Re: Down parkas?
Hi. I'm new to this forum, so please excuse me for starting off on a jacket related thread, rather than a topid that is more directly related to guns/shooting (I'll admit, it does seem sacrilegious to do things this way).
Anyway, I have had the MH Sub Zero SL Jacket for about 10 years, and I've been fairly happy with it. The jacket has a lot of loft, and is quite warm (not so much as their "Absolute Zero" line, but I don't assume you are planning to use this jacket at the North Pole, or on an ascent of an 8,000 meter peak). Nevertheless, I've used my coat on many winter backpacking trips, including high climbs in the Presidential Range in winter (Mt. Washington, etc), and many winter ascents of Colorado peaks (including some of our 14'ers).
My favorite part about the Sub Zero Jacket is its wonderful hood. The hood is very lofty, warm, and adjustable, and the jacket simply wouldn't be in the same league without it. I'm also happy with the wind/water resistance that is provided by the shell material on this garment. It isn't a rain coat to be sure, but it has protected me against plenty of slushy/wet snow squalls over the years.
My biggest gripe with the jacket is that the down has migrated a bit in the elbows, leaving a somewhat uninsulated layer near the fold of the elbow (of course, now the back of the elbow is even more insulated). Natuarally, with the down movement away from the inside of the elbow, arm movements are more natural and less constricted. But, it is also less warm in that one specific area. Honestly, it isn't too much of an issue if I've properly layered under the coat, but I think it's a point worth mentioning.
I have found that you can redistribute the down to some degree by tumble drying the jacket with a few tennis balls. I do this about once a year and it works fine. I just wish the baffling would have been designed a bit better in that elbow area (elsewhere in the jacket it is fine, and things may have changed in the design to correct this problem in the 10 years since I bought the jacket).
Now, to move this answer in a bit of shooting related direction:
Keep in mind that this garment was designed for mountaineering related activities. As such, the shell material is (intentionally) fairly lightweight. While that is great for packing the jacket, you might want to consider what you are going to be asking of this coat. Are you going to be traveling through thick underbrush that could snag and tear it? Are you going to be shooting from the prone position with it? If so, will you be on a shooting mat, or crawling through the brush?
I mention these points just because they are worth considering if you haven't ever touched one of the jackets to evaluate the shell material for your purposes. These are fine jackets, but I wouldn't want to belly crawl in one! The material is certainly more substantial than some of the featherweight mountaineering jackets that are being sold today, but it also isn't a Carhart jacket, or an ice climbing hard shell!