115 replies to this topic

[CaptainSlug]

So, barring a magical reappearance of the abp5k prototype, I have only passing motivation to make a duplicate of that design right now. While in This weekend I started mulling over how to use what I learned making abp5k to improve an alternative concept I had never fully developed.

This one is nowhere near as pretty, but I think it will be much more war capable.

Feature List
- 11" Aluminum barrel
- Gravity clip (6 round capacity default, expandable to 12 rounds with optional attachment)
- Actuated ram loads dart into rear of barrel when tank is pressurized.
- 6.5 cubic inches of volume in an inline aluminum tank
- Operable from a tank or a pump (minimum firing pressure is 30psi)
- Low restriction directional control valve
- Ready access to fittings and tubing without disassembly
- Can be completely dissected with only a philips head screwdriver and a monkey wrench
- Easier to machine (aside from valve parts there are only 16 parts to make, the rest is off-the-shelf hardware)
- Should be friggin indestructible
- Will fire darts of varying lengths (2 inch maximum, 1 inch minimum)

More design details to follow.

Edited by CaptainSlug, 22 October 2007 - 02:09 PM.

[Prometheus]

Will there be a follower to help the darts enter the breech? I would assume their own mass would be insufficient.

Why does everyone swear by Phillips screws? Robinson are easily a better design, or even Torx for that matter.

[Cmdrmack]

Phillips head screwdrivers are more widely available. So if it breaks at a war, you're more likely to find someone with a phillips head screwdriver than another kind of driver.

[jwasko]

Personally, I just don't trust gravity clips. If you want to do away with the LS-style box magazine, however, perhaps you could try an internal box magazine (see: M1903 Springfield, Mosin-Nagant). Similar, but slightly different, would be Boltsniper's NTS (aka the BS-9).

And, of course, there's no reason you couldn't make those feed from the top...but then, how would you aim?

Of course, it's up to you. In any case, hope this one doesn't take as long as the last!

Edited by jwasko, 22 October 2007 - 09:50 AM.

[Rover]

Honestly, I kind of like the way it looks. As for battle practicality, having a fixed gravity feed magazine might be a good thing. Hope this works out for you!

[CaptainSlug]

I don't particularly understand this distrust of gravity clips. Magazines and springs are only a recent development and everything prior to those involved gravity feed from a deodorant clip, cassette tape clip, or hopper.
I want to be able to reload with just my left hand, something not easy to do if you have to hold a follower down while loading darts.

Keep in mind that this gun does not have a breech made from brass or plastic tube. The darts are simply ram-loaded into the back of the barrel, and the ram then seals the end of the barrel.

And, of course, there's no reason you couldn't make those feed from the top...but then, how would you aim?

It's not like the gravity clip is 12 inches tall. To fit 6 rounds it only has to be 3 inches tall. The sights will be on the sliding door on the top of the clip.

Edited by CaptainSlug, 22 October 2007 - 01:57 PM.

[Carbon]

I don't particularly understand this distrust of gravity clips. Magazines and springs are only a recent development and everything prior to those involved gravity feed from a deodorant clip, cassette tape clip, or hopper.

There’s a couple problems with them which makes them less them optimal.

Jostling: If the mag is less than full and you shake (i.e. run with) the gun, darts can turn sideways, screwing up the feed. A weighted follower can reduce this effect, but the follower can also turn, causing the same problem.

Loading: Unless you use some manner of follower, getting front-weighted darts to load without going point-down can be challenging.

Also related to loading, the gun needs to be pretty well level in order for a gravity mag to work well. In a semi-auto, I'd wonder about how well it would fire if it was tilted.

My deodorant clips used a weighted, guided follower and they still weren’t entirely reliable (whether that was because of the design of my breech or not is up to debate).

At any rate, I’m not going to be using them again…I’ve been liking in-line mags or turret methods as of late. Just my two cents.

EDIT: Just saw your edit. Your design may mitigate the problems, but I think jostling and tilt will still be problems. Only one way to find out!

Edited by Carbon, 22 October 2007 - 02:09 PM.

[CaptainSlug]

Loading: Unless you use some manner of follower, getting front-weighted darts to load without going point-down can be challenging.

I was thinking I'd just tip the gun sideways and put three in at a time.
As for jostling, I'm not sure how much of a problem that would be if the darts fit the clip perfectly. Should it turn out that I need a follower it would only be a matter of replacing two frame pieces with an alternate design. But I would prefer to do without a follower if I can.

