So being near the ocean and lots of bayou/swamp areas I have been pondering building an AR specifically resistant to this environment, as a new work gun, we do various shipboard security/anti-piracy contracting.
Looking at major components in QPQ (Melonite) finish, NP3, and possibly cerakote, trying to eliminate as much ferrous to ferrous metal contact as possible so the idea is in making the rifle fairly amphibious.
I’m not new to building AR’s, just first time I have contemplated something more specialized.
Currently running a Mk18-esque pistol build with melonite barrel and bcg, either thinking upgrade or start from scratch.
I’ve got time for further research I am putting in for a stamp on a lower next month for either this or another project.
Back in the mid 80’s I was living in Austin Texas, one day I was heading out of town up to Belton and stopped at McBrides and wound up buying a Colt CAR15 for $365. On the way out of town I stopped at a couple of North Austin pawn shops, one had a Colt factory nickle SP1 made for the Italian market and chambered in .222 (military caliber not allowed) for about the same price. To this day this is one of the deals I regret passing on. Oh and the other pawn show had a paratrooper FNC for about the same price, having just bought the CAR I talked myself out of the other two even though I had the money in pocket, you know what they say about hinesight. Except for the caliber that nickle SP1 would have made a sweet boat gun.
The overall look isn’t really that important, it’s going to get beat up. Obviously I will try to put it together to not look like hammered dog crap, but the corrosion resistance is more important than aesthetics. Nothing some duracoat can’t cover up.
For exposed metal you’ll need some kind of coating, be it Duracoat or Cerakote. I’m not into camo patterns on my weapons so I have them done in the underlying color: steel parts are Colt Gray (an excellent Duracoat color that matches Parkerizing very well), and aluminum parts are done in black. If there is a scratch you won’t see it unless you look real close as the underlying color is the same.
For the BCG either hard chrome (Daniel Defense makes a nice one) or perhaps a Sionics NP3 finished one.
Those things should just about make it weatherproof!
Not a build, but I’m likely going to be picking up one of Robar’s Polymar-15s. Likely the 16” TI version in black. Price is up there, but sounds like a lot of win there.
Most components in an AR are anodized/coated aluminum anyway, so you just need to focus on the few critical parts that are not. For example, choose a handguard that uses a treated/coated barrel nut such as Geissele. Use a standard stainless grip screw, and a V7 aluminum castle nut. That leaves the barrel, and bcg. There are plenty of QPQ/nitride coated barrels out there, Faxon comes to mind here. BCGs can be had in QPQ/nitride as well, Toolcraft makes an excellent nitride bcg that can be found for a very reasonable price.
What about the trigger group? Detents and springs? Euro put up a post a couple of weeks ago about what a single drop of water can do to a detent spring. I am not so sure trying to corrosion proof everything wouldn’t be more trouble than an accelerated maintenance regime. Components don’t go from like new to corroded beyond being serviceable overnight.
This is exactly what I am looking at Robar is high on list of options, it’s the small parts-- detents, roll pins, screws that I am definitely looking to source in coated or otherwise resistant materials.
There are Nickel Boron trigger groups, ALG ACT comes to mind. As far as small parts are concerned, when you find a source is of readily available corrosion resistant parts, do me and the rest of the group a favor and tell us where you found it.
Bottom line I don’t think building a completely maritime resistant AR is possible right now. The best you can do, is select the most corrosion resistant materials you can. The rest of the parts will require your attention from time to time, to make sure they are properly lubricated, and in good functioning condition.
If you do find a source for corrosion resistant small parts, please inform the rest of the forum, as this type of info would benefit all of us. In the meantime, a little bit of PMCS goes a long way toward keeping your weapon in tip top shape. I would suggest more frequent tear downs for inspection, and keeping an ample supply of spare parts on hand.
Unless I am mistaken the safety/pivot/takedown detents are made of hardened stainless. If that stainless is in the 300 series it has the best corrosion resistance.
When it comes to the springs I would just make sure they have a fluid rust preventing lubricant that won’t evaporate at the temperature highs it experiences.
I might be the wrong person to weigh in on this. Like I grew up on a beach so I am aware how salty it can be, but I spent all my gun time in the most Arid of deserts.
Are you not massively over thinking this? A 6920 should have the same or similar corrosion resistance than what a majority of Navy and USMC units are using. Im assuming they just do a regular inspection and replace parts as neccesary? If you need I can ask a buddy thats a recondo, but I doubt his answer will be different.
My answer; buy parts that are not bare steel, which shouldnt be too terribly difficult. Nitride BCGs and barrels. As mentioned a ALG trigger and LPK would be probably your best bet. I also like the V7 Al castle nut that someone else mentioned. Wouldnt want a rusted castle nut to break and cause a total failure.
Off the top of my head, correct MILSPEC pins are made from 1215L with a cadmium chromate coating for corrosion reasons and to prevent them from seizing in the hole.
yes constant maintenance, part of what I am looking at is not replacing good maintenance habits but improving the ability of the weapon to withstand the harsh environment which aids in that and increases longevity in theory.