View Full Version : Polishing chrome-lined barrel chamber?

June 22, 2007, 20:13
Yet another bright idea in this experiment called DIYFAL. I've been shooting Hirt through a new chromelined DSA barrel and even with the setting on 1 I cannot count on successful cycling of my FAL. My rifle has been plagued with weird symptoms since it was first built. Now I get acceptable battlerifle accuracy, but the spent brass has a mottled appearance to it after ejection, making me wonder if the chamber finish is too rough. Is there a way to safely polish the chamber further without risking damage to the chrome lining?
To date, I've thread-taped the threads on the gas tube, checked to make sure the pin is in place and tube is relatively tight, checked headspacing, tried a new piston, checked for piston binding, enlarged and smoothed upper receiver opening, checked the gas plug setting, checked the drilled gas hole in barrel to insure it's clear of debris, barrel timing, new bolt/bolt carrier, and finally the new DSA barrel. I'm thinking that all that's left unchecked is the gas plug seal, replacement spring set, polishing the chamber, replacing the gas tube itself, and finally enlarging the gas hole in the barrel itself. Anybody got some other ideas I might try?

June 23, 2007, 18:19
My usual setup for polishing the chamber on a rifle that's already together goes like this;

Cut a short strip of cotton Tee shirt material about 3x3"
Apply Flitz metal polish and work it into the material so it's completely imbeded
Wrap the material around the front section of an M14 chamber brush
Attach 2 sections of USGI metal cleaning rod to the brush
Chuck rod in battery drill and go to town on the chamber
Replace material & polish when it get's dirty and "clogged" looking

If it's pretty bad I'll usually start with JB Bore Compound first and then move on to the flitz. Use this as a guide and adapt to you'r own supplies, it's worked on more than a few rifles, chromed or not. You wont hurt chrome, it's super hard. Make sure to clean it good afterwards.

Cheers, YV

June 23, 2007, 18:33
Thanks for the help!

June 23, 2007, 19:35
What length barrel?

June 23, 2007, 19:50
Originally posted by W.E.G.
What length barrel?

It's DSA's 21" G-1 barrel

June 28, 2007, 01:15
I use a fired brass case that has had the primer pocket drilled out and a small machine screw stuck through it from the case mouth and double nut holding it tight. I embed it with polishing compound, making a new one for each grit. I chuck it in a cordless drill/screw driver and polish the minimum needed. Try to keep everything straight and the pressure even. Flush liberally after and between grits. It has worked on three different calibers of rifles.


June 29, 2007, 00:31
I think you've still got a gas leak.

July 04, 2007, 13:31
Buy a new gas tube from DSA ! Also make sure you check heaspace ! The weak part of Fal system is the small threads on the Gas Tube that wear out over time. This provides a huge spot for gas to escape. Get a new one and see what happens. You might also want to get a DSA made piston as they are a little oversized and should help. Good luck !

July 04, 2007, 13:34
What is the diameter of the gas port?

July 05, 2007, 23:04
Make sure the problem isn't some where else before polishing the chamber. Polishing the chamber too much will reduce friction between the cartridge case and chamber walls during firing. You need some level of friction or resistance to blow back or you will increase the pressure against the bolt head unnecessarily. I belive this principle is common with most fire arms and accounted for in the design. Just don't over do it.

July 08, 2007, 20:44
My apologies for the absence of an update. Today I finally polished the chamber. I tried to stay off the neck and shoulder area and mainly just polish the body area of the chamber. I checked the gas port hole and barely got a .098" diameter drill bit to go through the hole. I'm waiting on this heatwave to subside and will test the rifle for function again. This sure has been a difficult problem to pin down! If this doesn't work, I'll try some of you folks other ideas. Thanks for the help guys!