about where the tip of the screw is. If you're not doing anything with the original plunger head, you probably could just slice the back of it off. It already has a hole with the right cross-section.

Another thing I would investigate is the overall effect of just cutting off that portion, after drilling deeper for the screw. In the Disk Shot pistol, you can actually gain more plunger travel that way. In the LS, I think you would get a little more spring compression and a little more dead space, and also there's the possibility that it wouldn't be able to reach the catch any more - but it's worth looking into.

That's a good idea, and I think slicing off the back of the stock plunger head is definitely a good idea, I'll check out the feasibility compared to using epoxy putty or suchlike when I get back into the project.

Cutting off that portion would preclude the plunger traveling the full distance unless you shaved the larger portion of the back of the rod down some to allow a greater travel length. That would facilitate a longer distance but would probably interfere with the catch mechanism.

There's only about 1/8" of material available to shave off before you run into the angled section of the rear of the rod.

The hex rod is about 1/4" long and if you cut it off you'll lose that much travel distance unless you thicken the front part that moves the plunger head back. Which completely negates the purpose.

So without some major mods to the plunger rod (Replacing it with nylon rod or somesuch) you're not going to get that extra 1/4" of distance. I don't think you're going to get much benefit out of that for all that trouble.

I'm going to do some experimenting with epoxy putty and maybe some PVC. We'll see how it goes.

[Glint]

I can vouch for the actually working of this thing. Hereticorp sent me the idea when we were discussion an LS Mod over PM, and I tried it myself. Very good improvement. Kudos for the idea goes to CS, but hopefully you'll be able to improve on it.

Make sure you still lube the plunger head and tube though, for anyone who's going to do this.

Edited by Glint, 10 February 2009 - 04:10 PM.

[nerfer34]

Hmm..This is strange. I did this and I'm still for some reason getting worse ranges than before I did this. I'll eventually figure this out and update this post.

How much lube do you recomend for this?

[hereticorp]

Hmm..This is strange. I did this and I'm still for some reason getting worse ranges than before I did this. I'll eventually figure this out and update this post.

How much lube do you recomend for this?

Depends on how tight you are and what you're trying to stuff in there.

But really, just a 2-3 second spray of silicon lube should be perfect.

[autonerf]

I tried doing this before and my rubber washer dried out very quickly, slowing it down a ton. That also may have been because my spring combo was not powerful enough. Since the rubber washer bends in the plunger tube I could never get it to stay in the center of the steel washers. Captain Slug had a neoprene washer that was more thin and flexible, so I think that's why his worked well.

[hereticorp]

I tried doing this before and my rubber washer dried out very quickly, slowing it down a ton. That also may have been because my spring combo was not powerful enough. Since the rubber washer bends in the plunger tube I could never get it to stay in the center of the steel washers. Captain Slug had a neoprene washer that was more thin and flexible, so I think that's why his worked well.

I've had my plunger going for a long while now and it never dried out. Probably because I used silicon lube. It keeps things nice and slick.

CS also got his from McMaster before they stopped carrying non-reinforced rubber washers, the ones he used are no longer available from McMaster and I haven't gone searching for other sources because mine works fine.

[CaptainSlug]

CS also got his from McMaster

No, I bought it at the nearest Home Depot which never restocked with a similar washer. I couldn't find an alternate source after that.

[Draconis]

Both of the Home Depots in my area still carry a suitable washer. So do the ACE, and both Lowe's.

[hereticorp]

CS also got his from McMaster

No, I bought it at the nearest Home Depot which never restocked with a similar washer. I couldn't find an alternate source after that.

Whoops, I assumed from the McMaster Part for the Rubber Washer that's in the original thread about this mod that you got them from there.

[autonerf]

I must have the wrong kind of Silicone Lube then. I used Ace Pure Silicone Lubricant, but it must be more for metals and not plastics. I sprayed a good amount in the plunger tube and on the washer, but everything seemed to dry out after a few shots.



Are you using some kind of other lube or something?

[Draconis]

I can't tell from the can, but that is likely to be a dry lube, then. You want something that is a wet type. I'm using some awesome 3M brand stuff I bought at Carquest. Definitely worth the $8 for big can.

