Funny how life works. Here's some background on the design process for this iteration of the SNAP...
After I finished up the SNAP-4, I went to work on the SNAP-5. I had initially decided to scrap pretty much everything and start with a totally new concept. But as I worked, I noticed things getting more and more complex...which goes against pretty much everything that I want the SNAP series to be. So, I lost interest in building...and then a whole lot of life happened.
SPANO this last summer was educational in a lot of ways. Being my first war, I was able to see what really worked. And the basic SNAP performed well all day. Simple is better.
Getting back into building, I decided that the only way I would approach a new SNAP would be to address issues with the design of the SNAP-1. Why mess with what already works?
One of the things that bugs me about the basic SNAP is the stick that comes out of the back when it's ready to fire. However, the SNAP uses a narrow spring and wide tubing. Even if I were to use a wider spring, that would present a problem with the spring bending slightly and snagging on the catchpin. And, no stick coming out of the back also creates the problem of how to cock the system. Approaching all of these issues led to the SNAP-5. (As per usual, I'm posting it when it still has issues to work, but the entire concept is sound.)
As per usual, this gun wouldn't have been possible without all the fantastic work that comes out of the Haven, with a particular debt to Boltsniper, Ompa and Carrtoon.
Looks a lot like the other ones, right? The differences are mainly under the hood.
This design addresses the problem of the chargerod sticking out the back, and how to charge the gun if that isn't used. The spring uses a collapsing guiderod, as well as a chargerod which can float on the plunger. The barrel slides back into the gun to press the plunger back, and then slides forward to firing position.
So, let's break it down, shall we?
The charging system:
It's my usual reducing bushing combo, but the 1/2" part has been bored out slightly to allow the 1/2" PVC to slide snugly. I was initially concerned about this area being a major air loss, but that doesn't seem to be the case. Even so, I have an O-ring installed to minimize any potential leaks. The pushing end of the barrel uses a 3/4" -> 1/2" reducing bushing, rather than just a portion of 3/4" coupler; if it didn't, the rubber washer would bind against the end of the rod.
The bushing is needed to make sure that the barrel doesn't wobble.
The rear is 17/32" brass, and the front guiderod is 1/2" aluminum (parts I had around that nested well). The aluminum is held loosely in the plunger head with a cotter pin, so the guiderod can slide into the plunger when it's pulled back. (This is the same concept that I used in the SNAP-3. It's actually the same plunger, just a little shorter. Modular parts are great, it saves me a lot of building time.)
The rear of the gun is also a reducing bushing:
The brass was another part I already had on hand: a 17/32" brass barrel mounted in a stub of 1/2" PVC... Recycling! I just cut the PVC and brass a little shorter, and capped it off with a 1/2" endcap.
The other issue was how to load the gun, since the barrel would be moving back and forth. For the time being, I think my turret fits the concept well. With one hand, you can charge the gun with a pump action, and rotate a new barrel into place, four total shots.
Everything else is stock standard (clothespin trigger, plunger chamber style). I'm working on a new trigger cocepet, but that's coming later.
Things to address:
1. I still need to properly finalize my turret, and put long enough barrels on it. Also, I'm rather amazed that the PVC stub on the turret hasn't broken off yet. I need to epoxy that joint, as it's a major weak point.
2. The barrel isn't indexed at all so it rotates freely. It needs some kind of cowling over the entire thing so the rotating turret doesn't cause problems with a rotating barrel.
3. It doesn't give any indication on whether it's cocked or not. One good purpose for the chargerod!
3. Dead space. Just by nature of how it cocks, it has a lot of it. And of course, as I sit here typing and looking at the thing, I'm realizing that it's another good candidate for the in-line clip...definitely less bulky and complicated. I'll be testing it with that concept in place, and report on how it works.
It has the same general engine as all the SNAPs, so I i'm expecting similar ranges (no, I haven't tested it yet). Performance is patchy right now, partially because of the inconsistent barrels on the turrest. But the overall concept is sound.
More reports as they happen.
Edited by Carbon, 17 May 2016 - 10:56 PM.