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Deltaten
September 30, 2001, 07:13
Last nite I decide it was time to dry-fit the group buy Imbel bbl into the new WAC receiver. Cleaned the threads and checked for burrs; all OK.

Barrel stopped at about 30 degrees short! Chamber to inner face mic'd out to about 8 thou, so I've got room there. Broke out the calculator and found I needed about 5 1/4 thousandths to reach TDC.

So how much should I remove? Search for thread on WAC ft/lbs-o'clock setting, no joy. What?, about 11:00 ? 11:15?

Anybody else come up this short?

TIA
Paul

kotengu
September 30, 2001, 10:55
The only way to KNOW for sure is to take off "just a little bit" at a time and keep checking it. Everytime I try to out think and calculate I end up missing something....

Deltaten
September 30, 2001, 11:01
roger that!

Radio
September 30, 2001, 15:17
You need to search harder. ;) There was another thread within just the last few days about this very question.

SHORT ANSWER: Time initially to about 11:30, which is about 15 degrees. This is what a board member quoted Dwight as specifying after the confusion introduced by the 45 degree comment below, in light of his earlier comments.

LONG ANSWER:
FAL ALUMINUM RECEIVER DISCUSSION
http://www.l1a1.com/cgi-bin/forums/ultimatebb.cgi?ubb=get_topic&f=1&t=011643
Posted by Dwight August 06, 2001
"To answer your question, because of the hard anodizing you don't want to be WECSOG-ing these receivers. The barrel timing is adjusted between 5-8 degrees BTDC. I realize that that is not normal for most of you, however is quite necessary in the aluminum receiver. 7075-T651 aluminum doesn't compress like 4140 does, and with the hard anodizing as well, if you try torquing the barrel with 15 to 20 degrees TDC, you'll destroy the receiver or break your receiver wrench.
"My opinion of current barrel timing differs from some here based upon my manufacturing experiences as well as knowing the details in how manufactures come about BTDC engagement, but it's not necessary to over torque a barrel, on any receiver, except a full-automatic as a rule."

What o'clock for Williams
http://www.l1a1.com/cgi-bin/forums/ultimatebb.cgi?ubb=get_topic&f=3&t=003224
Posted by Dwight September 26, 2001
"Because of the various barrels that are available for build, the timing we have found varies from about 90 degrees (9 o'clock) to around 30 degrees (11 o'clock) BTDC, depending upon a new IMBEL barrel to a used R1 barrel. I would not recommend that you attempt torquing a barrel to TDC that hand indexes before 45 degrees (10:30). If the barrel hand indexes 45 degrees or greater BTDC, the barrel shoulder should be turned to bring into correct timing prior to torquing into TDC."

Some additional information useful when headspacing, from the August thread:
"Typical initial set-back is between .0005 and .0008 on the average. The reason for that is the charcteristics of 7075-T651 aluminum. I won't go in great detail at this point, but in this application, its compression strength in this specific design are stronger than steel. The ability to return to static position better than steel. Our steel receivers that we build after 5,000 rounds, have a headspace correction set-back of usually .0025. Which is typical. On the aluminum the receiver that we currently have 9,224 rounds through have a current set-back of .0008."


There's a wealth of information on the four-page August thread; good reading.

--Radio

Deltaten
September 30, 2001, 16:58
Thanks Radio, I needed that! Musta searched the wrong place...Geeze, now I'll hafta change my handle to ATF :(

Paul

Radio
October 01, 2001, 00:37
Don't do that!! :eek:

Unless you mean... Automatic Transmission Fluid???

--Radio ;)