I had a customer bring in a Rem m700 .308 this week that another 'smith had allegedly blued. The complaint was that this previously slick operating action now was sticking cases so that a block of wood was needed to beat the bolt open, even after using factory ammo and only moderate handloads. He brought me a half dozen fired cases. They showed no excessive pressure signs with normal looking primers. The cases exhibited moderate scratching around the entire circumference from neck to case head. From my inspection, the finish appears to be a black, gritty Parkerized finish on the outside and in the bore and chamber-not bluing.

The plan is to chemically remove the Parkerization and then polish the chamber with steel wool and oil. My research suggests 10% phosphoric acid on metal warmed to around 180 F should do the trick at around 10 minutes duration. I'd warm it by pouring boiling water through the bore for a minute or so.

I've never tried this before. Does anyone else have any prior experience with this and could share some best practices?

Thanks in advance,

Bob

YIKES! The chamber and bore are already etched from the phosphating; you don't want to etch it any more with acid. Any "gunsmith" who parkerized a bore should be beat with the barrel. Just polish the chamber a bit and maybe use some diamond paste to polish the bore. I would definitely not introduce any acid into the chamber or bore. That will not help smooth things out at all; it will leave them just as rough as they are now if not more so.

yep just polish the chamber it will be fine.

One more thing you know; do not try to make the chamber too smooth.

You might have to do it with more than steel wool .Maybe 400 grit abrasive paper and oil.Go easy ,check often.

take it back to the plumber, tell HIM to fix it -- do NOTHING -- as the other guy will blame you for everything..

nothing you do will make a good chamber, and will only add headspace --

jeffeosso is right.

however, refurbed M1 Garands had their chambers parkerized (unless rebarreled), and they shoot fine. the bores were not parked. a parked chamber, with nothing more, should not be a death sentence.

Thanks for the feedback! Sounds like good advice. I think I will try the steel wool oil polish first, test fire and go from there. Progressing to a 400 grit polish if need be. If that doesn't do it, I'll return it to the owner and recommend he get the other 'smith to pay for a re-barrel.

Jeffeosso; The owner agreed not to hold me responsible if I can't fix it. He blames the other 'smith entirely. If it can't be fixed he is going to re-barrel. I agreed not to charge him if I couldn't fix it.

K. Try this then Drill a fired in that rifle case out and epoxy in rod. This is going to be your polishing tool. Over the case with flitz or mothers billet polish and insert in the chamber. Turn with a very slow turning drill to polish the "top" of the parkerizing without removing a lot of material

Of course a set back and rechamber would be better

If it were mine I would set the barrel back & recut the chamber. No risk of ending up with an oversized chamber due to excessive polishing trying to get that rough park out. That is unless you screw up the chambering job.

quote:

Originally posted by Bobster:
Thanks for the feedback! Sounds like good advice. I think I will try the steel wool oil polish first, test fire and go from there. Progressing to a 400 grit polish if need be. If that doesn't do it, I'll return it to the owner and recommend he get the other 'smith to pay for a re-barrel.


Jeffeosso; The owner agreed not to hold me responsible if I can't fix it. He blames the other 'smith entirely. If it can't be fixed he is going to re-barrel. I agreed not to charge him if I couldn't fix it.

Bobster,
The steel wool and oil will do nothing except polish the roughness. I don't know of anyone who goes through most of the steps suggested here when finishing a new chamber. You can use a 320 Emery cloth wrapped around a wood dowel to cut the roughness out of the chamber and get a nice finish polish in the chamber. No, it won't change the headspace either, unless you polish half a day!

That will do it; the 320 on a stick idea; won't take much. I remember those Garands; they worked fine with parked chambers but they weren't too rough. Chambers are supposed to be a bit rough (320 grit or so) to let the brass grab; lessens back thrust on the bolt. Unless it is a G3 and you want the case to blow itself out.

Unless it is causing extraction problems it won't be a problem. Although its best not to Park the bore, a few shots will remove most all of it.