Edited by CaptainSlug, 22 October 2007 - 02:26 PM.

[Lynx]

Well, I bet that you could pull off a back weighted follower to top the front weight.

If you don't want the follower to fall out of the mag, I recommend putting fishing line through (answer if I used the right word or spelling) the follower and putting the line through the top of the magazine.

[murakumo32]

What are you using as the ram and how will it be actuated?

The shape kind of looks funny, but it's what is inside that counts right?

[Carbon]

As for jostling, I'm not sure how much of a problem that would be if the darts fit the clip perfectly. Should it turn out that I need a follower it would only be a matter of replacing two frame pieces with an alternate design. But I would prefer to do without a follower if I can.

Very true. With your machining capabilities, you could make a mag with much closer tolerances than the usual off-the-shelf parts. Then it'd just depend on reasonably uniform stefans, and figuring how short of a dart could be used before it would rotate.

[CaptainSlug]

What are you using as the ram and how will it be actuated?

The ram is a 1/2" OD plastic rod with an o-ring groove to seal it to the inside of the barrel.
It will be actuated by a single acting spring return air cylinder.

Edited by CaptainSlug, 22 October 2007 - 03:02 PM.

[jwasko]

I don't particularly understand this distrust of gravity clips. Magazines and springs are only a recent development and everything prior to those involved gravity feed from a deodorant clip, cassette tape clip, or hopper.
I want to be able to reload with just my left hand, something not easy to do if you have to hold a follower down while loading darts.

Keep in mind that this gun does not have a breech made from brass or plastic tube. The darts are simply ram-loaded into the back of the barrel, and the ram then seals the end of the barrel.

It's not like the gravity clip is 12 inches tall. To fit 6 rounds it only has to be 3 inches tall. The sights will be on the sliding door on the top of the clip.

Well, I wasn't really around in those classical days of pure gravity feeding. I guess these modern times have made me greedy.

If I remember correctly, there are (real) bolt-action rifles whose fixed, internal box magazines can be loaded by (basically) just pushing the cartridges in – once the bolt is open, of course. It seems to me that , if you are able to build a system similar to such bolt-action rifles, you should be able to pretty much just push darts straight down into the internal box magazine any time the breech is open. And I don't think that it would be too difficult to reproduce, really, considering the style of your breech. If you need, I might be able to get some pictures...when I visit home in 2 weeks. I hate being living at college: I can’t get anything Nerf-related done here except think.

Of course, the ability to create something like the above system is dependent upon whether or not your bolt stays open (or, can be kept open) for a significant length of time. Does it? If not, then I think the above is pretty much impossible.

If you want to stick with the gravity clip but require a follower, you could simply have the follower lock in the “loading position.” The process would be something like:

1. Push follower up and then slightly forward (to lock at top)
2. Load darts through use of a side port.
3. Pull follower back slightly to allow it to drop onto the darts.

As far as aiming, I had originally not noticed how tall this thing is (when compared to the level of the barrel) even without a magazine/clip on top. In my mind, I was picturing an MP5 with several inches of magazine sticking up off the top. My mistake.

By the way, that breech is amazingly simple yet brilliantly unique. It was a big "duh" moment for me. I mean, seriously: It's really just a typical (real) bolt action...only it's moved forward and back by air pressure. Is this how the ABP5k's breech worked, too? I'm afraid I never fully understood its inner workings...

[CaptainSlug]

I'm thinking I might put this design aside, or alter it so that that internal magazine feeds in a more traditional manner with a spring. I'm working on a completely different configuration at the moment.

If I remember correctly, there are (real) bolt-action rifles whose fixed, internal box magazines can be loaded by (basically) just pushing the cartridges in – once the bolt is open, of course.

Yes, I own a bolt action rifle with an internal magazine. An identical configuration is not possible because in order for the bolt to be out of the way for reloading the inline tank in the gun would have to be depressurized so that the air cylinder would retract the ram. This would be possible with a pump, but not with a tank. The darts would have to be loaded from a side trap door, a hole, or something else.

Wen the gun is hooke up to a tank the bolt only stays in the retracted position for a second or two (as long as you're holding down the trigger).

By the way, that breech is amazingly simple yet brilliantly unique. It was a big "duh" moment for me. I mean, seriously: It's really just a typical (real) bolt action...only it's moved forward and back by air pressure. Is this how the ABP5k's breech worked, too? I'm afraid I never fully understood its inner workings...

Yes. This design actuates the ram. The abp5k actuated the barrel instead.

