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View Full Version : Breeching washer/Locking Shoulder question....


K. Funk
September 04, 2001, 19:55
I have an L1A1 that was built by an non-FAL-enlightened smithy a few years back (say '92-93). It is my belief that the barrel is slightly over-timed as confirmed by the rod method. My best guess puts it at no more than 3 deg over. Assuming that I decide to tear this thing apart, how much thicker than the present one must my new breeching washer be to bring it back to TDC? Must the Locking Shoulder then be an equal amount larger? Are Inch and Metric Locking Shoulders interchangeable?

Sorry for the Dutch accent, I've been living amongst these Mennonites way too long!!

krf

Radio
September 04, 2001, 20:11
The rod method, which I use by the way, is not foolproof. Is this your only evidence of overtiming? I noticed you didn't mention the classic symptom, the rifle shooting WAAAY right or left, not enough windage adjustment in the world to compensate. If your sights are properly regulated and your rifle shoots to POA, forget about "what the rods say" and pile up brass.

If you really have an out-of-time problem I would not try to "mathematize" my way around it but custom-measure all the way. Un-barrel (de-barrel?) your receiver and test-fit the barrel again, measuring the needed breaching washer thickness with good old-fashioned automotive feeler gauges. Find out what value will be needed for the barrel to hand-tighted to about 11:00 (as viewed from front to rear).

Custom-measure the headspace as well. Frankly, I doubt your headspace setting will change very much from adjusting the barrel timing by such a small amount, but it HAS been a number of years since the rifle was assembled. Good idea to check it out. Lots of "articles" on how to headspace by FAL Files "authors" in the FAQ.

By the way, so far as I know both Inch and Metric locking shoulders are completely interchangable, provided the shank diameter is the same. There was "standard" and three oversizes (four sizes total) IIRC. If I'm incorrect, RKIs please chip in.

--Radio

[ September 04, 2001: Message edited by: Radio ]

K. Funk
September 04, 2001, 20:42
Thanks Radio. Yes there are classic symptoms. Rifle shot many inches to the right and took ALL of the adjustment in the rear sight to bring it back to POA. Another question for ya: At what point does over/under timing interfere with piston travel?

Thanks,

krf

Radio
September 04, 2001, 21:11
That's a very good question. I can only answer it in a general sense, having merely "played around" with gas system misalignment.

When I barrel a receiver, I use the "rod method" to bring the barrel close to TDC. I then drop a known-straight gas piston through its bore to check for binding. If all goes well and the previous two methods agree, I complete the build and perform the ultimate test at the range: does it shoot to POA? Only then am I satisfied the build has been successfully completed and another FAL has truly been reborn.

To check the accuracy of what I was doing, I once screwed a barrel into a receiver (IMBEL) one full revolution out from all the way down, then installed a gas tube (properly pinned), with adjustment ring, gas nut and carrying handle. I screwed in a front sight and mounted everything to a lower. I then twisted the barrel back and forth, looking down the sights, while testing how far to either side the gas piston would still drop and move freely. I was surprised to discover it was a substantial amount; not just a degree or three as I had imagined.

A more sure test would of course be to fully barrel the receiver, then deliberately wrench the barrel out of time while continuing to shoot after each adjustment, until the gas system no longer cycles. This is just a little more trouble than I really wanna tackle, but I think the informal version taught me enough about under- or over-timing.

Rods are great, I use them. Checking for piston travel is great, I use it. But if you've seen Gunplumber's video, he looks down the sights when he barrels a receiver. The entire idea of timing, after all, is to insure the stinkin' front sight is dead-vertical... what better way to check than to LOOK at it??

Bottom line, I guess, is to take out your rifle and shoot it; THEN you'll know how good a job you did during assembly. Pile up that brass, baby...

--Radio