Project: Old-Fashioned Tailoring Meets Modern 'Combat' Jacket

Years ago for paintball I bought a "Tru-Spec" jacket in a civilian variant of woodland MARPAT. Well, for some reason I bought it in a large size (42R-45R) even though I'm a medium (39R). Because of this I never used the jacket and threw it in the closet. 

Well, I'm getting into airsoft and decided to check out the jacket again. Yup, still too large; actually it looked like a balloon on me. So rather than put it away and never use it I decided to try a fun little sewing project. Check it out below.

Here's the jacket front just to give you an idea (pardon the pics, they don't show colors very accurately).

click images to enlarge

While I didn't get any "before" pics of the back, my jacket had just a plain back like any other shirt or jacket you might own. It looked like this:

Well, on each back seam I took in about 1 1/4", making the jacket fit me a lot better. I pinned and then sewed the pleats just under the armpit where I then opened it up, did some interesting pressing, pinning and sewing, and gave the jacket a bi-swing back with a gusset at each shoulder as well as open gussets on the jacket skirt. 

Here's the straight-on view of the back: 

What is a bi-swing back? Below is a WW2 service jacket with bi-swing gussets and belted back. These are old-fashioned features rarely seen on suits or coats today but were pretty commonplace back in the 1930s-1940s.

The bi-swing gussets were hidden 'boxes' of extra material and were there to allow the wearer to move further and more comfortably, especially considering the M39 service jacket shown was meant to be used in combat. 

I added these gussets to my jacket. Here is the left gusset during the pinning stage while at rest:

And here is the gusset in use and extended:

 I took some more inspiration from the WW2 service jacket I posted up above.

It has a piece of elastic connecting the two inner pieces of the shoulder gussets together, keeping them organized, flat, and pulled in while at rest: 

I added a piece of elastic between the two internal 'blades' of my jacket's gussets, producing the same result as the WW2 jacket.  Without elastic the fairly flimsy fabric of the MARPAT jacket renders the gussets pretty much useless: there isn't enough 'weight' in the fabric to push the gussets back in.  Hence the need for it in this garment.

Now, with just a plain seam below the shoulder gussets the bottom of the jacket back would have been a tad tighter than I like and I wanted better mobility so I opened it up from just below the shoulder gussets all the way to the bottom of the jacket skirt. What previously would have been just a seam is now pleated just like the shoulder gusset. At rest it just lays flat while in use it can expand, giving me extra mobility and room to move.

Here's an illustration of a similar gusset in use on the black overcoat: 

My jacket's right side gusset at rest: 

And expanded:

Here are a couple more shots of the finished product, well fitted yet with enough features to give me extra mobility.

There are a few minor things I'd do differently if I had another chance and a couple areas of pulling/wrinkling that could be fixed but I'm quite happy with how it turned out.  It will serve me well for the intended purpose and I look forward to using it in the future.  

It's always fun combining old and new techniques and technologies to produce something new and better.  That's true innovation.