Edited by CaptainSlug, 22 October 2007 - 05:03 PM.

[Prometheus]

Sounds kinda like that blow-forward breech, good luck building it. Also, gravity feed clips are a real pain in the ass, the darts will flip if there is no follower (that is unless you are standing still of course) and loading them isn't so easy either.

Sluggy's stefans have a slightly different weight distribution, and knowing him, they are all the same length, allowing for a very close tolerance grav feed.

[CaptainSlug]

If I were to go with a tube magazine and a carrier the gun would end up looking like this. The downside to this design is that the darts will have to be a uniform length in order to be fed through the mechanism properly.

The air cylinder in this design actuates both the ram, and a dart carrier that moves dart ejected from the tube magazine to the barrel.
To load the magazine you lift up a spring-loaded door and insert darts. To load more easily there's a handle on the magazine follower than you can hold down.

Sounds kinda like that blow-forward breech, good luck building it.

It's not a blow-forward system because the exhaust is not what's actuating the breech. The tank pressure prior to firing is actuating the breech.
There is no wasted potential energy using this method.
Considering I have already made and successfully tested something similar, I now have a clear concept of what works and what doesn't.

Edited by CaptainSlug, 22 October 2007 - 07:57 PM.

[Prometheus]

Way fucking cooler looking. I'm intrigued as to the workings of the carrier. Anyway you could make a door you press down, instead of lifting it? Lifting seems to necessitate the use of a second hand. Also, you most likely would have a larger capacity with the tube mag than with the grav feed.

[Z-man12]

Anyway you could make a door you press down, instead of lifting it? Lifting seems to necessitate the use of a second hand. Also, you most likely would have a larger capacity with the tube mag than with the grav feed.

It would also be possible to make a door that slid down that served the same pourpose....



I was wondering if some one could explane how the tub magazine works. Is it the same thing as what Frost used in his guns?

[SHADOW HUNTER ALPHA]

No. It's more like my shotgun's feed system. Darts are stacked end-to-end in a horizontal tube above or below the barrel. A carrier will load them into the breech one by one as they are needed (one dart per firing). The magazine does not constitute part of the actual barrel like the In-line clip does.

[Prometheus]

Anyway you could make a door you press down, instead of lifting it? Lifting seems to necessitate the use of a second hand. Also, you most likely would have a larger capacity with the tube mag than with the grav feed.

It would also be possible to make a door that slid down that served the same pourpose....



I was wondering if some one could explane how the tub magazine works. Is it the same thing as what Frost used in his guns?

I was thinking more Halo shotgun loading door kinda idea.

[CaptainSlug]

A hinged door will actually work better. The sliding door would have caused some issues with the carrier actuation.



Edit: Updated

Edited by CaptainSlug, 22 October 2007 - 11:20 PM.

[Prometheus]

Fucking ingenious. Is that Ronster's carrier idea, but modified?

Edit:
What stops the stefans from falling on top of the ram, and potentially flipping front down when it retracts?

Edited by Prometheus, 22 October 2007 - 10:55 PM.

[jwasko]

Before everyone starts asking stupid questions about tube magazines and/or "shotgun"-type actions, I suggest taking a look through this thread here.

Yeah...I think my brain can't comprehend CAD (or whatever those images are).

Good luck with that action and magazine, CS.

Remember: timing is key! Also, (although you may have addressed this already) you have to keep the darts from coming out until you want them to come out; it's not like you're just stripping them off of a box magazine.

EDIT: I believe Prometheus said the same thing as I did in my last sentence.
EDIT 2: Maybe he didn't...I need sleep.

Edited by jwasko, 22 October 2007 - 11:00 PM.

[CaptainSlug]

1. Is that Ronster's carrier idea, but modified?
2. What stops the stefans from falling on top of the ram, and potentially flipping front down when it retracts?

1. I haven't look at that thread in forever. There are only so many ways to design a carrier.
2. The stefan might fall down towards the ram a bit, but there's not enough room for it to get askew or anything. There had to be a little room so that the door could hinge down enough to access the magazine even when a dart is inbetween the ram and the bottom of the carrier.

After a dart has been fired the ram retracts, then the "waiting" dart is pushed down by the carrier to be inline with the barrel.
When the trigger is released the ram moves forward 2 inches and has pushed the dart most of the way into the barrel. The last 1 inch of stroke pushes the carrier up, and the next "wating" dart pops out of the magazine.

Edited by CaptainSlug, 22 October 2007 - 11:20 PM.