Parkerizing

[oldyeller]

Can I park my un-barreled receiver with trunions installed? My worry is that it will mess with the surface the barrel presses into.

[MrNiceGuy]

I would say don't do it.
I've read the same thing, someone parked a trunnion with no barrel, next time you know the barrel slide into the trunnion with some room to spare.
Obviously there might be other unknowns involved, maybe they over parked it, who knows, but I wouldn't risk it.

[Rule .308]

Not that I have done it, because I have not, but I would not do it. If you look at the surfaces of both the barrel and the trunion they are typically polished, I would think that parking them would only create friction when you go to press it all back together. I have parked and rebuilt plenty of rifles in the past but it has all been screw together stuff, i.e. FAL's.

[dwtt]

You should not do it unless you have a way to mask off the inside of the trunnion to prevent the phosphoric acid from contacting it. Parkerizing consumes a bit of the underlying steel and it will screw tight tolerances. It won't build up material, which you can later sand or lap down, but will remove it, which you can't replace. Don't ask me how I found out, but NDS will remake your receiver with the same serial number if you parkerize it too long and things get too loose. Installing another trunnion is your responsibility, though.

[tophatjones]

IMHO, the parkerizing process itself only removes a fraction of a thousandth of an inch of metal. In fact, it builds up the phosphate crystals and could make a tight fit even tighter. The main issue is the blasting process, which could remove quite a bit of surface depending on how you do it.

[JamesY]

I've done it. I "masked" off the inside of the trunnion with black electrical tape and it worked fine. I did the same thing to the barrel. I'll try to remember to bring it at the BP. I think it turned out great.