This is really intended to be a question for Mike Bellm but all opinions welcome.

The new NEF's are coming with rough chambers which is making extraction/ejection difficult. The fix is to polish the chambers from what I hear.

What is the proper technique for someone to polish their own chamber? Or is something like that best left to the pros?

$bob$

Bob,
You want to knock the tops off of the peaks of the finish. Simply polishing tends to perpetuate the lows in the finish while also polishing the highs.

The RMS symbol used in conjunction with surface finish numbers means Root Mean Square, a calculated average of the peaks and valleys in the finish as measured with a profilometer, a gizmo that slides a stylus across the finish and measures the highs and lows.

I had to chuckle at the owner of the grinding shop I use. After grinding my Encore pins to diameter, I asked him what finish they had.... not that it really mattered that much since they are hand polished afterward anyway. He ran a fingernail across the surface and said, "That's a 25 finish." And without having plates to compare against, from what I know, I wouldn't argue his assessment of it.

Back to the point, lapping with a solid lap is best. You turn aluminum or brass to just a thous or so larger than all diameters of the case body, spin the barrel in the lathe, dope the lap with valve grinding compound, then work the lap in a little at a time with rapid cross hatch motions like you would honing an engine cylinder wall. Naturally, the lap wants to seize since it is larger, but after it grabs a few times, you'll get the feel for how much to feed it in.

The solid lap very effectively knocks the tops off the rough finish without unduly perpetuating the valleys in the finish.

You will no doubt get all sorts of differing opinions about dowel rods in an electric drill with emery paper, etc., and extraction can no doubt be improved. But this is hardly the best way to go about it.

I am also finding that lapping the chamber, then leaving the final polished finish no finer than produced with 320 grit emery paper "cross hatched" with the barrel spinning at high speed in the lathe produces the best finish for case adhesion to the chamber wall, thereby reducing case head back thrust, while giving completely reliable extraction. Ie, a high polish in a break open gun is not a good thing. Don't go for super smooth.

Mike

Thanks Mike,

May I quote you in an NEF forum? (with credit to you and your website link included)

I can't imagine how many times I've asked your advise and have received it in written in detail.

Yer the Greatest Mike!

Thanks again.....

$bob$

Sure. Thanks for asking though. All I ask is credit for the source, as you offered.

Mike