[venom213]

Thanks for the writeup. I was planning to do this, but I wasn't sure exactly how to. How long are the sections of AR-15 Springs that you use in your Longshots?

[hereticorp]

Thanks for the writeup. I was planning to do this, but I wasn't sure exactly how to. How long are the sections of AR-15 Springs that you use in your Longshots?

You should read my longshot writeup. It has the length of the AR-15 spring in it, and a lot of instructions.

However, for your lazyness and lack of searching, it's 4 3/4"

[sputnik]

Thought somebody could use this.

From Ace Hardware:


1 - Rubber Washer, 1 1/2" OD, 1/4" ID, 1/16" Thick [Ace #RM1214]=$.85 each.
1 - Flat Washer #6 Size, 5/32" ID, 3/8" OD [Ace #546563]=$.09 each.
2 - Flat Washer, 1/4" ID, 1-1/4" OD [Ace #546608]=$.29 each.



The last washer ID is 1/4" instead of 7/32", but it works fine.

[Daniel Beaver]

Would this be possible to do in any plunger gun? What sort of increments in OD do rubber washers come in?

[hereticorp]

Thought somebody could use this.
(INFO)

Added to the first post, thanks!

Would this be possible to do in any plunger gun? What sort of increments in OD do rubber washers come in?

Theoretically, but the plunger takes a LOT of force to move, the double springs of the LS/AR-15 do that job well, an NF would have more trouble.

I think they go in 1/16" increments but they probably go in 1/32" if you look around hard enough. Lowes does not sell a huge variety over here.

Edited by hereticorp, 11 February 2009 - 07:29 PM.

[sputnik]

Thought somebody could use this.
(INFO)

Added to the first post, thanks!

You are welcome my friend.

[venom213]

You should read my longshot writeup. It has the length of the AR-15 spring in it, and a lot of instructions.

However, for your lazyness and lack of searching, it's 4 3/4"

Sorry. I have looked over that write-up a few times, but because there is so much information being presented, I accidentally skipped over said information.

Sputnik: Thanks for the info. I had the parts needed for this written down the last time I went to the store. I didn't even bother looking for them because I had no idea how to make sense of the old part list (because it was intended to be used for ordering the parts from McMaster).

[sputnik]

Sputnik: Thanks for the info. I had the parts needed for this written down the last time I went to the store. I didn't even bother looking for them because I had no idea how to make sense of the old part list (because it was intended to be used for ordering the parts from McMaster).

No problem.
It took like 45 minutes to find all the right parts.
Several drawers were mislabeled.

---------------------------------------------------------------------------
With the Ace washers, I recommend using one #6 washer flush with the screw, and one against the plunger rod.

Edited by sputnik, 11 February 2009 - 11:13 PM.

[hereticorp]

Writeup has been updated with new instructions, based on suggestions from posters.

[hereticorp]

Nice bushing fabrication - cheap, readily available, and no sacrifice of other parts.

The pre-load seems like a good idea, too - as long as nobody goes overboard with it. Of course if they do and strip their screw-hole out, they could drill deeper and use a longer screw.

I thought about trying to find a nylon spacer the right size and then I realized that CPVC is the perfect size.

Pre-load?

The screw is pretty long as it is, you'd have to get quite a long tap to get threads any deeper than they are, and it's a pretty heavy thread so I doubt anyone's gonna have an issue with thread stripping.

Edited by hereticorp, 13 February 2009 - 07:15 AM.

[Draconis]

I agree, that's a perfect addition to the stability of the head. Gotta go take my LS apart... Be back later... Actually, the only thing I've been thinking of changing on this design is switching out the front steel washer with one made of nylon or polycarbonate. Just save a little mass and increase the acceleration of the plunger.

[wingd man]

Do you still need to lubricate the plunger head? I wouldn't think so. Also, would you recommend a recon spring in addition to an AR-15, MS, BBB, etc.?

[Draconis]

Do you still need to lubricate the plunger head? I wouldn't think so. Also, would you recommend a recon spring in addition to an AR-15, MS, BBB, etc.?

Why wouldn't you need any lubricant? Of course you need to lube the plunger! Just the LS and AR-15 or LS and BBB springs. Don't do any more than that without reinforcing stuff.

Edited by Draconis, 22 February 2009 - 06:51 PM.