February 17, 2018, 03:40:01 pm

Author Topic: CUstom gun start-to-finish thread: SMG15 (MP5SD6 base)  (Read 737 times)

Offline Redtail

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CUstom gun start-to-finish thread: SMG15 (MP5SD6 base)
« on: January 21, 2015, 11:12:08 pm »
I know there was a little bit of interest in this, so here goes.

A little while back, Method told me that he had a junker MP5SD6 that he'd managed to salvage after a theft. Given that many of the original parts were missing, this evolved into a Pimp My Ride style customization. I intend to document the entire build over the next couple of weeks, HOPEFULLY ending before March 15th. This is an extremely fast project and I honestly don't know if I'll be able to pull it off. I think I can though.

First part of the process is conceptualization. For this step I browse for photos of the gun in real life and the airsoft version. If I have the gun in hand, I can do more technical stuff because at that moment I can take it apart, draw something out and get an idea of how I want things to work.

The first step then was design and conceptualization. I didn't really know for sure what all would be missing off of the gun I was getting to work with, so I assumed everything would be there and figured I'd work around everything else.

The assumption of the full gun's look.

The first concept drawing.
I drew one with a silencer too, but nobody liked it, myself included, so I have misplaced it on the internet somewhere. It might be on the Violence Industries main group.

THen the gun arrived a few weeks later. There's always a moment of shock and panic, deer-in-the-headlights moment where you've got a whole project in front of you and you have no idea where to start. I am all too familiar with this feeling, and have found my favorite and probably the most effective way to go about this is to just pick a random-ass spot to start, convince myself that I was asked to start there if possible, then plan the rest of the build around that. Try to figure out if there are any problems with starting there, and then if I can't come up with anything, assume that I can work around any problems that come up as a result. Plastic isn't all that expensive, after all, and I have about 2 1/2 sheets left, so the only thing I really risk wasting is time.

I decided to start... Here.

Started hacking away the guts of the rear iron sight because at the time my idea was to use the rear sight to mount the new top rail assembly.
When I started taking the front end of the gun apart, I discovered this wasn't happening, changed the plan a little bit, and repurposed this newly reinforced area as a bolt-through point to secure the rail after it's slid on with the gas tube assembly.

With somewhere to test-fit said rail, it was time at that point to start making the rail.

Made two of these, glued them together, then squared off all edges with a coping saw and a rasp.

Not all that pretty, but relatively square and solid enough that I should be able to glue to it at a good 90-degree interface. These two were very flat and had a lot of surface area, so I welded them chemically using solvent only. THis tends to lead to a very nice, strong bond, but requires lots of surface area to work. It's best for joining plates flat to flat for making a large block, as well as lap joints between plates. THe technique involves test-fitting, smoothing out (some surface texture is fine, but you don't want jagged edges or warping) brushing some ABS/PVC/CPVC cleaner fluid on both surfaces to be joined, letting it soak in a bit to dissolve the outer layer of the plastic in question, waiting for it to dry up a little bit, brushinmg some more solution onto both plates, positioning them perfectly in place, holding them until the solvent begins to evaporate out, squishing some of the fluid out if possible (a vise works nicely for this, but only if it has very precise and very smooth jaws), and then once everything's dry, neatening up the squeezed-out blobs of chemically melted plastic with a file, a craft knife, or a milling bit on a rotary tool if you've got a lot of this chem-kerf.

THis part was the result of all of this.

This is its first finished test-fit on the gun. Since I'm a lazy duplicator and I can't find my aluminum meterstick, I've been using less than perfect tools to draw my lines. The reason you don't want to do this, is because you get sloppy results.

You can't see here, but the right-hand side of this block flared out at the bottom because my top rail wasn't perfectly square and I was a tad overzealous with my use of the vise to square everything up, which only works if everything is square to begin with.

But, not to worry. this is a long, flat corner joint and the heat gun solves problems like this very effectively. Warmed up the plastic with the heat gun for a few minutes, and when it began to get pliable, I placed the thing back in the vise with the other side which was significantly closer to being 90 degrees, and gently cranked it down until the affected side had been stretched back to the desired angle.

That's as far as I got tonight.

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